DỰ BÁO TUỔI THỌ SỬ DỤNG CỦA CẦU BÊ TÔNG CỐT THÉP VEN BIỂN VIỆT NAM DO XÂM NHẬP CLO

Header Page of 123 B GIO DC V O TO TRNG I HC GIAO THễNG VN TI O VN DINH D BO TUI TH S DNG CA CU Bấ TễNG CT THẫP VEN BIN VIT NAM DO XM NHP CLO CHUYÊN NGàNH : Kỹ THUậT XÂY DựNG CÔNG TRìNH ĐặC BIệT Mã Số : 62.58.02.06 LUậN áN TIếN Sĩ Kỹ THUậT Người Hướng dẫn khoa học: GS.TS PHM DUY HU PGS.TS BI TRNG CU H NI - 2014 Footer Page of 123 Header Page of 123 i LI CAM OAN Tụi xin cam ủoan lun ỏn ny l cụng trỡnh nghiờn cu ca cỏ nhõn tụi Cỏc kt qu nờu lun l trung thc v cha ủc cụng b cỏc cụng trỡnh khỏc H NI NGY THNG NM 2014 TC GI O VN DINH Footer Page of 123 Header Page of 123 ii LI CM N Lun ỏn ủc thc hin di s hng dn trc tip ca GS.TS Phm Duy Hu v PGS.TS Bựi Trng Cu Tụi xin chõn thnh cm n cỏc thy hng dn ủó ch dn tn tỡnh v ủó ủúng gúp cỏc ý kin quý bỏu ủ giỳp tụi thc hin lun ỏn ny Tụi xin cm n cỏc quý thy cụ b mụn Cụng Trỡnh Giao Thụng Thnh Ph v Cụng trỡnh Thy, ủc bit l GS.TS Nguyn Vit Trung ủó giỳp ủ tụi rt nhiu quỏ trỡnh hc nghiờn cu Tụi xin trõn trng cm n PGS.TS Trn Quang Vinh ủó ủúng gúp cỏc ý kin cho lun ỏn Tụi xin trõn trng cm n Phũng o to sau i hc trng i hc Giao Thụng Vn ti ủó to ủiu kin thun li cho tụi quỏ trỡnh hc nghiờn cu Tụi cng xin trõn trng cm n Ban Giỏm Hiu trng i hc Giao Thụng Vn ti, lónh ủo khoa Cụng Trỡnh ủó to ủiu kin ủ tụi ủc hc v nghiờn cu Cui cựng tụi by t cm n cỏc ủng nghip, gia ủỡnh ngi thõn ủó giỳp ủ tụi quỏ trỡnh hc tp, nghiờn cu H NI NGY THNG NM 2014 TC GI O VN DINH Footer Page of 123 Header Page of 123 iii MC LC Li cam ủoan i Li cm n ii Mc lc iii Danh mc cỏc bng biu vi Danh mc cỏc hỡnh v vii Danh mc cỏc ch vit tt, cỏc ký hiu ix M U CHNG TNG QUAN CC NGHIấN CU V TUI TH S DNG CA CU Bấ TễNG CT THẫP DO XM NHP CLO TRấN TH GII V VIT NAM 1.1 M ủu 1.2 Cỏc nghiờn cu v ủ bn v tui th s dng trờn th gii 1.2.1 Cỏc nghiờn cu v lý thuyt ủ bn ca bờ tụng 1.2.2 Cỏc nghiờn cu v c ch xõm nhp clo vo bờ tụng 10 1.2.3 Cỏc nghiờn cu c ch n mũn ct thộp 13 1.2.4 Cỏc thớ nghim v sc khỏng xõm nhp clo ca bờ tụng 21 1.2.5 Cỏc nghiờn cu v h s khuch tỏn 30 1.2.6 Cỏc nghiờn cu v thi gian ủu n mũn v thi gian lan truyn n mũn, tui th s dng 32 1.3 Cỏc nghiờn cu nc 35 1.4 Nhn xột v hng nghiờn cu ca lun ỏn 37 1.5 Mc tiờu ca lun ỏn 38 1.6 Ni dung v phng phỏp nghiờn cu 38 1.6.1 Ni dung nghiờn cu 38 1.6.2 Phng phỏp nghiờn cu 38 CHNG NGHIấN CU XC NH H S KHUCH TN CLO TRONG Bấ TễNG 39 2.1 Gii thiu chung 39 2.2 Thớ nghim v xỏc ủnh h s khuch tỏn clo bờ tụng 40 2.2.1 Thớ nghim thm nhanh clo ASTM C1202 40 2.2.2 Kt qu thớ nghim thm nhanh clo ASTM C1202 48 Footer Page of 123 Header Page of 123 iv 2.2.3 Xõy dng cụng thc xỏc ủnh h s khuch tỏn clo t kt qu thớ nghim C1202 49 2.2.4 p dng phng trỡnh DC1202 tớnh h s khuch tỏn clo t kt qu thớ nghim C1202 50 2.3 Tng kt cỏc kt qu d bỏo h s khuch tỏn trờn th gii 51 2.3.1 D bỏo h s khuch tỏn (D28) t t l nc trờn xi mng 52 2.3.2 nh hng ca nhit ủ ủn h s khuch tỏn 52 2.3.3 nh hng ca thi gian ủn h s khuch tỏn 53 2.3.4 nh hng ca mui silic ủn h s khuch tỏn 55 2.3.5 nh hng ca ủ m ủn h s khuch tỏn 57 2.3.6 nh hng ca nt ủn h s khuch tỏn 57 2.3.7 H s khuch tỏn biu kin 58 2.3.8 Tớnh h s khuch tỏn theo d bỏo v theo cụng thc kinh nghim 59 2.4 So sỏnh cỏc kt qu tớnh toỏn v tho lun 60 2.4.1 So sỏnh kt qu tớnh h s khuch tỏn D 60 2.4.2 Phõn tớch, nhn xột kt qu tớnh h s khuch tỏn D 63 2.5 Kt lun chng 63 CHNG XY DNG Mễ HèNH D BO TUI TH S DNG CU Bấ TễNG CT THẫP VEN BIN VIT NAM DO XM NHP CLO 65 3.1 Gii thiu chung 65 3.1.1 Khỏi nim tui th s dng 66 3.1.2 Tui th s dng theo tỏc ủng ca s xõm nhp clo mụi trng bin 67 3.2 Xõy dng mụ hỡnh d bỏo thi gian ủu n mũn 71 3.2.1 Tng quỏt 71 3.2.2 Cỏc tham s ca mụ hỡnh 71 3.2.3 Xõy dng mụ hỡnh d bỏo thi gian ủu n mũn 80 3.2.4 Xõy dng chng trỡnh tớnh thi gian ủu n mũn bng Mathlab 88 3.3 Xõy dng mụ hỡnh d bỏo thi gian lan truyn n mũn 88 3.3.1 Cỏc ủ chung 88 3.3.2 Xem xột cỏc mụ hỡnh hin cú 89 Footer Page of 123 Header Page of 123 v 3.3.3 Mụ hỡnh ủ xut 94 3.4 S ủ thut toỏn tớnh tui th s dng ca cu bờ tụng LifeConBridge 109 3.5 Kt qu tớnh v nhn xột 111 3.5.1 Kim chng kt qu tớnh ca mụ hỡnh ủ xut 111 3.5.2 Kt qu tớnh toỏn thớ d 112 3.5.3 Nhn xột kt qu: 114 3.6 D bỏo tui th s dng ca cu bờ tụng ct thộp ven bin Vit Nam 115 3.6.1 c ủim khớ hu vựng ven bin Vit Nam v bin ủi khớ hu 115 3.6.2 D bỏo tui th s dng ca cu bờ tụng ct thộp ven bin Vit Nam 118 3.7 Kt lun chng 120 CHNG CC BIN PHP KẫO DI TUI TH S DNG V TH D TNH TON .122 4.1 Cỏc bin phỏp di tui th s dng 122 4.1.1 Vi cỏc kt cu mi 122 4.1.2 Vi cỏc kt cu c 127 4.2 Thớ d tớnh toỏn cho mt s b phn cu T 127 4.2.1 Cỏc thụng sụ tớnh tui th s dung ca cu T 127 4.2.2 Kt qu tớnh toỏn tui th s dng 129 4.2.3 Cỏc kt lun rỳt t thớ d nghiờn cu 130 4.3 Kt lun chng 131 KT LUN V KIN NGH 132 1/ Kt lun 132 2/ Kin ngh 134 3/ Hng nghiờn cu tip theo 135 DANH MC CễNG TRèNH CA TC GI .136 TI LIU THAM KHO 137 PH LC 145 PH LC 155 Footer Page of 123 Header Page of 123 vi Danh mc cỏc bng biu Bng 1.1 nh hng ca cỏc tham s khỏc ủi vi quỏ trỡnh n mũn 21 Bng 1.2 Tng kt cỏc phng phỏp thớ nghim xõm nhp clo 30 Bng 2.1 Thnh phn bờ tụng ca cỏc t mu 42 Bng 2.2 Mc ủ thm ion clo 45 Bng 2.3 Kt qu thớ nghim theo ASTM C1202 48 Bng 2.4 Kt qu tớnh DC1202 t thớ nghim 51 Bng 2.5 Cỏc giỏ tr m cho cỏc loi bờ tụng 54 Bng 2.6 Kt qu D theo d bỏo v cỏc cụng thc kinh nghim 60 Bng 2.7 DC1202, D d bỏo v cỏc cụng thc kinh nghim 61 Bng 2.8 So sỏnh kt qu tớnh h s D 62 Bng 3.1 Tc ủ tớch ly v nng ủ ln nht ca clo b mt 73 Bng 3.2 Túm tt cỏc tiờu chun xỏc ủnh gii hn ti cho phộp ca clo va v bờ tụng d ng lc 78 Bng 3.3 nh hng ca canxi nitrit (CNI) trờn ngng clo ti hn 79 Bng 3.4 Kt qu tinh thi gian ủu n mũn H=100% 111 Bng 3.5 Kt qu tinh thi gian ủu n mũn H=75% 112 Bng 3.6 Kt qu tinh thi gian lan truyn n mũn theo nt bờ tụng bo v 112 Bng 3.7 Kt qu tinh thi gian ủu n mũn theo cỏc tham s 113 Bng 3.8 Kt qu tớnh thi gian lan truyn n mũn theo cỏc tham s (quan ủim 1: nt hon ton bờ tụng bo v) 113 Bng 3.9 Kt qu tớnh thi gian lan truyn n mũn theo cỏc tham s (quan ủim 2: n mũn gõy nguy him) 114 Bng 4.1 Kt qu tớnh tui th s dng, vi cỏc gii phỏp kt hp 126 Bng 4.2 Thụng s kt cu v vt liu 128 Bng 4.3 Thụng s mụi trng 129 Bng 4.4 Kt qu tớnh tui th s dng, bi toỏn 1D 129 Bng 4.5 Kt qu tớnh tui th s dng, bi toỏn 2D 130 Bng 4.6 Kt qu tớnh thi gian lan truyn n mũn t2 130 Footer Page of 123 Header Page of 123 vii Danh mc cỏc hỡnh v Hỡnh 1.1: S lng cỏc h hi quan sỏt ủc Nht bn (ngun d liu Prof Hiroshi Mutsuyoshi 2001) Hỡnh 1.2: Biu ủ Pourbaix quan h th ủin cc v ủ pH ca h Fe-H2O 15 Hỡnh 1.3 Cỏc phn ng cc dng v cc õm (Beeby) 18 Hỡnh 1.4 Th tớch tng ủi ca cỏc sn phm n mũn st 20 Hỡnh 1.5 Biu ủ th hin cỏc h hi n mũn gõy nt, v, tỏch lp 20 Hỡnh 1.6 S ủ thớ nghim theo AASHTO T259 (salt ponding) 21 Hỡnh 1.7 S ủ thớ nghim khuch tỏn khi- Bulk Diffusion Test (NordTest NTBuild 443) 22 Hỡnh 1.8 S ủ thớ nghim AASHTO T277 (ASTM C1202) 23 Hỡnh 1.9 S ủ thớ nghim k thut ủin di 25 Hỡnh 1.10 S ủ thớ nghim ủin di ca Tang v Nilsson 26 Hỡnh 1.11 S ủ thớ nghim ủin di nhanh (NordTest NTBuild 492) 27 Hỡnh 1.12 Thit b ủo ủin tr sut mt chiu 29 Hỡnh 1.13 S ủ phng phỏp ủim ủo ca Wenner 29 Hỡnh 1.14: Tui th s dng ca kt cu bờ tụng ct thộp: Mụ hỡnh hai giai ủon ca Tuuti 1980 33 Hỡnh 2.1 S ủ bm hỳt chõn khụng mu th C1202 43 Hỡnh 2.2 S ủ ủo ủin tớch 44 Hỡnh 2.3 Cỏc nh thớ nghim thm nhanh clo theo ASTM C1202 47 Hỡnh 2.4 nh hng ca t l W/C trờn h s khuch tỏn Clo bờ tụng nhit ủ 20oC 52 Hỡnh 2.5 nh hng ca tro bay v x ủi vi h s khuch tỏn 55 Hỡnh 2.6 nh hng ca silica fum ủi vi h s khuch tỏn Hỡnh 2.7 Biu ủ cỏc kt qu tớnh D 62 Hỡnh 3.1: nh ngha tui th s dng v kộo di tui th s dng 67 Hỡnh 3.2: nh hng ca mng v sn ph b mt 75 Hỡnh 3.3: gúc phn t ct 2D 84 Hỡnh 3.4: Cỏc bin gúc phn t ct 2D 85 Hỡnh 3.5: p lc trờn bờ tụng hỡnh thnh cỏc sn phm n mũn (Mụ hỡnh ca Liu) 91 Footer Page of 123 Header Page of 123 viii Hỡnh 3.6: Lý tng húa ca bờ tụng bo v nh l mt hỡnh tr thnh dy: 95 Hỡnh 3.7: Khong thi gian t ủu n mũn thộp ủn nt hon ton bờ tụng bo v v ti nguy him chu lc 96 Hỡnh 3.8: S ủ c lng cho mt mỏt bỏn kớnh thộp rs2 102 Hỡnh 3.9: Mi quan h gia tc ủ n mũn v ủ m tng ủi vi bờ tụng tui nm cú hm lng ion Cl- l 1.8kg/m3 nhit ủ 23oC 105 Hỡnh 3.10 Mt ủ dũng n mũn vi thi gian Ccl=1.25kg/m3, nhit ủ 20oC, ủ m H=75% theo Liu v Weyers 107 Hỡnh 3.11 S ủ thut toỏn tớnh tui th s dng xõm nhp clo 110 Hỡnh 3.12: Mc tng nhit ủ trung bỡnh nm (oC) vo gia th k 21 theo kch bn phỏt thi trung bỡnh 116 Hỡnh 3.13: Mc tng nhit ủ trung bỡnh nm (oC) vo cui th k 21 theo kch bn phỏt thi trung bỡnh 117 Hỡnh 3.14: Cỏc vựng mụi trng bin ca tr cu bờ tụng 119 Hỡnh 3.15: nh tớnh v phõn b nng ủ clo b mt 120 Hỡnh 4.1: Quan h gia chiu dy lp bờ tụng bo v vi thi gian ủu n mũn w/c=0.35, nhit ủ 20oC, ủ m H=80% cho vựng khớ quyn bin 123 Hỡnh 4.2: Quan h gia chiu dy lp bờ tụng bo v vi thi gian t ủu n mũn ủn nt cho bờ tụng fc=40MPa,ủng kớnh ct thộp d=16mm, nhit ủ 20oC, ủ m H=80% cho vựng khớ quyn bin 123 Hỡnh 4.3: Quan h gia t l nc trờn xi mng w/c vi thi gian ủu n mũn (chiu dy lp bờ tụng bo v L=70mm, nhit ủ 20oC, ủ m H=75% cho vựng khớ quyn bin) 124 Hỡnh 4.4: Quan h gia t l mui si lớc (silica fume) vi thi gian ủu n mũn (chiu dy lp bờ tụng bo v L=75mm, nhit ủ 25oC, ủ m H=75% cho vựng khớ quyn bin) 125 Footer Page of 123 Header Page 10 of 123 ix Danh mc cỏc ch vit tt, cỏc ký hiu rs1 Lng gim bỏn kớnh ca ct thộp ti thi ủim bt ủu nt rs Lng gim bỏn kớnh ca ct thộp g chốn vo vt nt Ecef Mụ ủun ủn hi cú hiu (xột ủn t bin); H s t bin ca bờ tụng; Chiu dy vựng xp bao quanh ct thộp; c H s poisson ca bờ tụng c=0,18-0,20; Chuyn v hng tõm ca bờ tụng; d S thay ủi ủng kớnh ca ct thộp r H s poisson ca g st; rust Chuyn v nộn hng tõm ca g (cỏc sn phm n mũn) T l mc tng nhit ủ thớ nghim C1202 LifeConBridge- Service Life of concrete Bridge- Tui th s dng ca cu bờ tụng A Din tớch tit din mu th BTCT Bờ tụng ct thộp C Nng ủ clo C(x,t) Nng ủ clo ti chiu sõu x v thi gian t C0 Nng ủ clo ban ủu bờ tụng CNI Canxi nitrit Cs Nng ủ clo ti b mt bờ tụng Cs(t) Nng ủ clo ti b mt bờ tụng ti thi ủim t d ng kớnh ct thộp D H s khuch tỏn clo bờ tụng D(t) H s khuch tỏn clo bờ tụng thi ủim t D(T) H s khuch tỏn clo bờ tụng nhit ủ T D28 H s khuch tỏn clo bờ tụng tui 28 ngy DPC H s khuch tỏn clo bờ tụng thng DSF H s khuch tỏn clo bờ tụng cú mui silic (silica fume) E in th ỏp dng Footer Page 10 of 123 Header Page 153 of 123 141 40 Mark G Richardson (2004), Fundamentals of durable reinforced concrete, published in the Taylor & Francis e-Library, simultaneously published in the USA and Canada 41 Morinagn, S (1989) Prediction of Service Lives of Reinforced Concrete Buildings Based on Rate of Corrosion of Reinforcing Steel,S pecial Report of the Institute of Technology, Skimiza Corporation, Japan 42 Morris, W., Moreno, E.I and Sagues, A A.(1996), Practical Evaluation of Resistivity of Concrete in TestCylinders using a Wenner Array Probe, Cement and Concrete Research, Vol 26, No 12, pp.1779-1787 43 M.S Shetty (2005) Concrete Technology: Theory and Practice published by S Chand & Company Pvt.Ltd 7361, Ram Naga, New Delhi 44 Mutsuyoshi, H (2001): Present Situation of durability of posttensioned pc bridges in Japan, in: Durability of post-tensioning tendons (Taerwe, L ed.), Fộdộration Internationale du Bộton, Lausanne, pp 75-88 45 NCHRP- NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM, REPORT 558-Manual on Service Life of CorrosionDamaged Reinforced Concrete Bridge Superstructure Elements 46 Nielsen A (1985) Durability, pp 200-243 in Beton Bogen, Aalborg Cement Company, Aalborg, Portland 47 Omar S Baghabra Al-Amoudi, Walid A Al-Kutti, Shamsad Ahmad, Mohammed Maslehuddin (2009) Correlation between compressive strength and certain durability indices of plain and blended cement concretes Cement & Concrete Composites 31 672676 48 P Vassie (1984), Reinforcement corrosion and the durability of concrete bridges, Proceeding of Institution of Civil Engineers 76, 713 723 Footer Page 153 of 123 Header Page 154 of 123 142 49 Purvis RL, Babaei K, Clear KC, Markow MJ (1994), Life-cycle cost analysis for protection and rehabilitation of concrete bridges relative to reinforcement corrosion, Washington, DC: Strategic Highway Research Program, National Research Council 50 Rodriguez, O.G & Hooton, R.D (March 2003), Influence of cracks on chlo-ride ingress into concrete, ACI Materials Journal, Vol 100, No 2, p 120-126 51 Schieòl P.; Wiens U (1995), Rapid Determination of Chloride Diffusivity in Concrete with Blending Agents, Proceedings of RILEM International Workshop on Chloride Penetration into Concrete, St.Rộmy-lốs-Chevreuse, France, pp 115-125 52 Sharif, A., Loughlin, K F., Azad, A K and Nawaz, C M.,(1999), Determination of the effective diffusion coefficient in concrete via a gas diffusion technique, Proceedings of the international conference on concrete durability and repair technology, Edited by Dhir R K and McCarthy M J., published by Thomas Telford 53 Stanish, K (2000), Predicting the Diffusion Coefficient of Concrete from Mix Parameters, University of Toronto Report 54 Swamy,R.N., Hamada and Laiw,J.C, (Jul 1994) A citical evaluation of chloride penetration into concrete in marine environment, in Corrosion and Corrosion Protection of steel in concrete Proceedings of an International Conference, University of Sheffield, England, 404-419 55 Tang, L and Nilsson, L-O (1992), Chloride diffusivity in high strength concrete at different ages. Nordic Concrete Research, pp 162-171 56 Tang Luping, Joost Gulikers (2007) On the mathematics of timedependent apparent chloride diffusion coefficient in concrete - Cement and Concrete Research 37, 589595 57 Technical Research Centre of Finland (VTT) (2003), LIFECON Deliverable D 3.2, Service Life ModelsLife -Cycle Management of Footer Page 154 of 123 Header Page 155 of 123 143 Concrete Infrastructures for Improved Sustainability, Project funded by the European Community under the Competitive and Sustainable Growth Programme (2001-2003) 58 TRB (1996), Transverse cracking in newly constructed bridge decks, National Co-operative Highway Research Program Report 380, Transportation Research Board, National Academy Press, Washington, 126 p 59 Tuutti, K (1980) Service life of structures with regard to corrosion of embedded steel, Proceedings of the International Conference on Performance of Concrete in Marine Environment, ACI SP-65, pp 223236 60.57 T Liu, R.W Weyers (1998), Modeling the dynamic corrosion process in chloride contaminated concrete structures, Cement and Concrete Research 28 (3) 365379 61 Uhlig, H H (1971), Corrosion and Corrosion Control, Wiley, New York 62 Vu, K A T and Stewart, M G (2000): Structural reliability of concrete bridges including improved chloride-induced corrosion models, Structural Safety, Vol 22, pp 313-333 63 Weyers, R.E (1998), Service life model for concrete structures in chloride laden environments. ACI Materials Journal, Vol 95 (4), pp 445-453 64 Whiting, D (1981), Rapid Measurement of the Chloride Permeability of Concrete, Public Roads, Vol 45,No 3, pp 101-112 65 W Lúpez, J.A Gonzỏlez (1993), Influence of the degree of pore saturation on the resistivity of concrete and the corrosion rate of steel reinforcement, Cement and Concrete Research 23 (2) 368376 66 Youping Liu (October 21, 1996), Modeling the Time-to-Corrosion Cracking of the Cover Concrete in Chloride Contaminated Reinforced Footer Page 155 of 123 Header Page 156 of 123 144 Concrete Structures, Doctor of Philosophy, Virginia Polytechnic Institute and State University 67 Zhang, and Gjorv, O.E (October 1995), Effect of Ionic Interaction in Migration Testing of Chloride Diffusivity in Concrete, Cement and Concrete Research, V.25, No.7, pp.1535-1542 Footer Page 156 of 123 145 Header Page 157 of 123 PH LC Phn mm LifeConBridge BI TON 1D VNG THY TRIU % Du bao tuoi tho su dung cau be tong cot thep ven bien Viet Nam xam nhap clo-"Sevice Life Concrete Bridges" % Phuong phap sai phan huu han Crank-Nicholson clear all; % Cac thong so dau vao co ban cua bai toan fc = 50; %Cuong chiu nen cua be tong o 28 MPa fsp = 0.59*sqrt(fc); %Cuong chiu keo uon MPa gammac = 2500; % Trong luong rieng cua be tong kg/m3 Ec = 0.043*(gammac)^(1.5)*sqrt(fc);%Mo-duyn dan hoi cua be tong phi = 2;% He so tu bien cua be tong Ecef =Ec/(1+phi); roth =2.5; % Phan tram mat mat dien tich TD thep toi han db = 16; %Duong kinh cot thep vc = 0.18; % He so poisson n = 2.7; %He so gian no the tich n=2.7-3.0 k1 = 0.5; % muc lap day vao vet nut delta0 = 15; % chieu day lop xi micro - m r0 = db/2+delta0/1000; b = 1000; Lc = 75; %Chieu day cau kien -mm % Chieu day lop be tong bao ve-mm dt = 0.1; % buoc thoi gian tinh bang nam dx =5; %Do lon cua luoi chia theo chieu day - mm nx1 =Lc/dx; % So buoc chia cua khoang cach nx = b/dx; NX = 0.35; %Ty le nuoc/xi mang FA = 0; % phu gia Tro bay SF= 2;% phu gia silica-fume SG=0; %Phu gia xi lo Tref = 293.15; T = 299.05; % Nhiet tuyet doi K D28 = exp(-0.165*SF)*10^(-12.06+2.4*NX); % He so khuech tan o 28 tuoi m = 0.2+0.4*(FA/50+SG/70); % D28 thi nghiem Hc = 0.75; %Hc = 75% am chuan H = 0.80; %Do dam tuong doi cua mtH U = 35000; G = 8.314; fT = exp(U/G*(1/Tref-1/T)); fH = 1/(1+((1-H)/(1-Hc))^4); Footer Page 157 of 123 Header Page 158 of 123 146 ucth = 0.15; uth = 0.15*ones(nx1+1,1); % Nong clorua tai thoi diem t = for i = 1:nx+1 x(i) =(i-1)*dx; u(i,1) =0; end k=1; u_new =u; while u_new(nx1+1)