The Research On Mechanism And Prevention Measures Of Cracks In The Wall Filled With Autoclaved Aerated Concrete Wall Panels

Due to the rapid development of prefabricated buildings and the more advancement of wall material innovation in our country,the autoclaved aerated concrete wall panels that have multiple functions such as energy saving,light weight,waste reduction,heat preservation,etc.are ushering in broad development prospects and have been widely used in frame structures.However,the wall filled with autoclaved aerated concrete wallboard is easy to crack.The cracks in the wall will reduce the durability and the thermal insulation performance of the wall,and cause psychological panic among residents,which will hinder the further promotion and application of autoclaved aerated concrete slabs.Therefore,the study of effective wall crack prevention measures has extraordinary social significance and extremely high engineering value.The paper researched the causes,forms and characteristics of the cracks in the infill wall by looking over literature.It is clear that the cracks in the infill wall of wall panels are mainly non-load cracks such as temperature cracks and dry shrinkage cracks.The lacking of the understanding of drying shrinkage performance of autoclaved aerated concrete and the quantitative research on the influencing factors of cracks make the current crack prevention measures based on actual engineering experience often be less effort.The research object is the infilled wall with autoclaved aerated concrete.The paper carried out theoretical analysis,experimental research and finite element analysis to explore effective wall crack prevention measures.The following research is carried out:(1)The types of shrinkage deformation of autoclaved aerated concrete slabs are analyzed and summarized.It is clear that the shrinkage deformation of autoclaved aerated concrete slabs during the use stage is mainly dry shrinkage and temperature shrinkage.Based on the relationship between the pore structure and micro-material composition of autoclaved aerated concrete and its drying shrinkage performance,the effects of curing age,curing environment and other factors on the drying shrinkage performance of autoclaved aerated concrete slabs are analyzed.(2)In order to explore the best upper wall moisture content and the best curing age of autoclaved aerated concrete slabs,the cube compressive strength test,equilibrium moisture content test and drying shrinkage performance test were carried out.Through the cube compressive strength test of autoclaved aerated concrete slab,the influence of moisture content on the cube compressive strength and failure form of the wallboard material is analyzed,and the empirical formula of the wallboard material compressive strength and moisture content is obtained by fitting.Based on the influence of moisture content on strength,recommendations for the limit of wall moisture content on wall panels are proposed.(3)The equilibrium moisture content test of autoclaved aerated concrete slabs studied the influence of environmental temperature and relative humidity on the water loss rate and equilibrium moisture content of wallboard materials.According to the test results,the model of water content change over time and the model of Equilibrium moisture content prediction of wallboard materialsare are obtained by fitting,which provides a theoretical basis for the limits of the wall moisture content of wallboards in different environmental temperature and humidity areas.(4)The drying shrinkage performance test of autoclaved aerated concrete slabs is intended to explore the drying shrinkage performance of wallboards in natural and standard curing environments.According to the test results,the relationship between the drying shrinkage value,moisture content and time of the wallboard material is obtained,and the drying shrinkage time-varying model of the wallboard material is obtained by fitting.Based on the relationship between drying shrinkage,moisture content and time,the limit of Moisture content during wall installation and the limit of wall installation time are proposed.(5)Abaqus was used to simulate the cracking process of the infilled wall with autoclaved aerated concrete under temperature and drying shrinkage,and the effect of the wall length,boundary constraints,mortar bond strength,wall strength,structural measures and other factors on the wall crack in the infill wall was analyzed.the influence mechanism of the above factors are analyzed.Based on the engineering experience and the research results of this paper,the paper proposes several key anti-cracking measures for the infill wall with autoclaved aerated concrete slabs,which is expected to reduce the cracking situation and further promote the use of autoclaved aerated concrete slabs.