Influence Of Low Temperature Environment On The Compressive Strength And Splitting Tensile Strength Of Desert Sand C25 Concrete

Concrete is the most widely used building construction material,the sand is the necessary raw material for concrete,China contains an abundant desert sand resources,which can replace the medium sand which is lack of resources,and this can provide a solution in the large demand for medium fine sand in concrete for infrastructure projects.In recent years,with the rapid application of hydraulic construction in engineering during the winter period,the low-temperature mechanical properties of concrete gained more and more attention from the researchers worldwide.In recent years,with the rapid increase in the application of winter hydraulic construction in engineering,the low-temperature mechanical properties of concrete have received more and more attention from domestic and foreign researchers.A series of researches are conducted on the mechanical properties of desert sand concrete at normal temperature and high temperature,but less research on the mechanical properties of desert sand concrete at low temperature.Therefore,this paper analyzes the effects of temperature,desert sand replacement rate,and fly ash content on the compressive strength and tensile strength of desert sand concrete at low temperature through the compressive strength test and split tensile strength test of desert sand concrete at low temperature.The main research contents are as follows:(1)Design of four-factor four-level orthogonal test for the compressive test of C25 concrete at low temperature,analyzing the impact of temperature,the replacement rate of desert sand,and fly ash content to the pressure resistance of low-temperature desert sand concrete.Know from the stepwise analysis of orthogonal test and variance analysis:under the circumstances of the water-binder ratio is 0.65,and the sand rate is 37%,the primary and secondary order of compressive strength of the desert sand C25 concrete after low-temperature is temperature,fly ash replacement rate,and desert sand replacement rate.When the fly ash content is 10%,the desert sand C25 concrete reaches maximum compressive strength after low temperature;(2)Based on the orthogonal test,replace cement with 10%fly ash,replace medium sand with desert sand replacement rates of 0%,10%,30%,50%,and 70%,take temperature as-20℃,-30℃,-40℃,the compressive strength test was conducted after 28 days curing in standard conditions.Experiments show:when the fly ash replacement rate is 10%,the desert sand replacement rate is fixed(0%,10%,30%,50%,70%),as temperature decreases,the overall compressive strength of the concrete present increasing trend.(3)Through the low-temperature cracking tensile strength test of desert sand concrete,analyze the effects of temperature,desert sand replacement rate and fly ash content on the low-temperature cracking tensile strength of desert sand concrete,and establish the low-temperature cracking tensile strength.Desert sand concrete model,model of the relationship between the temperature and the replacement rate of desert sand.Studies have shown that as the temperature decreases,the tensile strength of low-temperature cleavage increases first and then decreases.When the fly ash substitution rate is 30%,the splitting strength at the lowest temperature is the highest.