Experimental Study On Thermal Properties Of Concrete With Different Mix Ratios Under Constant Strength Conditions

The addition of a large amount of mineral admixture in concrete can effectively reduce the heat of hydration of the cementitious material in the concrete,thereby controlling the temperature stress and slowing the temperature cracks.In addition,the calculation of the adiabatic temperature rise of the concrete in the actual project can help analyze the temperature field to grasp the development process and distribution law of the concrete thermal stress.At present,most studies on the hydration heat of cementitious materials in concrete are based on the study of unit heat release and hydration process of cementitious materials(different mixing amount and admixtures).There is very little concept of strength,and it is very Less reflects the concrete mix ratio.For this reason,based on a large number of concrete mix ratio tests,under the conditions of equal strength(C45,C60,C65),a large amount of mineral admixture was studied using the hydration heat analyzer and the adiabatic temperature rise hyperbola expression of concrete,respectively.The effect of heat of hydration of cementitious materials in concrete and the adiabatic temperature rise of concrete is then optimized by the economic calculation of concrete under equal strength conditions,and the mix ratio of concrete under equal strength conditions is optimized.Research indicates:(1)The concrete mixed with mineral admixture(single doped fly ash,single doped slag powder,mixed fly ash and slag powder)under the conditions of equal strength(C45,C60,C65)effectively reduced the cementitious material system The hydration temperature and heat of hydration,and the greater the amount of mineral admixture,the greater the decrease;in addition,the induction and acceleration periods of the gelling material system are also shortened,causing the second exothermic peak to be delayed.It also delays the initial set time of the cementitious material and affects the initial and final set time of the concrete.(2)Under the conditions of equal strength(C45,C60,C65),the linear fitting result of adiabatic temperature rise hyperbola expression of concrete is very good;the adiabatic temperature rise gradually decreases with the addition of mineral admixture,but with the age of the concrete With the increase of the period,the effect of reducing the adiabatic temperature rise of concrete has become less apparent.The adiabatic temperature rise of concrete is not only affected by the heat of hydration of the cement in the concrete,but also by the amount of cementitious material in the concrete.At the same time,the higher the strength of the concrete,the more the adiabatic temperature rise of the concrete is affected by the amount of cementitious material in the concrete.(3)Under the conditions of equal strength(C45,C60,C65),the cost of concrete shows a decreasing trend as the mineral admixture content increases.The concrete cost of C45 and C65 concrete mixed with mineral admixtures is lower than that of ordinary concrete;when the blending amount of the mineral admixtures in the concrete is the same,the cost of the cementitious material mixed with the(1/1)fly ash and the ore powder concrete< Single fly ash concrete costs.