Optimization Of Straw-magnesium Oxychloride Cement Composites And Axial Compression Test Of Masonry Walls

Straw-magnesium oxychloride cement composite material?hereinafter referred to as SMC?is made of straw as filling material,magnesium oxychloride cement as cementing material,mixed with appropriate proportion of mineral admixture and additive,and subjected to pressure-locking process.The new building materials have certain strength,good thermal insulation performance,volume stability,good ductility,excellent mechanical processing performance,can be used as load-bearing wall materials,infill wall materials and decorative materials,and are applied to rural housing construction and thermal insulation transformation.The material can solve the problem of waste of straw and magnesium oxychloride cement in China and meet the demand for new materials in the construction of new countryside.At present,the optimum mix ratio of SMC preparation process,compressive strength and thermal conductivity independent index control,and softening coefficient under modifier conditions have been studied,and the insulation of rural houses has been carried out as a thermal insulation board and Quasi-static test study of steel skeleton wall.However,in practical applications,materials need to consider not only compressive strength and thermal conductivity,but also other test indicators.It is of great significance to obtain the optimal mix ratio under the influence of various indicators.In addition,the material mix ratio lacks the necessary theoretical guidance,and the formulation process is blind.The purpose of material development lies in the application.The masonry structure is widely used in rural areas.Combined with the rich characteristics of rural straw resources,the material can be used to make blocks and build masonry structure houses.However,in practical application,it is lacking that is the material wall compressive stress-strain relationship of the axial compression performance parameters and the finite element analysis of the material.In view of the current situation of the above materials and the needs in reality,the following research was carried out:1)Increase the material density to 1200kg/m³ to improve the material strength;design a blend of fly ash,phosphorus iron powder and ferrous sulfate in a certain proportion to improve the phenomenon of frost on some parts of the material.Orthogonal tests were designed to determine material compressive and flexural strength,thermal conductivity,moisture content,water absorption,degree of frosting,and porosity.The optimum mixture ratio under the compressive strength,flexural strength,thermal conductivity,water absorption and frosting degree was obtained by orthogonal test range analysis,and the matrix analysis method was used to determine the most comprehensive conditions under multiple conditions.Excellent mix ratio is A1B1C1D2E3(the straw content is 10%,the M_mcs:M_mop is 1:0.9,the M_moc:M_s is 1:0,the admixture content is 10%,and the additive content is 2%).The average compressive strength of the specific material is 3.87MPa,the average rupture strength is 4.6MPa,the average thermal conductivity is 0.096W·?k·m?^-1,and the average water absorption is 17%,and no pan frost phenomenon.2)There is a significant correlation between the compressive strength and the flexural strength of the material.The mean value of the compression ratio is 0.93.Based on the quantitative characterization of the mixture ratio,a multivariate regression analysis method was used to establish the mixing ratio design method of compressive strength,thermal conductivity and water absorption.It provides a necessary reference for determining material properties according to different mix ratios.3)The design specification of small block is 39032403190mm³.The masonry mortar is selected according to the compressive strength of the optimum formula block.The experimental study of the masonry wall under axial compression is carried out.The failure form and bearing capacity of the wall under axial compression are obtained.According to the vertical through cracks in the final destruction of the wall,it is recommended to add a glass fiber reinforced mesh cloth to the horizontal horizontal gray joint.The method is tested to effectively avoid the damage caused by the vertical through cracks in the unstressed masonry wall during the process of compression and damage.4)Establish a uniaxial compressive stress-strain full curve model of the material to provide a basis for finite element simulation.