The Performance Optimization And Interface Strengthening Of Composite Sandwich Thermal Insulation Wall Materials Prepared By Foam Concrete And Full Lightweight Aggregate Concrete

Developing new types of thermal insulation walling material that integrate with excellent load-bearing performance is an imperative to enhance building energy efficiency in practical applications.It is a novel approach to prepare sandwich thermal insulation walling material by applying lightweight aggregate concrete as load-bearing layer and the foam concrete as inner thermal insulation layer.In order to realize the industrial production of the sandwich thermal insulation walling material,only commercially available raw materials were applied in this contribution on the basis of the previous research results.The targeted sandwich thermal insulation walling material was prepared by both adjusting the addition of additives and optimizing mix proportion of foam concrete and full lightweight aggregate concrete respectively.To further enhance the interface bonding performance of this sandwich walling material,inter facial modifying agent,tabling structure,fiberglass mesh,and optimization design on the thickness of both layers were applied.The life cycle cost of the sandwich thermal insulation walling material was analyzed afterwards.In addition,analysis on both technical and economic feasibility in regard to industrial production of this walling material were obtained.The feasibility of using commercially available raw materials to prepare the full lightweight aggregate concrete was studied first.Research results indicated that a kind of full lightweight aggregate concrete with a density of 1200kg/m3,28 d compressive strength up to 15 MPa while thermal conductivity of 0.35W/(m.K)can be successfully prepared by optimizing its mix proportion with 600-grade shale crushed stone ceramsites and 700-grade spherical ceramic sand.The performance of prepared foam concrete which satisfy the requirements of thermal insulation walling material was studied afterwards.Test results shown that on the basis of 500kg/m3 targeted density grade,foam concrete with density of 500kg/m3,28 d compressive strength exceed 2MPa and thermal conductivity of 0.11W/(m.K)can be obtained in conditions of using foaming agent with high expansion ratio and superior stability,adjusting water/cement ratio to maintain its foam surplus coefficient to 1.15 while incorporating 1.8% FDN,0.1% HPMC and 0.02% triethanolamine relative to the mass of cementitious material.The properties of foam concrete were significantly affected by the initial setting time of the cement paste that applied in its preparation.This high correlation between initial setting time and foam concrete properties make it practicable to be applied as a parameter to characterize the impact on the performance of foam concrete.The interface strengthening effects of the sandwich walling material were studied subsequently.Results shown that the interface bonding strength was enhanced by using inter facial modifying agent.Moreover,the splitting tensile strength of the interface can be improved by either increasing the interface contact area via using tabling structure,using fiberglass mesh as reinforcement or changing the bidentate arrangement within tabling structure.The interface splitting tensile strength of sandwich thermal insulation walling material can be increased from 0.31 MPa to 0.59 MPa in conditions of total thickness was 150 mm,thermal insulation layer thickness was 50 mm,adopting 20 mm in thickness and 30 mm in width respectively for the tabling unit while using positive and negative double-tooth structure using emulsion-type interfacial modifying agent and fiberglass mesh for the interface strengthening.After that,the force bearing status of the sandwich thermal insulation walling material was calculated and analyzed comparing with the five typical destructional forms.When the splitting tensile strength of both supporting layer and insulation layer as well as tabling unit thickness remained constant,there exist an optimum width of the tabling unit to achieve optimal performance of the sandwich thermal insulation walling material.In this paper,the calculated optimum tabling unit width was 50 mm,which is consistent with the experimental results.Finally,the whole life cycle cost of the sandwich thermal insulation walling material that prepared by full lightweight aggregate concrete and foam concrete was analyzed.Results indicated that the cost of raw materials manufacturing cost were higher than that of traditional walling materials.The manufacturing process was more complicated than that of traditional ones as well.However,its total cost was 28.70% lower than that of thermal insulation composite prepared with lime-sand bricks and foam concrete and 4.6% lower than that of the aerated concrete masonry wall.The operating cost of it was better than that of traditional external thermal insulation walling system,basically equal to that of 700-grade autoclaved aerated concrete masonry wall with the same thickness.In this paper,a type of sandwich thermal insulation walling material was prepared with a dry apparent density of 974kg/m3,8.7MPa in compressive strength,0.59 MPa in splitting tensile strength while heat transfer coefficient was 1.11(W/m2.K)and thermal inertia factor D was 5.53,which could meet the 50% energy saving amount in thermal design requirements of walling system that mentioned in common policies formulated for hot summer and warm winter region.