Qua trinh trao ddi ntpoc giOa cot lieu rong va da xi mang trong be tong tu* bSo du'&ng
Moving process of water between lightweigh aggregates with cementitious matrix in self-curing concrete
Ngay nhan bai: 15/12/2015 Ngay su:a bai: 22/01/2016 Ngay chap nhan dang: 9/03/2016
TOM TAT
Di dkm bao chat liiOng cho be tong trong nhflng tnidng hdp ma
vi^c bao diiSng thong thi(6ng la khong kha thi hoac doi vcfi be t6ng ciicJng do cao hay chjtt liidng cao, giai phap noi bao dU5ng (IC) da dil^c de xuat. Theo do can sii dung cot lieu rong (CLR) bao hoa niidc trUdc khi tron h6n hop be tong. Bai bao nay trinh bay mpt so ket qua nghien cflu tinh toan sil chuyen dich cua nflclc trong be tong khi thiic hien noi bao dflSng. Ket qua phan tich cho thay, nfldc dfl trfl tii CLR da xkm nhap kha sau vao he 16 rong cua nen xi mang, tao dieu kien tot de thuy hoa chat ket dinh, nang cao do dac chac va tinh dong nhat vi mo cua be tong.
Ttf K H O A : Cot Ueu rong; npi bao dfl5ng (IC); nfldc mao quan;
nfldc tham nhap.
ABSTRACT
To ensure the quality of the concrete in the cases, that the ordinary curing is not feasible for example for high-strength or high performance concrete, internal curing solution (IC) has been proposed Accordingly lighweight aggregates should use saturated with water before mixing the concrete mixture; This paper presents some results of theoretical calculating about moving of water in the concrete. These analyzes showed that effect of IC is feasible.
Keywords: Lightweight aggregate; internal curmg; capillary water; migration of water.
GVC. TS. N g u y i n Duy Hi^u
Trfldng bo m o n Khoa hoc Vkt lieu xay dflng, Trfldng Dai hoc Kien true Ha Npi MobUe: 0912396397 Email: [email protected]. vn
Nguyen Duy Hieu
I.DATVAND£
Ban chat cita hho duflng til ben trong ctio be tong hay c6n gpi la npi hho dudng - Internal Curing (IC) la dUa vao be tong m p t lupng nU6c d u t r f l tiiong qua cac vat lieu co kha nang ngam nU6c d mile dp phil hop (thudng ditng la cac hat cot iieu rong nhhn tao (CLR)), luong nUcfc nay khong tham gia vao nUdc tron be tong. He 16 rong cua CLR chiia i3ay nUdc dong vai tro nhU nhu'ng "vi gieng" cap nUdc khi can, duy tri sU bao hoa am trong mao quhn 3h xi mang. Hieu qua ctlia IC phu thupc cac yeu to: lupng nudc dutriirtrong CLR, khS nang giiJnUdc va sil phan bo cCia CLR; khoang each tham nhap eiia nudc dU trCt vao nen cho da xi mang; nhiet dp cOa he... [2]. Neu be tong, ma trong do npi hho dudng p h i t huy tac dung tot, n h d do g i i m nhe hoac khong can thtfc hien cong tac hho dudng thdng thudng, cd t h e got la bi tdng t u bao dudng.
2. TRAO e d i N\SOC GIUTA C 6 T L I | U R 6 N G V A D A XI MANG 2.1, Oong lUc chuyen dich nUdc trong be tdng
Khi dUa mpt lUpng CLR ngam nUdc nhat dinh vao trong be tdng, Sli trao dot nUdc giu'a CLR va nen vda xay ra ngay kht trpn h6n hpp, chieu va mtJc 3 6 cCta qua tr'inh nay phu thupc chenh lee SLfc hut mao quan trong cac 15 rong ci!ia CLR va nen xi mang. Neu CLR trudc khi trpn d trang thai khd hoac chua bao hda, cd the nd se hut pha long trong nen theo chieu ha thap chenh lech ham am. Trong dieu kien ngUpc lai, nudc tir he mao q u i n ciJa CLR se chuyen dich cho nen da xi mang. Hinh 2.1 md t i s u t r a o S o i nudc kht cd chenh lech dUongvesiJc hut mao q u i n giSa 16 rdng cita nen da xi mang va CLR.
Htnh 2.1. Mo hlnh chuyen dich rUSc IC trong be tong, v6i r{t)< fla
He thong lo rong trong da xi mang cd kich thUdc be hon va giam dan theo thdi gian, so vdi he lo rong tdn hOn va gan nhU bat bien trong cot lieu rong. Xet mao qu^n hoac 16 rong gel trong da xi mang, ban kinh tUong dUong r = r(t) [c6 the xac dmh t i f dudng cong thUc nghiem md t i p h i n bo the ti'ch 16 rong theo ban kmh cila no:
dV/d(lnr) = f(lnr)), noi thdng vdi mao q u i n cd ban kfnh tUong dUong Ra CLia CLR. Sde hiit giOa mao q u i n giifa hai he 16 r6ng se la [1,2]
4P(l) = Pa-P{m) (2.1) Trong d 6 :
Pa va P(m) - Ap suat hcri bao hda tUong iing tren mat cong chat I6ng trong 16 r6ng e6a CLR va da xi mang,
Om vei o - Silc cang be mat tUCJng ilng ciJa dung djch long (trong nen xi mang) v i nudc (trong CLR);
(pm va (p - Gdc tham udt tuong ifng cija dung djch I6ng trong mao q u i n d a x i m a n g v a n u d c trong CLR;
r(t) va Ra - Ban kinh mao q u i n tUOng ung ciJa da xi mang va cilia CLR.
Co the coi cjm = CT va ipm = tp (va khong doi theo tuoi cua be tong), khi d 6 AP(t) = f(r(t)) » 0, do vay nUdc trong cot lieu rdng se chuyen cho da xi mang vdt he 16 rong cd dp am va kich thUdc g i i m dan d o qua trinh hydrat eiia ehe khoang trong xt mang.
2.2. Tinh todn khodng edeh chuyen dieh eda nUde ndi bdo dUdng LUu lupng ddng chay cua nUdc cap tif CLR can bang vdi lUOng nudc c3n thiet de giCftrang thai bao hoa trong c i c 16 rong cua da xi mang bao quanh nd. Cd the cho rang sU van chuyen cua chat Idng trong he dang xet tuan theo quy luat chay dong. Gpi chieu sau tham nhap nddc la L (m), theo 1;^ thuyet thuy life ap dung cho chat Idng c h i y dong trong ong tru nhd, lUu luong dong ehhy Q (mVs) dUpc m d t i theo phuong trinh Hagen - Poiseuille:
Q=—=u.n.r'[t)=Hl^2:5™=iH!WM™ (2.2) Trong dd;
V - T h ^ tich chuyen djch cOa c h i t Idng (m^);
" u, - Van toe c h i y trung binh eiia chat Idng trong ong;
l i = ^ - O a i luong m d t i tinh tham cua vifa xi m i n g ; s
Jl - dp nhdt cilia chat Idng trong 15 rong (Pa.s).
De y rang, luu lupng nUdc cap t i l CLR vao ho xi mang la de can b i n g vdi the tich nUdc can thiet bit d i p co hoa hpc dien ra trong be tdng [2], Tif 36 cd the m d t i t h ^ tich nUdc Vn can thiet bii co hda hpc cua c h i t kit dfnh, phu thudc qua trinh hydrat theo thdi gian t, b i n g phUdng t r i n h :
;D/P„ (2.3)
Trong dd:
CS - D d CO hda hpc cua chat ket d i n h ; CKD - Luong chat ket dinh trong be tdng, k g ; pn-TJ khoi ctJa nUdc;
a - H^ so mo ta mifc dp hydrat cua chat ket dinh;
^ - Bi^n thien mifc hydrat cua chat ket dinh theo thdi oian;
at ^ Goi ID la phan dd rong trong vCfa xi mang can giu'trang thai bao hoa.
Bi^n thien the tich nudc theo thdi gian, ^ , tinh cho mdt don vi dd rdnq O a ' . a , chfnh la t6c do tham nhap nUdc trong mao q u i n {fc/ hieu la ^ ) .
VJ lUu lUOng ddng c h i y Q se dUpc xac dinh:
Q . „ - ( , 1 . L | .
Can b i n g phuong trinh 2.2 va 2.5 ta cd:
, lk.AP(t)
PhifOng trinh 2.6 cho ph^p tinh gan diing chieu sau tham nhap L eiia nudc t i t CLR vao nen ket di'nh d cac dp tuoi khae nhau cua be t d n g , n^u biet Sa (dao ham mifc dp hydrat ciia chat ket dinh theo thdi
d d rong * cua be t d n g , coi gdc t h a m udt cpn, = ip = 0. Tn sfi i ^ c6 the at xke dinh tren cd s6 khao sat nhiet t h u ^ hoa ciia chat ket dinh theo then"
gian. B i n g 2.1 trinh bay nhiet hydrat ciJa cac khoang trong clinker xi mang theo logarit cO so t i l nhien cua tudi be tdng (ngay). TCf 2.1 vh thanh phan k h o i n g , ta xac dmh gan d u n g nhiet thiiy hda cua xi mang theo tu6i cCta nd. Gan d i i n g , cd the g i i thiet, sau 90 ngay [In90 = 4,5) xi mang thCiy hda dat 80%, tii dd t i m dupc he so thdy hda tUdng doi a (Bing 2 2)
B i n g 2.1. Nhi^t thCiy hda cac khoang [3]
Nhiet thtjy hda theo thdi gian cOa cac k h o i n g , Cal/g
Loai khoang
CJS CJS CiA C A F
Thdi gian thuy hda, n g i y 3 1 7 [ 28 j 90
Ln(t) 1.1
96.
15.
141 42.
1,95 100.6 24.8 157.6 59.6
3.33 116.2 39.6 2086 90.3
4.50 124.3 43.9 221.7 99.4
tg 2.2, Heso th jy hoa theo ln(t).
He 50 thfly hoa tuon
Loat XI mang
Nghi'Son (XMNS) Chinfon(XMCF) HoSnqThacli{XMHT)
dot, a Thciiqianthfiy hda, ngiy 3 1 7 1 28 1 90
tn(t) l.IO 0.54 0.54 0.55
195 0.60 0.60 0.60
3 } } 0.74 074 07S
4J0 OiO OSD 0,80
ooavixVo'idi (¥ = 0.9 38
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7
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nBarjXMCFJjn*
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gian), b i n kfnh tUdng d g Ra va r(t), lupng CKD va dp co CS cua nd,
ln[tl Hinh 2 2 Quan he mOc thuy hoa ciia xi mang theo thdi gian
Tlf so lieu trong bang 2.2, cd t h e xay difng do tht (hinh 2.2) va quan lie ham thuc nghiem a(t) cCia cac loai xt mang gan dting theo dang:
a ( t ) = 0,08ln[t) + 0,45 (2.7)
=> So.^0^ (2.8) dt t
Tn 50 0 trong cdng thtic (2.4) cd t h i dUpc x i c djnh gan dOng theo ty l | nudc-chat ket dfnh va he so thuy hda [3]:
O = [N/CKD - 0,2^.a{t]] / [N/CKD + 0,323 (2.9) Bang thUc nghiem hien dai cd the xac djnh dUdc b i n kinh tiWng duong Ra va r(t) tif pho phan bd the tich rong, hoac cd the gan cho Ra vh r(t) cac tn so trong pho lo rong ciia nd [dien hinh khoing l O i i m - l mmd^ivdi CLR; 1 - lOOnm dot vdi da xt mang, tif dd tinh toan duoctrj so L.
Neu coi chat I6ng t r o n g he 16 r6ng la nUdc {is aCC) t h i do nhdt \i
= 0.001002 Pa.5 va sO'c cang b^ m a t a = 0.07275 Pa.m. B i n g 2 3 trinh bay kit q u i tfnh t o i n k h o i n g c i c h L khi be t d n g cd N/XIW=0,35, xi mang X=500 kg/m^BT, 6 cac t u o i 3 , 1 4 , 2 8 v i 56 ngay. vdi ban kinh mao quan dten hinh ci!ta CLR lay bSng 0,1 m m va cita da xi mang t i f 1 - 100 n m . B i n g 2.3. Ket q u i tinh t o i n khoang each t h i m n h i p L.
X, kq 500 500 500 500
N, kq 180 180 180 180
r{t), m 10-' 10-^
10"' IO-'"
Ra,
10-.
10-*
10-"
IO-' t, n g i y
3 14 28 56
0.0022020 0.0005271 0.0002782 0.0001473
L, m m 28.7 18.6 8.!
3.5 Theo t i n h t o i n so bp, khoang each tham nhap cua nudc trong CLR vao d i XI mang trong be t d n g dat k h o i n g 2 M- 3cm d tuoi 3 -^ 14 ngay, 5 -;- 8 mm d t u o i 28 n g i y v i khoeing 2 - ^ 4 m m d tuoi 56 -^ 90 ngay. Ket qua nay cho t h i y , nudc IC cd t h e t h i m n h i p phan Idn viing da chat ket dinh trong bi t d n g n^u k i l m soat dupc k h o i n g each giifa cac hat cCia cot lieu hay hesodUvCfa cua b e t d n g .
3 . K £ T L U A N
Tif ket q u i p h i n tich va t i n h t o i n tren cd sd ly thuyet ket hap thuc nghiem, cd t h e k i t l u i n :
- LUOTg nUdc chtia s i n trong cac hat CLR bao hda trUdc se chuyen dich cho nen d i chat ket dinh trong be t d n g , phat huy vai trd b i i co, duy tri d d am b i o hda t r o n g hi 16 r6ng cita d i xi mang, thitc d i y stl hydrat cita chat ket d i n h . . . nghia la se p h i t huy hieu q u i cua ndi b i o dUdng.
• Vtec t i n h toan khoang each tham nhap eua nUdc d u trCr trong CLR v i o n l n da xi mang cd g i i tr[ minh chifng va djnh hUdng trong chpn vat lieu, t h i l t ke va ddng n h i t h o n hpp eung n h u edng nghe thUc hi^n ndi bao d u d n g eho bi t d n g .
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3. IU. M. Bazenov, Bach Dinh Thien, Tran Ngoc Tinh, Cong nghe be long, Nxb Xay dung, 2004, 4. T. C. Powers, The Nonevaporable Water Content of Hardened Portland-CemenI Paste - Its Significance for Concrete Reseadi and Its Method of Determination, ASTIVl Bulletin No. 158,1949, pp 68-76.
5. D.P. Bentz, E.A.B Koenders, S. Monnig, H.W. Reinhardt, K.van Breugel. and G. Ve, Materials Sdence-Based Models in Support of Internal Curing, To be published as part of a RILEM state-of- the-art report, 2006.
6. S. Zhutovsliy, K Kovler, and A. Bentur, Assessment of Water Migration Distance in Internal Curing of Hight-Strength Concrete, Special Pulication, IWarch 1,2004.
04.2016 gnnivii