Optimized Temperature Calculation And Compressive Strength Prediction Of Concrete In Winter Construction

For the concrete in winter construction,the mechanical property of concrete decreases due to the slow hydration process of cement and the freezing of mixed water at low temperature.Improper curing will not only cause quality problems such as cracks,insufficient strength and durability of concrete,but also significantly increase the risk of engineering accidents.Therefore,the curing design based on thermal calculation is a key scientific and technical problem to be solved for the concrete in winter construction.However,there are still some problems to be improved and optimized in the aspects of scientificity,accuracy and efficiency.In this study,a calculation method based on Python program was put forward to estimate cooling temperature of concrete with thermal insulation curing.Then using the integral method to calculate the maturity,and the compressive strength of concrete can be predicted according to the maturity method.By programming the cooling temperature calculation and strength prediction method of non-mass concrete based on transient heat transfer theory,it not only saves a lot of time,but also avoids calculation error to some extent.Moreover,the calculation accuracy was increased from the average daily temperature to the average hourly temperature.On this basis,the original algorithm was optimized in the aspects of the air permeability coefficient,the cement hydration rate and varying ambient temperature.Air permeability coefficient was replaced by convection heat transfer coefficient.The hydration rate of cement at different temperature was calculated iteratively.The cooling temperature and compressive strength of concrete under the condition of real-time varying ambient temperature were calculated.At last,the design of program and software was optimized based on the above improved methods.Then the above optimized calculation method was verified by curing tests of concrete under constant negative temperature environment and natural varying negative temperature environment respectively.The results of constant negative temperature verification test were in good consistency with the calculated temperature and predicted strength,which preliminarily verifies the feasibility and applicability of the calculation method in this paper.The experimental results show that the proposed method is suitable for predicting the fluctuation range of concrete temperature and the average temperature of concrete in the early stage,as well as roughly estimating the compressive strength of concrete under the condition of varying negative temperature.Considering different thermal insulation curing conditions,the influence on temperature drop of concrete was discussed in view of the insulation material thickness and thermal conductivity,the surface area to volume ratio of concrete,the ambient temperature and the initial concrete temperature.The research results show that the higher the initial temperature of concrete and ambient temperature,the thicker the curing material,the lower the thermal conductivity of the curing material and the smaller the surface area volume ratio of concrete,the time for concrete temperature drop to 0? will be longer.And the compressive strength of the concrete at early and later age will both be higher.In addition,within the optional range of curing materials,the selection of curing materials has little impact on the curing effect.Generally speaking,this work provides theoretical analysis and numerical calculation for predicting the temperature history and compressive strength of cold weather concretes before the construction,which can effectively guide the optimization curing design and timely adjustment in winter construction,so as to improve the accuracy and reliability of concrete strength prediction.