GS.TS. PHM DUY HU (Ch bin) PGS.TS. V C CHNH TS. O VN NG

THS. NGUYN THANH SANG

B TNG ASPHALT

NH XUT BN GIAO THNG VN TI

Vin khoa hc v cng ngh xy dng giao thng Trng i hc GTVT

Huuphamduy@gmail.com

LI NI U

B tng asphalt v cc vt liu hn hp khongbitum khc l vt liu chnh xy dng mt ng t v sn bay, ng st v cc cng trnh thu li.

Ni dung ca gio trnh trnh by v cc nguyn l, vt liu ch to, cc tnh cht vt l v c hc, phng php thit k thnh phn, cng ngh ch to b tng asphalt.

Gio trnh bao gm 12 chng c phn cng bin son nh sau:

Ch bin: Chng 1, 2, 3, 4, 5, 6, 9GS. TS. Phm Duy Hu

Chng 7, 8PGS.TS. V c Chnh

Chng 7, 11, 12TS. o Vn ng

Chng 9, 10ThS. Nguyn Thanh Sang

Gio trnh l ti liu hc tp cho sinh vin chuyn ngnh vt liu v cng ngh xy dng, sinh vin ngnh xy dng cng trnh giao thng ca Trng i hc Giao thng Vn ti. Gio trnh cn l ti liu tham kho cho cc k s xy dng giao thng v xy dng dn dng, cc hc vin cao hc, nghin cu sinh v cc c gi cn quan tm.

Trong qu trnh bin son chng ti nhn c kin ng gp ca cc ng nghip, cc nh khoa hc k thut thuc B GTVT, B Xy dng v cc trng i hc trong v ngoi nc. Chng ti nhn c cc ti liu qu bu ca trng Xy dng ng v t ca Nga v cc ti liu ca cng ty Shell Anh Quc.

Chng ti rt cm n v mong nhn c kin ng gp ca bn c cho cun sch c hon thin hn.

Cc tc gi

CC T KHA

Phm Duy Hu, B tng asphalt, bitum, vt liu khong, b tng ri ngui,

bn Marshall, cu trc ca b tng asphalt, hn hp vt liu khong -bitum, SMA.

Chng 1

KHI NIM V PHN LOI B TNG ASPHALT

1.1. KHI NIM

B tng asphalt l vt liu khongbitum xy dng ng, nhn c khi lm c hn hp b tng asphalt. Hn hp b tng asphalt bao gm dm (hoc si), ct, bt khong, bitum du m, ph gia. Hn hp c thit k hp l v gia nhit t 1201600C. Thnh phn ca b tng asphalt theo khi lng thng thng nh sau: dm: 2065%; ct: 3066%; bt khong: 414%; bitum: 57%; v ph gia tu theo kt qu th nghim.

Trn c s cht kt dnh hu c (bitum, gurng, nh tng) trong xy dng ng thng dng cc vt liu hn hp khong v cht kt dnh hu c. Ph bin nht v c cht lng cao nht t vt liu khongbi tum l b tng asphalt. B tng asphalt l sn phm nhn c khi lm c v rn chc hn hp asphaltb tng.

Hn hp b tng asphalt bao gm: dm, ct, bt khong v bi tum c la chn thnh phn hp l, nho trn v gia cng thnh mt hn hp ng nht. Ct liu ln lm tng khi lng hn hp, lm gim gi thnh ca b tng asphalt v tng cng v n nh. Ct liu nh khi trn vi bitum to thnh va asphalt lm tng tnh do ca hn hp, nh hng n kh nng lm vic v phm vi ng dng ca b tng asphalt. Bt khong lm thay i t l ct liu nh lm hn hp c hn v tng t l b mt ca cc ct liu, n kt hp vi bitum to nn cht kt dnh mi bao bc v bi trn b mt ct liu. Cht lng ca b tng asphalt ph thuc vo ngun gc ca ct liu, bt khong v qunh/ nht ca bitum.

B tng asphalt l tt nht so vi cc hn hp vt liu khongbitum khc ch n c c, cng , n nh v bn cao do s tham gia ca bt khong trong thnh phn.

B tng asphalt c s dng lm lp ph mt ng c lng giao thng cao nh ng cao tc, ng thnh ph v sn bay.

B tng asphalt i hi kt cu pha di c cng cao m bo khng b nt gy trong qu trnh khai thc. ng thi vic ci tin nhm m bo cho xe chy vi tc cao l vn cn ang tip tc nghin cu.

Cng v n nh ca b tng asphalt c hnh thnh nh s lin kt gia ct liu vi bt khong v bitum. Thnh phn ca b tng asphalt c th c thit k

theo tiu chun Vit Nam v tiu chun ca Vin Asphalt Hoa K. Thnh phn hn hp vt liu khong theo cc tiu chun ny v cn bn l ging nhau. Tuy nhin, vn lng bitum ti u cn c nhng im cha thng nht.

Cc tnh cht ca b tng asphalt ph thuc vo nhit thi cng v nhit khai thc. Theo cc ti liu quc t th b tng asphalt c th khai thc nhit t 500C n +600C. Cc gii php tng cng n nh nhit ca b tng asphalt cn c bit lu khi s dng b tng asphalt trong iu kin kh hu nhit i. Trong qu trnh khai thc b tng asphalt chu nh hng ca cc yu t nhit v thi tit nn n b gi i, nt n, b mi mn v bin dng lm gim tui th khai thc ca b tng asphalt. Tui th trung bnh ca cc lp ph mt ng bng b tng asphalt khong 10 n 15 nm. Trong iu kin thit k, thi cng, bo dng v khai thc hp l th tui th ti a c th t n 20 nm.

Yu cu v thnh phn hn hp, tnh cht ca b tng asphalt v phng php thit k thnh phn c ghi r trong tiu chun TCVN v TCN GTVT. C th tham kho tiu chun 912884 hoc 2.05.0285 hoc 1280184 ca Nga; tiu chun ca Vin Asphalt Hoa K.

B tng asphalt c s dng xy dng khong 50% cc con ng trn ton th gii v khong 15% cc con ng Vit Nam.

B tng asphalt cn c th s dng lm va h, khu vui chi gii tr, cng trnh th thao v cc cng trnh thu li. B tng asphalt ch yu c mu en nhng trong iu kin yu cu cng c th ch to b tng asphalt c mu khc.

1. 2. PHN LOI B TNG ASPHALT

B tng asphalt l vt liu khongbitum c cht lng cao. Ngoi ra cn c cc loi hn hp khc nh: vt liu nha macadam, nha cp phi c, nha cng cao, nha ht mn (va asphalt), hn hp to nhm, nha thm nc. S khc nhau c bn gia hn hp asphalt v nha l cp phi ca hn hp. Cp phi ct liu trong asphalt thng bao gm ct liu ln, ct liu mn v bt . Trong cc hn hp nha thng t s dng bt . Cc hn hp to nhm v nha thm nc thng s dng cc cp phi gin on.

B tng nha cn c th c ch to t cc loi bitum polyme hoc cc loi nh tng bitum.

Cng ca b tng asphalt thay i t 115MPa v ph thuc vo nhit . B tng asphalt c th c phn loi theo cc yu t sau:

Theo cc tiu chun quc t v 22TCN 24998 ca B Giao thng vn ti qui nh nh sau:

Hn hp b tng asphalt v b tng asphalt c phn loi theo cc c im sau:

Theo nhit thi cng: Hn hp b tng asphalt trong lp ph mt ng c chia ra loi nng, m v ngui. Hn hp nng c ri v bt u lm c khi nhit khng nh hn 120oC. Hn hp ny thng dng bi tum c qunh 40/60, 60/70 v 70/100. Hn hp m c ri v bt u lm c khi nhit khng nh hn 900C v

thng dng bitum lng s 1, 2, 3. Hn hp ngui dng bi tum lng c nht 70/130 c ri nhit khng kh khng nh hn 5oC v c gi nhit thng.

Theo c (hoc rng d): Theo ch tiu rng d b tng asphalt c chia lm 3 loi: loi c c rng 25%, loi rng c rng 612% v loi rt rng c rng 1225% theo th tch.

Theo ln ca ht ct liu: Theo ng knh ln nht ca ht vt liu khong c chia ra 3 loi: loi ln (Dmax 40mm), loi trung bnh (Dmax 20mm) v loi nh (hn hp ht nh v hn hp ct Dmax 5mm).

Theo tiu chun M b tng asphalt chia lm 21 loi k hiu l s Lam v c ch tiu ph l a, b, c, d...V d Ia,..., IId... Vi Dmax l 2,5 in, 1,5 in, 1 in, 0,5 in v 3/8 in, Dmin l mt sng s N

o200 (0,071 mm).

Theo hm lng gia dm (hoc si) v ct: B tng asphalt nng hoc m, c c chia lm 3 loi: loi A nu t l dmhn hp ct liu trong khong 5065%; loi B: 3550%; loi C: 2035%; loi D: b tng asphalt ct thin nhin; loi G: b tng asphalt ct nghin. B tng asphalt ngui c chia lm 2 loi: BN: 3550%; CN: 2035%. B tng asphalt ct ri ngui c k hiu: DN v GN.

Theo cht lng ca vt liu v tnh cht c l: B tng asphalt cn chia ra loi sau:

I, II, v III: B tng asphalt c v nng.

I,II: B tng asphalt nng rng v rt rng.

I,II: B tng asphalt ngui.

V c bn cch phn loi b tng theo cc tiu chun l thng nht tuy c quy nh khc nhau v n v o kch thc ht ct liu v k hiu loi b tng. Theo tiu chun Vit Nam v Nga n v o l mm, tiu chun Anh, M l in.

1.3. CC YU CU CHUNG I VI B TNG ASPHALT

B tng asphalt l mt loi vt liu c bit vi cc tnh cht thay i nhiu theo nhit ca mi trng v theo ma. Vo ma h nhit b tng trong lp ph mt ng c th t 50600C, cng ch cn 11.5MPa, b tng asphalt tr nn do v c th b chy. V ma ng cng t t 1015MPa, b tng asphalt tr nn n hi thm tr c th dn.

Trong c nm mc ti trng chuyn ng trn mt ng l khng i. Nh vy vic thit k thnh phn b tng, thit k kt cu mt ng, thit k cng ngh thi cng l mt bi ton rt l phc tp m bo yu cu thay i trng thi ng sut bin dng trong cc iu kin thay i nhit khc nhau. Bi ton c gii quyt bng cch la chn dng, kiu, vt liu, kt cu mt ng hp l c xt n s ph hp gia iu kin vn ti v kh hu. B tng asphalt cn m bo cc yu cu v cng , n nh, bin dng nhit cao v chng li s ph hoi do nt nhit thp. Khi m bo c cc yu t trn b tng asphalt c th t tui th t 15 n 20 nm.

1.4. KT CU MT NG B TNG ASPHALT

Kt cu mt ng t ch yu gm mt s lp: lp mt, mng v lp nn mng. Hnh 1.1 m t mt mt ct ngang in hnh ca mt con ng. Cc lp kt cu mt

ng b tng asphalt m t hnh 1.2. Kt cu mt ng c kh nng phn b hiu qu ti trng xe, m bo kh nng chu ti, tui th, chi ph u t xy dng v bo dng hp l. Kt cu mt ng c thit k m bo di tc dng ca ti trng xe ng sut trn mt ng v nn ng khng vt qu cc gii hn cho php. Ngy nay ti trng trc xe thit k thng t 1013 tn, trong tng lai c th n 15 tn. Ti trng ca my bay c th pht trin n 25 tn. Cc tc ng ca mi trng nh m, lng ma, mc nc ngm, cc iu kin kh hu cng nh hng ln n cht lng mt ng.

Lp mt ng thng bao gm 2 lp: lp trn thng c gi l lp o (lp mt). Lp ny thng s dng b tng asphalt c ht nh. Lp di thng s dng b tng asphalt ri nng hoc m rng v ht ln. Lp trn ca mt ng phi m bo kh nng chng li bin dng di tc dng ca ti trng xe, khng thm nc bo v lp di ca mt ng. Trong nhng con ng c bit c th s dng cc lp bitum rng thm nc hoc cc lp matt asphalt cng.

Hnh 1.1. Mt ct ngang ng t in hnh

Mt ng b tng asphalt l loi mt ng chnh trong giao thng th, ngoi th, ng cao tc v ng nhiu xe chy.

Hnh 1.2. Cu to cc lp mt ng t

Lp mng l b phn kt cu chnh trong kt cu mt ng phn b ti trng m bo cc lp di khng b qu ti. y l lp chu lc chnh, c kh nng chng li bin dng d v s nt gy do mi v ng sut pht sinh do chnh lch nhit . Lp

mng c th chia ra lm 2 lp: lp mng trn v lp mng di (lp cp phi dm tiu chun). Lp mng trn thng s dng cc vt liu dnh kt, lp mng di s dng vt liu c gia cng. Cc vt liu dnh kt bao gm b tng asphalt c rng cao, vt liu khongbitum, cc vt liu hoc nn mng c gia cng bng cht dnh kt v c. Lp gia cng gm c dm, ct, vt liu khong t cc i hoc cc sn phm cht thi cng nghip. Tng mng cng c th s dng cc loi b tng ngho.

Lp nn mng ca kt cu mt ng c bn gm 2 lp: lp nn trn thng bng vt liu ht c cht lng tt, lp nn di l t t nhin hoc t c gia c nhm to lp lp mt tt ca nn ng. i khi cng b sung mt s lp: lp ph nn c th bng t t nhin hoc ct liu ht th c gia c vi v xi mng. Lp thot nc t do to thnh mt lp thot nc ra khi mt ng bng dc ngang lp ny c th dng ct vi tiu chun k thut m bo.

CU HI N TP 1. Khi nim v phn loi b tng asphalt 2. Cc yu cu chung i vi b tng asphalt 3. Kt cu mt ng b tng asphalt

Chng 2

CHT KT DNH BITUM

2.1. KHI NIM V PHN LOI BITUM LM NG 2.1.1. KHI NIM

Nhng loi vt liu nh bitum, gurng, nh tng, nha mu l cc cht kt dnh hu c. Chng c th dng cng, qunh, lng (thnh phn ch yu l hirccbon cao phn t v mt s hp cht khc), c kh nng trn ln v dnh kt cc vt liu khong, to thnh vt liu nhn to c nhng tnh cht vt l, c hc ph hp xy dng ng t v sn bay. Cc cht kt dnh hu c cn c dng lm vt liu lp, cch nc, chng thm v bo v cc p nc, cc cng trnh kin trc, lm nn, gia c nn ng st, sn th thao, ng ua t v m t. Cht dnh kt trong b tng asphalt thng s dng bitum du m qunh hoc lng, nh tng bitum hoc bitum polyme.

2.1.2. PHN LOI

Bitum c cc loi sau:

Bitum du msn phm cui cng ca qu trnh chng ct du m, c nhiu M, Nga v Trung ng.

Bitum dusn phm khi chng du. du c th cha n 12% bitum. Bitum du c sn xut Php v Thu S.

Bitum thin nhinloi bitum thng gp trong thin nhin dng tinh khit hay ln vi cc loi . c khai thc ti cc m u tin Ty Ban Nha.

Nh tng bitum: l mt loi bitum lng bao gm cc ht bitum phn tn trong mi trng nc v cht nh ho.

Bitum polyme ci tin: l loi bitum ci tin c thm thnh phn polyme hu c hoc cc cht polyme to mu. Bitum polyme c tnh n nh nhit hoc to mu sc cho cng trnh. Gi thnh ca bitum polyme cao nn c s dng trong cc cng trnh ng cao cp, c cc yu cu c bit.

Bitum rn v bitum oxi ho: nhit 2025oC l mt cht rn c tnh gin v tnh n hi, nhit 180200oC th c tnh cht ca mt cht lng.

Bitum qunh: nhit 2025oC l mt cht mm, c tnh do cao v n hi khng ln lm.

Bitum lng: nhit 2025oC l cht lng v c cha thnh phn hyrcacbon d bay hi, c kh nng ng c li sau khi thnh phn nh bay hi, v sau c tnh cht gn vi tnh cht ca bitum qunh.

2.2. THNH PHN V CU TRC CA BITUM 2.2.1. THNH PHN CU TO CA BITUM

Bitum du m l mt hn hp phc tp ca cc hp cht hyrcacbon cao phn t (metan, naftalen, cc loi mch vng). Bitum c mu en, ho tan c trong benzen (C6H6), cloruafooc (CHCl3), disunfuacacbon (CS2) v mt s dung mi hu c khc, cc nhm chc nng c cha lu hunh, nit v nguyn t xy. Bitum cng cha mt s lng nh kim loi nh niken, st, magi, canxy di dng mui hu c.

Thnh phn ho hc ca bitum du m nh sau:

C = 8288%; S = 06%; N = 0,51%;

H = 811%; O = 01,5%.

Da trn c s l thuyt v nhm ho hc ngi ta chia bitum du m thnh 3 nhm chnh (nhm cht du, nhm cht nha, nhm asphalt) v cc nhm ph. Nhn chung, c th tch thnh phn ho hc ca bitum thnh hai nhm asphalt v maltel. Nhm cc maltel c th chia ra thnh cc cht bo ho, cc cht nha, cc cht thm (phn loi theo tiu chun Anh).

Nhm cht du(thm) gm nhng hp cht c phn t lng thp (300600), khng mu, khi lng ring nh (0,910,925). Nhm cht du lm cho bitum c tnh lng. Nu hm lng ca nhm ny tng ln, tnh qunh ca bitum gim. Trong bitum nhm cht du chim khong 4560%.

Nhm cht nha gm nhng hp cht c phn t lng cao hn (600900), khi lng ring xp x bng 1, mu nu sm. N c th ho tan trong benzen, etxng, clorofooc. Nhm cht nha trung tnh (t l H/C = 1,61,8) lm cho bitum c tnh do. Hm lng ca n tng, do ca bitum cng tng ln. Nha axit (H/C = 1,31,4) lm tng tnh dnh bm ca bitum vo . Hm lng ca nhm cht nha trong bitum du m vo khong 1530%.

Nhm asphalt rn, gin gm nhng hp cht c phn t lng ln (100030000), khi lng ring 1,101,15, c mu nu sm hoc en, khng b phn gii khi t. Khi nhit ln hn 300oC th b phn gii ra kh v cc, t l H/C = 1,1.

Asphalt c th ho tan trong clorofooc, ttraclorua cacbon (CCl4), khng ho tan trong te, du ho v axtn (C3H5OH). Tnh qunh v s bin i tnh cht theo nhit ca bitum ph thuc ch yu vo nhm ny.

Hm lng nhm asphalt tng ln th tnh qunh, nhit ho mm ca bitum cng tng ln. Hm lng ca nhm asphalt trong bitum vo khong 1025%.

Nhm cacben v cacbit. Tnh cht ca cacben gn ging nh cht asphalt, ch khc l khng ho tan trong benzen v trong CCl4, ho tan c trong isunfuacacbon, khi lng ring ln hn 1.

Cacbit l mt cht rn dng mui, khng ho tan trong bt c dung mi no.

Hm lng ca cc cht ny trong bitum nh hn 1,5%, lm bitum km do.

Nhm axit asphalt v anhyrit. Nhm ny l nhng cht nha ho (nha axit) mang cc tnh (gm nhng phn t c cha gc cacbxynCOOH), n l thnh phn hot tnh b mt ln nht ca bitum, d ho tan trong ru cn, benzen, clorofooc v kh ho tan trong etxng. Axit asphalt c khi lng ring nh hn 1, mu nu sm, hm lng trong bitum nh hn 1%. Khi hm lng tng ln, kh nng thm t v cng lin kt ca bitum vi b mt vt liu khong dng ccbonat tng ln.

Nhm parafin (cc cht no) l nhng hyr cacbua bo dng chui thng hoc phn nhnh c phn t lng trung bnh, bao gm cc cht parafin v khng thuc dng parafin. Papafin c th lm gim kh nmg phn tn v ho tan ca asphalt vo trong cc nhm khc, c th lm gim tnh ng nht ca bitum. Nu t l parafin tng ln, nhit ho mm, tnh gin ca bitum nhit thp s tng ln, bitum ho lng nhit thp hn so vi bitum khng cha parafin. T l ca parafin trong bitum du m n 5%.

Tnh cht ca bitum ph thuc vo thnh phn v tnh cht ca hn hp cc nhm cu to ho hc. Da vo nhm cu to ho hc c th chia bitum du m thnh 3 loi: loi 1, loi 2 v loi 3. Bitum loi 1 c nhm asphalt > 25%, nha < 24% v dung dch ccbon > 50%. Bitum loi 2 c hm lng nhm cu to ho hc tng ng l > 18%; > 36% v < 48%. Bitum loi 3 c cc nhm cu to ho hc tng ng l 2123%; 3034% v 4549%. Ba loi bitum trn c bin dng khc nhau. Thnh phn ho hc ca chng thay i theo thi gian s dng kt cu mt ng.

Hnh 2.1 m t quan h tng i gia hm lng cc nhm cht ho hc ch yu trong bitum vi ch s kim ln.

Hnh 2.1. Quan h gia cc nhm cht

ho hc ch yu vi ch s kim ln

2.2.2. CU TRC CA BITUM

-1-2 0 1 2 3 4 5 6 7 8 90

10

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Nhm cht bo ho

Nhm cht thm

Nhm cht nha

Nhm asphalt

Ph

ntr

m

-1-2 0 1 2 3 4 5 6 7 8 90

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20

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Nhm cht bo ho

Nhm cht thm

Nhm cht nha

Nhm asphalt

Ph

ntr

m

Tnh cht ca bitum ph thuc vo cu trc ca n. Bitum l mt h thng keo phc tp c cu trc c bn l cu trc mixen asphalt.

Trong l thuyt mixen i vi nhng cht cao phn t, Menep v Mark coi cu trc ca chng nh mt h thng tinh th (mixen). Trong h thng ny cc mixen b bao quanh bi mt s lng ln cc phn t c phn t lng nh bng nhng lc tng h. Khi lc tng h ln th mi mt mixen l mt nt ca mng. Mixen c coi l pha phn tn, cc phn t c phn t lng nh hn ng vai tr l mi trng phn tn. Vi bitum, pha phn tn l nhm asphalt, xung quanh chng l nhng cht nha v mi trng phn tn l cht du.

Trong bitum qunh v cng, mixen chim t l ln. Cn trong bitum lng chng chim mt t l nh n ni khng c tng tc g vi nhau nn c th chuyn ng t do trong cht du.

Quan h gia hm lng v cu to ca cc nhm trong bitum (du, nha, asphalt) c th to nn cc cu trc phn tn khc nhau (sol, gel, solgel) c nhng tnh cht cl nht nh (Hnh 2.2).

Cu trc sol c trng cho bitum c hm lng cht du v cht nha ln. Khi cc mixen asphalt khng to ra c tc dng tng h ln nhau v chuyn ng t do trong mi trng du. Cu trc sol c trong bitum lng v bitum qunh nu nng chy.

Khi t l asphalt trong bitum ln v khng cht du v thm s to nn cu trc gel. Trong cu trc gel cc ht nhn asphalt m rng ra, cc mixen asphalt xch li gn nhau v c tc dng tng h ln nhau, to nn mng cu trc khng gian. Cu trc to ra tnh n hi cho cht kt dnh v l c trng cho cu trc ca bitum cng nhit thp.

Cu trc solgel c trng cho bitum qunh nhit thng. nhit ny vt liu s c tnh n hi do v tnh nht.

b Cu truc vng thm

b Cu truc vng

thm

eS cu trc bitum dng gel

Hnh 2.2. Cc nhm cu to ca bitum (a, b, c,d, e)

aCu to ho hc ca nhm atsphatl bCu trc vng thm(Nhm cht du); cNhm hydrocacbon no

dNhm cu trc bitum dng sol; eCu trc bitum gel 2.3. CC TNH CHT CA BITUM QUNH XY DNG NG 2.3.1. TNH QUNH (TCVN 74952004, AASHTO T4989, ASTM D5, BS 2000)

Tnh qunh ca bitum qunh v bitum oxi ho c o bng kim ln. Tnh qunh biu th sc bn ni ti v c phn cp theo kim ln, kim ln bin i t 20300 . N nh hng nhiu n cc tnh cht c hc ca hn hp vt liu khong vi bitum, ng thi quyt nh cng ngh ch to v thi cng loi vt liu c s dng bitum.

qunh ca bitum ph thuc vo hm lng cc nhm cu to v nhit ca mi trng. Khi hm lng nhm asphalt tng ln v hm lng nhm cht du gim, qunh ca bitum tng ln. Khi nhit ca mi trng tng cao, nhm cht nha s b chy lng, qunh ca bitum gim xung. nh gi qunh ca bitum ngi ta dng ch tiu cm su ca kim (trng lng 100g, ng knh 1mm) ca dng c tiu chun (Hnh 2.3) vo bitum nhit 25oC trong 5 giy. kim ln k hiu l P, o bng (1 bng 0,1mm). Tr s P cng nh qunh ca bitum cng cao.

Theo kim ln c th chia bitum lm 5 loi:1, 2, 3, 4, v 5 vi kim ln 250C bin i t 30040 .

Hnh 2.3. Dng c o qunh

2.3.2. KO DI (TCVN 74962005, ASTM 11389)

Tnh do c trng cho kh nng kt dnh ni ti ca bitum di tc dng ca ngoi lc.

Tnh do ca bitum cng nh tnh qunh, ph thuc vo nhit v thnh phn nhm cht. Khi nhit tng, tnh do cng tng. Ngc li khi nhit gim tnh do cng gim, ngha l bitum tr nn gin. Trong trng hp , bitum dng lm mt ng hay trong cc kt cu khc c th to thnh cc vt nt.

Tnh do ca bitum c nh gi bng ko di, k hiu l L (cm), ca mu tiu chun v c xc nh bng dng c o hnh 2.4 (ASTM D113).

ko di biu th tnh kt dnh ni ti ca bitum. Sc bn ni ti ca cc loi bitum khc nhau th biu th bng ko di khc nhau. Trong th nghim ny ba si mu bitum c nh hnh ging nhau, trong mi trng nc v c ko ra vi tc u l 50 mm/pht cho n khi b t. Nhit th nghim c iu chnh theo kim ln ca bitum, v d 100C cho bitum 80 n 100; 130C cho bitum 60 n 70; 170C cho bitum 40 n 50. Khong cch m cc si mu bitum c ko di n t so vi mu ban u c coi l bn ni ti hoc kh nng chu ko di ca mu bitum. Trong trng hp cn xc nh n hi do ( n hi 250C) th th nghim n mt di no sau ct mu th mu co li bng chiu di ban u. Tr s t l gia bin dng n hi v ko di (t) theo qui nh l t 5570%.

Nhit th nghim tnh do l 25oC, tc ko l 5cm/pht. ko di ti thiu cho cc loi bitum qunh lm ng l 100 mm.

Hnh 2.4. Dng c o ko di

2.3.3. NHIT HO MM V NHIT HO CNG (TCVN 74972005)

Khi nhit thay i, tnh qunh, tnh do ca bitum thay i. S thay i cng nh, bitum c n nh nhit cng cao.

Tnh n nh nhit ca bitum ph thuc vo thnh phn ho hc ca n. Khi hm lng nhm asphalt tng, tnh n nh nhit ca bitum tng, hm lng nhm asphalt gim tnh cht ny gim xung.

Bc chuyn ca bitum t trng thi rn sang trng thi qunh ri ho lng, v ngc li, t trng thi lng sang trng thi qunh, ri ho rn xy ra trong khong nhit nht nh. Do tnh n nh nhit ca bitum c th biu th bng khong nhit . Khong bin i nhit , k hiu l T, c xc nh bng cng thc sau:

T = TmTc,

trong : Tm nhit ho mm ca bitum, l nhit chuyn bitum t trng thi qunh sang trng thi lng;

Tc nhit ho cng ca bitum l nhit chuyn bitum t trng thi lng sang trng thi rn.

Nu T cng ln tnh n nhit nh nhit ca bitum cng cao.

Tr s nhit ho mm ca bitum ngoi vic dng xc nh khong bin i nhit T, n cn c ngha thc tin rt quan trng. Trong xy dng ng, ngi ta thng dng bitum ri mt ng, do khi gp nhit cao, nu Tm khng thch hp, bitum c th b chy lm cho mt ng c dng ln sng, dn ng... tr ngi cho xe c i li v dn n h hng mt ng.

Nhit ho mm l mt ch tiu k thut nh gi cht lng ca bitum. Nhit ho mm ca bitum c xc nh bng dng c vng v bi (Hnh 2.5). Khi lng ca vin bi bng 3,5g, ng knh 9,53 mm.

Hnh 2.5. Th nghim vng v bi

Hnh 2.6. Dng c Fraxa

1. Nhit k; 2. Cun thanh thp; 3. Mu th (thanh thp); 4. M uara; 5. ng nghim.

xc nh nhit ho mm ngi ta un nng bnh cha cht lng (thng l nc) vi tc 5oC/pht. Di tc dng ca nhit tng dn, n mt lc no bitum b nng chy lng ra, vin bi cng bitum ri xung. Nhit cht lng trong bnh ng vi lc vin bi tip xc vi bng di ca gi c xem l nhit ho mm ca bitum.

Nhit ho cng ca bitum c th xc nh bng dng c o kim ln. Nhit ho cng l nhit ng vi kim ln bng 1 n 1,25. Nhit ho cng cng c th o bng dng c Fraxa (Hnh 2.6).

Tt c bitum u th hin c tnh chu tc ng ca nhit: nhit caomm, nhit thpcng, v c biu th bng cng thc Pfeiffer v Van Doormaal:

LogP = AT+K (2.1)

trong : A linh ng vi nhit theo log ca kim ln, v bng 0,0150,06

Kh s thc nghim

Pfeiffer v Van Doormaal xy dng mt khi nim trong gi nh rng mn cm vi nhit ca cc loi bitum dng cho xy dng ng c gi tr bng 0. T cc tc gi a ra cng thc tnh ch s kim ln (PI) nh sau:

50A1

25A)20(1PI

+

= (2.2)

Gi tr PI thay i t 3 i vi bitum c mn cm vi nhit cao cho n +7 i vi cc loi bitum c mn cm vi nhit thp.

2.3.4. BN CA BITUM

Hnh 2.7. Ha gi ca bitum khi trn, lu kho, vn chuyn, thi cng v khai thc.

(Lu : Ch s ho gi thng l t l ca 2 gi tr nh nht, cng hay kim ln).

Do nh hng ca thi tit m tnh cht v thnh phn ho hc ca bitum b thay i. Ngi ta gi s thay i l s ha gi ca bitum. Nguyn nhn ca hin tng l v t l ca nhm asphalt trong bitum tng ln.

bn ca bitum c th nh ngha nh kh nng duy tr tt cc c tnh lu bin, kt dnh ni ti, kt dnh vi ct liu trong qu trnh s dng lu di vi mt ng. Cc yu t c bn c tc ng n qu trnh trn l: s ho cng do bay hi; s ho cng do xy ho; v s ho cng do ct liu.

S bay hi ca nhm cht du lm tnh qunh v tnh gin ca bitum tng ln, lm thay i cu to phn t, to nn cc hp cht mi. Qu trnh ho gi ca bitum s dn n qu trnh ho gi ca btng asphalt. gin ca bitum lm xut hin cc vt nt trong lp ph mt ng, tng qu trnh ph hoi do n mn. Qu trnh ho gi ca lp ph mt ng c th chia lm 2 giai on. Giai on 1 cng v tnh n nh bin dng tng. Giai on 2 bitum bt u gi, cu trc thay i, lm lp ph b ph hoi. Tuy vy, s ho gi ca bitum pht trin chm, thng sau 10 nm s dng s ho gi mi mc cao.

S ho cng do xy ho l nguyn nhn chnh lm cho bitum tr nn lo ho. Ngoi ra cc thnh phn d bay hi ca bitum cng c ng gp ng k.

Th nghim mng mng bitum quay trong l (ASTM D 2872) xc nh s ho cng do nguyn nhn xy ho v bay hi. Th nghim mng mng bitum quay trong l c m t hnh 2.8.

Hnh 2.8. Th nghim mng mng bitum quay trong l (The rolling thin film oven test)

2.3.5. NHIT BC CHY (TCVN 74982005)

Trong khi un bitum n mt nhit nht nh th cc cht du nh trong bitum bc hi ho ln vo mi trng xung quanh to nn mt hn hp d chy.

xc nh nhit bc chy, ngi ta dng dng c ring. Trong th nghim, nu ngn la lan khp mt bitum th nhit lc c xem l nhit bc chy. Nhit bc chy ca bitum thng ln hn 2200C. Nhit ny l mt ch tiu quan trng v an ton khi gia cng bitum.

2.3.6. TNH DNH BM (LIN KT) CA BITUM VI B MT VT LIU KHONG (TCVN 75042005)

Mt trong nhng chc nng quan trng nht ca bitum l dnh bm vi b mt cc ht ct liu v lin kt chng li vi nhau, hoc lin kt vi b mt kt cu c sn.

S lin kt ca bitum vi b mt vt liu khong c lin quan n qu trnh thay i hol khi hai cht tip xc v tng tc vi nhau. Cht lng ca mi lin kt ny ng vai tr quan trng trong vic to nn cng , tnh n nh nc v n nh nhit hn hp bitum v vt liu khong.

C rt nhiu cc yu t nh hng n cht lng dnh bm gia bitum v vt liu khong. Cc yu t ph thuc c vo c tnh ca vt liu cng nh cc yu t bn ngoi. Bng 2.1. lit k cc yu t c bn nh hng n cht lng dnh bm ca bitum vi vt liu khong.

Bng 2.1. Cc tnh cht vt liu v cc tc ng bn ngoi nh hng n dnh bm gia bitum vi ct liu

Cc tnh cht vt liu

Cc tnh cht ca bitum

Cc tnh cht ca hn hp

Cc tc ng bn ngoi

Khong vt c trng b mt rng Bi bn Din tch b mt ht nc Hm lng m Hnh dng Tnh chu thi tit

Lu bin Phn cc Thnh phn ho hc

rng Thm nc Hm lng bitum Chiu dy mn bitum Loi cht lm y Cp phi ct liu Loi hn hp

Lng ma m pH ca nc S c mt ca mui Nhit Chu k nhit Giao thng Thit k Tay ngh thi cng Thot nc

2.3.6.1. dnh bm khi khng c nc

Khi nho trn bitum vi vt liu khong, bitum s thm t b mt cc ht vt liu khong v to thnh mt lp hp ph. Khi cc phn t bitum trong lp hp ph s tng tc vi cc phn t ca vt liu khong lp b mt. Tng tc c th l tng tc l hc hay ho hc.

Lin kt ca bitum vi vt liu khong trc ht ph thuc vo tnh cht ca bitum. Trong nht v tnh phn cc ca bitum l kh quan trng. bitum dnh bm tt vi cc ht ct liu v qua c th lin kt cc ht ct liu vi nhau th bitum cn phi lm t tt c b mt tng ht ct liu, tc l bc ph tt b mt cc ht ct liu vi dy thch hp. Qu trnh ny ph thuc rt nhiu bi nht ca bitum. nht cng cao th thi gian cn thit lm t b mt cc ht ct liu cng lu. Trong thc t nho trn, vic lm t v bc kn b mt ct liu phi din ra tc th.

V vy, nu nht qu cao s dn n tnh trng bitum khng bc ph c hon ton b mt cc ht ct liu.

Lin kt ca bitum vi vt liu khong ph thuc vo mc phn cc ca bitum. phn cc ca bitum ph thuc vo hm lng nhm cht nha, c bit l nha axt. Bitum cha nhm cht nha cng nhiu th s lin kt ca n vi vt liu khong cng tt.

Lin kt ca bitum vi vt liu khong cng ph thuc vo tnh cht ca vt liu khong. Nhn chung, bitum dnh kt tt vi hu ht cc ct liu khong khi cc ct liu c b mt sch v kh. Tnh cht ho l ca ct liu nh hng ln n tnh dnh bm. Cc tnh cht ny lin quan cht ch n thnh phn khong vt, hnh dng, cu trc, cn bng in tch v din tch b mt. Xt v thnh phn khong vt, i a s cc ct liu c phn thnh hai nhm: a nc v k du. Cc ct liu c hm lng oxt silc cao nh ct liu c ngun gc thch anh, grant, tc l ct liu axt thng kh c bc ph bitum hn nhng ct liu baz nh vi hay bazan.

2.3.6.2. dnh bm khi c nc

Thng thng s c mt ca nc lm gim cht lng mi lin kt bitumct liu. S c mt ca nc trong mi lin kt bitumct liu c th n t hai ngun: nc trong ct liu m trc khi nho trn v nc ma thm vo cc lp vt liu trong thi gian khai thc.

Cc ct liu c in tch b mt khng cn bng s to ra nng lng b mt. Nu b mt ct liu c bao bc bng mt cht lng c in tch tri du th s ht bm s xy ra v to ra lc dnh kt. Nc thng c phn cc mnh hn cc loi bitum nn kh nng chim ch ca nc trong h bitumct liu d xy ra, to thnh lp ngn cch v gim tnh dnh bm ca bitum vi b mt ct liu khi nho trn hoc gia lp vt liu ri sau vi lp trc . ng thi cng c th l nguyn nhn lm gim mi lin kt bitumvt liu khong, dn ti bc, tch mng bitum khi b mt vt liu khong trong cc lp vt liu trong qu trnh khai thc.

Cc ct liu c tnh axt a nc hn cc ct liu baz. V vy vic s dng ct liu ngun gc axt s to ra vt liu km bn nc hn so vi vic s dng ct liu c ngun gc baz.

S n nh nc ca hn hp vt liu khongbitum ph thuc vo ho tan trong nc ca cc hp cht mi to thnh. Nu nh cc hp cht mi to thnh l nhng mui kali, natri ca cc axt hu c, th n s ho tan trong nc v nh vy lm cho hn hp km n nh nc. Nu nhng hp cht y l cc mui ca can xi, st, nhm, l nhng hp cht khng ho tan trong nc th hn hp n nh nc.

m bo cht lng dnh bm gia bitum v vt liu khong, ct liu cn c nung nng trc khi nho trn vi bitum loi b lp mng nc bm trn b mt.

Mc lin kt ca bitum vi b mt vt liu hoa c th nh gi theo bn ca mng bitum trn b mt hoa khi nhng trong nc si. Sau khi th nghim xc nh cp lin kt gia bitum vi (xem bng 2.2.).

Thc t khi ch to hn hp bitum v vt liu khong, nhiu loi khc nhau c s dng, do mc lin kt ca n cng c th khc nhau. nh gi mc

lin kt ca bitum trong trng hp ny cng tin hnh theo nguyn tc tng t. Sau khi th nghim, em kt qu so snh vi thang nh gi ch tiu lin kt ghi bng 2.2.

Trng hp hot tnh ca bitum thp, s lin kt ca n vi b mt vt liu khong km th cn cho thm vo bitum cht ph gia hot tnh b mt.

Bng 2.2. Phn cp dnh bm gia bitum v vt liu khong

c trng ca mng bitum trn b mt vt liu khong

Cp dnh bm

Mng bitum cn bm nguyn vn, bc ton b b mt vin .

Dnh bm ttcp 5

Mng bitum bc ton b vin nhng c dy mng khc nhau

Dnh bm khcp 4

Mng bitum bc ton b vin , i ch b bong trc Dnh bm trung bnhcp 3

Mng bitum b bong ra khi mt nhng l ch vn cn bitum bm.

Dnh bm kmcp 2

B mt vin sch khng cn vt bitum bm Dnh bm rt kmcp 1

2.3.7. TAN TRONG TRICHLOROENTHYLEN

Phng php th nghim ny dng xc nh tan trong trichloroenthylen ca bitum cha t hoc khng cha vt liu khong.

tan ca bitum trong trichloroenthylen l t l (% khi lng) gia khi lng bitum tan ht trong trichloroenthylen so vi khi lng mu th nghim.

Phn tan trong trichloroenthylen l cht kt dnh.

Phn khng tan hay phn trm ho tan nh sau:

% phn khng tan = 100B

AC

(2.3)

% phn tan = 100B

A)(CB

(2.4)

trong : Akhi lng bnh v b lc

Bkhi lng mu th nghim

Ckhi lng bnh, b lc v vt liu khng tan

2.3.8. HM LNG PARAFIN

Hm lng parafin, thnh phn lm gim tnh dnh bm v n nh ca bitum, c th nghim theo TCVN 2004 (DIN 52015)

2.3.9. NHT

y l mt c tnh quan trng ca bitum v n xc nh ng x ca vt liu mt nhit nht nh hoc trong mt phm vi nhit no .

n v c bn ca nht l pascal giy (Pas). nht c th c xc nh bng nhiu phng php khc nhau. nht ca bitum c th c xc nh theo phng php nht tuyt i hay nht ng lc. l t s gia ng sut ct t vo mu th bitum (Pa) chia cho tc ct trong mt giy. T l ny biu th sc khng chy ca bitum.

nht ca bitum cn c th c nh gi thng qua nht ng hc (m2/s; mm2/s). nht ng hc l t s gia nht ng lc so vi khi lng ring ca bitum v c biu th bng cng thc 2.5

nht ng hc = nht ng lc/ khi lng ring (2.5)

Nhn chung, nht ca bitum c xc nh bng vic o thi gian cn thit mt th tch bitum nht nh chy qua mt l c kch thc tiu chun mt nhit xc nh. V d, theo tiu chun ASTM D217095 nht ng hc c xc nh bng cch o thi gian mt th tch bitum nht nh chy qua mt on ng dng mao dn bng thy tinh ca nht k nhit 135oC vi bitum c, hoc 60oC vi bitum lng. Khi lng ring ca bitum 135oC bng 0.934 ln so vi khi lng ring ca n 25oC. Thi gian xc nh chnh xc n 0.1 giy.

Thit b o nht ng hc ca bitum c trnh by hnh 2.9:

Hnh 2.9. Nht k

2.3.10. YU CU K THUT CA BITUM QUNH XY DNG NG

Cht lng ca bitum c dng trong xy dng ng c quy nh nh gi theo 10 ch tiu k thut tng ng vi 5 mc ca bitum lm ng theo 22TCN 27901 c ghi trong bng 2.3.

Bng 2.3. Cc ch tiu k thut ca 5 mc ca bitum lm ng theo tiu chun ngnh giao thng vn ti 2001 (22TCN 27901).

Tr s tiu chun theo cp kim ln (mc)

TT

Cc ch tiu

n v

40/ 60 60/ 70 70/ 100 100/ 150

150/ 250

Phng php th nghim

(1) (2) (3) (4) (5) (6) (7) (8) (9)

1

kim ln 250C

0.1mm 40 60

60 70

70 100

100 150

150 250

22TCN 6384

ASTM D586

AASHTO T4989

2

ko di 250C, nh nht

cm 100

22TCN 6384

ASTM D13386

AASHTO T5189

3

Nhit ho mm (phng php vng v bi)

0C 49 58 46 55 43 51 39 47

35 43

22TCN 6384

AASHTO T5189

4

Nhit bt la nh nht

0C 230 220

22TCN 8384

ASTM D9285

AASHTO T4889

5

Lng tn tht sau khi un nng 1630C trong 5

% 0,5 0,8 ASTM D680

AASHTO T4783

gi

(1) (2) (3) (4) (5) (6) (7) (8) (9)

6

T l kim ln ca nha ng sau khi un nng 1630C trong 5 gi so vi kim ln 250C, nh nht

% 80 75 70 65 60 ASTM D605

7

Lng ho tan nh nht trong Trichlorocethylene, C2HCl3

% 99

ASTM D204281

AASHTO T44901

8

Khi lng ring 250C

g/cm3 1,001,05

ASTM D13386

AASHTO T5189

9

dnh bm ti thiu i vi

cp cp 3 22TCN 6384

10

Hm lng Paraphin ln nht

% 2,2 S c quy nh ring

. Bng 2.4. Bitum, yu cu k thut v phng php th (Tiu chun Vit Nam

2004)

Mc theo kim ln TT

Cc ch tiu 2030 4050 6070 85100 120150 200300

1 kim ln 250C, 0.1mm

2030 4050 6070 85100 120150 200300

2 ko di 250C, cm

40 80 100 100 100 100

3 Nhit ho mm, 0C

52 49 46 43 39 35

4 Nhit bt la, 0C

240 232 232 232 230 220

5 Lng tn tht sau khi un 5 gi 1630C, max, %

0.2 0.5 0.5 0.8 0.8 1.0

6 T l kim ln sau khi un so vi ban u, %

80 80 75 75 75 70

7 Lng ho tan trong tricloroethylene, %

99 99 99 99 99 99

8 Khi lng ring, g/cm3

11.05

9 Hm lng parafin, max, %

2.2 2.2 2.2 2.2 2.2 2.2

10 nht 1350C, cSt

515 305 285 235 185 150

. Bng 2.5. Bitum du m loi qunh dng trong xy dng ng ca Nga

Qui nh theo mc

Cc ch tiu 1 (200/300)

2 (130/200)

3 (90/130)

4 (60/90)

5 (40/60

1. kim ln:

Khi 25o C, trong gii hn

201300

131200

91130

6190

4160

Khi 0oC, khng nh hn

45 35 28 20 13

2. ko di 25oC, cm, khng nh hn

khng qui nh

65 60 50 40

3. Nhit ho mm, oC,

khng thp hn

35

39

43

47

51

4. Th nghim lin kt vi hoa hay ct.

Chu c th nghim (lin kt tt)

5. S thay i nhit ho mm sau khi gia nhit, oC, khng ln hn

8 7 6 6 6

6. Hm lng cc hp cht ho tan trong nc, khng ln hn

0,2 0,2 0,3 0,3 0,3

7. Nhit bc chy, oC, khng thp hn

200 220 220 220 220

8. Nhit bitum khi nho trn

110120 120130 130140 135145 140160

* Cc quy nh v nha c ca M (AC) (theo AASHTOM20).

Nha c sn xut t du m ca M dng cho xy dng ng c chia ra 5 cp theo kim ln, v phi tho mn cc ch tiu c l sau (bng 2.6).

Bng 2.6. Cc ch tiu c l ca nha c theo AASHTO M20

Cp nha theo kim ln K hiu

th nghim Cc ch tiu

4050 6070 85100 120150 200300 D5 T49

(1) (2) (3) (4) (5) (6) (7)

1. kim ln (77 oF, 100 g, 5 giy)

4050 6070 85100 120150

200300

D5T49

(1) (2) (3) (4) (5) (6) (7)

2. Nhit bc chy (theo Chereland), oF

450+ 450+ 450+ 425+ 350+ D92T40

3. ko di 77oF, 5cm/pht; cm

100+ 100+ 100+ 100+ D113T51

4. ho tan trong trichloroithylini, %

99+ 99+ 99+ 99+ 99+ D2042

T44

5. Th nghim mng mng quay trong l (1/5 in, 325oF, 5gi)

D1754

T79

6. Lng tn tht sau khi un nng, %

0,8 0,8 1,0 1,3 1,5 D6T47

7. kim ln ca nha sau khi un nng,%, so vi lc cha un nng

58+ 54+ 50+ 46+ 40+ D5T49

8. ko di ca nha sau khi un nng (77oF, 5cm/ pht), cm

50+ 75+ 100+ 40+

9. nht 275 oF, nht ng lc, cSt nht Saybolt Furol, scc

240+ 200+ 170+ 140+ 100+ D2170T201

10. Nhit ho mm, oC, (th nghim vng v bi)

120+ 4954 85+ 70+ 50+ E102 D36

Hu ht cc loi bitum phn cp theo kim ln c s dng lm ng t. Loi c kim ln t 35100 dng trong sn xut b tng asphalt. Loi c kim ln t 3515 dng ch to matit asphalt. Loi c kim ln t 100 tr ln dng ch to hn hp bitum ( nha).

Trong xy dng, ngoi nhng loi bitum du m xy dng ng, cn c nhng loi bitum du m xy dng khc, v d bitum xy ho, c s dng trong cng nghip sn xut tm lp, sn, v.v...

Bng 2.7. Ch tiu k thut i vi cc loi bitum phn loi theo kim ln (Theo BS 3690).

Phn cp Bitum c tnh

25 35 40 50 70 100 200 300

(1) (2) (3) (4) (5) (6) (7) (8) (9)

ln 250C, 0.1mm 255 355 4010 5010 7010 10020 20030 30045

(1) (2) (3) (4) (5) (6) (7) (8) (9)

im ho mm, 0C

min 57 57 58 47 44 41 33 30 max 69 69 68 58 54 51 42 39 Hao ht sau khi gia nhit 5 gi nhit 1630C (Tn tht khi lng, %, max) 0,2 0,2 0,2 0,2 0,2 0,5 0,5 1,0 a. S gim kim ln, %, max 20 20 20 20 20 20 20 25 b. Kh nng hon tan trong

Trichlogoetylen,%, theo khi lng, min

99,5 99,5 99,5 99,5 99,5 99,5 99,5 99,5

Hng s in mi 250C v 1592 Hz,min

2630

2630

2630

2630

2630

2630

2.4. BITUM LNG LM NG 2.4.1. PHN LOI

Bitum lng c thnh phn l bitum c c kim ln t 100200 pha vi dung mi l mazut, du ho hoc etxng to ra bitum lng c nht yu cu

C 3 loi bitum lng tu theo tc ng c li khc nhau:

Loi RC: ng c nhanh

Loi MC: ng c trung bnh

Loi SC : ng c chm.

Thnh phn dung mi tu theo cc nc c quy nh trong cc tiu chun lin quan. Theo tiu chun M bitum lng c cc mc: RC; MC; SC. Theo tiu chun ca Nga bitum lng c cc mc: MG; CG v c phn loi theo nht.

Cc tnh cht ch yu ca bitum lng l nht v tnh d bay hi ca dung mi.

2.4.2. CC TNH CHT

2.4.2.1. nht (AASHTO 73290)

nht ca bitum lng ph thuc vo cu trc ca bitum lng. Bitum lng c nhiu thnh phn nhm cht nha, cht rn v cha t nhm cht du th nht ca n tng ln. nht ca bitum lng c xc nh bng nht k Saybolt (hnh 2.10). nht ca bitum lng c c trng bng thi gian 50ml bitum lng chy qua l y ca dng c c ng knh 5 mm, nhit 60oC.

2.4.2.2. Phn ct (thnh phn d bay hi)

S lng v cht lng ca phn ct l ch tiu gin tip biu th tc ng c li ca bitum lng mt ng. Nu bitum lng cha nhiu thnh phn ny v n c nhit si thp th qu trnh ng c ca bitum s nhanh. xc nh phn ct ca bitum lng cn ct cc nhit khc nhau: 225o, 316o v 360oC. Tnh cht ca phn cn li sau khi ct n nhit 360oC s c trng cho loi bitum lng v tnh cht ca n trong thi gian s dng ng. Cc tnh cht ny c xc nh nh vi bitum c qunh.

2.4.3. YU CU K THUT CA BITUM LNG XY DNG NG.

Bitum du m loi lng dng xy dng ng Nga chia ra 2 loi: ng c va v ng c chm.

Cc ch tiu k thut ca bitum lng ng c va c gii thiu bng 2.8, cn ca loi ng c chm bng 2.9.

Bng 2.8. Cc ch tiu k thut ca bitum lng ng c va

Quy nh theo mc Cc ch tiu

40 / 70 70/130 130/ 200 40/70 70/130

1. nht theo nht k ng knh l 5mm, 60oC, giy, trong khong

4070 71130 131200 4070 71130

2. Lng bay hi sau khi nung, %, khng nh hn

10 8 7 8 7

3. Nhit ho mm ca phn cn li sau khi nung xc nh lng bay hi, oC, khng nh hn

37 39 39 28 29

4. Nhit bc chy, oC, khng nh hn

45 50 60 100 110

5. Th nghim lin kt vi hoa hoc ct

tt tt tt tt tt

Bng 2.9. Cc ch tiu k thut ca bitum lng ng c chm

Quy nh v mc Cc ch tiu

130/200 40/70 70/130 130/200

Hnh 2.10. Nht k Saybolt

(1) (2) (3) (4) (5)

1. nht theo nht k c d = 5mm, 60oC, giy

131200 4070 71130 131200

2. Lng bc hi sau khi nung, %, 5

(1) (2) (3) (4) (5)

3. Nhit ho mm ca phn cn li sau khi nung xc nh lng bc hi, oC 30

4. Nhit bc chy, oC 110 120 160 180

5. Th nghim lin kt vi hoa hay ct tt tt tt tt

* Cc quy nh v bitum lng ca M.

C 3 loi bitum lng dng trong xy dng ng, gm: bitum lng ng c nhanh (RC); bitum lng ng c va (MC) v bitum lng ng c chm (SC). Chng c chia ra cc cp khc nhau theo nht. Cc ch tiu c l ca cc loi bitum lng c quy nh nh bng 2.10.

Bng 2.10. Cc ch tiu c l ca cc loi bitum lng theo ASTM

Cp BT lng theo nht Cc ch tiu

RC70 RC250 RC300 RC3000

K hiu th nghim

1 nht ng lc 140 oF; cSt

70140 250500 800 6000 30006000 D2170T201

2Nhit bc chy, F

80+ 80+ D1310T79

3Sn phm ct (% theo th tch ca tng lng sn phm ct):

n 374 oF n 437 oF n 500 oF n 600 oF

10+ 50+ 70+ 85+

35+ 60+ 80+

15+ 15+ 75+

25+ 70+

B nha sau khi ct n 680 oF, % theo th tch

55+ 65+ 75+ 80+

D402T76

4Th nghim trn b nha sau khi chng ct

kim ln 77 oF; 100g; 5giy

80120 30120 80120 80120 D5T49

ko di, 77 oF; 100+ 100+ 100+ 100+ D148T51

cm ho tan trong trichlorolthylene; %

99,5+ 99,5+ 99,5+ 99,5+ D2042T44

5Hm lng nc; %

0.2 0.2 0.2 0.2 D95T55

Tiu chun BS 3690 (Anh Quc) nu cc ch tiu k thut i vi bitum lng v c ghi bng 2.11.

Bng 2.11. Cc ch tiu k thut i vi bitum lng (BS3690)

Phn cp bitum lng c tnh

Phng php th 50 giy 100 giy 200 giy

nht 400C, l 10mm, giy BS200072 5010 10020 20040 Chng ct: BS200027 n 2250C, % th tch max n 3600C, % th tch

1 103

1 93

1 73

kim ln 250C sau khi chng ct ti 3600C, dmm

BS200049 100350 100350 100350

ho tan trong Trichlorothylen, % theo khi lng, min

BS200047 99.5 99.5 99.5

2.5. CC LOI BITUM CI TIN LM NG T V SN BAY 2.5.1. M U

Bitum du m xy dng ng l mt loi vt liu truyn thng p ng tt cc yu cu v xy dng ng t v sn bay. Tuy nhin, hin nay nhu cu v lu lng xe v ti trng trc xe c xu hng tng ln r rt. Nh vy vt liu lm ng cn c ci tin ph hp vi yu cu xy dng ng t v sn bay cp cao. Bitum ci tin l nhng vt liu mi p ng c cc yu cu .

u im ca loi bitum ci tin l tng kh nng chu lc v bin dng ca kt cu mt ng b tng asphalt.

Thnh phn ch yu ca bitum ci tin l bitum v ph gia. Ph gia thng dng l bt cao su, mangan hu c, lu hunh hoc cc polyme do nhit. Cc ph gia trc y c pha vo b tng asphalt khi ch to. Ngy nay cc cht ny c trn vi bitum ti nh my sn xut bitum c c bitum ci tin.

Mt khc vic s dng bitum ci tin a ra mt gii php nhm lm tng cht lng ca cng tc bo dng ng, tng tui th phc v,v.v... t hiu qu kinh t bi tum ci tin thng c s dng kt hp vi cc ct liu c cht lng cao trong hn hp nha thot nc hoc cc khu vc c yu cu v tnh chng ro hoc bin dng c bit. Trong cc con ng bnh thng khng nn dng v gi thnh ca bitum ci tin cn cao.

Ci tin n gin nht v tnh chng bin dng c th t c bng cch s dng bt cao su t lp t c. Cc hp cht mangan hu c, lu hunh v cc cht polyme

do nhit c th nng cao tnh d thi cng trong thi gian m ln v tnh chng bin dng ca b tng asphalt. Nhm p ng tt hn nhu cu ca giao thng, cc loi cao su do nhit c s dng nhm nng cao c tnh chng bin dng v chng ro.

Bitum l vt liu c tnh n hido(nht). Tnh cht ny nh hng nhiu n cc c tnh k thut ca b tng asphalt lm ng. in hnh l tnh chng bin dng d v nt. Bin dng ca bitum tng theo thi gian chu ti v nhit .

S bin dng do tc ng ca ti trng cho thy phn ng n hi tc thi xy ra, sau s tng ln dn n s bin dng theo thi gian cho n khi ti trng c loi b. Sau khi b ti, s bin dng n hi tc thi c phc hi ngay. S phc hi tip theo xy ra theo thi gian. S phc hi dn dn theo thi gian ca vt liu c xem nh l tnh n hi chm. Cui cng mt s bin dng vnh vin cn li vn gi nguyn m khng th phc hi c do tnh nht trc tip gy ra.

Phn ng vi mt ti trng ko gy ra i vi mt thnh phn trong vt liu bitum do ti trng xe di ng gy ra. y khng th phn bit c hai thnh phn phn ng n hi, nhng cho thy mt s bin dng d. Khi nhiu ti trng ko tc ng ln mt ng s hnh thnh s tch lu ln, iu ny l nguyn nhn to nn s bin dng d trn b mt ng. T nhng iu trn cho thy r rng v sao s bin dng xy ra nhiu hn khi nhit mi trng cao, nhng ni c tc giao thng thp hoc nhng khu vc giao thng tnh, cc nt giao thng ni phng tin dng .

Mt trong nhng vai tr c bn ca cht ci tin bitum l tng tnh chu bin dng ca b tng asphalt vi bin dng d khi nhit mt ng cao, m khng tc ng xu n cc c tnh k thut ca bitum hoc b tng asphalt cc nhit khc. C th t c iu ny bng cch lm cng ho bitum tng phn ng n hido (nht) ca asphalt b gim i vi mc gim tng ng ca bin dng d hoc bng cch tng tnh n hi ca bitum, do gim bin dng do (nht) m t lm gim bin dng d.

Tng cng ca bitum lm tng cng ng hc ca hn hp b tng asphalt. Do ci tin kh nng phn tn lc ca vt liu v tng bn kt cu v tui th thit k ca con ung hoc l to ra kt cu c tui th v bn tng t nh vi cc lp mng hn. Nh vy vi ti trng khng i c th gim bt chiu dy ca kt cu o ng.

2.5.2. PHN LOI BITUM CI TIN

Phng php chnh ch to bitum ci tin l cho thm vo bitum cc cht bt, cc khong cht c bit, cc si khong v cao su. C th la chn cc cht ci bin theo hai yu t l tnh kh thi v tnh kinh t. Chng phi p ng c cc yu cu sau:

Sn c;

Khng bin cht nhit trn thm;

C th trn c vo bitum;

Khng lm cho bitum qu nht nhit trn thm, nhit m nn trn b mt ng, khng lm bitum b cng hoc dn khi phi lm vic nhit thp;

C hiu qu kinh t.

Sau khi trn cc cht ci tin (ph gia), bitum phi c cc c tnh sau:

Gi cc c tnh k thut trong thi gian bo qun, thi cng trn mt ng v khi con ng c a vo s dng;

C th c ch to bng cc thit b v cng ngh thng thng;

n nh v lho hc trong thi gian bo qun, s dng v khai thc;

t c nht khi trn v phun nhit s dng.

2.5.3. BITUM C PHA THM LU HUNH

C hai cch s dng lu hunh trong b tng asphalt lm o ng. Th nht: asphalt c cho thm mt lng tng i nh lu hunh di dng mt cht ho tan trong bitum. Cch gia cng th hai c bit n vi tn gi l THERMOPAVE, s dng hm lng lu hunh cao. Lng lu hunh d ra ng vai tr nh mt cht khong t ri. Khi trn vi ct liu s to ra mt hn hp rt d thi cng v khi ngui c kh nng chng bin dng cao.

Shell cng pht trin mt sn phm c tn gi THERMOPATICH y l mt loi asphalt c hm lng lu hunh cao sa cha g, s dng phc hi ng, c th s dng cho c ng b tng asphalt hoc mt ng b tng xi mng. Bitum th lng chy t do c rt vo l, khe nt trn mt ng v bitum ngui i c th cho xe chy ngay. Tuy nhin b tng asphalt c s dng lu hunh th lu hunh s c phn ng vi bitum, tu thuc vo nhit v thnh phn ho hc ca bitum. Cc nghin cu ch ra rng lu hunh ch yu phn ng vi thnh phn naphthen thm ca bitum, bng cch cng thm vo phn t hoc bng cch xy ho bitum thng qua vic ly hydr to ra hydr sunfua. khong nhit 119,30C l nhit im si ca lu hunh n nguyn cht v 1500C th phn ng ch yu l cng thm lu hunh vo lm tng thm vng cht thm phn cc v mt thay i rt nh trong c tnh lu bin ca bitum. Trn 1500C phn ng xy ho cnh tranh tng ln r rt lm cho hm lng nhm asphalt tng ln v tc ng bt li n cc c tnh ca bitum, tng t nh tc ng ca qu trnh sc kh.

S tin trin ca hydro sunfua nhit trn 1500C r rng l khng th chp nhn c. V vy nn thn trng khi s dng bitum lu hunh.

2.5.4. BITUM PHA THM CAO SU

Polyputadien, polyisopren, cao su thin nhin, cao su butyl, chloropren, styrenebutadien cao su, v.v. tt c c s dng cng vi bitum nhng tc dng ca chng lm tng nht ca bitum. Trong mt s trng hp, cao su c s dng trng thi lu ho, v d nh nhng mnh lp ti ch, nhng dng ny kh phn tn trong bitum. V vy, cn mt nhit cao v thi gian bin i chuyn ho di v c th to ra cht lin kt khng ng nht trong cht cao su hot ng ch yu nh mt cht do.

2.5.5. BITUM THM CC HP CHT MANGAN HU C

Vic s dng hp cht mangan hu c trong bitum l mt pht minh ca c Hoa K v ca Vng quc Anh. C th nng cao bn ca vt liu ri ng bng cch cho thm vo bitum mt hp cht mangan hu c, hoc kt hp gia mangan hu c vi coban hu c, hay hp cht ng hu c. Sn phm ny c bit n nhiu di

ci tn CHEMCRETE. S dng bitum ci tin bng mangan hu c trong asphalt v hn hp nha c gii thch l ci thin tnh mn cm vi nhit ca hn hp v qua nng cao cc c tnh ho l ca chng nh n nh Marshall, chng bin dng d v cng ng hc.

thc y hp cht mangan hu c phn tn nhanh trong bitum, vt liu c trn vi mt cht cha cc cht ci bin khc nhau, thng lin quan n chng loi v nng hp cht hu c kim loi v nht ca du lm cht cha cc cht ci bin c s dng. C hai kha cnh ny cn phi c xem xt m bo l s dng cc cht ci bin ph hp cho tng ng dng ring bit.

C ch c xut trong bng sng ch CHEMCRETE l s dng cc hp cht c cu trc vng nht nh trong bitum. Mangan xc tin vic to thnh mt hp cht dicetone m sau to thnh phc cht n nh. Cc phc cht ny lin kt cht ch vi phn t bitum, nng cao tnh mn cm vi nhit ca bitum v tng bn ca hn hp bitum.

Phn ng lu ho ph thuc vo s c mt xy trong bitum, dy ca lp bitum v nhit . Cc th nghim c bo qun bng CHEMCRETE cho thy rng mt bitum 100 cha 2% theo khi lng cht ci bin mangan bo qun nhit 1600C trong 28 ngy b cng ho ( kim ln t 127 xung cn 100 ).

n nh Marshall v thng s c c trn hai loi b tng asphalt mn c sn xut t bitum 100 cha CHEMCRETE, cn li c sn xut t bitum 50 thng thng. c tnh ban u ca hai hn hp ny l rt ging nhau, tuy nhin sau 12 thng n nh Marshall ca b tng asphalt mn tng ln hn 400%. Trong thi gian 12 thng do Marshall tng ln 75% dn n mt s tng ln ton b thng s Marshall hn 200%. S gia tng do Marshall l biu hin ca kt qu t c bn trong thi gian lu ho. Nhng ci tin tng t c xc nh bng cch s dng th nghim hnh thnh vt ln bnh xe trong phng th nghim trn cc mu b tng asphalt ly t on ng th nghim. bin dng 450C ngay sau khi ri b tng i vi asphalt c ci tin v asphalt thng thng rt ging nhau (5mm/h), tuy nhin sau 6 thng bin dng asphalt ci tin gim xung di 1mm/h.

2.5.6. BITUM PHA THM CC POLYME DO NHIT

Polyethylen, polypropylen, polyvinyl chlorit, polystyren v ethylen vinyl acetate (EVA) l cc polyme do nhit ch yu c kim chng qua cc th nghim v cc cht lin kt c ci tin cho ng b. Cc cht do di tc ng ca nhit c c tnh l mn i khi nng ln v cng li khi ngui i.

Cc polyme do nhit khi trn vi bitum, khi nhit mi trng bnh thng lin kt vi bitum v lm tng nht ca bitum. Tuy nhin, cc cht polyme do nhit khng lm tng ng k n hi ca bitum. Khi b nung nng chng c th tch ra khi bitum, m iu ny c th dn n phn tn th khi ngui i. Tuy vy chp nhn nhng hn ch ny vic s dng EVA vi nng 5% cho bitum c kim ln 70 tr nn rt thng dng. Cc th nghim Vit Nam cng cho kt qu tng t.

Cht ng trng hp (copolymer) EVA l cc vt liu do nhit c cu trc ngu nhin c sn xut bng cch ng trng hp ethylen v vinyl acetat. Cc cht ng trng hp c hm lng vinyl acetat thp c c tnh ging nh mt polyethylen t trng thp. Thnh phn vinyl acetat tng ln th cc c tnh ca cht ng trng hp

thay i. Cc c tnh ca cht ng trng hp EVA c kim sot bi trng lng phn t v hm lng vinyl acetat.

Trng lng cc phn t: trng lng phn t ca nhiu polyme c xc nh theo cc c tnh khc nhau. Tiu chun thc hin i vi EVA nhm xc nh nhit ho mm (Melt Flow IndexMFI). Th nghim v nht ngc li c lin quan n trng lng phn t. MFI cng cao trng lng phn t v nht cng thp v iu ny tng t nh th nghim kim ln i vi bitumkim ln cng cao th trng lng phn t trung bnh v nht ca bitum cng thp.

Hm lng vinyl acetat: xc nh cc tc ng chnh ca vinyl acetat n cc c tnh ca cc cht lin kt c ci bin, ta thy phn polyethylen thng thng ca chui c th xp rt st nhau v to ra vng kt tinh. N cng cho thy cc nhm vinyl acetat ln ph v s sp xp st nhau ny nh th no to ra cc vng cao su thm khng kt tinh, vng tinh th tng i cng, trong khi vng thm li mm do. Cng nhiu nhm vinyl acetat (hoc hm lng vinyl acetat cng cao) t l vng mm do cng cao, v ngc li t l vng tinh th cng thp.

Cc cht ng trng hp EVA sn c c phn loi bng MFI v hm lng vinyl acetat. V d EVA c MFI l 150 v hm lng vinyl acetat l 19 th phm cp c ghi l 150/19. T cc loi cht trng hp EVA a dng sn c, phm cp 150/19 v vi qui m nh hn cc phm cp 45/33 l thng dng nht. Chng thng trn vi bitum 70 , cc cht ng trng hp EVA d c phn tn trong bitum v rt thch hp vi bitum. Chng n nh vi nhit nhit nho trn hn hp asphalt thng thng. Tuy vy, trong qu trnh bo qun tnh c th xy ra s phn ly. Do , cc sn phm hn hp c xut cho lu thng tun hon trc khi s dng.

Bng 2.12. cho thy nhng thay i ph bin v kim ln v im ho mm khi cho thm 5% hai loi phm cp EVA vo bitum 70 , cc c tnh Marshall v vt ln bnh xe ca asphalt lu nng c sn xut t cc cht lin kt c ci tin.

Bng 2.12. Tc ng ca cc phm cp EVA 150/19 v 45/33 n cc c tnh ca bitum v asphalt nng ri lp mt ng.

Cc c tnh ca cht lin kt

Cc c tnh ca Marshall

Cht lin kt Kim ln 250C, 0.1 mm

im mm (IP),

0C

n nh, kN

chy, mm

T s, kN/mm

ln bnh xe

450C, mm/h

70 68 49,0 6,3 3,3 1,9 4,4 70+5%EVA 50/19 50 66,5 7,6 3,2 2,4 0,8 70+5% EVA 45/33 57 58,0 8,0 2,7 3,0 1,0

Cc kt qu th nghim vt ln bnh xe cho thy ln gim i 4 ln khi cho thm EVA ca tng phm cp ni trn vo bitum 70. Mc chng li s bin dng cng t nhy cm ng k i vi s thay i nhit . S tng ln ca n nh

Marshall l khng ln nh mt d on da trn kt qu th nghim vt ln bnh xe. V vy, phn ln cc hn hp polyme ci bin c kim tra trong th nghim Marsahll, cc kt qu ca th nghim Marshall v cc vt liu ci bin bng cch cho thm polyme cn c xem xt mt cch thn trng.

2.5.7. BITUM CHO THM CAO SU DO NHIT

Trong 4 nhm cht n hi do nng chnh gm: polyurethane; cht ng trng hp polyetherpolyester; cc cht alken ng trng hp; v cht ng trng hp c on styren, cc cht ng trng hp c on styren c chng minh l c tim nng ln nht khi c trn vi bitum.

Cht ng trng hp c on styren thng c gi l cao su nhit do (TR). Cao su nhit do c th c to ra bng c ch to chui ca phn ng polyme ho lin tc styrenbutaienstyren (SBS) hoc styrenisoprenstyren (SIS). to ra cc polyme nu trn cn c cht xc tc trong phn ng ghp ni. i vi polyme khng ch c cc cht ng trng hp thng m cn c cc cht ng trng hp nhiu nhnh c th c to ra, nhng cht ny thng c gi l cc cht ng trng hp phn nhnh hoc hnh r qut, hnh sao.

Cao su nhit do c sc bn v tnh n hi do lin kt ngang vt l ca cc phn t trong mng li khng gian ba chiu. iu ny c c do lin kt ca on styren cui vi cc khi ring r, to ra lin kt ngang l hc i vi khi cao su polyisopren hoc polybutaien ba chiu. on cui polystyren s to cho polyme c sc bn v on gia s lmcho vt liu ny c tnh n hi c bit.

nhit trn im nhit ho thu tinh ca polystyren (1000C), polystyren mm i v lin kt khi yu i v thm ch s b tch ra di tc ng ca mt ng sut, n mc cho php gia cng d rng. Khi ngui i, cc khi s li lin kt li, sc bn v tnh n hi s c phc hi, iu ny ng ngha vt liu ny l mt cht do nhit.

Cho thm cao su nhit do vi trng lng phn t bng hoc cao hn cc nhm cht asphalt s lm xo trn s cn bng pha. Polyme v asphalt cnh tranh nhau v lc ho tan ca malten, nu khng c malten, c th xy ra hin tng tch pha. Cu trc ca cc h thng bitum/polyme thch hp v khng thch hp c quan st bng knh hin vi. H thng tng thch c cu trc u mn ng cht trong khi h thng khng tng thch c cu trc th t qung.

S tch pha hay tnh khng tng thch c th c kim tra bng mt th nghim bo qun nng n gin. Cc th nghim c thc hin vi mu bitum ly t nh, mt phn ba gia v 1/3 y bnh ng mu.

Cc nhn t chnh nh hng n n nh cc c tnh k thut ca bitum trong qu trnh bo qun l:

S lng v trng lng phn t ca cc nhm cht asphalt;

thm ca pha malten;

Lng polyme c mt;

Trng lng phn t v cu trc ca polyme;

Nhit bo qun.

Cht lng ca s phn tn polyme t c b nh hng bi mt s yu t, nhng c bn l ph thuc vo cng x di tc ng ca my trn. Khi polyme c cho thm vo bitum nng, bitum s ngay lp tc bt u nhp vo cc ht polyme lm cho cc chui styren ca polyme phng trng ln v d ho tan hn. Khi iu xy ra, lc x ln s tc ng vo cc ht b trng v s l yu t quyt nh c th t c s phn tn hon ton ca cc ht phn t polyme trong thi gian trn thc t. Nh vy, cn s dng cc my trn c lc x cao hoc trung bnh phn tn hon ton cao su do nhit vo bitum.

* Cc c tnh ca hn hp bitum cao su do nhit

Hng Shell Bitumen ca Vng quc Anh sn xut hai loi cht lin kt polyme SBS ci tin l CARIPHALTE DM v DA.

Bng 2.13. Cc c tnh k thut i vi CARIPHALTE DM v CARIPHALTE DA

Th nghim/ cht lin kt CARIPHALTE DM CARIPHALTE DA

kim ln 250C, dmm 90 20 130 20 im mm (IP), 0C 85 10 80 10 nht Brookfreld 1500C: mc x sau 3,36 giy, Poise ko di 50C, cm

10 4

> 50 9 4

M un cng ti thiu 400C: thi gian chu ti sau 1000 giy vi mc x 2,5.104s1, kN/m2

> 3

n nh bo qun: s khc nhau v im mm nh xung y sau 7 ngy bo qun trong mt thit b hnh tr 1600C, 0C

< 5 < 5

Hm lng polyme, % 7,0 1,0 6,0 1,0

CARIPHALTE DM c pht trin s dng trong hn hp b tng asphalt lu nng cht v hn hp b tng asphalt ci tin lp nn lm bng b tng ngho v mt ng b tng c b nhit gy ra mt s dch chuyn lp b tng dn n hin tng nt phn hi ti b mt ng.

CARIPHALTE DA c pht trin s dng trong hn hp nha thot nc v hn hp ri lp to ma st.

Cc yu t v k thut chi tit ca hai loi cht lin kt ny c chi tit ho bng 2.13.

Quan h gia nht v nhit ca CARIPHALTE DM v bitum qunh 50 cho thy r l nhit cao ca con ng, v d 600C, CARIPHALTE DM cng hn ng k so vi bitum 50 v do chng bin dng tt hn. nhit thp, < 00C, CARIPHALTE DM do hn bitum 50 v do chng nt tt hn.

Mc ci thin kh nng chng bin dng c kim tra bng cc th nghim vt ln bnh xe do c phng th nghim ng b v vn ti (TRRL) v Shell Research Limited thc hin, c trnh by bng 2.14. R rng l c mt s tng ln ng k v kh nng chng bin dng, tng t vi kh nng chng bin dng ca bitum chu ti nng (HD) c pht trin chuyn dng chng bin dng. Nhng u im ny c khng nh qua cc cuc kim nghim ton din trn thc a.

do ca hn hp bitum c nh lng bng th nghim robin dng khng i do TRRL v Shell Research Limited tin hnh. Th nghim mi c Shell Research Limited thc hin trn hn hp b tng asphalt lu nng thi cng 50C vi tn s l 50 Hz cho thy vi mt phm vi rng v ti trng tc ng ln mu th nghim CARIPHALTE DM, tui th ro ca mt ng nng ln t nht l 3 ln.

Bng 2.14. So snh mc vt ln bnh xe ca mt ng c ri bng asphalt lu nng lm t bitum 50, HD40 v CARIPHALTE DM

Cc c tnh ca cht lin kt

Cht lin kt Kim ln 250C, dmm

im mm (IP), oC

ln vt bnh xe 450C

mm/h

50 pen

HD40

CARIPHALTE DM

56

42

34

52

68

90

3,2

0,7

0,7

2.5.8. CC BITUM POLYME CHU NHIT

Cc cht polyme chu nhit c sn xut bng cch trn hai thnh phn lng, thnh phn u l cht nha v phn cn li cha cht lm cng. Hai thnh phn ny kt hp vi nhau v mt ho hc to ra mt cu trc 3 chiu vng chc. Hp cht nha 2 thnh phn ny khi trn vi bitum s th hin cc c tnh ni tri ca cc cht nha chu nhit hn l cc c tnh ca bitum. Cc loi hp cht nha chu nhit 2 thnh phn ny c pht trin khong 30 nm trc y v hin nay ang c ng dng rng ri bc ph b mt v lm cc cht dnh kt.

Nhng s khc nhau c bn gia bitum (mt cht do nhit) v cc bitum polyme chu nhit l nh sau:

Khi hai thnh phn trong bitum polyme chu nhit c trn th thi gian s dng sn phm ny s b gii hn, thi hn ny ph thuc nhiu vo nhit , nhit cng cao th thi hn s dng cng ngn.

Sau khi mt sn phm chu nhit c s dng n tip tc c lu ho v tng cng v sc bn, tc lu ho trn mt ng ph thuc vo nhit mi trng.

Khi nhit tng ln bitum b mm ra v chy, cc bitum polyme chu nhit t mn cm vi nhit hn v trong thc t khng b tc ng ca s thay i nhit trn ng.

Bitum polyme chu nhit l mt vt liu n hi, khng th hin c tnh nht chy, n nh vi ho cht, dung mi, nhin liu v du.

Ba loi bitum polyme chu nhit c bit n ph bin l: Shell grip/spray grrip; Erophalt; v Sheliepoxy asphalt. Cc loi ny c s dng rng ri trn th gii t nm 1986. Tuy nhin, Vit Nam ang trong giai on nghin cu.

2.5.9. TIU CHUN 22TCN319042004 GTVT V BITUM POLYME

C th tham kho tiu chun k thut vt liu bitum polyme dng cho ng t v sn bay c quy nh theo 22TCN 319042004 GTVT.

Bng 2.15. Tiu chun k thut vt liu bitum polyme cho ng t v sn bay (22TCN 319042004)

Tr s tiu chun theo mc bitum polyme

TT Cc ch tiu n

v PMBI

PMBII PMBIII

1 Nhit ho mm (phng php vng v bi), min

oC 60 70 80

2 kim ln 250C 0.1mm 5070 4070 3 Nhit bt la, min oC 230 4 Lng tn tht sau khi un nng

1630C trong 5 gi, max % 0.6

5 T l kim ln ca nha ng sau khi un nng 1630C trong 5 gi so vi kim ln 250C, min

% 65

6 Lng ho tan trong trichloroethytylen, min

% 99

7 Khi lng ring 250C g/cm3 1.001.05 8 dnh bm vi , min cp cp 4 9 n hi ( 250C mu ko di

10cm), min % 60 65 70

10 n nh lu tr (gia nhit 1630C trong 48 gi, sai khc nhit ho mm ca phn trn v di ca mu), max

oC 3.0

11 nht 1350C (nht k Pa.s 3.0

Brookfield), max

2.6. NH TNG XY DNG NG (22TCN 3542006) 2.6.1. KHI NIM V PHN LOI NH TNG

2.6.1.1. Khi nim

Nh tng l mt h thng keo phc tp bao gm hai cht lng khng ho tan ln nhau. Trong , mt cht lng phn tn trong cht lng kia di dng nhng git nh li ti, gi l pha phn tn, cn cht lng kia gi l mi trng phn tn.

cho nh tng c n nh ngi ta cho thm vo cht nh ha (cht ph gia hot tnh b mt). Cht nh ha s hp ph trn b mt cc git bitum hay gurng, lm gim sc cng b mt mt phn chia ca bitum hay gurng vi nc. ng thi n to ra trn b mt cc git bitum mt mng mng kt cu bn vng, c tc dng ngn cn s kt t ca chng, lm cho nh tng n nh.

Nh tng bitum l mt hp cht gm hai thnh phn d th c bn l bitum v nc, c gi l hai pha nc v pha bitum. Bitum c phn tn trong nc di dng cc ht ring r c ng knh t 0,15 micrn. Cc ht bitum c gi trng thi l lng tch in v c n nh bng cht nh ho.

2.6.1.2. Phn loi nh tng

Cn c vo c trng ca pha phn tn v mi trng phn tn, nh tng c chia ra hai loi:

Nu pha phn tn l bitum, cn mi trng phn tn l nc th gi l nh tng dunc (DN), hay cn gi l nh tng thun.

Nu pha phn tn l nhng git nc, cn bitum hay gurng l mi trng phn tn, th gi l nh tng ncdu (ND), hay cn gi l nh tng nghch.

Theo kh nng trn ln ca nh tng vi vt liu khong chia nh tng ra lm ba loi: 1, 2, 3 (theo quy phm 1865981Nga).

Cn c vo cht nh ha, nh tng c chia ra lm cc loi sau:

Nh tng anion hot tnh (nh tng kim)dng cht nh ha l nhng mui kim ca axit bo, axit naftalen, nha hay nhng axit sunfua, pH ca nh tng t 912.

Nh tng cation hot tnh (nh tng axit)dng cht nh ha l cc mui ca cc cht amniac bc bn, iamin, v.v., pH trong nh tng ny mn trong gii hn t 26.

Nh tng trung tnh (khng sinh ra ion)l nh tng dng cht nh ha khng sinh ra ion nh opanol (cao su tng hp), plyizbutilen v.v. pH bng 7.

Nh tng l loi bt nho khi dng cht nh ha dng bt v c nh bt vi ti, t st do, trpen, iatmit.

Thut ng anion v cation ch cc in tch bao quanh cc ht bitum. Hin tng ny bt ngun t mt quy lut c bn v in. Cc in tch cng du y nhau, cc in tch khc du ht nhau. Nu dng in chy qua mt dung dch nh tng cha

ht bitum tch in m, chng s di chuyn v pha ant. Bi vy nh tng ny c gi l nh tng anion. Ngc li cc ht bitum c tch in dng s di chuyn v pha catt. Nh tng l cc ht trung tnh s khng di chuyn ti bt k cc cc no. Nh tng trung tnh rt him khi c s dng trong xy dng ng.

2.6.2. VT LIU CH TO NH TNG

2.6.2.1. Cht kt dnh

ch to nh tng, c th dng cc cht kt dnh hu c nh bitum du m loi c, loi lng v gurng than xy dng ng. Khi dng cht nh ha dng bt (bt vi ti, t st) th c th dng cc loi mc thp (s 13), cn khi xy dng mt ng nhng vng kh hu nngdng cc loi mc cao (bitum mc s5).

2.6.2.2. Nc

Nc dng ch to nh tng khi dng cht nh ha anion hot tnh th phi l nc mm (nc c cng khng ln hn 3 mili ng lng gam/lt).

2.6.2.3. Cht nh ha

Cht nh ha l cht hot tnh b mt, nhng phn t ca n bao gm phn khng mang cc tnh l nhng gc hyr ccbua, v phn mang cc tnh. Cht ny c kh nng hp th trn b mt git bitum hay gurng lm cho nh tng n nh. Khi gc hyr cacbua (nhm khng mang cc tnh), l nhm k nc, nn n lun lun n pha c cc tnh nh hnhng vo bitum; cn nhm c cc tnh, l nhm a nc, th hng vo nc. Do cu trc phn t ca cht hot tnh b mt khng i xng nh vy, nn lp b mt, chng nh hng ph hp vi quy lut cn bng cc tnh, v lm gim sc cng b mt mt phn chia gia nc v bitum, tc l n lm gim s khc nhau v sc cng b mt ca bitum v nc.

Cht nh ha c chia ra cc loi anion hot tnh, cation hot tnh v loi khng sinh ra ion.

Cht nh ho anion hot tnh bao gm c x phng ca cc axit bo, axit nha, axit naftalen v cc axit sunfua naftalen.

Cht nh ho cation hot tnh l nhng mui ca cc hp cht amniac bc bn, cc amin bc nht, bc hai v cc mui ca chng; cc iamin v.v.

Nhm khng sinh ra ion bao gm cc hp cht khng ho tan trong nc, ch yu l cc te.

Ngoi nhng loi cht nh ha dng hu c trn ra, khi ch to nh tng cn dng cht nh ha dng bt v c. Nhng cht nh ha dng bt v c hay dng l vi bt, vi ti, t st, t hong th.

Trong thc t xy dng ng, ng dng rng ri nht l nhng cht nh ha anion hot tnh, ch to nh tng thun.

2.6.3. CC CH TIU K THUT NH TNG LM NG

2.6.3.1. nht

Nh tng lm ng cn c nht hp l m bo khi s dng c th nho trn vi vt liu khong hoc phun c ln b mt vt liu khong bng cc thit b phun.

nht ca nh tng thng c xc nh bng nht k tiu chun (xem mc 2.4.2) hay nht k Engler. nht ca nh tng thng dao ng trong phm vi sau:

C320 = 550 sec.

Tng nht ca nh tng bng cch tng t l bitum, thay i dung dch nh ho hoc gim nht ca bitum. Hnh 2.11. m t mi quan h gia nht ca nh tng vi hm lng ca bitum.

2.6.3.2. phn tch

Nh tng sau khi thi cng phi tch nc nhanh v dnh bm tt vi b mt vt liu khong vt. Hnh 2.12. m t qu trnh phn tch v dnh bm vi b mt vt liu khong ca nh tng.

Hnh 2.12. S m t qu trnh phn tch v dnh bm vi b mt vt liu khong ca nh tng.

phn tch c xc nh bng h s:

Hnh 2.11. nht ca nh tng ( Engler) l mt hm ca tc chy vi cc hm lng bitum khc nhau.

100,%N

NP

2

1 = (2.6)

trong : N1lng nha cn li sau khi th nghim

N2lng nha trn mt si trc khi th nghim.

Th nghim c tin hnh nh sau: Nhng si c ng knh t 6 n 12mm vo nh tng trong 2 pht, ngoi khng kh 30 pht, ra mu trong nc 15 pht

P = 10050, %, phn tch nhanh

P = 1050, %, phn tch va

P nh hn 10, %, phn tch chm.

2.6.3.3. Tnh n nh khi vn chuyn v bo qun

Tnh n nh khi bo qun c trng cho kh nng ca nh tng bo ton c cc tnh cht khi nhit thay i, ngha l n khng lng ng, khng to thnh lp v v bo ton tnh ng nht trong mt khong thi gian nht nh. Tnh n nh thng c xc nh sau 7 v 30 ngy bo qun (theo tiu chun 1865981 Lin X c). Cc loi nh tng c thnh phn khc nhau c th n nh trong lc bo qun nhit t +3oC n +40oC trong 30 ngy.

Tnh n nh khi vn chuyn hay khi chu tc dng ca ngoi lc c xc nh bng kh nng ca nh tng bo ton tnh cht khi chuyn ch v khi thi cng.

xc nh tnh n nh khi bo qun v khi vn chuyn, ly nh tng bo qun sau 7 ngy v 30 ngy cho chy qua sng c kch thc l sng 0,14mm. Yu cu l lng st trn sng khng qu 0,1% theo khi lng v m bo cc tnh cht khc theo tiu chun Nh nc.

Tnh n nh khi vn chuyn c kim tra theo cc tnh cht ca bitum sau 2 gi vn chuyn phi m bo cc yu cu k thut.

Nh tng c nht cao, t l cht nh ho cao, c kch thc ht ng u s n nh khi bo qun.

2.6.3.4. Tnh dnh bm ca mng cht dnh kt vi b mt vt liu khong

Tnh dnh bm c kim tra bng tr s b mt ca dm vn cn c ph nh tng sau khi ra cc mu th sau khi nhng vo nh tng bng nc nhit 100oC. Tr s b mt phi khng nh hn 75% (vi nh tng anion) v khng nh hn 95% (vi nh tng cation).

2.6.3.5 Tnh cht phn cn li sau khi chng ct

Sau khi chng ct nhit 360oC, cho phn dung mi bay hi ht, tnh cht ca phn cn li phi ph hp vi tiu chun nh vi bitum lng.

2.6.4. THNH PHN CA NH TNG VIT NAM

Vit nam bc u nghin cu thnh cng mt s nh tng thun loi kim, dng cht nh ho anion hot tnh nh x phng bt, du gai, du s, du tru, v.v. thnh phn ca nh tng nh sau:

50% bitum s 5 + 50% nc + (0,51)% x phng bt + (0,10,15)% NaOH.

50% bitum s 5 + 50% nc + (0,51,2)% du thc vt + (0,20,3)% NaOH.

Ngoi ra, khi cn ch to nh tng c th tham kho thnh phn nh tng ca Nga (Tiu chun 1865981), ca M ASTM, v.v.

2.6.5. CC YU CU V NH TNG CA M (EMULOIFIED ASPHALT)

M c nhiu loi nh tng nha, ch yu thng dng trong xy dng ng l nh tng anion (AEA) v nh tng cation (CEA). Mi loi nh tng nha c chia ra nhiu cp theo tc phn tch v nht. Cc yu cu v tnh cht c l ca nh tng c ghi trong bng 2.16.

Bng 2.16. Cc yu cu k thut ca nh tng.

.

Cp

Phn tch nhanh Phn tch va

Phn tch chm

Cc ch tiu

RS1 RS2 MS2 SS1 SS1h

K hiu th nghim

(1) (2) (3) (4) (5) (6) (7)

1 nht Furol 77oF, scc

20 100 100+ 20100 20100 22TCN 2542006

2 nht Furol 122oF, scc

75400 cng quy nh tng t

(1) (2) (3) (4) (5) (6) (7)

3B nha sau khi ct, % theo khi lng

54+ 62+ 62+ 57+ 57+

4Lng ng 5 ngy, khc nhau gia lp trn v lp di, %

3 3 3 3 3 D224T59

5 kh nh:

Khi dng 35ml 0,02N CaCl2,%

60+ 50+

2.6.6. NG DNG CA NH TNG BITUM LM NG

2.6.6.1. Nh tng bitum lm ng

Hn hp nh tng bitum ct liu c sn xut v s dng Php t nhng nm 50 v c s dng ph bin chu u, chu Phi, M cho n ngy nay. Chng loi hn hp ch yu l nha nh tng c s dng lm lp mng trn ca ng b. Tuy nhin, mt s loi hn hp c sn xut t nh tng bitum dnh cho ri lp trn ca mt ng cng c p dng thnh cng.

Mt vn quan trng khi s dng nh tng bitum trong hn hp lm ng l cn to ra rng tng i cao nc c th thot nhanh trong qu trnh m nn v khi con ng i vo hot ng. Hn na bn ca mt ng c gia cng vi hn hp nh tngct liu c hnh thnh tng i chm. V c hai l do ny m

Khi dng 50ml ca 0,01N CaCl2,%

30

6Th nghim ry (phn trn ry No20),%

0,10 0,10 0,10 0,10 0,10

7Th nghim trn vi ximng, %

2,0 2,0 D5T49

8Th nghim trn b nha sau khi trng ct nh tng nha:

kim ln, 77oF, 100g, 5s

100200 100200 100200

100200

4090 D2042T44

ho tan trong Trichloroithylene, %

97,5+ 97,5+ 97,5+ 97,5+ 90,5+ D113T51

ko di, 77oF, cm

40+ 40+ 40+ 40+ 40+

9Hm lng bitum,%

60+ 65+ 65+ 57+ 57+

10Hm lng du, %

3 3 12

cc hn hp nh tngct liu ch ph hp vi cc con ng chu ti nh. Do vy, loi vt liu ny ch c s dng rt hn ch.

Trc y, cc hn hp nha ng kt chm hoc c sn xut vi vic s dng mt phm cp bitum lng vi nhiu loi du pha khc nhau. Cc vt liu ny ch yu c s dng cho vic duy tu sa cha ng. S pht trin ca cc nh tng ph ct liu to ra mt s loi hn hp nh tngct liu dng cho nhng mc ch c th trong xy dng ng giao thng.

Mt ng dng khc ca nh tng bitum trong hn hp lm ng l khi phc mt ng theo phng php trn ngui ti ch. My lm ng lin hp c s dng bc lp mt ng, ri nghin lp bc mt ng thnh cc ht ct liu theo kch c yu cu v sng lc loi b cc ht khng ng kch thc. Sau ct liu ti ch c phun mt lp nh tng, sau mi ln phun nh tng thit b o lp ct liu c s dng nh tng bm dnh u vi ct liu. Qu trnh phun v o li khong t 2 n 3 ln. Tip theo, xe lu trng lng 810 tn c s dng m nn lp nh tngct liu v cui cng mt ng c lng mt hn hp mn chng thm.

Nh tng bitum cng c s dng lm lp dnh bm. l mt k thut c p dng m bo s lin kt bm dnh gia cc lp ca mt ng.

2.6.6.2. Cc ng dng khc ca nh tng bitum.

C th s dng nh tng lm n nh t, chng thm, lp ph bo v, trm khe cc khe h v lm lp chng thm.

CU HI N TP 1. Khi nim v phn loi bitum lm ng 2. Thnh phn v cu trc ca bitum 3. Cc tnh cht ca bitum du m qunh xy dng ng 4. Thnh phn v cc tnh cht ca bitum lng lm ng 5. Cc loi bitum ci tin lm ng 6. Thnh phn v cc tnh cht ca nh tng xy dng ng

Chng 3

CT LIU CHO B TNG ASPHALT

3.1. M U

Ct liu ng vai tr rt quan trng trong hn hp b tng asphalt. N chim khong 92 n 96 % tng khi lng vt liu trong b tng asphalt v chim khong trn 30% gi thnh ca kt cu mt ng. V vy, n nh hng kh nhiu ti gi thnh ca kt cu mt ng.

Ct liu ch yu ca b tng asphalt l dm (hoc si), ct (ct t nhin hoc ct nghin), bt vi, cc ct liu nhn to (si keramdit, x l cao, xi mng), hoc cc vt liu thi khc.

3.2. PHN LOI V PHNG PHP SN XUT CT LIU. 3.2.1. PHN LOI

Ct liu bao gm cc loi ct, si, nghin, x, hay thnh phn vt liu khong khc. Chng c th c nho trn vi nhau v s dng cng vi cht kt dnh hu c to thnh vt liu b tng asphalt.

Ct liu c th phn loi theo ngun gc t nhin hay nhn to. Ct liu t nhin c ly t nhin v trong qu trnh khai thc, sn xut khng lm thay i bn cht ca chng, ch s dng cch nghin, o, sng hay ra. Trong nhm ny, dm, si v ct l ph bin nht, mc d c th c thm bt, v s, qung st, v vi. Ct liu nhn to bao gm x l cao, t st nung, ct liu nh, v cc vt liu thi.

Theo ng knh ln nht, ct liu c chia ra 2 loi: ht mn v ht ln. Loi ht ln l ht phn ln nm trn sng No8(2.36 mm). Loi ht mn phn ln lt qua sng 2.36 mm.

Kch thc cc mt sng, mm, cho ct liu b tng asphalt nh sau: 50; 37,5; 25; 19; 12,5; 9,5; 4,75; 2,36; 1,18; 0,6; 0,3; 0,15; 0,075.

Tu theo loi b tng asphalt c th dng cc ng knh ln nht khc nhau v c thnh phn cp phi ht khc nhau c quy nh theo cc tiu chun k thut.

Theo tiu chun Chu u EN 130432002 kch thc c sng ghi bng 3.1.

Bng 3.1. Cc loi c sng phn loi cc c ht ct liu cho b tng asphalt (EN 130432002)

B sng c bn, c sng, mm Loi 1, c sng, mm Loi 2, c sng, mm

(1) (2) (3)

0

1

2

(1)

0

1

2

(2)

0

1

2

(3)

4

8

4

5.6 (5)

8

11.2

4

6.3 (6)

8

10

12.5

14

16

31.5 (32)

63

16

22.4 (22)

31.5 (32)

45

63

16

20

31.5

40

63

Thnh phn ht c quy nh theo EN 93311997 ph thuc vo t l d/D (trong D v d l ng knh c sng ln v nh nht ca b sng), v c quy nh bng 3.2 v 3.3.

Bng 3.2. Cc yu cu v thnh phn ht ct liu

Lng lt sng theo khi lng, % Ct liu

C sng, mm 2D 1.4D D d d/2

K hiu

100 100 9099 010 02 GC90/10

100 98100 9099 015 05 GC90/15

100 98100 9099 020 05 GC90/20

100 98100 8599 015 02 GC85/15

100 98100 8599 020 05 GC85/20

Th D >2

100 98100 8599 035 05 GC85/35

Ht mn D2 100 8599 GF85

Hn hp

D45 v d=0

100

100

98100

98100

9099

8599

GA90

GA85

Bng 3.3. Cc gii hn chung v dung sai cho cp phi hn hp ht th ti c sng trung gian.

Gii hn phn trm lt theo khi lng D/d

C sng trung gian, mm

Gii hn Dung sai K hiu

2580 15 G25/15

Nguyn tc c bn nht ca qu trnh khai thc, gia cng ct liu l t c cht lng ct liu cao nht vi gi thnh hp l. Qu trnh khai thc, gia cng gm cc bc: o, vn chuyn, ra, nghin, sng phn loi, nh gi cht lng vt liu v kt thc bng giai on ct vo kho hay chuyn ra cng trng.

Sau khi ct liu c khai thc, chng c ch bng bng ti, tu ho, xe ti n ni x l, ch to. Cng ngh ch to thng theo cc bc sau:

Ra sch: Qu trnh x l u tin l loi b cc vt liu khng th chp nhn c. Nhng vt liu b loi b l nhng vt liu c th lm gim cht lng n sn phm cui cng nu s dng loi ct liu . Mt phng php loi b vt liu (st, bn, l cy v.v) l ra ct liu. C th s dng bng chuyn, vn chuyn ct liu thng qua h thng vi phun nc ra ct liu.

Nghin nh: Qu trnh tip theo l lm gim kch thc ca hay si. Trong qu trnh ny c th s dng rt nhiu loi my nghin. Loi c nht l loi my nghin c mt m nghin c nh v mt m nghin di ng, n thch hp i vi tt c cc loi cng. Loi my mi l my nghin m kt hp vi my nghin trc c cng sut ln hn. Cc loi my nghin thng gim kch thc vi t l 6:1 hoc thp hn. C th s dng cc loi nghin sng di ng hoc trm tnh vi kch thc ca ban u t 340510 mm v nng sut t 6.5100 m3/h. Cc loi my thng dng Vit Nam c ch to ti Trung Quc, Nga, Nht Bn v M.

a) b)

Hnh 3.1. S cng ngh ra (a) v nghin (b)

Hnh 3.2. S cc bc b tr trm nghin sng di ng

Cc sng rung c s dng i vi ct liu ln v dng c phn loi thu lc i vi ct liu nh. Trong qu trnh sng khong 70% vt liu lt qua sng v trong qu trnh sng c th loi bt mt s ht qu ln. L sng c hnh vung hoc hnh trn.

Phn loi theo kch thc, ngun gc ct liu: Si bao gm cc ht trn t nhin do qu trnh phong ho hoc mi mn ca hay do qu trnh cui kt. Ct bao gm cc vin b phong ho t nhin; nhng ht ct liu ni chung c hnh dng gc cnh nhng phi chu nh hng ca mi trng, thi tit. Ct l loi ct liu mn thu c t t nhin do qu trnh phong ho, mi mn hay qu trnh gia cng cc loi sa thch d v. nghin l mt sn phm ca qu trnh nghin (nhn to) tng, cui. Ct nghin chnh l nghin c kch thc nh tng ng vi kch thc ca ct t nhin. Si v nghin c coi l ct liu ln.

Ct liu c hnh dng rt khc nhau. Si c b mt trn nhn, trong khi nghin c b mt x x. Ct liu cn c s khc bit rt ln v rng. nghin v si c rng thp.

gc

Nghin th

Sng

Nghin m

Nghin nh

Sng

Phn loi A, B, C

3.3. CT LIU NHN TO

Ct liu nhn to do con ngi ch to ra. Mt trong s l x l cao (c lm ngui bng khng kh) (aircooled blastfurnace slag). Chng l mt loi ct liu nhn to c s dng ph bin trong xy dng ng cao tc. Tiu chun ASTM C125 v b tng v ct liu b tng (Concrete and Concrete Aggregates) xc nh rng x l cao ngui trong khng kh l loi vt liu thu c do s rn chc li ca x l cao nng chy trong mi trng khng kh. Qu trnh lm ngui c th c lm tng nhanh bng cch phun nc vo b mt ho cng. X l cao c coi l sn phm khng cha kim loi (nonmetallic), chng ch yu l silicat v alumosilicat canxi v nhng thnh phn khc. Chng c hnh thnh trong iu kin nng chy cng vi st trong l cao. Vic s dng ct liu nhn to ny trong cng nghip l khng ph bin. Mt s loi x l cao nh hn ct liu t nhin, n c khi lng ring t 2.0 2.5 g/cm3 trong khi ct liu t nhin c khi lng ring t 2.3 3.2 g/cm3.

Mc d khi nim v ct liu nhn to a ra y l kh y trong hu ht mi trng hp, nhng vn c cch phn loi ct liu nhn to nh l mt sn phm trc tip ch khng phi l sn phm gin tip (sn phm tha). Theo ngha ny, x l mt loi ct liu nhn to thc s c ch to ra c mc ch. Ct liu nh c coi l ct liu nhn to. Ct liu nh c th l x than, t st nung, v s hay x qung. Nhng loi ct liu ny c s dng sn xut b tng nh ni m ti trng bn thn ng vai tr quan trng.

3.4. S DNG CT LIU A PHNG

Trong nhiu vng Vit Nam, ct liu tt khan him v gi chuyn ch n ni s dng rt t. Khi , ct liu a phng c th c xem xt s dng. Tuy nhin, phi loi b mt s vt liu c cht lng km ct liu tun th theo tiu chun. Trong mt s trng hp c th tn dng ct liu t c nhng sn phm kinh t.

Khi tn dng ct liu a phng cn phi tin hnh mt s qu trnh: ra; phn tch ct liu nng; phn tch cc thnh phn ht mm yu; v sng.

Ct liu xu c ra loi b lp ph bn ngoi hay thay i cp phi. Lng ht mn c th c loi b bng cch xi nc vo trong khi sng hoc s dng cc thng ra c bit. nh lut Stock c th c s dng loi b nhng ht mn. Khi dng nc 77 0F (25 0C) v dng ct c khi lng ring 2.65, th nh lut Stock nh sau:

V = 9000D2 (3.1)

trong : V tc dng chy

D ng knh ht

V vy nu ct c a vo u mt thng cha di, th dng nc c th phn chia ring cc kch c ht ra.

Phn tch ct liu nng s dng nguyn tc trng lng ring ca nhng vt liu b loi b nh hn trng lng ring ca nhng vt liu tt. Phng php ny gn lin vi phng php quy trong thng nc sink float method. Khi quy th manhetit v

ferrosilicat s l lng trong nc. Nhng vt liu cn loi b c trng lng ring nh, ni trong nc cn vt liu tt s chm xung y thng cha.

Phng php rung c th c s dng phn tch cc vt liu ht nng nhng mm. Ct liu ri xung t mt mng nghing, v cht lng ca chng c o bi khong cch chng ny ln khi b mt. Cc hn ny ln c la chn theo 3 ngn ring bit, chng c t hp l thu c nhng ht da vo kh nng ny ln ca chng. Nhng vin yu, mm, d v ch ny ln mt on thp cn nhng vin ct liu tt ny ln cao hn. Qu trnh phn tch thnh phn mm s loi b nhng ht mm yu. Qu trnh ny khng loi b nhng ht c mun n hi ln. Do vy phng php ny cn tin hnh cng vi phng php phn tch ct liu nng m bo loi b ht tt c ct liu km.

3.5. NGUYN L V CT LIU CH TO B TNG ASPHALT 3.5.1. TNH CHT CA CT LIU CH TO B TNG ASPHALT

nh hng ca ct liu n tnh cht v kh nng chu lc ca hn hp b tng asphalt l rt ln. Ct liu l tng cho hn hp b tng asphalt phi c cp phi hp l, cng , kh nng chu hao mn ln v hnh dng gc cnh. Nhng tnh cht khc bao gm rng thp, b mt x x, khng b bn, v c tnh ght nc. Bng 3.4 v 3.5 a ra mt s cc c tnh ch yu ca ct liu dng cho hn hp b tng asphalt.

Cp phi, cng , hao mn, v hnh dng ca ct liu l rt quan trng nh hng n s n nh ca kt cu. rng v c trng b mt vt liu khong nh hng rt ln i vi mi lin kt gia bitum v b mt vt liu khong. Cht kt dnh asphalt hay cc sn phm ca n phi dnh cht vo ct liu v ng thi phi bao ph ton b b mt ct liu. Nu ct liu c rng thp v trn nhn cht kt dnh asphalt khng th dnh vo ct liu. S dnh bm tr thnh mt ch tiu rt quan trng khi hn hp b tng b t trong mi trng nc. Nu ct liu rt d thm t, nc s cnh tranh vi bitum ngm vo b mt ct liu v ct liu s b tch ra khng dnh vo bitum. Hin tng ny c bit v n c gi l s bong, trc ca bitum vi vt liu khong.

Bng 3.4. Cc tnh cht vt l ca mt s loi

hao mn khi dng my, %

Loi

Khi lng th

tch, g/cm3

ht nc

% Devan Los Angelet

mi

mn, g/cm2

bn dai, va chm, N.m

(1) (2) (3) (4) (5) (6) (7) magma Granit Syenit Diorit Gabro Peridotit

2.65 2.74 2.92 2.96 3.31

0.3 0.4 0.3 0.3 0.3

4.3 4.1 3.1 3.0 4.1

38 24

18

18 18 18 18 15

9

14 15 14 9

Felsit Bazan Diaba

(1)

2.66 2.86 2.96 (2)

0.8 0.5 0.3 (3)

3.8 3.1 2.6 (4)

18 14 18 (5)

18 17 18 (6)

17 19 20 (7)

trm tch vi lomit phin st sa thch phin silic Cui kt Breccia bin cht gnai dip thch Amphibn phin slate quczit hoa Secpentin

2.66 2.70

1.852.5 2.54 2.50 2.68 2.59

2.74 2.85 3.02 2.74 2.69 2.63 2.62

0.9 1.1

1.8 1.6 1.2 1.8

0.3 0.4 0.4 0.5 0.3 0.2 0.9

5.7 5.5

7.0 8.4

10.0 6.4

5.9 5.5 3.9 4.7 3.3 6.3 6.3

26 25

38 26

45 38 35 20 28 47 19

14 14

15 19 16 17

18 17 16 15 19 13 15

8 9

11 12 8

11

9 12 14 18 16 6

14

Ghi ch:

Ct 2 vt liu c nhng ngp trong nc ti p sut kh quyn v nhit thng;

Ct 3 ly theo AASHTO T3 hay ASTM D289;

Ct 4 ly theo AASHTO T96 hay ASTM C131;

Ct 5 ly theo Dorry hardness test U.S Dept. Agr. Bull 949;

Ct 6 ly theo AASHTO T5 hay ASTM D3a.

Bng 3.5. Cc yu cu k thut ca mt s loi

Loi Cng

bn

n nh ho cht

c trng b mt

Tn ti ht c cht

lng thp

Hnh dng sau

khi nghin

(1) (2) (3) (4) (5) (6) (7)

magma Granit,syenit, diorit Felsit Bazan, diaba, gabro

Tt Tt Tt

Tt Tt Tt

Tt

Cha r Tt

Tt TB Tt

C th C th

Him gp

Tt TB TB

Peridotit

trm tch vi, lomit sa thch

(1)

Tt

TB TB (2)

TB

TB TB (3)

Cha r

Tt Tt (4)

Tt

Tt Tt (5)

C th

C th Him gp

(6)

Tt

Tt Tt (7)

phin silic Cui kt, breccia phin st

bin cht gnai, dip thch quczit hoa secpentin amphibn phin slate

Tt TB

Km

Tt Tt TB TB Tt Tt

Km TB

Km

Tt Tt Tt TB Tt Tt

Km Tt

Tt Tt Tt Tt Tt Tt

TB Tt Tt

Tt Tt Tt TB Tt TB

t gp Him gp

C th

Him gp Him gp

C th C th

Him gp Him gp

Km TB TB

Tt TB Tt TB TB

Km

3.5.2. DM HAY SI

Cht lng dm hay si v cng , tnh ng nht, hnh dng, trng thi b mt, thnh phn khong vt, v.v. c nh hng rt ln n cht lng ca b tng asphalt.

dm dng ch to b tng asphalt c th l dm sn xut t thin nhin, dm ch to t cui, hoc dm ch to t x l cao, nhng phi ph hp vi cc yu cu ca tiu chun. Khng cho php dng dm ch to t vi st, sa thch st v phin thch st. Cc tiu chun th nghim vt liu c trnh by trong bng 3.6.

Bng 3.6. Cc tiu chun th nghim lm b tng asphalt

Tiu chun M TT Ni dung

Tiu chun Vit Nam ASTM AASHTO

Ghi ch

a. Ct

1 Xc nh hm lng chung bi bn st (ht

dp v, hao mn...)

2 hao mn Los Angeles C131 T96

Thnh phn ht ca dm hay si c phn ra ba nhm, gm: 20 40; 10 20 v 510 mm (TCVN). Theo tiu chun M t 3/8 in n 21/2 in.

Tu theo cng chu nn ca gc m dm dng ch to b tng asphalt c cc loi mc khc nhau nh ghi trong bng 3.7.

Bng 3.7. Quy nh v mc nn ca (si) dng cho b tng asphalt

Quy nh theo mc hn hp

I II III Ch tiu

A B A B A B

Cng , daN/cm2, khng nh hn

1 dm t mcma v bin cht

1200 1200 1000 1000 1000 600800

2 dm t trm tch dng cacbonat.

1000 600 400600

3 dm t trm tch dng khi ln.

1200 1000 1000 1000 600 600

4 Si*. p8 p8 p12 p16 p16

(*): mc nn dp trong xilanh.

Cng ca gc lm dm cho b tng nha ngui ti thiu l 800 daN/cm2.

dm (hay si) dng ch to b tng asphalt ch c php cha cc ht dt: i vi b tng loi A: < 20%, i vi loi B v Bx: < 25%; loi C v Cx: < 3,5% theo khi lng.

dm cn phi lin kt tt vi bitum. V mt ny, th cc loi vi, lmit, iaba tt hn cc loi axit. Nu dng loi lin kt km vi bitum th phi gia cng bng cht ph gia hot tnh nh vi, ximng hoc cho thm cht ph gia hot tnh b mt vo bitum.

cn phi sch, lng ngm cht bn khng c ln hn 1% theo khi lng.

3.5.3. CT

Vai tr ca ct trong hn hp b tng asphalt l chn k h gia cc ht ct liu ln, lm tng c ca hn hp. C th dng ct thin nhin hay ct nhn to, c cc ch tiu k thut ph hp vi quy phm nh khi dng cho b tng nng (TCVN).

Ct thin nhin ch to b tng asphalt ch dng loi ht ln vi m un ln Ml 2,5. Khi khng c ct ht ln th thnh phn hn hp b tng asphalt loi A v B s la chn dng ct ht nh theo nguyn tc thnh phn ht khng lin tc.

Theo TCVN 75702006 m un ln ca ct c tnh theo cng thc sau:

100

AAAAAM 0,140,3150,651,252,5dl

++++= (3.2)

trong : Ai lng st tch lu trn sn.

Mun ln, biu th mn ca ct mt cch tng i, c tnh theo phn trm ca tng cc lng st tch ly trn sng tiu chun trong th nghim sng ct tiu chun. Su c sng c dng th nghim gm cc c sng s 4, 8, 16, 30, 50, v 100. M un ln cng nh th ct cng mn. Mun ln ca ct tt nht l nm trong phm vi t 2,25 3,25.

Thnh phn ht ca ct c lp theo quan h gia kch thc mt sng vi lng st tch lu phi ph hp vi cc quy nh ca tng loi b tng khc nhau (xem phn b tng ximng). Phng php xc nh thnh phn bi, bn st, tp cht hu c, hm lng sunfat theo TCVN 334, 345, 3461986.

Ct nghin cn phi ch to t gc c cng khng nh hn cng ca dng lm dm (600 1000 daN/cm2).

i vi hn hp b tng asphalt loi G s dng ct nghin. Ct ny c nghin t mcma c mc khng nh hn 1000. Hm lng cc ht nh hn 0,071mm trong ct nghin khng c ln hn 14% theo khi lng, trong lng ht st khng c ln hn 0,5%, lng ht nh hn 0,14mm khng ln hn 20%.

Yu cu v ct lm b tng asphalt c th tham kho tiu chun 873685 hoc 2619384, 334483 ca Nga.

3.5.4. BT KHONG

Bt khong l thnh phn quan trng trong hn hp b tng asphalt. N khng nhng nht y l rng gia cc loi ct liu ln hn (ct, dm hay si) lm tng c ca hn hp m cn lm tng din tch tip xc, lm cho mng bitum trn mt ht khong cng mng v nh vy lc tong tc gia chng tng ln, cng v bn nc ca b tng asphalt cng tng ln.

Khi trn vi bitum trong hn hp b tng asphalt, bt khong cn to nn mt lp hot tnh, n nh nc. Mi quan h vt l, ho hc gia b mt ht bt khong v bitum lm tng cng ca b tng asphalt, nhng cng lm tng tnh gin ca n. V vy, lng bt khong trong b tng ch c dng trong mt gii hn nht nh trnh lm tng tc ho gi ca bitum trong b tng. Bt khong ch to b tng asphalt thng s dng cc loi bt mn t vi v lmit. Cng chu nn ca khng nh hn 200 daN/cm2. Vt liu ch to bt khong cn sch, khng cha cc cht bn v st qu 5%.

Bt khong cn phi kh, xp khi trn vi bitum, khng c vn cc, c kh nng ht bitum tt v phi tho mn cc yu cu sau (c th tham kho tiu chun Nga 1655788):

nh: Lng lt qua sng c kch thc l sng:

1,25mm 100%

0,315mm 90%

0,071mm 70%

Lng bt khong ht ht 15g bitum mc 60/70 khng nh hn 40g.

trng n ca mu th hn hp gia bt khong v bitum khng c ln hn 1,5%.

cha bitum khng c ln hn 65%

m khng ln hn 1%

rng khi ln cht vi ti trng 400 daN/cm2 i vi tro, bi ximng, x, khng c ln hn 30%, cn i vi loi bt c chc th khng ln hn 35%.

H s u nc Ku c xc nh bng cng thc:

2

1u V

VK = (3.3)

trong : V1 th tch lng trong nc ca 5g bt khong,

V2 th tch lng trong du (mi trng khng phn cc) ca 5g bt khong.

Nu Ku > 1 th vt liu u nc v ngc li Ku < 1 vt liu ght nc. Bt khong ght nc lin kt tt vi bi tum lm tng cng b tng asphalt. i vi nhng ht ng knh < 1,25mm, quy nh Ku >1.

Vi hn hp loi b tng asphalt loi II, III c th dng bt khong t tro than , bi ximng, bt v s hn,... ph hp quy nh ca tiu chun 9128 84 ca Nga. Bt khong c tng cng cht lng bng cch hot ho b mt khi nghin. Hn hp hot tnh b mt gm bitum v cht hot tnh b mt vi t l t 1/1 n 1/1,1. Lng hn hp hot tnh phi hp vi lng bt khong theo t l 1,5 2,5%. Bt khong cn c kh nng tng cng li ca bitum. Th nghim vi mu bitum bt t l l 4/6 c nhit ho mm thp hn nhit ho mm ca bitum l 10 200C.

3.6. CC TIU CHUN ASTM I VI CT LIU

Phn ny gii thiu cc tiu chun th nghim ASTM, chng nhn mnh vo cc th nghim s dng trong thit k.

Tiu chun ASTM D75: mc ch ca th nghim ny l gii thiu cch ly mu th nghim cho ct liu th.

Tiu chun ASTM C136 (sng, phn loi v nh gi ct liu mn v ct liu th). Mc ch ca th nghim ny l xc nh kch thc ht ca ct liu mn v ct liu th c s dng trong cc t