Optimized Preparation And Performance Of Engineering Mud Recycled Cement-based Thermal Insulation Core Material For Prefabricated Wall Panels

Cement-based porous materials have excellent comprehensive performance and become the preferred thermal insulation core materials for prefabricated wallboard.However,compared with organic thermal insulation core materials,there is still a certain gap in thermal insulation performance.Micron-size or nano-size pore instead of air void can improve the thermal insulation ability of cement-based porous materials.However,the high cost of micron-size and nano-size pore-forming agent limits its application in thermal insulation performance.Based on this,this paper proposes to use low-cost engineering mud as micron-size or nano-size pore forming agent and pre-foaming process to design and prepare mud-recycled cement-based thermal insulation core material in the prefabricated wallboard with rich micron-size or nano-size pore structure,and the research on the influence of mix ratio and modifier on the pore structure and performance of the thermal insulation core material is also studied,obtaining modified cement-based thermal insulation core material with low cost and good insulation performance.The main research conclusions are as follows:Porous cement-based thermal insulation core material was successfully prepared by using engineering mud and pre-foaming method.When the design dry density was 400kg/m~3,the addition of mud would led to the reduction of compressive strength,while the design dry density was 600kg/m~3,the addition of mud would firstly increase and then decrease the compressive strength of the core material,which could reduce the thermal conductivity.When the mud replacement rate was 20%,the compressive strength of the core material improved,and the thermal conductivity was the lowest when the mud replacement rate was 40%.The increase of mud density led to porosity deterioration,and the thermal conductivity of the sample decreased,but it was not conducive to the improvement of compressive strength.With the increase of water-cement ratio,the pore diameter in core materials became larger.The compressive strength of low-density samples firstly increased and then decreased with the increase of water-cement ratio,while that of high-density core materials firstly decreased and then increased with the increase of water-cement ratio.The addition of fly ash led to the deterioration of air voids in the core material,the thermal conductivity of the core material firstly increased and then decreased,and the compressive strength decreased,while the addition of slag led to the refinement of pores inside the core material.With the increase of slag content,the thermal conductivity and compressive strength increased firstly and then decreased.18%lime can improve the early compressive strength of thermal insulation core material with a design dry density of 400kg/m~3,while the optimized lime content was 12%for the design dry density of 600kg/m~3.Water glass was not conducive to improving the performance of core materials.When foam was replaced by mud at a volume of 40%,mud density of 1300kg/m~3,water-cement ratio of 0.45,slag content of 35%and 12%of lime,the thermal insulation core material with dry density of 302kg/m~3～907kg/m~3 can be prepared.The thermal conductivity ranged from 0.09W/(m·K)to 0.20W/(m·K),the corresponding 28-day compressive strength ranged from 0.17MPa to 6.73MPa,and the 56-day compressive strength ranged from 0.18MPa to 6.88MPa.When this core material was applied to prefabricated wallboard with 200 mm,the heat transfer coefficient of prefabricated energy-saving wallboard can be obtained,which was in the range of 0.91W/(m~2·K)～1.39W/(m~2·K),compressive strength was in the range of7.57MPa～16.47MPa,and the thermal insulation properties improved with the increase of dry density.