| In the process of mix proportion design,production and construction of mass concrete,technical measures such as optimizing mix proportion,optimizing raw materials,cooling by circulating cooling water are adopted to ensure that the working performance and mechanical properties of concrete meet the requirements of design and construction,at the same time,the hydration heat release and adiabatic temperature rise of concrete can be effectively reduced,and the risk of temperature cracks caused by temperature stress can be reduced.In this paper,the hydration exothermic characteristics of different kinds of cement,fly ash and slag powder are studied and analyzed,and the cementitious material system that meets the temperature control requirements of mass concrete is optimized.According to the basic mix ratio obtained by calculation,the mix ratio was optimized by adding mineral admixtures,admixtures and aggregate,etc.The effects of the key parameters of mix ratio on the working performance,mechanical properties and setting time of mass concrete were studied,and the optimal mix ratio of mass concrete was determined.According to the requirement of temperature control of mass concrete,the thermal insulation temperature rise and temperature stress field of concrete are simulated and analyzed,and reasonable circulating cooling water pipes are arranged and temperature monitoring is carried out.The main conclusions are as follows:(1)The hydration heat release test of cementing materials shows that: liu zongqi cement has the highest hydration heat release,followed by yongfa and yuzhu cement,and jiahua cement has the lowest hydration heat release in 3d and 7d.The hydration heat temperature is ranked as: liu zongqi cement > yongfa cement > yuzhu cement >jiahua cement.In the cement-fly ash cementitious material system,the hydration heat ofhengyang fly ash cementitious material is less than that of hanhua fly ash.In the cement-slag powder cementitious material system,the total hydration heat of deyuan slag powder is less than that of sanhe slag powder.After the addition of mineral admixtures,the hydration heat of cementitious materials was significantly lower than that of pure cement.(2)The use of large amount of admixture can effectively improve the performance of concrete,and can ensure the strength of concrete grade requirements;The hydration heat of the system using 15% fly ash + slag powder cementitious material is low,the compressive strength of the 7d phase reaches more than 120% of the designed strength,and the 28 d compressive strength reaches more than 137% of the designed strength.The best aggregate proportion is :1#:2#:3#=10%:78%:12%,the best aggregate fraction is44%,good aggregate gradation can effectively improve the density of concrete,improve the performance of concrete,improve the durability of concrete.(3)This topic C40 concrete mixture ratio of the theoretical calculation for pile caps is the highest temperature of 62.4 ?,the maximum temperature rise of 34.3 ?,the maximum LiBiao temperature is 18.7 ?,can satisfy the requirements of the specification and design;Temperature monitoring in the process of concrete core and the top of the concrete temperature 23.6?,the maximum and lateral maximum temperature24.5?,the average temperature of the cooling rate at 0.8~1.9?/d,temperature control indicators conform to the requirements of the temperature control of mass concrete.(4)With the increase of the content of admixture,the anti-cracking performance of concrete shows a trend of increasing and then decreasing.When the content of admixture is small or too large,the anti-cracking performance of concrete is poor.When the content of admixture is 17%,the anti-cracking performance of concrete is the best.The type and content of mineral admixtures have an effect on the carbonation resistance,and the carbonation depth of hanhua fly ash and deyuan slag powder is obviously reduced at different ages.The concrete with 15% fly ash and 15% slag powder has the lowest carbonation depth and the best carbonation resistance. |
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