KHOA HOC-CdNG N G H £ 3610/2018
Nghien cuu (Jac tinh co ngot cua be tong cot soi polypropylen Forta-ferro
• TS. T R A N VIET HUNG; ThS. Lg Q U V N H NGA - TrUdng Dai hoc Giao thdng van tdi
TOM TAT: Bai bao trinh bay nhung nghien cuu thuc nghiem xac dmh anh hudng cua ham luQng sQi polypropylen (PP) den dgc tinh co ngot cda be tong x( mang. Cot spi PP khi them vao be tong se ng§n ngUa su hinh thanh vet nut, tang cuong do d^o dai va kha nang hap thu nang luong Ham lupng cot spi sd dung trong nghien cuu dao dpng td 0 den 0,5% theo the tich cua hon hpp be tong, Ket q u i nghien cuu cho thay, vi§c bo sung cot spi da lam giam dang ke co ngot cda be tong xi mang.
Ham lupng spi eang tang thi eang giam dp co ngot cua hon hpp Viec g i l m dang ke co ngot cua be tong XI mang cot spi PP se co y nghTa Ion trong viec lam tang tuoi tho su dung cho ket cau su dgng vat lieu nay.
T u KHOA: Be tong cot spi, polypropylen, ham lupng spi, co ngot
ABSTRACT: This paper presents empirical research to determine the effect pf polypropylene (PP) fiber content on shrinkage properties of cement concrete PP Fiber will prevent crack formation, increase toughness and absorb energy.
The fiber content used in this research ranged from 0 to 0.5% by volume of the concrete mix Research results show that fiber reinforcement significantly reduces shrinkage of cement concrete.
The higher the fiber content, the less the shrinkage of the concrete Significant reduction of shrinkage of PP reinforced cpncrete will increase lifetime of PP concrete structure
KEYWORDS: Fiber reinforced concrete, polypropylen, fiber content, shrinkage
1. DAT VAN O^
Co ngot cLia be tdng la sU g i l m the tich dudi nhiet dp khdng doi do mat do am sau khi be tdng da ddng cufng. Co ngdt va ndt d tuoi sdm cd the day nhanh sy hu hdng, thuc day q u i trinh an mon cot thep va ve lau dai se gay anh hudng dang keden dp ben eua be tdng. Co ngdt trong be tdng do mat nUdc lien quan chat che den tinh chat cua vUa xi mang. Ky thuat hieu q u i nhat de giam
thieu ndt do co ngdt la ngan chan sU mat nUde t d be mat be tong b i n g each tien hanh b i o dudng sdm va keo dai.
Tuy nhien, trong mot so trUdng hop, can p h l i cd cac bien phIp bo sung ap dyng bao gom kiem solt nhiet do, che chan gid va sddyng cac phy gia giam CO ngdt.
Mot ky thuat dem lai hieu q u i cao trong viec kiem solt nUt do CO ngdt la t i n g cUdng be tdng b i n g cot soi.
Viee ket hpp sOi vao be tong xi mang se tang cUdng dp deo dai va k h i nang chdng ndt cho be tong. Cac sOi dUOc tron vao hon hop ed phan bd ngau nhien se tao cac lUc ket ndi glUa eae vet nut va do do ngan chung phat trien. Trong tat ca cac soi dupe sd dyng hien nay thi spi polypropylen duoc eoi la hieu qua nhat do gia thanh re, tro trong mdi trudng xi mang ed do PH cao. Viee bo sung edt soi vao be tdng se giiip eli thien tinh deo dai eua be tong, do ben keo trude khi nUt, kha nang chiu va dap, do ben gay...
Soi polypropylen la mdt loai spi hda hpe, dUde sd dung lam vat lieu dang spi ngan khdng lien tuc de san xuat be tdng cot thep gia cudng cot spi trong cac Ung dung be tdng thanh mdng hole eae tam phCi lien tuc [5]. Soi PP cd the dupe them vao be tdng mot clch don gian, q u i trinh thi cdng be tdng cot soi PP la de dang.
Viee them soi PP se lam eho ket eau be tdng g i l m eo ngdt va ndt do nhiet. Hien nay, cd nhieu loai sOi polypropylen dang dugc sd dung tren thj trudng nham tang eUdng cac tinh chat co hoc eua be tdng. Trong nghien cdu nly, tac gia nghien cdu anh hudng cua viec tang cudng cot sOi polypropylen forta-ferro den d i e tinh co ngdt ciia be tdng xi mang.
2. CAC LOAI CO N G 6 T TRONG B £ T 6 N G Be tdng cd 4 loai eo ngdt la: Co ngot dec, co ngdt t u sinh, CO ngdt carbonat va eo ngdt khd. Co ngot deo lien quan den sU mat dd am cua be tong mdi do, van d trang thai deo, dang hinh thanh cau true va ehua chju lUc. Co ngdt carbonat la do phan dng hda hoe cua cle san pham trong q u i trinh hydrat hda xi mang vdi carbon dioxit ed trong khdng khi. Co ngdt tU sinh la do phan Ung hda hpe xay ra do suthuy hda eua cac hat xi mang. Co ngdt tusinh phu thude chu yeu vao thanh phan cua be tdng. Co ngdt khd xay ra khi nude bi bay hoi ra ngoai be mat be tdng.
Co ngdt kho phy thupe vao tuoi bat dau say khd va cac thdng so ben ngoai nhu dp I'm tUdng doi v l kich thude mau thCf.
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KHOA H O C - C O N G NGHg
Trong phan tich ket eau be tong thi hai loai co ngdt duoc quan tam den la co ngdt kho va eo ngdt tusinh.Ty le gida eo ngdt t u sinh va eo ngdt kho eija be tdng dUOc minh hoa so bp nhutrong Hinh 2.1.
A Co ngot
XimSng PCMlkg) 378
Ikg) S11
ea dam (kg) M ' 1664
Phvgia SikamenHMflU)
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Hinh 2.1: Thanh phan bien dang co ngot cua be tdng thdng thudng [6J
3. V A T Lieu VA C H I T A O M A U THlJ 3.1. Scri polypropylen
Soi PP sd dung trong nghien cdu la loai sOi FORTA- FERRO (My), ed dang eau true boi xoan Idn, Dae diem cua soi PP sd dung nhU sau:
D u d n g k i n h q u y d o i eua cac soi dOn Chieu dai sa\
Nhiet do n o n g chay Op d a n dai d u t gay M 6 - d u n dan hoi D o b e n keo Khdi l u a n g rieng MUe d 6 chiu axit va kiem Hap t h u n u d e
0.3mm SOrnm 1 6 0 - 1 7 0 ' ' C 8 - 1 5 %
> SOOOMPa
> eOOMPa 0.91 ± 0 . 0 1 g/em^
m d c cao k h o n g
Hinh 3.1: Sd PP FORTA-FERRO siidung cho nghien cuu 3.2. Ty le thanh phan be tong cot scri PP Cac bude thiet ke thanh phan be tdng dupc tien hanh theo hudng dan eua ACI 211.1-91 [3] ddi vdi be tdng thudng. Thiet ke thanh phan be tdng xi mang nham muc tieu cd duuc eUdng dd nen dae UUngf' = 30MPa.
Ty le thanh phan cac vat lieu cho 01 m' be tdng nhusau:
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Ham luong soi PP dUOc lua chon dUa theo hai tieu chi la tinh kinh te va hieu q u i dat duac. Ham luong spi PP sCf dyng trong nghien edu nay dUpc lUa chon theo i^ \^iii 0 - 0.5% theo the tich theo kinh nghiem cua cac nghien cUu da thue hien [2,4,7,8].
Ty le khdi lupng spi PP tren moi 01 m^ be tdng, dupe tinh lai theo ty le the tieh lUa chon nhu sau:
1 Ten hon hop Tyle theo the tich (%) 1 khdi iLfong sOi PP
PP-1 0.1
PP-2 0.2 0.882 1.763
PP-3 0 3 2 645
PP-4 0.4 3,526
PP-5 0.5 4.408
3.3. Qua trinh tron va chS tao m l u thi nghiem Lan luot do da nghien, soi PP va cat vao trong mIy tron. Sau khi khuay tron khoang hai phut, spi PP se phan tin hoan toan, sau do them xi mang, nUde va khuay tron blnh thudng. Qua trinh che tao mau thdva bao dudng duacti^n hanh tuong t u nhu be tdng xi mang thong thudng.
Hinh 3.2: Tron va che tao mau thube tdng edt spi PP Mau be tong dung de do co ngdt dupe che tao hinh lang tru cd kich thude 150x150x600mm. Cac mau sau khi che tao, t h I o khudn se duoc ngam vao nude 3 ngay roi lay ra khoi thung ngam va lau khd be mat. Tien hanh do tren hai loai mau la: Mau duoc bao dUdng blnh thudng (Hinh 3.3a) va duac boc kin bang giay nhdm mdng (Hinh 3.3b). Cac mau dupc boc kin, se khong ed sutrao ddi do
KHOA HOC-CONG NGHe 3610/2018 am vdi moi trudng xung quanh.Tren hai mat tiep giap vdi
thanh khuon cue cac mau se gan hai chot do bang keo hai thanh phan vdi khoing each co dinh b i n g chieu dai thanh chuan tren thiet bi do.
Hinh 3.3: Mau thube tdng eoi soi PP d^xae dinh bien dang co ngdt Thiet bj do bien dang bao gom mot thanh ehuan ed kich thude 300mm va mot thude do sU thay doi khoing each cua hai chdt do tren mau bdi mot dong ho thien phIn ke nhu tren Hinh 3.4. Phuong phap va each thUe tien hanhtheoTCVN 3117:1993 [I].
4. K^T QUATHt NGHIEM VA D A N H G I A Cle mau sau khi dUOe ehuan bj theo dung yeu eau se duoc xae dinh do eo tat tdng thdi diem theo cong thdc:
\ ^<
^ ) ITrong do; A/^^^- Chenh lech chieu dai gida cac chdt do eua mau tai thdi diem t so vdi ban dau tinh bang pirn; I - Khoing clch gida cle chdt do, doi vdi thiet bj thi nghiem SLf dung t h i / - 0 . 3 m .
Op CO dupe tien hanh do sau khi che tao va hoan thien mau be tdng. Thdi diem tien hanh do co ngdt dupe xae dinh d elc tuoi 1,3,7,14,28, 56, 70,90 ngay.
Ket qua thi nghiem se xlc djnh dupe eo ngdt tong cong tren eae mau bao dudng d dieu kien binh thudng (Hinh 4.1) va co ngdt tUsinh d elc mau dUOc bpc kin bang giay nhdm (Hinh 4.2).
E
1
6t long c5n Con
-100-
-200-
-300-
-400-
-500-
^
^ ^ ^ E ^
- - - O P C - c ^ p p . l - a - . PP-2 - ; ^ P P - 3
— ^ P P - 4
—U—PP-5
0 10 20 30 40 50 60 70 Thdi gian (ng^y)
Hinh 4.1: Co ngdt tdng cdng cua cac mau thi nghiem
1 2- o
-50
-100'
-150- Y ' ^ ^
^ ^ % - - - X — -
- — O P C
• O •- PP-1 - A - PP-2 - <^ PP-3 - E> PP-4 - -k- PP-5
3
Hinh 3.4: Thiet bi va each do eo ngat tren mau thi nghiem
70 80 90 100 Thdi gian (ng^y)
Hinh 4.2: Co ngot tusinh c6a cic mau thi nghiem Ket q u i thi nghiem tren c l mau be tong thudng va be tong cot sOi PP cho thay, ty le co ngdt t u sinh va co ngdt tong cong Idn nhat trong 3 ngay dau tien va giam dan theo thdi gian den khi ket thue thi nghiem la 90 ngay.
Viec them cot spi PP vao da lam giam d i n g ke t^ le co ngdt trong be tdng. Ham lUpng edt spi them vao eang cao thi eang giam duoc mdc dp eo ngdt cua be tdng.
Boi vdi CO ngdt tU sinh, bien dang eo ngdt khi tang ham luong soi PP t d 0.1% den 0.5% la g i l m t d 5% den 19%.
Dot vdi eo ngdt tong cong, khi tang ham luong cot soi PP t d 0.1% den 0.5% thi bien dang co ngdt tuong Ung g i l m t d 14% den 26%.
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KHOA H O C - C d N G N G H £
Thai gian (ngay) Hinh 4.3: Ca ngdt kho aia be tdng cat soi PP Hinh 4.3 the hien dp co ngot kho dUoc tinh bang hieu cua eo ngdt tong the va co ngdt tU sinh. Bien dang CO ngdt eung giam khi ham luong spi them vao hon hpp tang tU 0.1% den 0.5%. Cd the thay ring viee them spi vao hon hop lam giam dang ke eo khd, mUe giam nay tuong dng tU 18-30%.
[7]. Ramakrishnan V., Wu G.Y. va Hosallt G. (1989), Flexural Behavior and Toughness of fiber Reinforced Concrefe, Transportation Reseach Record 1226, National Reseach Council, Washington DC.
[8]. Chuan Mein WONG (2004), Use of Short Fibres in Structural Concrete to Enhance Mechanical PropertiesCourse ENG 4111 and ENG 4112 Research Project.
Ngdy nhan bai: 27/8/2018 Ngdy ch^p nhdn dang: 9/9/2018 NgUdi phin bi^n: TS.Ta Duy Hien
TS. Nguyen Xuan Tung
5. KET LUAN
TCr ele ket qua thue nghiem trong nghien edu nay, cac ket luan va kien nghi sau eo the duac rut ra;
- Bien dang eo ngdt eua be tong xi mang va be tdng edt spi PPIdn nhat trong 3 ngay dau sau khi e h e t a o v l t y 1& CO ngdt g i l m dan theo thdi gian;
- Co ngdt tong cdng, co ngdt tU sinh va co ngdt khd cua b^ tong cot soi PP thap hon dang ke so vdi be tdng xi mang thdng thudng;
- Do g i l m bien dang eo ngdt phu thuoc vao ham luong soi them vao. Khi tang lam lUOng sOt tdO.1% den 0.5% thi dp giam eo ngdt tuong dng gilm, mdc cao nhat ddi vdi be tdng cot soi PP 5% la g i l m duoe 30% co ngdt kho so vdi be tdng xi mang thudng.
Tai lieu tham khio
[ll.TCVN 3117:1993; Be tdng nang - Phuang phdp xdc dinh do CO.
[2]. Nguyen Tien Blnh (2005), Nghien cUu che tgo be tdng cot sai sieu manh Polypropylene dung cho sCta ehda cdng trinh trong dieu kien khi hau nong am Viet Nam, Vien Khoa hpe eong nghe Xay dung.
[3]. ACI 211.1 {199i;, Standard Praef/ce for Se/ect/ng Proportions for Normal Heavyweight and Mass Concrete, American Concrete Institute.
[4]. Zollo R.F., liter J.A. v l Bouehacourt G.B. (1986).
Plastic and Drying Shrinkage in Concrete Containing Collated FIbrillated Polypropylene Fibre, Third International Symposium on Developments in Fibre Reinfoced Cement and Concrete, RILEM Symposium FRC 86, RILEM Technical Committee 49-TFR.
[5]. Swamy R.N (1975), Fiber reinforcement of Cement and Concrete, Materital and structures. 8(45), pp.235-254.
[6]. K. Sakata va T. Shimomura (2004), Recent progress in research on and evaluation of concrete creep and shrinkage in Japan, Journal of Advanced Concrete Technology. 2(2), pp.133-140.
