Nghien CLPU che tao be t o n g cot so*! chat liFO'ng sieu cao d u n g c h o k i t cau dac biet cua nha sieu cao t a n g Study of producing ultra-high performance fiber reinforced concrete for special
structures of super-tall buildings ^^^^^^__ „
Ngay nhan bai: 15/9/2014 Ngay sLfe bai: 5/11/2014 Ngay chap nhan dang: 10/12/2014
Tdm tdt:
Trong xiy diing nha sieu cao tang, vat lifu xay diing can thiet phai co chit lU^ng dam bao cho Icha nang chju liic dac biet ciia no; trong do be tong sii dung cho cac cong trinh niy thudng phai la loai co chat lildng cao. Tuy nhien, left cau cho cac cong trinh nay rat da d^ng, trong do co loai cau kien phai co sM deo dai, tinh dong nhat cao di chiu tai trong dpng hay kich thu6c rat mong tham chi khong the bo tri diioc cot thep ldn nen thiidng phai dung vat lieu kim loai. Vi?c sil dijng kim loai lam tang tai trong va tang gid thanh c6ng trinh l^n rlt nhieu va tuoi thp co the bi suy giam do k^m bSn an mon.
Xult phdt tii thiic tien tren, de tai nghien ciiu che logi be tong cot spi chit liiong sieu cao vdi cii6ng d6 nen ldn hon 150 MPa va cifdng dp uon tren 35 MPa. Logi be tdng nay khdng nhiing lim giam kich thiidc cau kien ma con co the giam lifPng cot th^p, thgm chi khong can cdt thep nhii hi tdng cot thep truyen thong, day se la vat lieu rat hi?u qua sii dyng cho cac ket cau mdng, diic sSn cua nha sieu cao tang.
Tii khda: nha sieu cao tang, b^ tdng chat lUpng sieu cao, be tong cdt spi.
Abstract:
For super-tall buildings, materials, i.e. concrete, used need to be ensured a good quality for its special bearing capacity . However, the development in construction technology covering various structures, materials applied in these buildings makes it possible to create components with a high flexural toughness, a high uniformity to bear dynamic loads, or to make very thin shell structures. In fact, reinforcing bars even can not be used in these very thin shell structures, and metal has to be used to make these structures. The use of metal will increase the loads, costs, and reducing the service life caused by corrosion. This paper presents some exprimental studies in making Ultra High Performance Fiber Reinforced Concrete with compressive strength of over 150 MPa and flexural strength of over 35 MPa. This concrete not only reduces structural component size, but also can reduce the amount of reinforcement, even without reinforcement as traditional reinforced concrete. It will be very effective materials used to produce precast, thin shell structures of super-tall buildings.
Key words: super-tall buildings, ultra hight Performance, Fiber Reinforced Concrete Pham Hiiu Hanh - Bd mdn vgt li?u tnidng Dai hpc xly diing.
Email [email protected]. vn DT: 0903263129
Nguyen \ ^ "nian, Nguyen Cong Thing Khoa Vat lieu xay diing, Trifdng Dai hpc Xay di/ng
Pham Hu'u Hanh, Nguyin Van Tuan, Nguyen Cong Thang
Dan so the gidi ngay cing phat trien va vdi xu the toan cau hda, do do Imh vac xSy dirng vci cac cdng trinh dap iJmg nhu cau nhi d, van phong, thuang mai va djch vu ngay cang tang.
Nha sieu cao tang (Super-tall buildings- theo dinh nghia cua CTBUH (IJ co chieu cao tren 300m) la phuang an tdi Uu de xay dung cac ngoi nha vdi nhu'ng chu'c nang da dang do de dap ung yeu cau nghy cang cao trong xay diitig dan dung. Xay dung nha siSu cao tang con lien quan den viec hlnh thanh mdt si^u do thi phat tri^n mang dSng cap ve kien true. Do dd, phat trien xay diing nha si^u cao tang tren the gi6i ngay cang tang. Den nam 2010 cd 39 toa nha, tLf 2010 den 2014 co them 46 toa nhi dUdc xiy dung them, va rieng nam 2014 da hoan thanh dupc 11 toa nh^ [1 ]. 0 V\it Nam mdi co 06 tda nha cao tang (tren 200m) vci trong do co toa nha Keangnam cao tren 300m.
Vat lieu cho ket cau nh^ sieu cao tang chu yeu la thep, be tdng cdt th^p vh hdn hpp thep- be tdng cdt thep ket hpp. Trong do be tflng cot th^p duac sil dung chu yeu nhiing nd cd nhi/pc diem la nang lam tang tcii trpng cho tda nha, nhan cong Idn v^ thdi gian thi cdng dai. Trong thuc te viec sii dung be tdng chat lupng cao vdi muc dich la giim kich thudc cCia cau kien tCf do giSm tk\ trong cua ket Ctiu la mdt phuong ^n hieu quS, dong thdi mang lai Ipi ich v^ md rdng khdng gian sCr dung, va giam chi phi duy tu d^i han. Tuy nhien, loai bd tdng nay van chua d^p ifng dupc y^u cau ddi vdi mdt sd kft cau dac biet cOa nhd si^u cao tang la can cd cUdng do rat cao, do ben Idn va kich thudc rat mdng. Xuat phat tCr nhifng ca sd tren, de tai dua ra hudng nghien cdu loai be tdng nen chat lUpng sieu cao (BTCL5C- Ultra High Performance Concrete) vi sau dd phoi hpp vdi spi thep d^ ducjc loai be tdng cot spi chat lutmg sieu cao (BTCSCLSC-Ultra High Performance Fiber Reinforced Concrete) [2-3]
vdi cudng dd n^n I6n hon ISO MPa, va cudng dd udn Idn hon 35 MPa, do rdng rat thip vi dd ben deo dai cao. Vi^c sd dung BTCSCLSC se hudng tdi viec gidm hay thSm chi \h loai bd cac thanh cot thep trong ehe ket cau dac biet ciia
82BiininDt'i 11-2015
Being 2.1 Mdt sd t i n h c h i t co ly cila vat lieu sd dung
STT
1 2
Chi tieu t h i nghiem
Khdi lupng ridng Dudng kfnh cd hat trung binh
Dtfnvi
g / c m '
| j m
Ham luang, % Cdt
2.65 180
Xi mdng
3.15 11.4
Silica fume 2.20 0.15
X i l d cao 2.94 7.2
B3ng 2.2 Cap phdi BTCLSC sd dung trong nghien cOu Ky hieu
CPI CP2 CP3 CP4 CPS CP6 CP7 CP8 CP9 CP10
N/CKD 0,15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15
Cat/CKD 0 9 0 9 1.0 1.1 0.9 1.0 1.1 0.9 1.0 1.1
SF/CKD, %
10 10 10 10 10 10
BFS/CKD,%
40 40 40 20 20 20 30 30 30
PGSD/CKD, % 1.0 1 0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
CKD, kg 1237 1223 1169 1120 1210 1157 1108 1206 1154 1105 Bdng 2.3 CSp ph6\ hi tdng chat lUpng sieu cao sd dung cdt soi phan ta
KV hidu FO Fl F2 F3 F4
CKD, kq 1206 1194 1182 1170 1158
N/CKD 0.15 0,15 0.15 0.15 0.15
Cat/CKD 0.9 0.9 0.9 0.9 0.9
SF,%
0.1 0.1 0.1 0.1 0.1
BFS,%
0.3 0.3 0.3 0.3 0.3
n trong nghidn cUu S D %
1.0 1.0 1.0 1.0 1.0
Sdi thep, % 0.0 1 0 2.0 3.0 4.0 nha sieu cao tSng [4].
I.Thi^t k £ t h i n h phan be tong 1.1V4tll4usddvng
Xl mdng: Xi mSng dUpc sd dung trong nghidn cdu Ici xi m i n g Nghi Son PC40 vdi cudng dd ndn d tuoi 28 ngdy 48 MPa vh dc tinh chat ky thuat dat tidu c h u i n TCVN 2682-2009.
Cot lidu mjn: Cdt li^u min sd dung la cat thach anh nghlSn cd hat nSm trong khodng 100-600 pm.
Silica fume: Oi tdi da sd dung silica fume dang hat rdi cua Cdng t y Elkem cung cap co chi sfi hoat tinh cudng d d 110%.
XI16 cao; De tdi sd dyng xl 16 cao Hda Phat vdi chi sfi hogt tfnh cUdng d d 98%.
Tfnh c h i t CO \'f cCia v^t lieu s d d u n g t h i hidn
Htril>ri>nBClt.|%)
Hlnh 2.2 Oo IJn chSt cda hfin hap hat gom: Cat - CKD (XI d Bdng 2.1,
Cdt spi thep: Soi thep loai soi OLl 3/0.2 c h l l u ddi 13mm, dudng kfnh 0,2 m m , luc keo ddt 2750 MPa.
Ngodi ra, nghidn cdu nay cdn sd dung phu gia hod hoc ciJa hang BASF, day la loai phu gia sidu ddo gfic polycarboxylate.
2.2 Thiit ki^dnh phdn bi tdng BTCLSC Trong nghien cdu nay sif dung md hlnh do De Larrard d l xuat d l tinh toan [5], vdi hd hdn hop hat gfim 3 cdu t d bao gdm Cat - Chdt k i t dinh (gfim xi mdng va phu gia khoang), trong do h^ sfi n^n K dugc lay bdng 12.5 theo de x u l t ciia Jones vd cdc cong sU[6].Thfing thudng, phu gia khoang Id silica fume vdi ham lupng thay ddi 10-30%, day Id loai vat lieu phdi nhap ngoai vdi gia thdnh cao,Trong nghien cdu nay cd dinh hdm lupng silica fume la 10% do sU dnh hudng c6 loi d i n cd ttnh cfing tac va cudng do nen ciia BTCLSC[7].Trong hon hop hated s d d u n g thdm phu gia khoang la xl Id cao trong thanh phan cila chat k i t dinh hfin hop, ham lupng sd dung thay dfii tdO-40% [8].. K i t qua do ldn chdt cCia he vdi 3 c3u t d bao gfim hdn hap hat gom Cat - Xi mang - PKG {PGK = SF + BFS, SF = 10%) dUOC t h i hidn d hlnh 2.2:
Dua t r i n k i t qud tinh toan thi iuong dCing hpp ly duoc xdc dinh vdi t^ Id dupc tien hdnh khdo sdt cdc cap phfii BTCLSC vdi t ^ Id thdnh phan vat lidu dupc cho d bdng 2
TCr cdc k i t qua nghien cdu trong phdng t h nghidm (phan 3.1) de tdi da chpn cap phfii bt tong chat lUOng sidu cao dat cdc tinh chdt tfii nhdt Id CP8 de khao sat nghien cdu vdi hdn- luong soi thay ddi n h u bang 2.3.Tren co sd nd) de tdi nghien cdu anh hudng cda ham lupng sp thdp phdn tan d i n cac tinh chat cila BTCSCLSC (phan 3.2).
2. Ket qud va binh l u i n J . 1 Bi tdng chdt lUUng aiu cao 3.1.1 Tinh cdng tde cCia hon hap bi tdng Ket qud thi nghiem tinh cong tdc cua hdn hop BTCLSC the hidn d Hinh 3.1. Qua ket q u i thf nghiem ta thay khi co mat cila phu gia hoai tfnh hon hap (silica fume va troxl) Idm tang tinh d^o cCia hdn hap be tdng, Idn nhat Id d CP2 Idr khodng 12.8%. Dieu ndy cung gidi thfch khi cd mat cila phu gia hoat tinh qua trinh phdn bfi vi bdi tran tham udt cua chat ket dinh, cung nhu cdu trdc cua he tot hem. Dieu ndy cung phii hap trong viing nghien cdu vi khi tang ham lUpng phu gia hoat tinh t d 30% len 40% da cdi thi^n hon hap be tdng tang mac du khdng Idn nhung dudng kinh trung binh do chay loang cila hfin hap be tong deu Idn han 200 mm, trong khi dfi ham lupng nay la 30% van co trUdng hap do chdy khong dgt yeu cdu d CP7.
Khi efi dinh hdm lupng phu gia khodng thi t^ \i C/CKD tang thi tinh cdng tac cila hon hpp bd tong gidm nhU qui luat thong thudng, tuy nhien trong pham vi khdo sat thi tinh cflng tdc cila hfin hpp bd tfing thay doi khfing n h i l u .
Hlnh 31 Anh hucing cUa phu gia khoang va ty le C/CKD Sit tinh cong ticcis) hSn hcip be tfing
Khi sd dung phu gia khoang hoat tinh v d loai khde nhau thi xl 16 cao cdi thidn tinh cflng tdc cua hfin hpp bd tflng tot hPn so vdi khi sC dung silica fume. Dieu nay cung gidi thfch dc dfi mm cila silica fume cao hon, mat khac thdnh phdn cCia xl da sd ta pha thuy tinh ddc c h i c ndr lupng can nudc nhd hon vdi loai be tdng chl si!
dung 40% xl Id cao do chdy 228 mm, trong kh dfi neu sd dung hdn hpp 30% xl Id cao vd 1 0 * silica fume do chdy loang giam xudng 218 mm, Nhu vay, neu chi xet ve tinh cflng tdc thi b3i budc phdi sd dung them phu gia khoang hoai tinh {neu khdng sd d y n g do chdy loang thdp 178 mm). Trong cdc trUdng hpp sd dung p h i gia khodng hoat tinh vcfi hdm lupng den AO'H tdt cd cac cap phdi deu dat do chdy trdn 20C m m ; con khi s d d u n g phu gia hoat tinh vdi hdn- lupng 30% chl cd cap phoi vdi hdm lupng cd' cao (ty Id C/CKD= 1.1) Id khflng dat dfl c h i y thee yeu cdu. Ddc biet, khi cap phfii bd tflng sddunc
40% phu gia hoat tinh (trong d d chua 30% xi Id cao) thi hdn hpp vda dat tinh cdng tac vda dem lai hidu qua kinh te va moi trUdng rat phCi h p p vol xu hudng phdt trien xdy dUng ben vOng hien nay.
3.1.2 Cudng do nin eua be tong chdt luong siiu cao
Ket qua cudng d p nen cua BTCLSC the hien d Hlnh 3.2. Ket qud cho thay cudng do nen cila BTCLSC khi khdng sd dung phu gia khoang hoat tinh hodc chi sd dung xi Id cao thi cudng do nen d cdc tudi 28 ngay va 90 ngay deu nhd honlSOMPa.
Khi ham luong phu gia khoang sd dung den 30% (trong do silica fume 10% vd xi 16 cao 20%) d i u dat cudng d d 150 MPa d tuoi 90 ngay, cudng dd n^n chi ridng mau cd t y Id OCKD Id 1.1 d tudi 28 ngay la khflng dat (141.5 MPa)
Cdc mau be tflng khi sd dung phu gia khodng hoat tinh den 40% (trong do silica fume 10% va xi Id cao la 30%) chi cd mau bd tfing CP8 dat cudng dfl 150 MPa d tuoi 28 ngdy.
sd dung trong hdn hpp bd t o n g thi t i n h cdng tac eiia hon hpp bd t d n g gidm. Trong k i t qud nghien cdu cda de tai, khi ham lUpng sai tang d i n 4 % thi tinh cflng tac cda hdn hpp be t d n g gidm t d 22Smm {vdi mau ddi chiing) xudng cdn 195 m m (gidm 15% so vdi mau dfii chdng). Dieu nay cd the thay vide thi cflng loai be tflng cd ham lupng soi thep 4 % Id rat khd khan.
NhUvay trong dieu kien cdng n g h d t h U c t e de xuat ham lUOng spi dung trong be tdng tdi da id 3%.
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u , , , .
f
1
11
Hlnh 31 Cudng 66 nin cua be long (hit lumig sieu cao Bdn c^nh dfi k i t qud ciing chi ra rdng su phdt t n l n cudng dfi bd tdng tdng theo thtii gian, tuy nhidn d tuoi sdm, cudng dfl ndn cua BTCLSC tdng nhanh han so vdi bd tong thflng thudng. Khi sd dyng phy gia khodng trong bd tfing, n l u sd d y n g chi ndng xi Id cao, cudng do bd tdng phdt t n l n chdm hon so vc6 khi sd dyng hfin hpp 2 lo^i phy gia khoang silica fume va xi 16 cao.
Nhu vdy, neu xdt theo cac tinh chat ca \y thi CP8 efi tinh cfing tdc tfit vd cudng d p nen d tuoi 28 ngdy dat 1 SOMPa. Xet theo khia canh kinh te thi CP8 efi tong lupng dung cua phy gia khodng Id ldn nhdt, trong trUdng hpp nay Idn den 40% d l c h l tao BTCLSC. Oieu nay mang lai y nghTa Idn v l vi^c ddng phy gia khodng thay the xi mang d l c h l t^o BTCLSC trong vide phdt t r i l n ben vdng dfii vdi lo^i bd tfing nay. Tren co sd ndy de tai lua chon CPS Idm cdp phdi nen de nghiSn cdu i n h hudng cua efit sai thep phan tdn d i n edc t i n h chat cP ly cda hdn hop be tdng vd BTCLSC.
3.2 Bi tdng chdt lupng sieu cao sd dung cdtseiphdntdn
3 2.1 Anh hudng cua ham lugng sc^ den tinh edng tdc eua hdn hgp tx tong
K i t qud t h i nghiem tinh cdng tdc eda hon hop bd tdng dupc the hidn d Hinh 3 3 . K i t qud t h i nghidm cho thay khi dua spi thep vao thi tinh cfing tde eua hon hcrp bd tdng gidm so vdi mau ddi chdng khfing cd s d . Khi tdng ham lupng spi
L L L
Hinh 3 3 Anh htfcing o i a ham luong siH den tinh cong tac cua hon hop be tong
3 2.2 Anh htfdng eua ham lugng spJ' den cudng do nen cua bi tong chat luang siiu eao
Ket qua ve anh hUdng cda ham lUpng spi den cUdng do ndn cCia BTCLSC dUpc the hien d Hinh 3.4.
li
HSnilmTngsoKltlHinh 3 4 Anh liU<fng cua ham lUffng sdi ttiep den ctrtmg do nen ciia erase
Dua vdo k i t qud t h i nghidm cho thay, khi tang ham lupng spi len thi cUdng dp ndn cua be tflng tdng Khi tang hdm lUpng spi Idn den 2%
thi cudng dp nen tang len khong n h i l u , cudng do ndn d tuoi 28 ngay tang 5% so v6i mdu dfli chiJRig. Tuy nhlen, khi ham luang spi tdng Idn 3% vd 4 % thi mdc dfl tang cUdng dfl nen khd nhanh, cUdng d p ndn d tuoi 28 ngay tdng 16%
va 2 1 % so vdi cUdng dd ndn cda mau be tong khong s d d u n g spi Cudng d p nen d t u f i i 28 ngay dat gid tri ldn nhat khi sd dung 4 % soi tUcmg dng la 188MPa. Dieu nay cung cd t h i gidi thich, khi ham lupng cot spi thdp dd ldn m d cdi thien tdt cau tnic cda be tdng vd tam tdng khd ndng chiu lUc nen cda nfl.
3J.3 Anh hudng cua ham lugng sgi den cudng do uon cda be tdng chdt lugng sieu cao
Ket qua v l dnh hudng cda hdm lupng spi den cudng do ufin cda BTCLSC the hien d hinh 3 5 . 6 dieu kidn dudng hd thUdng khi tang ham lupng spi thep thi cudng dp udn tang, khi tang sc^ thdp
den 1 % va 2% thi cUdng do u -^"g tUPng Wig tdng 36% v i 56% so vdi mau doi chdng. Khi ham lupng spi thep tang den 3% va 4 % thi cUdng dp udn cua bd tfing tang len rdt ldn, tUPng dng tang 122% va 129% so vdi mau ddi chdng. NhU vay, khi cd mat cda cdt spi cucfng do chiu uon cda be tdng dupc edi thidn rat nhieu so vol cudng dfi chju nen tdng tuong dng dat 122% so voi 16%
{ v d ham lupng cot s d Id 3%) va gia u i eudng dfi udn dat 38.8 MPa {>35MPa) nen ham luong cot spi nay cung dUpc dung lam cap phdi be tflng cot s d c h i t lupng sieu cao.
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H'inh 3.S Anh hiTdng ciia h^m luong s d th^p den cucmg Sb u6ncilaBTCSClSC
3.2.4 Dd ben dio dai cOa be tdng cot sgi chdt luang sieu cao
Nang lUpng pha hily hay do ben d4o dai duoc nghidn cdu theo JSCE SF-4 [9], dua trdn viec phan tich dUdng cong tdi trpng - do vflng ket qud thi nghidm d hlnh 3 6.0 d i l u ki^n dUdng hd tidu chu^n, dd b i n ddo dai ciia mdu bd tfing dfii chiing {khdng cfl spi) la 5.6 KNmm, trong khi ham luong spi Id 1 % va 2% dfi b i n ddo dai tUang dng dd tang Idn d i n 113.2 vd 145.7 KNmm, t i l p tuc tdng hdm lupng spi den 3% vd 4 % thi dfl ben ddo dai cua be tflng tUong dng tdng Idn rdt Idn, den 199.2va216,8KNmm. NhUvay, vdi betflng cdt s d ndng luang phd hdy tdng rdt Idn (hon 20 Idn so vdt mau ddi chdng eda loai be tdng efit s d chi chda 1 % efit s d thep), khi hdm luong spi tdng, nang lucmg phd hiiy tiep tuc tdng nhung tii 3% den 4 % thi nang tuong pha hdy tdng khdng dang ke (38.7 lan so 35.5 lan)
CKD, kg N/CKD
Ifinh 3.6 Anh hu^g ciia ham luong soi thep den Dg b§i dfodaidiaUHPRC
Ket ludn:Td k i t qud t h i nghidm vd muc tieu dat ra ham lupng edt spi phan tdn hop ly Id 3.0%
va cap ptidi de xudt la:
Cat/CKD SF.% BFS,% S D % 1 S o i t h d p , %
84
" ^ ^ 3. Ket l u i n v i k i e n n g h j
''1"^ Dua trdn k i t qud nghidn cdu Sat dupc cila ' % d I t a i , mflt sd k i t ludn CO the rut ra n h u sau:
'*J* - C d till s d d y n g phy gia khoang silica fume 'Nbis vd xi hat hda de c h l tao bd t f i n g chat luong sidu
™'^; cao (vdi cudng d f i ndn > ISOMPa, vdi do chdy
^ > loang s 200 mm) trong dieu kien Vidt Nam.
'"'^'i Thanh phan cda io^i bd t o n g nay ngodi tUong ' * n tM n h u bd tdng chdt lupng cao thflng thudng , ^ - nhUng bdt budc phdi cd p h u gia seu ddo va p h u
"'^^ gia khodng hoat tinh.Trong do, xt Id cao cd t h i sd dung den 30% chdt ket dinh.
^~- - Be tflng chdt luong sidu cao t d nguydn ' ' vdt lieu d Viet Nam khi ket hpp vdi 3.0% cdt sol thep c6 t h e che tao dUpc loai be tflng cot spi chat lupng sidu cao cfl cudng dp ndn Idn han 150 MPa ddc biet efi eudng d f i ufin tren 35 MPa vd dfl ben ddo dai dat gan 200 kNmm.
_ _ ^ Loai be tflng cot spi chat lUpng sieu cao nay ' 1 cd t i l m ndng sd d u n g cho ket cau dac biet cfl kich thudc m d n g . Tuy nhidn, ve phdn ket cau ifliia can dUPc nghien cdu thdm d l cfl t h i dng dung hidu q u i hPn trong xdy d u n g nha sidu cao tdng g^idit vd cac cdng trinh ddc biet khde.
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%^i, Papers/ductal.pdf],2006[citedOS.Noveniber2011].
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^^j^jfe Concrete paving Flags, Dissertation, University of Liverpool, p.
llonloi ^^'
IJJI^; 5. de Lairard, F and T. Sedran, 1994, Optimization of ultra-
„ l i ^ j high-performance concrete by the use of a packing model.
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" 4 * . . 8. NguySn Cong ThSng, Nguyen Van Tuan, Le Trung Thanh,
" " " ^ Pham Hun Hanh, Ve Guang, 2013, Ultra high performance
" ' * * concrete using a combination of Silica fume and Ground Granulated Blast-fumace Slag in Vietnam, In: Proceedings of International conference on Sustainable BuiU Environment for
" ^ Now and the Future, SBE2013, pp. 303-309.
9. The Japan Society of Civil tngineering (JSCE), 1984, Method of tests for flexural strength and flexural toughness of steel fibre reinforced concrete, Concrete library of JSCE, Tokyo, Japan. VoL 3. p. 58-61.
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