Tóm tăt Luận án Effect of initial physical properties of roller compacted concrete to construction schedule of concrete gravity dam in Vietnam

The outstandingly advantages of Roller Compacted Concrete (RCC) are faster speed of construction, lower price. At present, its applications have been quite common in Vietnam. Almost the principal calculations in design and construction of RCC Dam inherited from basic concepts of normal concrete or taking from foreign documents. Recently, there have been some incidents happened at main dam of RCC dams, but no evaluations or deeply summaries addressed. Even though the scientific evident and theoretical calculations in applications of RCC technology used in Vietnam, but there is lack of in-depth research. The studies about construction schedule of RCC dams are vital in order to make projects become more reasonable and effective.

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MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT THUY LOI UNIVERISITY LE QUOC TOAN EFFECT OF INITIAL PHYSICAL PROPERTIES OF ROLLER COMPACTED CONCRETE TO CONSTRUCTION SCHEDULE OF CONCRETE GRAVITY DAM IN VIETNAM Major: Hydraulic engineering Code No: 62.58.40.01 SUMMARY OF DOCTORAL DISSERTATION HANOI, 2016 This scientific work has been accomplished at: Water Resources University Supervisor 1: Prof.Dr. Vu Thanh Te Supervisor 2: Assoc.Prof.Dr. Do Van Luong Reviewer 1: Assoc.Prof.Dr. Nguyen Thanh Sang Reviewer 2: Assoc.Prof.Dr. Vu Huu Hai Reviewer 3: Assoc.Prof.Dr. Hoang Pho Uyen This doctor dissertation will be defended at university graduate council of Thuy Loi Univeristy At h00, date month year 2016 It is possible to find out information about this document at: - National Library of Vietnam - Library of Thuy Loi University, Hanoi 1 INTRODUCTION 1. Reasons for choosing the research The outstandingly advantages of Roller Compacted Concrete (RCC) are faster speed of construction, lower price. At present, its applications have been quite common in Vietnam. Almost the principal calculations in design and construction of RCC Dam inherited from basic concepts of normal concrete or taking from foreign documents. Recently, there have been some incidents happened at main dam of RCC dams, but no evaluations or deeply summaries addressed. Even though the scientific evident and theoretical calculations in applications of RCC technology used in Vietnam, but there is lack of in-depth research. The studies about construction schedule of RCC dams are vital in order to make projects become more reasonable and effective. 2. The Purpose of Research This study focus on the behaviour and quantify initial physical properties of RCC, from the beginning of hydration to designated characteristic of RCC, in order to define the thermal evolution, thermal stresses. By doing this, the appropriate speed of construction can be established when building RCC dam project. 3. Research Objectives RCC dams are constructed and under construction in Vietnam. 4. Research scope This research aims at the effect of initial physical propertieson construction schedule of RCC dams, from the beginning of hydration to designated characteristic of RCC. 5. Methodology of Research This study uses the research methods according to present design codes. 6. Significance of Research - Clarify behavior, quantify and determine the impact of initial physical properties of RCC on the thermal evolution, thermal stress and construction schedule. Propose methods for determining reasonable construction schedule in the conditions of Vietnam - RCC technology has been applied on more than 20 concrete gravity dam in Vietnam. However, the quality of these buildings have not considered properly 2 and researched in systematical way. Therefore, results of this study aim to determine the method, providing reliable calculation tools for the design and construction of RCC. It is also suggested solutions to monitor, repair and ensure the safety for constructed buildings and under construction projects. 7. New aspects of Research This study has gained new points as follow: Find out information about relationships of two RCC aggregate gradation such as compressive strength development over time, tensile strength development over time, shrinkage strain over time, Elastic Modulus of Concrete over time. Completing and supplementing thermal evolution calculation and thermal stresses in ANSYS software in order to using as a tool for inspecting the construction speed of Dong Nai 4 dam. 8. Structure of Dissertation This dissertation includes introduction, four chapters, conclusion and discussions. 49 references, 04 authority publications. The main content of the document presented in 144 pages, with 69 tables, 116 figures and 06 appendices. CHAPTER 1: OVERVIEW OF ROLLER-COMPACTED CONCRETE AND RESEARCH QUESTIONS AND OBJECTIVES 1.1. History and development of roller compacted concrete in the world 1961, it was first used at Alpe Gera dam - Italia, Manicongan dam – Canada and Thach Mon - Taiwan; 1970 there is research about RCC in America; 1980 Willow Creek dam was built at Oregon state with a height of 52 m, and a length of 543 m, constructed of roller-compacted concrete; 1970 England, Dunstan, the Construction Industry Research and Information Association (CIRIA) carried out studies for high fly ash content RCC, testing at Water Treatment Plant Tamara – Coruwall (1976) & Wimbledall (1979); 1974, Japan began research about RCC and Shimajigawa dam, 89 m high and 240m length, was the first Japanese RCC dam with 165,000m3 placed RCC in total of 317,000m3 concrete for this dam . 1980, China researched and applied RCC technology; so far China is now the leading country of the world in the construction RCC dams; 3 1.2. Construction of RCC dam in Vietnam From 1996 to 2006, the number of RCC dams with higher cemetious content increased from 43.3% in 1996 to 47.4% in 2002 and 53.4% in 2006. Since December 2005, total 285 RCC dams have been constructed. 1.3. Researches of Roller-Compacted Concrete in Vietnam Vietnam has been researched about RCC dams since 1990. In 2003, Pleikrong hydraulic dams is the first RCC buildings in Vietnam. Until now, there were more than 20 gravity concrete dams completed or being under construction by using RCC technology. 1.4. Literature review of RCC research in Vietnam and the world 1.4.1. Literature review of RCC research in the world 1.4.1.1. Findings of roller compacted concrete in France From 1988 to 1996, France has implemented research projects nationally Bacara of RCC dam [4]. 1.4.1.2. Findings of roller compacted concrete in US The American Concrete Institute: provide high speed of construction and cost savings, but seepage and cracks easier occur easily 1.4.1.3. Findings of roller compacted concrete in Japan RCC has quality of waterproofing and strength as CVC 1.4.1.4. Findings of roller compacted concrete in China The method of RCCD in China based on the experience and lessons of two approaches RCD and RCC combined with fly ash additives available in domestic market. 1.4.2. Research on RCC in Vietnam Research about using domestic material to design aggregate gradation: documents [9]; [10]; [11]. Research about using mineral admixture: documents [12], [13], [14], [15], [16], [17], [18], [19]. Research about applying waterproofing material for RCC: documents [20], [21]; Research about thermal in RCC: documents [22], [23], [24], [25]; 4 Research about construction technologies for RCC: documents [26], [27], [28], [29]. 1.5. The remaining issues of RCC research, objective of dissertation 1.5.1. The remaining issues of RCC research - Improving the quality combined with surface layer to satisfy dam height - The quality of combined surface layer is a cause of seepage - The RCC construction schedule: it depends on thermal evolution, thermal stress, which ensure anti cracking ability of dam. These factors directly influenced by the initial physical parameters of RCC. Therefore, research is necessary to determine a reasonable construction schedule while building RCC dams. 1.5.2. Research orientation content of this research To select materials for RCC aggregate gradation, provide experimental method to figure out physical properties of RCC by current codes. To carry out experiments to manufacture 02 RCC aggregate gradation, which commonly use in Middle and South of Tay Nguyen, namely pozzolanic active mineral RCC and fly ash active mineral RCC. Design of experiments to figure out the development of RCC initial physical properties of 2 optimum aggregate RCC over designated time by using non- linear functions. Integrate ANSYS to calculate the heat & thermal stress in RCC dams. Using integrated ANSYS to find out the appropriate construction speed based on temperature control and thermal stresses in RCC dam. Research Process Flowchart shown in Figure 1.1 Figure 1. 1. Research process of Construction Schedule of RCC 5 CHAPTER 2 SCIENTIFIC BASIS AND EXPERIMENTAL METHODS TO DETERMINE AGGREATE GRADATION & PHYSICAL PARAMETORS RCC 2.1. Factors affecting the physical parameter of RCC The characteristic of materials manufactured RCC Ingredients of aggregate gradation RCC Construction Environment of RCC Construction process of RCC 2.2. Choice materials used in the research and manufacture of aggregate gradation RCC Testing materials are ensured about the number and the stability quality. It is also has been used in RCC building, near the construction site, the quality of materials to satisfy technical requirements for RCC. 2.2.1. Materials used for grading RCC-P (pozzolanic additives) - Concrete: concrete PCB40 Fico, TCVN 6260: 2009 [30] - Pozzolan: mine number 4A Dak Nong, TCVN 8825: 2011 “Mineral admixtures for RCC” [31] - Water: TCVN 4506: 2012 "Water for mixing concrete and mortar - Technical specification” [32] - Small aggregate: in Dak Nong, TCVN 7570: 2006 and ASTM C29: 2003. - Crushed stone: in Dak Nong, TCVN7570:2006“Aggregates for concrete and mortar - Specifications”. - Plasticizers and set-controlling admixtures: Plastiment 96, ASTM C494 type D. 2.2.2. Materials used for grading RCC-T (RCC using fly ash additives) - Concrete: concrete PC40 Ha Tien 1, TCVN 2682: 2009 [34] - Fly ash: Formosa, TCVN 8825: 2011 “Mineral admixtures for RCC”. - Water: TCVN 4506: 2012 "Water for mixing concrete and mortar - Technical specification”. - Sand: in Ninh Thuan, TCVN7570:2006“Aggregates for concrete and mortar - Specifications”. 6 - Crushed stone: in Ninh Thuan, TCVN7570:2006“Aggregates for concrete and mortar - Specifications”. - Fine admixtures: Non-active fillers, about 15% of the volume of sand. - Plasticizers and set-controlling admixtures: Plastiment 96, ASTM C494 type D. 2.3. Determine the optimum gradation RCC 2.3.1. Method to determine the optimum gradation RCC This study use the method to design gradation ACI 211.3R-2002 [5], using experiments and theory "Experimental planning" to figure out the optimum gradation RCC, especially in strength and using materials. 2.3.2. Experimental planning theory in determine gradation RCC [35] 2.4. Methods to determine physical properties of RCC The experimental procedure show in Figure below: Figure 2.3. Experimental procedure determine the physical properties RCC (There are 6 physical factors found in this procedures through headings 2.4.1 to 2.4.6, namely standard, sample and experimental apparatus; formula to determine these properties). 2.5. Determine optimum aggregate gradation RCC 2.5.1. Planning manipulate experimentally determined gradation 2.5.2. Determine optimal aggregate gradation RCC-P Ratio: mineral admixture/ adhesives = 0.63, 0.65 and 0.67; water/ adhesives = 0.56; 0.58 and 0.60; adhesives = 190 kg/m3; Sucking sand level Sand/(sand+ crushed stone) = 0.37; mineral admixtures = 1.8 liter/100kg adhesives Material of RCC Test Specimens Aggregate gradation Mixing, making Test , Experim ental apparatus Experim ental Results Define Propert ies Curing Test Specimen Formula Summary 7 Table 2. 1. Table encryption empirical coefficient Real variable Variable code -1 0 1 Δ PGK/CKD X1 0,55 0,6 0,65 0,05 N/CKD X2 0,56 0,58 0,6 0,02 Table 2. 2. The composition of aggregate RCC - P empirical Case Variable code Real variable Consumption materials for 1 m3 (Kg) Vc (s) C1 C2 MA/A W/A C MA S S W G1 -1 -1 0,55 0,56 85 106 1414 830 106 15 G2 1 -1 0,65 0,56 66 125 1417 832 106 13 G3 -1 1 0,55 0,60 85 106 1401 823 114 9 G4 1 1 0,65 0,60 66 125 1404 825 114 5 G5 -1,412 0 0,529 0,58 88 102 1407 826 110 16 G6 1,412 0 0,671 0,58 62 128 1411 829 110 8 G7 0 -1,412 0,60 0,552 75 115 1418 833 105 17 G8 0 1,412 0,60 0,608 75 115 1400 822 116 6 G9 0 0 0,60 0,58 75 115 1409 828 110 8 G10 0 0 0,60 0,58 75 115 1409 828 110 11 G11 0 0 0,60 0,58 75 115 1409 828 110 10 G12 0 0 0,60 0,58 75 115 1409 828 110 9 G13 0 0 0,60 0,58 75 115 1409 828 110 10 The samples according to the gradation on the result compressive strength Rn (MPa) at the age of 90 days and 365 days of age as follows: Table 2. 3. Results compressive strength RCC - P G G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 G13 Rn90 14,8 13,8 14,2 14 14,5 13,5 15,2 14,6 14 14,3 14,5 14,3 14,8 Rn365 15,4 15,11 15,1 15,0 15,4 15,0 15,5 15,2 15,2 15,1 15,3 15,4 15,3 The regression equation for compressive strength of 365 days (2.1): Rn365 =+15,26 - 0,12X1 – 0,10X2 + 0,047X1X2 – 0,061X12 + 0,014X22 The rate of mineral admixture/adhesives and rate of water/adhesives saw influences to strength of RCC, by following results: 8 Figure 2.12. The correlation of MA/adhesion and ratio Water/adhesion of Rn365 RCC-P Figure 2.13. The correlation contour plots of MA/adhesion and ratio Water/adhesion of Rn365 RCC-P The optimum aggregate gradation RCC-P: Cement: 75kg, mineral admixtures: 115Kg, sand 804kg, crushed stone 4, 75÷19 (mm): 722kg crushed stone 20÷50 (mm): 670kg, water 110 liter, chemical admixture 3.4 liter. 2.5.3. Determine optimal aggregate gradation RCC-T Ratio of admixture/ adhesives: 0.58; 0.6 and 0.62; water/ adhesives:0.56,0.58 and 0.6.Adhesives=200kg. Admixtures:15% weight of sand; Sucking sand level Sand/(sand+crushed stone)=0.34; chemical admixture=1.0 liter/100kg/adhesive. The regression equation for compressive strength of 365 days (2.2): Rn90 = - 785,34+1291,5X1+1471,34X2+ 231,25X1X2 - 1204,06X12 - 1391,56X22 Figure 2. 16. The correlation of MA/adhesion ratio and Water/adhesion ratio of Rn90 RCC-T Figure 2. 17. The correlation contour plots of MA/adhesion ratio and Water/adhesion ratio of Rn90 RCC-T Optimum gradation of RCC-T: Concrete: 80kg, Mineral Admixture: 120Kg, sand 687 kg; crushed stone: 5÷19 (mm): 479kg, 20÷39 (mm): 295kg, 40÷60 (mm): 628kg, water 115 liter, Chemical Admixture 2 liters. 9 CHAPTER 3 RESEARCH THE DEVELOPMENT OF SOME INITIAL PHYSICAL PARAMETER OF ROLLER COMPACTED CONCRETE 3.1. Research the development of some initial physical parameter of roller compacted concrete 3.1.1. Research the development of compressive strength of RCC (Rn) The correlation function show the development of Rn for gradation RCC-P: Yn1 = 2.64ln(x) + 2.24 with R2= 0.9 (3.1a); gradation of RCC-T: Yn2 = 4.54ln(x) + 2.52 với R2= 0.93 (3.1b) Table 3. 3. Compressive strength of RCC-P by calculations Time (date) 1 3 5 7 14 28 56 90 Compressive strength (Mpa) 2.24 5.14 6.49 7.38 9.21 10.4 12.87 14.12 % discrepancy with the previous day 26.30 9.99 5.84 10.68 19.87 16.58 9.73 Table 3. 4. Compressive strength of RCC-T by calculations Time (date) 1 3 5 7 14 28 56 90 Compressive strength (Mpa) 2.52 7.51 9.83 11.35 14.5 17.65 20.8 22.95 % discrepancy with the previous day 32.48 11.49 6.57 11.77 21.70 17.83 10.36 Figure 3.3. Compressive strength ~ time for 2 gradation RCC-P& RCC-T 3.1.2. Research the development of tensile strength of RCC (RK) The correlation function show the development of Rk for gradation RCC-P: Yk1 = 0.258ln(x) + 0.029 with R2 = 0.9764 (3.2a) for gradation RCC-T: Yk2 = 0.289ln(x) + 0.051 with R2= 0.971(3.2b). 10 Table 3.7. Compressive strength of two gradation RCC-P&RCC-T according two correlation and regression Age (days) 1 3 5 7 14 28 56 90 RCC- P Rk (Mpa) 0.02 0.28 0.39 0.47 0.63 0.89 1.07 1.19 (%) increase 50.33 14.89 8.10 2.76 1.06 0.43 0.24 RCC- T Rk (Mpa) 0.05 0.37 0.52 0.61 0.81 1.01 1.21 1.35 (%) increase 46.63 14.28 7.83 2.70 1.04 0.43 0.24 Figure 3.6. Correlation of Rk by ages of RCC-P&RCC-T Table 3.8. Compare the increasing speed of tensile strength, compressive strength of RCC Gradation Rn28 Rn90 Increasing rate (%) Rk28 Rk90 Increasing rate (%) RCC-P 11.8 15.2 129 0.91 1.28 140 RCC-T 18.8 20.8 111 1.09 1.31 120 3.1.3. Study of Shrinkage strain of RCC 3.1.3.1. Study of thermal shrinkage strain of RCC Figure 3.7. The development of thermal at some points of RCC sample 11 3.1.3.2. Study of thermal coefficient of RCC Table 3.12. Some thermal coefficient of RCC Original of Aggregate Water/(Cement Mineral Additives) Water (Kg/m3) Coef. BDN 10-6/0C River sand, gravel 0.44 70 9.064 Artificial sand, Crushed stone, limestone 0.86 93 5.803 3.1.3.3. Research shrinkage due to dehydration (dry shrinkage) of RCC Table 3.13. Volumetric shrinkage of RCC Coefficient of Volumetric shrinkage Cn (%*10-2) Age 1 2 3 4 5 6 7 14 28 56 90 365 RCC- P 0.30 0.61 1.11 1.51 1.91 2.11 2.48 2.79 3.44 3.95 4.02 4.23 RCC- T 0.42 0.61 0.90 1.11 1.61 1.80 2.02 2.21 2.51 2.65 2.78 - Figure 3.10. The relationship of shrinkage~time for two gradation: RCC- P&RCC-T Correlation and regression of shrinkage with time of gradation RCC-P: Ycn1 = 0.0075ln(x) + 0.0057 with R2= 0.9216 (3.3a); gradation BTĐL-T: Ycn2 = 0.0057ln(x) + 0.005 with R2= 0.9116 (3.3b) 3.1.4. Heat transfer coefficient, Coefficient of thermal conductivity 3.1.4.1. Heat transfer coefficient Heat transfer coefficient (HSTN) shows the diffusion of heat from concrete (unit m2/h and was marked as a). The bigger value of HSTN, the less time require to 12 temperature at points of concrete sample reach same values. HSTN of concrete depends on type of aggregate, the amount of aggregate, amount of water and weight of concrete. Generally, HSTN has the reverser trend when temperature increase, but it has the same pattern with proportion of aggregate in concrete. The reason for this is that RCC used less water and more aggregate than CVC so that HSTN of RCC larger than CVC, but the different are not so significant [41]. 3.1.4.2. Coefficient of thermal conductivity  = . C. γ; with  is Coefficient of thermal conductivity of concrete [KJ/(m.h .0C)]; : HSTN(m2/h); C: heat capacity of concrete [KJ/(Kg.0C)]; γ: Weight of concrete [Kg /(m3)] Table 3.14. Research results on the thermal characteristics of RCC Amount of adhesive (kg/m3) 120 150 160 210 236 t (0C) 40 60 40 60 40 60 40 60 40 60 ( m2/h) 0.0039 0.0038 0.0039 0.0038 0.0034 0.0033 0.0046 0.0049 0.0039 0.0038  [kJ/(m.h .0C)] 8.25 8.46 8.25 8.46 7.2 7.91 7.0 - 8.21 8.46 C [kJ/(kg .0C)] 0.87 0.91 0.84 0.9 0.84 0.9 0.96 - 0.87 0.91 a (10-6/0C) 9.06 9.06 9.25 9.25 8.35 8.35 10.4 10.4 9.06 9.06 3.1.5. Research Elastic modulus of RCC 3.1.5.1. Static Elastic modulus (EM) in compression Figure 3. 13. Evolutions of EM of RCC-P & RCC-T 13 The correlation functions saw EM of gradation RCC-P: Yđh1 = 0.4823ln(x) + 0.0946 with R2= 0.9758 (3.5a); gradation RCC-T: Yđh2 = 0.5031ln(x) + 0.0808 with R2 = 0.9831 (3.5b) EM of two gradation RCC-P & RCC-T shows no significant in the total amount of aggregate. However, the EM of RCC-T is higher than RCC-P due to the higher amount of adhesion of RCC-T in comparison to RCC-P. 3.1.5.2. Static Elastic modulus in tensile of RCC Static Elastic modulus in tensile of RCC influenced by many factors, which have similar rule. By [38], Elastic modulus in tensile of RCC at the age of 90 days (with RCC of 3 level gradation) = 1.3 ÷ 1.48 Elastic modulus in compression. Particularly, CVC has similar of Elastic modulus in tensile and compression. 3.1.5.3. Ultimate tensile strain of RCC It is the biggest value of Rk when the sample split of and using maximum value to present. It influenced by the amount of adhesion, Rk, Elastic modulus in tensile, age of concrete etc. (mainly on ad
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