| Foam concrete is a porous silicate material,because it is composed of a large number of air holes,it is also called lightweight concrete,which has the advantages of light weight,heat insulation,fire resistance and noncombustibility,widely used in non-load-bearing wall insulation building materials.With the development of high-rise and super-high-rise buildings,the requirements for lightweight,high-strength and functional wall materials are becoming higher and higher.In response to the development needs of extremely low energy consumption buildings in the future,research and development of low thermal conductivity ultra-lightweight foam concrete with small bulk density and high strength has become an inevitable trend for the development of new building materials.This article uses ceramic waste powder as the main raw material,preparation of low density(dry density ≤225 kg/m3),low thermal conductivity,high strength porous silicate materials by physical foaming and autoclave curing methods,studied the performance of different types of foaming agents,explored the mechanism of cement,quicklime,water-to-material ratio,and various additives in the experiment,discussed the influence of each raw material on the structure and performance of the product,prepared low-thermal-conductivity ultra-lightweight foam concrete samples with excellent comprehensive properties.The mechanism of foam formation and pore formation of the foaming agent was discussed through experiments,and the role of the foaming agent was explained;the relationship between the foaming multiple of compound,plant protein and animal protein foaming agents,and the amount of bleeding and sedimentation distance were studied,an animal protein C-type foaming agent with a foaming factor of 30 was selected to prepare a low thermal conductivity ultra-lightweight foam concrete.Using the method of orthogonal experiment and single factor experiment,combining SEM micro structure and XRD phase analysis,the effects of factors such as cement,quicklime,water-to-material ratio,early strength agent and water reducer on product performance have been studied,determined the best material mix ratio.Firstly,the results of orthogonal experiments were analyzed by the "comprehensive equilibrium method",comprehensive comparison of product dry density,compressive strength and thermal conductivity,combining analysis of variance and range analysis,the optimal mass ratio of basic materials was ceramic waste powder : cement : quicklime = 74 : 11 : 15,and the ratio of water to material was 0.86.Secondly,based on single-factor variable experiments,the effects of water reducing agents and early strength agents on product properties were further explored,under the experimental conditions,the ultra-lightweight foam concrete with volume density of 190 kg/m3,compressive strength of 0.60 MPa and thermal conductivity of 0.043 W/(m·k)and average aperture 1.19 mm was prepared.The optimal mass ratio of basic materials was ceramic waste powder : cement :quicklime = 74 : 11 : 15,and the ratio of water to material was 0.86.Also,water-reducing agent accounting for 1.5 wt.% of cementations material and early strength agent accounting for 2 wt.% of the total material are added,respectively.Finally,the phase composition and micro structure of the samples were analyzed by XRD and SEM.The results show that the crystalline phases are mainly quartz,tobermorite and gel-like amorphous phase materials;the product structure is composed of gas-solid two phases,and the pores are mainly closed pores,the pore wall is made of crystal and gel phase interspersed with each other,and the pore wall structure is dense.The crystalline tobermorite and CSH(B),C-S-H gel phases are cemented with an appropriate crystal-to-gel ratio and porcelain powder particles,so that the product has good mechanical strength and thermal insulation properties. |
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