Strdung cot stfi tif nguon cap thep phe thai de che tao be tong cot stfi phan tan lam dUcrng giao thong nong thdn Using fibers from wasted steel wire rope for fiber concrete to build rural roads
Ngay nhan bai: 5/02/2017 Ngay sCfia bai: 8/3/2017 Ngay chap nhan iJang: 5/4/2017 TOM TAT
Ndi dung bai bao trinh bay chddng trinh thi nghi?m va Icet qua thi nghiem cUdng do cluu keo uon, bien dang k^o uon cdc han cua be tong cdt sai phan tan vdi ngudn cdt sc?i tan dung tii ngudn cap thep phe thai. Ket qui thi nghiem doi vdi be tdng cdt sOi phan tan ddcjfc so sanh vdi be tong thddng cd ding ti le cap phdi.
Ket qua so sanh cddng do chiu keo uon va bien dang cdc han cua 2 loai vkt lieu vdi cung ti le cap phoi cho thay be tdng cdt sOi phan tan til nguon cdt sOi phe thai cd du diem vdot troi do so vdi be tdng thiidng. Tif ket qua nghien edu sc( bd cho thtiy, be tdng cdt soi ph5n tan tif ngudn cot soi phe thai co the thay the be tong thudng d^ lam dddng giao thdng ndng thdn vdi muc dich tang kha nang chiu ldc, giam thieu hd hdng va nang cao tudi tho.
Tit khoa: Cdt sOi, bi tdng cot sai, cot soi ph6 thai, diidng bi tdng
ABSTRACT
This article presents methodology and results of an experimental study of flexural strength and ultimate strain of fiber concrete whose fiber sourced from wasted steel wire rope. The testing result of fiber concrete is compared to that of usual heavy-weight concrete with the same concrete composition. It can be seen from the comparative result of flexural strength as well as ultimate strain between the two materials that fiber concrete has predominant advantages over usual heavy-weight concrete.
Preliminary experimental findings show that fiber concrete from wasted steel wire rope can replace usual heavy-weight concrete in building rural roads to increase strength, reducing thereby extending the service life.
Keywords: Fiber, fiberconcrete, concrete road
Ts. Nguyen Phan Duy
Trudng Dai hpc Xay ddng Mi^n Trung
Nguyen Phan Duy
I.Oatvande
Hien nay va trong nhi^u nam tdi, van de tam nong cd tam chien lUOc dac biet quan trong Gan lien vdi chien Idoc nay la ehdong trinh be tong hda giao thdng ndng thdn. Chdong trinh nay da mang lai nhdng thaydoi tich cdc, gop phan n§ng cao ddi sdng vung ndng thdn d nddc ta. Qiy eung la mdt trong nhdng muc tieu quan trong eda chdong trinh nong thdn mdi. Thdc tien cho thay, dddng be tdng mang lai hieu qu3 kmh l^
cao Tuy nhi§n, be tdng ed nhdng nhdoc diem nhat djnh, them vao 36 li tinh trang khai thSc dddng be tdng qua tai dan den nhCng hif hdng, kl ca ddi vdi cac doan dudng vda mdi thi edng xong. K^t qua khao sat vi phan tieh dc tuyen dddng be tdng ndng thon cho thay, loai mat difcmg nay thddng x l y ra mot sd hd hdng dien hinh nhd: mat dddng bi bao mon;
tam bl pha hoai 6 trong doan gida tam (vet ndt ngang), v^t ndt gay ngang trong doan gan mdi noi ngang; vet ndt gay dgdc; vet ndt gay sup '6qi';
tan chSn chim-taong vay; hd hong khe co gian Nguyen nhan chCi yeu la do kha nang chiu keo cua be tdng kem [5]. VI vSy, de dddng b& tdng phat huy nhung uu diem eua minh, can phai co nhQng g i l i phap c i i thien khi nang chiu keo cua vat lieu. Xuat p h i t t d van de dat ra, nhdm nghien ciili trddng Oai hoc Xay ddng Mien Trung tien hanh nghien cuVi be tong c6l soi phan tan vdi ngudn cot scri t d cap thep phe thai de dng dung lam dddng giao thdng ndng thdn vdi myc dfeh tang kha nang chiu ldc va tuoi thg cho mat dddng.
Be tdng cdt sol phan tan da dddc nghien edu va dng dung rdng rai tren the gidi, Tai Viet Nam, be tdng cdt soi budc dau duoc quan tam nghien edu rdng rai d mdt sd don vi trong thdi gian gan day, tieu bilu nhd: Vien Khoa hoc Cong nghe Xay ddng, Oai hoc Bach Khoa Tp. Ho Chi (Winh; Dai hoc Xay ddng; Vien Khoa hoe Cdng nghS Md, 0^1 hoc Giao thdng VSn tai v.v [1, 3, 4] Tuy dddc nghien edu nhi^u, nhdng viec dng dung be tdng edt sgi phan tan d nUde ta cht mdi ddng lai d mdc thi) nghiem. Mdt trong nhdng nguyen nhan ehinh la do ngudn edt sOi khang hiem va gia thanh eao. Xuat phat t d khia canh nay, them vao do nhan thay d nddc ta nguon cap thep phe t h i i kha ddi dao t d cac c i n g bien, nh^
may th^p, nha may san xuat ldp d td, tac gia tien hanh nghien edu vat lieu be tdng cot soi phan tan vdi cot soi tan dung t d cae nguon ke tren vcii muc dich tan dung triet de ngudn nguyen lieu phe thai.
2. Chuong trtnh thi nghiem va vat lieu siJrdung Muc dich thf nghiem vit lieu la de xac dinh cddng dd chju keo uon thUc te va bien dang keo cdc han khi udn eua be tdng cdt scji phan tan, danh gia du diem ve cddng dd va bien dang cua vat lieu nay so vdi v|t lieu bi tdng thddng vdi cdng cap phdi, trin ea sd dd de xuat sii dung bfi tdng cdt soi phan tan de lam dddng giao thdng ndng thdn.
De giai quyet bai toan dat ra tac gia tien hanh thf nghiem be tong col SOI phan tan vdi tren nen be tdng cd cac c^p dd ben 615, B20 vi 825 phoi hgp vdi hai bien sd la ham Idong cdt soi theo khdi Idong p< vh chieu dai cdt soi /. Phan tich cac nghi§n du khoa hoc trong ITnh vdc be tdng cot scfi phan tan va sd dung phdong phap quy hoach thi nghiem tic gia xSy ddng chdong trinh nghien ciiu nhU sau' be tdng sd dung cd cap do bin 615, B20 va 625; edt sdi th^p tdcae soi cap th^p phe thai vdi dddng ktnh nhd hon 1 mm cd c h i i u dai 20 mm, 30 mm va 40 mm; ham IdOng cot sOi
1 3 0 J B O i l i i l l B l (
theo khdi Idong fjt ddOc lay 0 % (be tdng thddng), 0,5 %, 1,0 %, 1,5 % va 2,0%.
De thi nghiem xac dinh eddng dd keo udn sd dung mau 150x150x600 m m ' . Ti^n hanh do mliu d l thi nghiSm, vdi mdi ti 1^ cap phdi do tdi t h i l u 3 mau Quy trinh do mau thi nghiem va cac thi nghiem ddoc tien hanh theo cac tieu chuan hien hanh [1,2].
vat li^u lam cdt soi sddung trong nghien edu dddc gia cdng dt ngSn t d nhdng soi cap thep phe thai cd dddng kinh nho hon 1 mm, eac soi cap ddoe c3t ngSn se ddoe eho vao may danh tcrt, trong qua trinh danh toi bSng quat xoay trong thung thep cot sol se bl udn eong ngau nhien dddi tac dung eda eae thanh canh quat, ffleu nay se lam tang lUc dinh bam giOa cdt soi va bi tdng sau nay.
De thuan tien eho cdng tac tron vi]^ be tdng cdt sol phan tan vi 36, thi nghiem sd dung be tdng cd do sut 6-8. Trong thi nghiem sd dung xi mang Podelang Nghi San PCB40, eat va da dam sd dung ngudn uai lieu tren dja ban tinh Phu Yen. Tat ca cac vat lieu dap dng yeu cau theo cac tl^u ehuIn hien hanh.
Trong qua trinh do mau thi nghiem n h i n thay, vdi ham Idong cdt sfli fjf=2% xay ra hien tUOng vdn cue va do sut trong trddng hop nay rat thap (khoang 2-3), hon nda ham Idong cdt soi Idn se lam giam dd ddo eda hdn hop vda gay khd khan trong cdng tac tron deu cdt soi trong bi tdng va cdng tae dd be tdng. Vi vay, trong ndi dung nghien edu kien nghi khdng
0.0 0 5 1.0 1.5 * ( ^ % 2.0 Hinh 1 Quan he giii^ alOng 6b chiu keo uon va ham lUOng cot sdi ciia be tong cot sOi pha tan tren nen be tong c6 cap do ben tifOng OifOng B15
H
^
1 1
^ . ;
1-20 mn rj 1=30 mm 1=40 mm
1
0.0 0.5 1 0 ^s p,% 2.0 Hinh J.OuarhSgtOacUftrgaothiu keo u6nva ham li/ongcotsfli ciia be tong cStsoi pha tan tren nSn be tdng c6 cap Sb ben tUOng dUDng B2S
s d d u n g h a m I d o n g c d t soi cao 3. Ket qua thi nghiem va ban luan
cac m i u thi nghiem khi ddoc bao dddng trong dieu kien phdng thi nghiem den dd tudi 28 ngay se tien hanh thi nghiem. Thi nghiSm ddoc tien hanh tai phdng thi nghiem trddng Dai hoe Xay ddng M i l n Trung, quy trinh thi nghiem cae mau t h d duoc tien hanh tuan thd theo c^c tieu chuan hien hanh.Td ket qua thi nghiem dc mau thd, tien hanh xay ddng bleu cae bieu do quan he gida cddng dd chiu keo udn cua cSc mSu vdi ham IdOng cdt soi (Hinh 1-3) eung nhd quan he gida eddng dd eda mSu so vdi chieu dai cdt soi cho tdng loai be tdng (Hinh 4-6).
Phan tieh ket qua thi nghiem cddng dd cua be tdng cdt Sdi phSn tan va bi tdng thddng eho thay, khi bd sung cot soi vao be tdng cUdng do chiu keo udn cua be tdng trung binh t d 6,6 % d i n 50,8 %. Khi tang ham Idong edt soi, cddng do chiu keo udn eda be tdng cdt sdi tang, tuy nhien t? le tang cddng do keo udn khdng d l u ddi vdi cae ham Iddng cdt soi khac nhau Cudng dd keo udn cua mau be tdng edt soi tang manh vdi ty le cdt soi thap, va gan nhd tuyen tinh. Vdi ham IdOng cdt sdi theo khdi Idong tang thi t^ le nay giam xudng va trong trddng hOp n j y quan he gida eudng do ehiu keo udn cua be tdng cdt soi va ham luong cdt soi co dang dddng eong;
1 —-—-^fe—^"^^^^^
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^ - f
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l=20mm l=30mm l=40mm 1 1 0.0 0.5 1.0 1,5 / i | . % 2 0 Hinh 2 Quan hegiiia dicing dochjukeouonva ham li/tmgccitsoi ciia be tongcotsoi pha tan tren nen be tong co cap do ben tuong duong B20
Hinh 4. Quan he giQa gi[fa cu£ing dS keo u6n va chieu dai cot sen (fftir/) ciia be tong cot soi phan t^n trSn nen be long co ty le cap phoi tuong dUOng B15
Hinh S. Quan he gifla giSa cuSng do keo ut tan tren nen be tong co ty le cap phoi tifung di
20 25 3 0 35 I, mm 4 0 {Rnrfl dia be long cot sdi phan Hinh 6 Quan he gifla gifla curmg do keo udn va chieu dai cot sen [Rhrti da be tong cot soi phan
tan tren nen be tong co t j le cap phoi tUOng dflong B25
Khi tang c h i l u dai cdt soi, ldc dinh bam gida bi tdng va cdt sdi se tang. Do dd, cddng dd keo udn eda b& tdng cdt soi cua edng mdt ty ii cap phdi va ham Idong cdt scrt thi cddng do keo udn cua be tdng cdt sdi tang;
Vdi ham Idong cdt sdi va chieu dai cdt sdi Idn, t? 1^ tang eddng dp eda be tdng cdt soi tang khdng dang ke do la do ti le tham gia lam viec cua cdt SOI vdi be tong. Khi sd dung cdt soi tron tron, t h i n g , khdng ed mdc neo d hai dau ldc dinh bam gida hai vSt lieu nay nhd, do dd khdng the tan dung het kha nang chiu ldc cua cdt sdi. Sau khi nut, mau se bi pha hoai hoan toan khi cdt sdi tudt khdi be tdng
Vdi edng mdt ham IdOng edt soi, t j le tang cddng dd chiu kia udn gida cac loai be tdng khdng d l u . Cu t h i , ddi vdi be tdng cd cap do ben thap, khi bd sung cdt soi t j le tSng tang eddng do chiu keo udn Idn hon so vdi cac cap do b i n eao.
De xay ddng b i l u do quan he dng suat-bien dang keo udn sd dung tenxo cam b i l n dan d vdng k^o khi thf nghiem k^o udn m5u. Td ket qua thi nghiem, tien hanh xay ddng cac bieu dd quan he dng suat-biln dang keo udn eda be tdng cdt sai phan tan va so sanh vdi be tdng thddng (Hinh 7 the hien 2 mau dien hinh). Phan tieh bieu dd quan he dng suat-bien dang keo udn rut ra nhan xit r i n g , b i l u dd quan he dng suat-bien dang keo udn ddoe hinh thanh bdi hai doan' doan thang t h d nhit dddc cho la giai doan lam viec dan hdi, quan he gida dng suat va bien dang la t u y l n tinh, b i l n dang d^o chda xuat hien hoae cd gia tri nhd; doan t h d 2 la doan sap pha boat, bien dang tang dang k l , dac biet la bien dang deo. Biln dang tai diem udn tren dd thi ddOc xem la biln dang dang keo uon cdc
g
t? 20 10
/ ' / /
-..
615-20-1,5-2
,
Bl5-0-2
Hinh 7 Bieu do quan he fltig suat-bien dang keo uon mau B15-0-2 (Belong thifimg) va mau B15-20-l,5-2 [Mau be long cot sgi,cbieu dai cot sai JOmm,hamluong cot sfli 1,5%)
Vi§c bd sung cdt soi vao trong be tdng tam thay ddi dang k l tinh gi6n eda be tdng, khi nSy bi tdng dio han. D i l u nay ddoc the hien rd tren do thi quan he dng suat-bien d^ng k^o udn; khi bien dang d^o xuat hl&n dang k l va bat dau xuat hien vet ndt, ddi vdi be tdng thddng se pha hoai ngay lap tdc. NgdOc lai, ddi vdi bS tdng cdt sdi phdn tan, sau khi xuat hiSn vet ndt mau van tiep tuc tiep nhan tai trong (sau d i l m udn tren bilu do quan he b i l n dang cdn tang ding ki). Ngoai ra, do cd lye dfnh bam giCfa be tdng va hai dau edt scfi n§n m i u be tdng cdt soi sau khi ndt van con lien ket ma khdng tach rdi ra, dac biet vdi cae mau vdi ehilu dai cot soi Idn. Quan sat thi nghiem keo udn tdlde gia tai d i n khi mau pha hoai tio^n toan cd nhan x^t rang, sau khi v i t ndt dau tien xuat hien trong be t6ng cdt sdi phan tan, mau van tiep tuc lam v'\ic vh t i l p n h i n tai trong binh thddng, mau chl bi pha hoai hoan toan khi cac cot soi bi tude khdi be t d n g . O i l u n a y t h l h i ^ n r d t r ^ n b i l u do quan he dng suat-bien dang l<^o udn cua mau doan nghieng di iin sau khi ndt. Ket qua thdng ke tdthi nghiem cho t h i y , tai trong tiep tuc tang sau khi m i u bl pha hoai khoSng 10 %. Ket qua sanh bien dang keo udn ede ban eda bS tdng thddng va be tdng cdt sdi pbSn tan cho thay, be tdng cdt sol phan tan cd b i l n dang kio udn cdc h^n cao hdn mau be tdng thddng, ti ie tang cd the dat flln 90,5 %. Viec bd sung cdt soi vao be tdng se lam vat lifu trd nen deo hon va nhd da d l cap d trSn, khi x u l t hien v i t ndt dau ti&n mau b^ tong thudng se pha hoai dot ngqt, ngUoc lai vdi be tdng edt sOi, sau khi xuat hien vet ndt ldc dinh bam gida be tdng va cdt sol chda bi pha hoai va cot SOI ddng vai trd la edt trdc t i l p t i l p nhSn ldc cang (Hinh 8). Day la mot trong nhdng tinh c h i t hdu ich de sd dung eho mat dddng giao th6ng.
Theo k i t qua khao sat dddng be tdng xi mang cho t h i y , khi bi ndt gay tam be tdng se bi ehia thanh cac phan nhd va cSc phan nhd nay tach red nhau. B i l u nay khdng chl i i m hd hdng mat dddng ma edn anh hudng nghiem trong den cac phdang tien giao thdng. Vdi mat dudng t d be tdng cdt sdi phan tan, trong trddng hap bat loi cac v i t ndt xuat hien, tuy nhien nhd cd edt sai ma cae tam bi tdng cdt sdi sau khi ndt van edn lien kit va lam vi§c cung nhau
4 . K i t lu^n
K i t qua thf nghiem xac dinh cddng dd va bien dang cdc han khi kio udn eda bS tdng cdt soi phan tan vdi cdt sen tan dung t d ngudn cap thep phe thai va ket qua so sanh vdi be tong thddng da chdng minh nhdng uti diem rd ret eda loai bS tdng nay. Viec sd dung nguon cap th^p p h i thai de lam cdt scfi cho be tdng cd the cat thien dang k l cddng dd cila belong, b§n canh do cdn ed ^ nghia to Idn ve mat bao vi mdi trddng. Vdi cU&ng dd va b i l n dang keo udn Idn, be tong cdt soi phan tan t d ngudn cap thep p h i thai hoan toan cd the sd dung ddoc eho mat dddng giao thdng nong thdn, dac biet eho nhQng doan dddng thddng xuyen bi qua tSi hoac doan dddng tr^n nen dat yeu
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Hmh 3 MSu be tflng cot soi phan tan sau khi thinghiem Iteo uon
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