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Cu 01: nh ngha, tnh nng ca B Tng Cng Cao?

nh ngha: BT CC l loi b tng c bit, c cng nn 28 ngy, mu th hnh tr

(15x30cm) > 55 Mpa, vi mu lp phng >60 Mpa S dng t l N/X thp, cc khong siu

mn, cc cht siu do v cc ct liu truyn thng

Tnh nng: Cng nn, cng ko khi un, cc bin dng (co ngt, t bin, nhit thy

ha), c tnh v nhit, bn, tnh dnh bm ct thp, tnh cng tc.

- Cng chu nn cao (c th ti 100Mpa), c v n hi hn b tng thng, m dun n hi

tng khong 20%, hnh thnh cng sm hn. Pht trin tuyn tnh v km theo s ph hoi

gin (km theo ting n khi ph hoi).

- Cng ko khi un: tng t 30-60%, c th t n 7Mpa

- Cc bin dng: t bin, co ngt v do nhit thy ha.

+ Do s dng nhiu xi mng nn co ngt do ln hn bnh thng. Dn n nguy c nt nhiu

hn b tng thng (bo dng sm, co ngt m).

+ T bin gim 35-45% so vi bnh thng. S dng trong kt cu b tng DUL l c li.

+ Nhit thy ha: dng nhiu xi mng, hn ch lng nhit thot ra => a thm nhiu cht kt

dnh ph v t ta nhit.

- Khi lng n v, khi lng th tch: BTCDC ckhi lng n v ln hn b tng thng,

M= 2,5 (tan/m3).

- Tnh cht v nhit : km hn so vi b tng thng: tc gim cng nhanh, n nh

v th tch nhit cao km hn bt thng, nhit nh hng khong 300 C

- Cc tnh cht v bn:

+ Do t l N/X thp -> rng thp -> kh nng chng thm tt.

+ Chng thm clo, co2

- Kh nng dnh bm ct thp tt hn, khng gy vt nt ln hn so vi BT thng. t chu mi

mn v chu mi mn tt hn.

- Tnh cng tc:

+ Do s dng cht tng do nn BTCDC c tnh cng tc tt mc d t l N/X thp, st ti

a l 25cm.

+ Gi c st cao t 2h-3h ch thi cng.

+ Thi gian nho trn lu hn (5-6 min/1 ln trn) gp 2,5 ln so vi BT thng c thi gian

cho h xi mng v khong siu mn thm t bng nc.

+ Lng nc t nn nhanh rn chc => qu trnh thi cng v chun b phi chi tit hn => bo

dng sm v u tin bng nc.

Cu 02: Thit k thnh phn B Tng Cng Cao?

M u: l vic xc nh Dmax ca ct liu, t l N/CKD, lng ct liu, ph gia v xi mng

bng bao nhiu % theo khi lng, theo c ca hn hp t yu cu v cng nn c

trng fc, st (cm), chy lan (cm), bn.

Phng php: phng php Bolomay, BS (Anh), EU, ACI 211.4.08, ACI 363.R.

Cc bc thit k: gm 2 bc

+ Tnh ton thnh phn => cng thc b tng.

+ Th nghim: trn th.

Cu 03: Vt liu ch to B Tng Cng Cao?

Xi mng, Ct liu, Cht kt dnh ph (SF, FA), Cht siu do, Nc.

- Xi mng: PC30, PC40, PC50, PC60

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+ Nn chn xi mng c cng cao nht c th.

+ vit nam: dng xi mng PC40 tr ln, khng dng PC 40.

- Ct liu:

+ vi, granit, bazan c cng ln hn 100 MPa

+ Cp phi ht theo tiu chun VN hoc tiu chun ASTM D448

+ i vi ct: dng ct ht ln c m dun ln ca ct Mk = 2.6-3.1

+ Chn cc ct liu c D nh :9.5-19mm hoc 10-20mm

- Cht kt dnh ph:

+ Mui silic: micro silica nhn c t qu trnh luyn thp, c cc tnh nng:

SiO2 > 98%, ng knh ht d=0.1micro met, ht l cu trc v nh hnh

+ Tro bay: c lng oxit . 45%, phn ln l CaO, h s nh hng 0.4-0.5 so vi xi mng. c

ly t cht thi nh my nhit in.

- Cht siu do: gm 3 loi chnh:

+ linin sunfurat t gc thin nhin (lignosulfonat) : gim nc 20%, tang st 2 ln (s=12+-

2)

+ polime, amin ( gc poly)

+ polycacbonxinate : gim nc 40%, s=20+-2

Ch khi thit k dng h s gim nc a=0.1-0.3

- Nc : s dng nc m bo yu cu v ha hc.

Cu 04: Hng ng dng ca B Tng Cng Cao?

ng dng 3 lnh vc chnh: nh cao tng, cc kt cu ngoi bin, kt cu cu.

- Nh cao tng: phn HPC thay th cc ct thp, xy tr nh cao tng (100 tng). T nm 1970

1980 pht trin mnh Bc M, Canada. Hin nay tp trung pht trin Trung ng, Php.

Vic s dng ct b tng cht lng cao s chu c ti trng ln hn, cho php gim kch

thc mt ct ct, yu cu lng ct thp v vn khun s dng t hn.

- Cc kt cu ngoi bin: Nauy, an Mch, Anh, yu cu tui th ti 100 nm do dng b tng

cht lng cao gim c trng lng bn thn, tng bn cho kt cu.

- Kt cu cu: Nga, Nht, M, Php, Hn Quc, B tng cht lng cao thng c s dng

cho cc dm cu b tng d ng lc vi mc ch gim ti trng bn thn dm v tng chiu

di kt cu nhp.

Cu 05: nh ngha, thnh phn vt liu ch to B Tng Cng Siu Cao?

nh ngha: l mt loi b tng mi (composite) c cng nn t 120 _ 200 (MPa), c th

ln n 300 (MPa), trn l thuyt c th t 800 (MPa) nu c p lc vi thnh phn s dng

N/X = 0.2, hm lng mui silic cao (25%), ct liu nh (bt) mang li cht lng v bn

cao (>100 nm).

Thnh phn vt liu ch to:

+ T l N/X: = 0.2 0.15

+ Ct liu ln (bt): d = 0.5 10 (mm)

+ Ct liu nh: d = 0.075 0.3 (mm)

+ Cht kt dnh: XM cp 40 60 (MPa)

+ Mui silic: 0.25X

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+ Cht siu do m bo chy lan 600 (mm): 25 40 (lit/m3)

+ Ct si thp: polime, chim 1 2% theo th tch.

Cu 06: Tnh nng B Tng Cng Siu Cao?

Cng chu nn: vi mu d = 10, H = 20 (cm) th fc = 120 250 (MPa).

Cng chu ko khi un: fku = 15 20 (MPa).

Ngoi ra cn c mt s tnh nng c bit: chu tc ng ca va chm tt hn nhiu b tng thng.

=.> C l v bn cc cao => Vt liu chng khng b tt.

dai: gp 100 ln b tng thng.

Tnh thm thp: gim kh nng thm thu hi m, clorua, tn cng ha hc.

Kh nng sc khng mi mn, n mn, xi mn cao hn b tng thng.

Cu 07: Mi quan tm v thp tin tin cht lng cao?

Mt vi ng dng b tn cng bi mi trng nh s n mn bi nc mui, vn bo v chng

n mn v ph hy bt u c nghin cu v pht trin. Tuy nhin, vt liu cng cao dn n

h s ti trng cao hn, tnh do cao hn, kt qu l thp chim u th cho cc cng trnh XD cao hn,

ln hn v ko di tui tho hn.

Nhng mi quan tm v thp tin tin hin nay: tnh chu la, buckling, s mi v t gy, kh

nng chng n mn, tnh cht hn v tnh do cho ti trng ng t.

+ Tnh chu la: ngy cng c quan tm v ch , nht l nhng b phn v khi lng kt

hp vi kt cu thp. S thm vo kh nng chu nhit dn ti gi thnh ca kt cu v nhng k s phi

lm vic theo hng gim gi thnh

+ Buckling: kt cu thp c nhng b phn nh hn v mc ng sut ln hn cc vt liu xy

dng khc.

+ S mi v t gy: s tng ng xut un, sc khng v vic s dng kt cu hn v kt qu

lm tng tn s mi v t gy trong cu v h thng cng nghip. S gy ca thp trong xy dng tr

thnh nghim trng trong kt cu c xt n ti trng ng t.

+ Kh nng chng n mn: Thp c th b n mn bi mi trng, v vn ny c th dn n

hng hng nghim trng. duy tr kh nng ny dn n gi cng trnh xy dng s tng ln.M in,

sn, v bao ph lp bo v n mn nhng chng c th lm tng gi thnh ch to ca thp. Do

nhng k s vn ang tm kim nhng phng php lm gim gi thnh ca n.

+ Tnh cht hn: Hn trong xy dng thng c s dng do n cho kt cu khe hn, cng

hn v gim trng lng v nhu cu vt liu. S tng cng chu un v tip tc da trn phng

php hn v thp cng cao hn thng kh hn .

+ Tnh do chu ng t: Ti trng ng t thit k l nhu cu cho mt vi h thng kt cu

cng trnh xy dng,v thp l vt liu l tng cho vic thit k vi ti trng ng t v n l vt liu

c tnh do cao, cng.

Cu 08: nh ngha, thnh phn B Tng Ct Si?

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a. nh ngha: l loi b tng c bit c ch to t hn hp xi mng, ct liu, nc, ph gia v si

gia cng ring r. Si phn tn ngu nhin hay lin tuc.

b. Thnh phn: gm vt liu nn (cht kt dnh) + si.

- Vt liu nn: thng l polime hoc xi mng.

- Si: c 5 h si (t nhin, thc vt, khong, thy tinh, carbon).

+ S thin nhin: si vi,..

+ Si thc vt: s da, v cy ch l, g,

+ Si thy tinh: ch to nhiu v bn rng ri ti Vit Nam, khi a si thy tinh vo b tng

th s hn ch c nh hng t nhit, ng xut ko do nhit gy ra. Si thy tinh + epoxy l loi vt

liu xy dng dng tm hoc ct c tnh cht tng t ct thp.

+ Si carbon: c cng chu ko khong 100 (MPa), moddun n hi cao 150 GPa thu c

khi lm nng chy cacbon ri ko thnh si. Kh nng dnh bm vi cc loi keo rt tt.

Cu 09: Tnh nng ca B Tng Ct Si?

Kh nng chng nt: ct si tng kh nng chng nt do co ngt do ca b tng.

ln co ngt: tc dng ngn ln do co ngt, gim t xut co ngt do.

Kh nng chu ko: tng cng kh nng chu ko cho b tng.

Tnh do: b tng l vt liu gin, ct si lm tng tnh do cho b tng.

thm: gim d thm nc, gim tc n mn.

Cu 10: Trnh by v thp thi tit?

Thp thi tit hay cn gi l thp chu n mn l loi thp c kh nng khng c s n mn do khng

kh tt hn so vi thp carbon. Khng tn thi gian v chi ph do phi sn v bo v kim loi.

Khi t loi thp ny 1 cch thch hp vo khng kh th n s c 1 lp g ng lm gim v tr hon s

n mn, lm tng tui th phc v.

Lp g ng bo v chng li s m t hoc mi mn v khng kh cc b khng bao gm nc mui

hoc hm lng cc cht ha hc.

Ty vo tng trng hp c th, loi thp thi tit mi c pht trin tng sc chu n mn do

mui.

Thp bn thi tit mi c mt kh nng cao hn ch s thm vo st ca clorua.

Chiu dy n mn i vi thp thi tit mi b n mn khng ln hn 0.15 (mm) trong 6 nm ti Nht

Bn.

Cu 11: nh ngha, phn loi B Tng T m?

nh ngha: SCC l b tng tnh nng cao, c linh ng rt cao, c th t chy di tc dng

ca trng lng bn thn lp y hon ton vn khun ngay c khi c mt b tr ct thp

dy c m khng cn m rung.

Phn loi: c 3 loi l loi bt, loi do, loi kt hp.

+ Loi bt: gim i 25% ct liu ln, tng 70 120 (kg) bt => kt cu b tng t

ct thp (

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+ Loi do: s dng lng ph gia siu do t 1 1.5 lit/ 100 kg xi mng => b tng

c lng ct thp va.

+ Loi kt hp: dng trong kt cu b tng c lng ct thp ln (300 kh/m3).

Cu 12: Thit k thnh phn B Tng T m?

C rt nhiu phng php thit k thnh phn b tng t m nhng hin ti khng c tiu chun

thit k.

V d: Okamura, tiu chun Nht Bn, tiu chun EU, tiu chun M.

Phng php Okamaru: l phng php thc nghim.

+ a ra mt thnh phn theo kinh nghim.

+ Tin hnh th nghim chng minh thnh phn a ra l t.

Phng php tiu chun Nht Bn: tnh ton + thc nghim.

Cu 13: Cng ngh B Tng T m?

Nguyn tc: dng t di ln.

Phng php : ch yu bng bm.

Trnh t theo hnh v:

Cu 14: Trnh by tnh t m v phng php xc nh ca B Tng T m?

Tnh t m: t bn thn b tng phi in y vo cc l rng ca vn khun, to ra b tng

c tnh nng cn thit => ci tin v mt thnh phn, cu trc m bo cc tnh nng.

Cc phng php kim sot tnh t m: gm 4 phng php.

+ Dng o chy lan: dng cn ngc Abram ngc 1 2 ( )2

D DD mm

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+ Dng c ng: hnh ch L bng thp:

+ TN vn dng l thuyt bnh thng nhau (TN phu ch U): 2

1

0.85H

H

+ TN dng king + phu.