Experimental Study On Basic Mechanical Properties And Freeze-thaw Cycle Of Thermal Insulation Concrete Influenced By Multi-factors

With the further implementation of national energy conservation and emission reduction policies,building energy conservation has become a major area of energy conservation and emission reduction.Finding building energy-saving materials with good working performance has become the focus and hotspot of research in this field.At the same time,in terms of agricultural production,a large amount of straw waste is treated by burning to cause great pollution to the environment.Therefore,this paper attempts to incorporate wheat straw powder,vitrified microbeads and polypropylene fibers into C30 concrete,and adopts orthogonal test method to design three-factor four-level orthogonal test,three of which are wheat straw powder content(A),the amount of vitrified beads(B)and the amount of polypropylene fiber(C).Firstly,this paper studied the 3D,7D,14D,28D cube compression,splitting tensile mechanical properties and 28D thermal conductivity of each group of concrete in the orthogonal test table.Then,the thermal conductivity and mass loss of concrete under the conditions of 0,20,40,60,and 80 cycles of freeze-thaw cycles were studied.The data obtained from the experiment were analyzed by means ofrange,variance,comprehensive index and fitting.The results show that:1.Only consider the optimal blending amount of each factor for individual performance indicators:Taking 28-day compressive strength of concrete as the index,the influence of three factors is the amount of vitrified beads(B)>wheat straw powder(A)>polypropylene fiber(C),of which factor A The optimal level is 0%,the optimal level of factor B is 0%,and the optimal level of factor C is 0%.Taking 28-day tensile strength of concrete as the index,the influence of three factors is the polypropylene fiber content(C)>wheat straw powder content(A)>vitrified microbead content(B),of which factor A The optimal level is 0%,the optimal level of factor B is 0%,and the optimal level of factor C is 0.7%.Taking the thermal conductivity of concrete for 28 days as the index,the order of strength of the three factors is the amount of vitrified beads(B)>the amount of wheat straw powder(A)>the amount of polypropylene fiber(C),of which factor A The optimal level is 4%,the optimal level of factor B is 30%,and the optimal level of factor C is 0.7%.2.The concrete comprehensive scoring standard was selected as 28D compressive strength:28D splitting tensile strength:28D thermal conductivity=0.5:5:6.The order of the influence of the three factors on the comprehensive performance is as follows:the amount of vitrified beads(B)>the amount of wheat straw powder(A)>the amount of polypropylene fiber(C)5 wherein the optimal level of factor A is 2%.The optimal level of factor B is 30%,and the optimal level of factor C is 0.7%.3.With the increase of the number of freeze-thaw cycles,the thermal conductivity of concrete slabs of each group increases,the thermal insulation performance of concrete decreases,and the mass loss of concrete slabs of each group also increases.After 80 freeze-thaw cycles,the influence of factors on the thermal conductivity of concrete is the order of wheat straw powder(A)>glass beads(B)>polypropylene fiber content(C).The order of influence of factors on concrete mass loss is wheat straw powder content(A)>polypropylene fiber content(C)>vitified microbead content(B).The polynomial function is used to fit the thermal conductivity and mass loss of each group of concrete slabs with the number of freeze-thaw cycles.The results are good and can provide some references for further research.Figure 47 table 35 reference 61...