Bao dudng be tong tiT len bang che phu ni long trong dieu kien mien Nam
Curing self compacting concrtete by covering nylon in miennam's climate
Ngay nhan bai: 16/02/2017 Ngay sCra bai: 5/3/2017 Ngay chap nhan dang: 6/4/2017
Nguyen Dinh Hiing; Nguyen The At, Angeli Doliente Cabaltica; Vu Hong Nghiep
T6M TAT
Be tong hi len dung trong mgt so ket cau cau cang, c6t nha cao tang, kSt cau cau co ty I? cot thep Idn co the mang 1^ gia tn kmh te cho c6ng trinh. Tuy nhien, chat liiong cua be t6ng tiJ len ciing inh hiidng bdi dieu kien khi hau va each bao dUflng. Do do, nghien cifu anh hildng cua bao dilSng phii ni Iflng trong dieu kien khi hau Mien Nam, miia imJa va mua kho, den chat liidng cua b^ tong tiJ len diidc thde hiin. Ket qua chi ra rang, tang th6i gian bao difSng be tong tii 1 ^ bang phu ni 16ng se lam tang cUdng do chm nen cua be tdng.
Cu6ng dp chiu nen be tong td len bao dUdng trong dieu kien miia miJa se cao hon so vdi miia khd, nhiing van chiia dat diicfc gia tri cildng dd ciia miu ngam trong dieu kien nhiet do phdng.
Tii khda: Be tdng td len, ciidng dp chju nen, dieu kien khi h^u, nhi$t dp, dp am, phu bang ni long.
ABSTRACT:
Self compacting concrete applied for reinforced concrete structures with high reinforcement ratio in port, tall building and bridge can bring benifit to the project. However, quality of sefl compacting concrete is affected by climate condition and curing method. Therefore, a studymg the effect of curing method by covering nylon in MienNam's climate, rainy and dry seasons, was conducted. Inceasement covering time by nylon to cure sefl-comopacting concrete results in increasement its compressive strength. Compressive strength of sefl- comopacting concrete cured in rainy season is larger than that in dry season, but it is still smaller than that cured by soaking under water in laboratory condition.
Keyword; Sel-compacting concrete, compressive strength, climate, temperature, humidity, covering by nylon.
Ts.Ngiiyen Dinh Hung, ThS.AngeIi Doliente Cabaltica Trddng dai hoc Quoc te - Dai hoc Quoc gia Tp Ho Chi Minh Nguyin The At, Ts.Vfl Hong Nghiep
Tnfdng dai hoc GTVT TPHCM
1.Gidi t h i e u
Be tong t u len trong eong nghe thi cdng khong c6 eong doan taa rung dong de len chat be tong. Oe lam day van khuon bSng trpng iuang tan than no, be tong tU len cin dat khS nSng t d chSy cao dong thcJi kfidng bi phan tang. Be tong t y len thich hdp cho nhung Cciu ki§n yeu cau tdc dp do be tong nhanh va hoac cau kien co mat do cdt thep Icm 3b\ hdi y§u cau dp chiy Idn.
Bae trdng ca ban cua loai be tong nay la sd can bSng giOa do chay va sU khdng phan tang ciia be tong tdoi. Do do, gicim ham Idang cdt lieu th5, sil dung phu gia sieu deo va phu gia khoang vat min ddpc ap dung. Do do. cap phdi cua be tong tdlen cung cd yeu eau khac ve so vcfi be tong thong thi/img.
Mpt sd ket cau du cang, cot nha cao tang, ket cau eau co yeu cau ve Xk trong I6n, do do thdftng la cau kien co kich Ihddc Idn va cd tj le cot thep Iciti.
Viec sir dung be tdng t d len trong cac ket cau nay, dac biet d Idiu vuc Mien Nam noi ri&ng, c6 the mang lai giS tri kinh te cho cdng trinh. Cung giong nha be tong thddng, chait Iddng cCia be tong t d l^n cung Snh hddng bdi viec b3o dddng be tdng t d len" Mot sd nghien cijiu chi ra ring chat Idong ciia be tong t d len 3nh hddng bdi dieu kien khi hau. Calado^ et al. nghien cdU anh hddng ciia be t6ng t d l§n trong khi hau ndng. K^t qua chl ra rang cinh hddng cua dieu kien khi hau nong len be tdng t u len tuong t u nhd be tdng thddng, Nghien edu nay khong quan tam den dp am cua khong khi. Trong khi do, Stegmaier" nghien edu iinh hddng eiia gia nhiet trong qua trinh b^o dddng 3in chat IdOng ciia be tdng t d len. Ket qua ciing chi ra rang khi ty sd nddc tren xi mang (W/C) nhd bao dddng d nhiet dd cao lam tang chat Idongciia be tdng t d l ^ n . T u y nhien, neu tyisd W/C Idn thi bao dddng d nhiet dp cao lam giSm chat lupng cua be tong t d len. Trong nghien citu nay, dd am ludn ddoc dat d 100%. Khi hau d Mien Nam gdm 2 mua rd ret c6 nhi§t do va dd am thay ddi. Do dd, nghien edu viee bao dddng cila be tdng t d l e n dddi anh hddngciia dieu kien khf hau Mien Namgiiipchoc^i thien chat Idpng ket c^u be tdng sir dung t d len trong ket eau can dng, ket cau nhS cao tang va ket cSu cau.
De ke d^n 3nh hddng eCia khf hau Mi4n Nam den chat Idpng be tdng t d len Dieu kien khi hau mua mda va mua khd, bao gdm nhiet dd va 36 am, dupe sif dung lam he sd nghien edu trong t h i nghifm. Khi hau miia khd CO nhift Sd t d 3S°C den 40°C va dd ^nn tdSO% d^n 70%. Khi h§u mCia mda duoe md phdng la ed nhiet dp t d 2 5 ^ den BO'C v^ dp am tif 70%
den 80%. Sau khi be tdng ddoe do vao khudn 10x10x10 cm, mang ni long ddoe sit dung de phii l^n hi mat eiia m i u thCf lan Idot la 4gi6, 6gi6 va 24gi6 di kiem tra sd Jnh hddng eua thdi gian bSo dddng len chat lu'ong eda be tdng khi khi hau thay doi theo mua d IVlien Nam
2.Cap phdi v ^ dc dac t i n h cua be t d n g t d len
Cap phdi la viec chpn t j If cac vat lieu de thda man ceie tieu chi ciia be tdng d c^ trang thai be tdng tUoi hay khi be tdng ddng cdng. Odi vdi be tdng thddng va be tdng eddng dp cao, each xac dinh cap phdi gom da, cat, xi mang nddc va phy gia ddoe trinh bay trong c^c ti^u ehu^n""
Tuy nhi§n, hien nay van chda cd tieu ehuan eu the cho viec thiet ke cap phdi cho be tdng t d len. Rat nhieu nha nghien edu, cac vien nghien ciAi, dc cdng ty da t d phat trien cap phdi b^ tdng t d len cho rieng h p * " * . Trong dd, ty le the tich ciia cac thanh phan cdt lieu de t d di4n vao Id rdng
1 2 6 ^Xif^'BB^ 04.2017
cae hat edt lieu lan nhau ddoc ddng lam nguyen tac chinh trong thiet ke cap phdi ciia be tdng t d len. Mot sd phdOng phap thiet ke dp phdi cd gSng toi du ve mat thanh ph5n hat lUldt sd phddng phap lai tdi du ve dd chay va do on dinh trudc, sau do xem xet den vda xi mang trddc khi nghi den them cot lieu tho vao de thanh be tdng t d len. Tuy chUa cd phdang phap thiet ke cap phdi cu the, nhdng rat nhieu be tdng t d len ed t j le cap phdi nam trong khoSng ddOc li§t ke trong B^ng 3.1*', The tich eCia da dam td0,27 den 0,36 la hOl nhd. The tieh da dam l^i 50% ddOc sit dung trong cap phdi be tdng t d len eiia Aggarwal et al '*
Be ddpc COI la hi tdng t d l^n, thdng thddng mdt sd chl ti§u ciia bi tdng tdai n h d d d linh ddng, tinh nhdt, kha nang t d l^n vi sdc khang phan tang phSi thda man mdt gia tn n h i t dinh. Dp linh ddng c6 the danh gia theo dddng kinh tdchSy ciia bi tdng t d l^n khi do bang cdn sut, goi la do ch^y xde. Tinh nhdt ddpc danh gia bSng thdi gian ma dddng kinh ciia be tdng do bang cdn sut dat gia tn 500mm hoac do bang thdi gian be tong t d len chay het khdi pheu V. Khi nang t d len ddOe danh gia thdng qua kha nang be tdng t d chay qua khe ciia cac thanh cot thep trong hdp t h d L, Trong khi dd, sdc khdng phan tang ddpc danh gia thdng qua thi nghiem sang ray. Mdt sd tieu chuan khac cd the sddung them mdt sd thi nghifm khac de danh gia tdng chl tieu". Trong nghien edu nay, trddc khi thf nghiem, cap phoi b e t d n g tdl&ncOng ddpcxac dinh t h d dda vao cac chi ti^u yeu eau eho be tdng tU l^n nhd dp linh ddng thdng qua dd ehut chay, tinh nhdt thdng qua T500 va p h l u V, kh^ nang t d len thdng qua hdp L Oa sd cae thi nghiem^' ch? can xSc djnh cac dac tinh nhd dp linh ddng, tinh nhdt, tinh t d len de xac dmh la be tdng t d len.
Cac gia tri do 3i xSc dinh la bi tdng t d l l n trong de nghien edu eung cdsdkhae nhau.Trong cac tieu chuan WioSngdo nay cung r^t khac nhau.
Bdng 3.2 li§t ke khoiing eda gia t n do thddng ddpc diing trong cap phdi cua be tdng t d len trong eac nghien edu trddc"'. Gia tri dd chay xde khdng nhd hon 500mm de dam be tdng cd the t u chSy vao trong khdng gian hep cua van khudn, trong khi dd gia tri Idn hon ddpc gidi han de tranh suphan tang trong be tong.Tang thdi gian chay qua pheu V c6 the I n h hudng den tinh linh ddng cira be tdng, nhdng lai cd kha nang chdng phan tang cua be tdng t d len. Trong tieu chuan ciia chau Au^', thdi gian qua pheu V ed the cho phep len den 25 giay.
Bang 3.1. Cap phdi be tong t d l e n "
Thanh phan vat lieu Phu gia khoang vat Vila xi mang Nddc Cdt li§u thd Cdt lieu mm (cat) Ty le nddc/phu gia khoang vat
Khdi lirong 380-600
150-200 750-1000
The tich
150-200 270-360 Can bSng t h i tfch vdi cac vdt l i l u khSc, khoang 48-55%
1 0,85-1,10 BAng 3.2: Bang cac chi tieu trong danh gia b§ tdng t d len
Phu'cmg phap thuT Od chay xde T,™
PheuV HdpL(H2/Hi)
Khoang 500-700 (mm) 2-5 (s) 6-12(3)
£0,8 3.Thi nghiem
3.1 .Trang thiet bj va vat lieu
May trdn cddng bile cd dung tich 250 lit duac sd dung de trdn be tdng trong t h i nghiem nay. Cdn sut, pheu V va hdp L ddOc diing de do cac dac tinh ciia be tdng tdoi di xic dmh b l tdng la be tdng t d len. Sau khi due mau be tdng ddoc bao dddng bSng tii bSo dddng Mau ddpc bao
dddng 28 ngay va ddpc nen bdi may nen be tdng. Ni tdng dung de che phu mSu trong qua trinh bao dddng.
Chat Idong eda be tdng t d len phu thudc vao chat Idpng cua cac nguyen vat lieu thanh phan. Oe sd dung chung mdt each h i l u qua, vat l i l u trddc khi sddyng can ddoc Ida chon, kiem tra chSt Idong va ddOc lam sach. XI mSng diJng trong betdng t d len la xi mSng Pooclang hon hc^.
Trong be tdng t d len viee sd dung phu gia khoang vat ed ham Idpng hat min (bdt) Idn ihm tang dd nhdt d i o cua b l tdng t d l l n . Phu gia khoang vilt la tro bay (FA) cua nha may nhiet 3\ir\ Vinh TSn d Ninh thuan. Vi§c sd dyng tro bay nay trong nghien edu va hu'dng den sd dung rpng rai gdp phan giai q u y l t v3n d l mdi trddng. Kht c h l tao b l tdng t d len, phu gia silu d i o giup cho giam ham Idpng nddc va giam cuon khi d l tang eudng dd cua be tdng. Yeu cau ddi vdi phu gia siiu d i o dung cho be tdng t d l^n ngoai vile tang dd chay eiia hon hop be tdng edn phai ed kha nang duy tri tinh cdng tac theo thdi gian. H i f n nay, phu gia si§u ddo gdc pal yea rboxy late cho kha nang duy tri tinh cdng tac cua hdn hop be tdng t u len cao hon so vdi eac loai phu gia khac
Cdt l i f u ddpc phan ra lam hai loai, cdt l i f u nhd (cat) va cdt lieu thd (da dam). Cdt lieu dung de thi nghiem d l u edt lieu dia phuong lay t d sdng Ddng Nai. Cdt lieu thd la loai da xanh den, khai thac d eie md da d d Binh Dddng. Cac edt lieu ddOc rda sach va say khd den khdi luang khdng doi trddc khi dd bi tdng. Do hut nddc ciia eat va da dam ddOc thi nghiem theo tieu ehuin ASTM CI 28" lan Idot la 1,6% va 0,1 %. Ldpng nddc hdt am cCia cat va da dam phai dddc ke den trong qua trinh thf nghiSm. Cat ddoc ddng d l thi n g h i l m cd kich cd lot qua cd sSng No,4 {4,75mm) va gid lai trin ed sSng No. 200 (0.075mm). Mddun do min eda cat ddac xac dinh theo tieu chuan ASTM CI 25 (2007)"" la 3,05. Khdi Idong the tich eda cat va cOa da ddoc do lan Idot bang thung 3 lit vi 1S lit I3n IdOt la 1546 kg/m^
va 1302kg/m'. Khdi IdOng neng cua cat va da dam ddpc do bang binh ty trong nhd theo ti^u ehuan ASTM CI 28" lan Idot la 2.67 t a n / m ' va 2,65 tan/m^. Trong betdng thddng edt lieu thd c h i l m 65-75%*' the tich va ddng mpt vai trd quan trong ddi vdi chat IdOng cua betdng nhdiam giam gia thanh, tang dd dn dmh cua be tdng Tuy nhi§n trong be tdng t u len, de dam bSo tinh ehat t d len, ham Idong edt lieu Idn ddac diing it han so vdi b& tdng thddng. Trong cac cap phdi nay the tich da dam ddoc lay la 45%. Hon nda. de tang kha nang t d chiy, t d len eda be tdng t d l^n phu thudevao kich thdde kich cd hat Idn nhat ciing han che. Cdt lieu thd ddpc sddung la loai cd kich cd hat Idn nhat bang 15mm. K i t hop vdi viec xac dinh cac d^c tinh ciia cac thanh phSn edt l i f u , cSp phdi eda be tdng tLE len ddOc xac djnh dda tren c§n bang the tich nhd trong Bang 3.3 Trongdd, cap phdi CI ddOc do t h d nghiem dau tien. Cap phdi C2 va C3 du'dc dieu chinh d l be tdng ddoc eoi la be tdng t d l l n . Ham Idong tro bay dung d l thay the cat mm la 16%'".
3.2.Cac budc t h i nghiem
Sau khi cac dac tinh eda eae vat lieu thanh phan trong cap phdi dupc xac dmh Cae thanh phan vat li^u duac can dong theo cap phdi. Cac thanh phan ddpc trdn theo mdt quy trinh nhat dinh dUoe I h i l t ke phu hop tr^n CO sd kinh nghiem thdc t l vi thuc nghigm. Trddc tien cho cat, xi mang, tro bay vao may trdn trddc trong thdi gian 30 giay. Nddc ddpc trdn thSm vao trong vdng 30 gray tiep theo khi may trdn van dang trdn. May t l l p tue trdn vda xi mang. cat va nddc them 1 phdt. Ket thdc qua trinh nay, da ddoc them vao va tiep tuc ddpc trdn them t d 2 den 3 phut den khi cae be tdng duac trdn deu
Bi tdng t d len ddpc k i l m tra dp chay xde bSng cdn sut theo tieu chuIn ASTM CI 43"'.Thi nghiem nay cSn do thdi gian khi dd chSy xde dat dudng kinh 500mm la bao nhieu giay va gia tn dd chay xde cudi cung Tiep sau dd, be tdng t d l l n ddpc kiem tra thdi gian chSy qua pheu V va tf' sd glda chieu cao be tdng HVHi trong hdp L Be tdng ddoc do vao khudn de tao mSu eho viec xac dmh cddng dp chjU nen. Trong moi me tron, be tdng t d l l n ddpc dd vao 4 to hop khudn ed kfch th dde nhd TCVN 239- 2006'", mdi khudn gdm 3 m i u . Trong dd, 01 to hop khdng ddOc ehe phd d l lam mSu ddi chdng. 03 t d hop con lai ddoc ehe phd ni Idng. Ca 4 td
04.2017 BWiliEflBai 1 2 7
hop sau do ddOc chuyen ngay vao tu dddng am. Ni Idng se ddpc th^o ra sau khi da che phd dddc lan Idpt 4 gid, 6 gid va 24 gid.Td di/dng am dddc dat dieu kien theo mua mda va mua nSng eua khi hau Mien Nam. Cddng dd ehiu n l n cua be tdng t d len dUoc xac dmh tai cac thdi diem 3 ngSy, 7 ngay va 28 ngay. NhdOc d i l m eda thi nghifm ngay la van chda ke den i n h hudng cua gid thdc the ngoai cdng trddng.
3.3.Ket qua va phan tich
Bing 3.4 liet kg ket qua do cae dac tfnh eiia be tdng tdoi Cap phdi CI ddac t h d nghiem dau tien de xac dinh be tdng t d len Ket qua do cac dac tinh eda be tdng tuai cho thay thdi gian dat TSM nhd hon 2 giay va thdi gian chay qua p h l u V nhd hon 6 giay. Hon nda, trong qua trinh do mau h i f n tupng phSn tang kha rd ret. Do dd, cap phdi CI chda phai la be tdng t d len. Sau dd, cap phdi C2 va C3 ddpc d\ t i l n . Ket q u i do cac dac tinh trong gian doan b§ tdng tdOi deu nam trong gidi han trong Bing 3.2 Trong qua trinh thi cdng mau due, hien tdong phSn tSng khdng rd ret. Do do, cd t h i khang dinh cap phdi be tdng C2 va C3 la cap phdi cua be tdng tdlen.
Ket qua nen cua tat ca dc m i u ciia cap phdi C2 va C3 d cac thdi diem 3 ngay, 7 ngay, 28 ngay nhd ddoe liet ke trong Bing 3.5. Ket qua thi nghiem eho thay, sd phat t r i l n cddng do betdng phu thudc rat Idn vao thdi gian b i o dddng betdng, dac d i l m khf hau ddpc dac trung bdi cac thdng sd nhift dd va dd am eiia khi h i u thi cdng, ty sd W/C. Ddi vdi mdi ty le W/C trong cac miia, d thdi diem 3 ngay, khi thdi gian phu ni Idng bao dddng tang t d 4 gid, 6 gid va 24 gid, ket q u i cddng dd ehiu nen khdng cd Sd thay ddi dang ke, Oieu nay la do, trong giai doan d i u , tdc do th6y hda cua xi mang gida cac mau thif chda cd sU khac biet nhieu lam. Khi ty le W/C giam td0,4 xudng 0.35, cddng do chiu nen trung binh d thcrt diem 3 ngay cung tang l l n l i n idot la 12,9% va 13,9% trong miia khd v i mua mda.
Tai thdi diem 7 ngiy, cddng dp chiu nen cua betdng tang len khi thdi gian bao dddng t i n g len trong t i t ca cac t^ le W/C va trong cac mda ddOc t h d nghiem.©leu do chdng td vifc k l o dai thdi gian bao difdng b l tdng b i n g phu ni Idng da g i d ddpc nUdc tdt hon cho qua trinh thuy hda tif 3 ngay den 7 ngay. Trong mdi ty le W/C d ca hai mda, cddng do chiu nen c i c mau dUpc b i o dddng tai 6 gid Idn hon mSu bao dddng 4 gid khdng dang ke. Trong khi dd, cddng dd ehiu nen ciia cac mau dupc b i o dddng 24 gid d l u dat gia tn cao n h i t .
Bing 3.3. Cap phdi cua be tdng t d l l n cho
d l l m 3 den 7 ngay d mua khd cao han mua mua. D i l u dd d i n den lam cho tdc do thuy hda eda xi mang trong be tdng gia doan dau ddac bSo dddng d miia khd nhanh hon so vdi tdc do thiiy hda trong b§ tdng di/pc b i o dudng trong mCia mda. Do dd lam cho cddng do be tdng giai doan dau t d 3 d i n 7 ngay cua b l tdng ddoe b i o dddng d mua khd eao hfln so vdi mua mda.
Bing 3.5 CUdng do chju n^n cua b& tdng
m i n g (kg)
NUdc (lit) (kg)
Phu gia si#u d i o (kg)
Bing 3.4 Cac d i e tinh eda Ccip phdi
CI C2 C3
Bochiy xde (mm) a 500 600 590
be tdnq tda T«,»(s)
< 2 3 2
PheuV (5)
5 7 9
HppL (H,/H,) 1 1 1 Bing 3.5 cung chi ra r i n g cddng do chiu nen trung binh ciia cac mlL dddc b i o dddng trong d i l u kifn khi hau mua khd Idn hon gia tn trung binh d mda mda d edng ty le W/C d c i thdi ffiem 3 ngay v i 7 ngay. Gii tri cddng dp chiu nen trung binh d mua khd tai thdi diem 3 ngay khi ty If W/C la 0,4 va 0,35 l i n Idot la 32,8 MPa va 37 MPa. Trong khi dd gia tn nay tai miia mus l i n Idpt l i 31,6 MPa va 36,0 MPa. G i i tri cddng dp chiu nen trung binh d mua khd tai thdi diem 7 ngay khi t f I f W/C la 0,4 va 0,35 lan IdOt la 42,7 MPa va 43,8 MPa. Trong khi dd g i i tri nay tai miia mda lan IdOt la 36,7 MPa va 42 MPa Oieu nay xay ra la do nhiet dp b i o dddng tai thdi
Mua
Mua khd Tn,= 35- 37"C; W =
50-70%
Ttb= 25- 28''C; W =
70-90%
W/C
0,40
0,35
0,40
0,35
•
nilon
4 gid 6 gid 24 gid Ogid 4 gid 6 gid 24 gid Ogid 4 g i d 6 gid 24 gid Ogid 4 gid 6 g i d 24 gid Ogid Ogid
Cu'dng dd chju nln{MPa) 3
ngay 35,4 30,8 32,1
36.2 36.9 37.9
32.6 31.1 31.2 30.5*
36.7 36,5 34.8 31.4*
7 ngay 42.2 42.3 43 6
43.4 43.6 44.3
35 5 36 5 38.2 3 6 1 * 40.4 40.6 45.1 41.9"
28 ngiy 43,0 44,8 45,7 40,1*
45.3 44.0 47.S 45.2*
42.9 44.5 47.4 41.2*
45.3 47.2 47.9 46.8*
52.1**
GhichO ' Khong phi ni-longva bio trong ciing dieu hen
*": Khdng phu ni-ldng Se trong giea hen nhiet do phong I ngdy, sau khi gd khuon Ihi ngam trong nddc Sdieu khien phdng 27 ngdy
Tuy nhien, ket qua nen tai thdi d i l m 28 ngay chl ra rSng. cdong do chiu nen t i n g l l n khi tang thdi gian phii ni Idng d tat c i cac ty le W/C trong ca 2 mua. Ngoai t r d trddng hop tai mua khd vdi t? 11 W/C = 0,35 eho thay cddng dp chiu nen eua mau phd 6 gid (44,0 MPa) nhd hon mot chiit so vdi mau phu 4 gid (45,3MPa). Bieu n i y cd the do c h i t Idong vat lifu khdng ddng d l u . Cac trddng hop khac, cddng dd chiu nen cua mau phu 4 gid deu nhd han mau phd 6 gid. Cung gidng nhd trong trddng hop 7 ngay, eddng dd ehiu nen cua m i u ddoc b i o dddng phii 24 gid la cao nhat. Khi ty le W/C g i i m , cddng dd chiu nen d l u tang len d c i hai mda Cl thdi diem 28 ngay, k i t q u i cho thay eddng dd chiu n l n d miia mifa Idn hon so vdi mua khd Dieu dd chdng t d , sau giai doan 7 ngiy, khi nhiet do tang cao ket hap vdi do am khdng khf thap da I i m cho nudc trong b&
tdng bdc hoi nhanh hon. D i l u dd dan den lam g i i m luang nddc cho qua trinh thiliy hda t i l p theo eCia xi mang trong be tdng sau 7 ngay. K^t quS l i Cddng dp chm n l n cua mtia khd nhd hon mda mda d c i i n g ty^ If W/C.
Thinghiem be tdng b i o dddng trong mua mua ddac tien hanh trddc.
Do han che ve sd IdOng khudn, ngn mSu ddi chdng khdng boc ni Idng tai thdi diem 3 n g i y va 7 n g i y trong dieu kien mda khd khdng dddc thi nghiem. K i t qua chl ra r i n g , cac mau di/oc b i o dddng phd ni tdng co Cddng do ehiu nen tai thdi diem 28 n g i y trong mua khd cao hon so vdi m i u ddi chdng khdng dddc phu ni Idng. Ddi ydi trddng hop mua^ mda.
cac mau dupc b i o dddng phii ni Idng da sd deu cao hon so vdi mau ^ i chdng trong cdng d i l u k i l n . T i t c i cic mau dddc phu ni Idng 24 gid deu ed cudng dd chiu n l n cao hon mau ddi chdng trong edng d i l u kiln khf
h i u . Mdt t d m i u lam m i u ddi chdng khdng bpc ni Idng, nhdng sau 24 [13] TCXDVN 239'20O6 (2006)'B§ tdng nang. Chl dan danh gia cddng dd gid d l d d i l u k i f n phdng thi ddoc ngam trong nddc d d i l u k i f n nhiet dp bi tdng tren ket cau cdng trinh.
phdng t h i nghiem. K i t q u i x i c dmh cddng dd chju n l n tai thdi diem 28 Ldi c i m On
ngay dat cddng dp l i 52,1 MPa. Gia tri nay Idn hon g i i tn eda mau ddOc Nghien edu n i y ddpc Trddng Oai hpc Qudc te - OHQG-HCM tai trp phu ni Idng trong 24 gid d t i t ca cac mau thf n g h i f m . Cd the ndi mau ddi trong d l t i i cd ma sd T2016-02-CE
chdng dUde ngam nUde iam ngan c i n sd mat nddc trong mau. Do do cddng dd chiu n l n eda m i u nay la Idn n h i t . D i l u dd cd nghia la cac be tdng dUdc do trong dieu kien mua mda hay miia khd deu cd eddng dp chiu nen khdng the Idn han gia tri eua betdng tdong tuduoe ngam trong nddc trong dieu k i f n n h i f t dd phdng thf n g h i f m . Theo k i t q u i t h i n g h i f m nay, eUdng dd chju nen cua be tdng ddpc b i o dddng phd ni Idng trong 24 gid trong d i l u k i l n khf hau mua mda chl b i n g 92% eddng do chiu nen cua m i u n g i m nddc 28 n g i y trong d i l u kifn n h i f t dp phdng t h i n g h i l m va cao hdn so vdi gia trj cddng dp chju n l n trong dieu kien khi hau mda khd.
4.Ket luan
Dda tren v i f c d i n h gia c i c d i e tinh trong giai doan b§ tdng tdOi, cd the chap nhan cap phdi be tdng C2 va C3 lan Idpt cd ty le W/C = 0,4 va 0,35 trong thi n g h i l m nay l i be tdng t d len. Khi ty If W/C g i i m thi cdcmg dp chiu nen tang Ign.Odi vdi giai doan trddc 3 n g i y , anh hudng eda v i l e bao dddng phd ni Idng t d 4 gid, 6 gid va 24 gid len cddng dp chiu nen ciia be tdng t d l^n la khdng rd ret. Td thdi diem 7 ngay t r d di, thdi gian bao dddng phd nl Idng tang t d 4 gid, 6 gid d i n 24 gio se lam cho cddng dd chju n^n ciia bi tdng t d len tang len. Ket q u i cung chl ra rang tai thai gian trddc 7 n g i y , be tdng t d l e n ddOc phd bao dddng t d 4 gid den 6 gid trong dieu kiin mda khd cd cddng dp chjU n l n eao hdn so vdi mua mda.
Oieu nay l i do n h i i t dp cao d miia khd lam cho t6c dd thdy hda nhanh han.Tai thdi diem 28 n g i y , t i n g thdi gian phO ni Idng se l i n g cddng do chju nen cua mau. Cddng dp chju nen tai thdi diem 28 ngay cua mua mda cao han so vdi cudng dd tai mda khd va cao hon so vdi mau ddi chdng khdng phd ni Idng va ddpc dat trong cdng dieu k i f n ve khi h i u la mua mda hay mua khd. Tuy nhien, g i i tri n i y van nhd ban so vdi cdiftig dd chiu nen eua mau khdng phd ni Idng v i n g i m trong nddc d dieu kien n h i f t dp phong.
TAILIEUTHAMKHAO
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