| Lightweight interior partition wall board,whose shape is like a hollow floor slab,is a new type of energy-saving material for walls.When the plate is installed,the tenons and mortises are assembled after being coated with a small amount of caulking mortar.Partition wallboard has large market demand in our country,however,the traditional interior partition wallboard has the problems of inflammability,high energy consumption and environmental pollution.The precast interior partition wallboard is made of foamed concrete,which is not only energy-saving,recyclable and environmentfriendly,but also has excellent properties of heat preservation,thermal insulation and fire resistance simultaneously.However,due to the existence of much free water and the lack of constrained aggregate,the shrinkage of foamed concrete is large in practical applications,which will resulte in a high risk of cracking and affect the safety offoamed concrete interior partition wallboard.Aiming at solving the problems of large shrinkage and poor crack resistance in the application of foamed concrete interior partition wallboard,this paper explores the effects of fine aggregates(machine-made sand,brick particles,rubber particles),fibers(PP fiber,dry hemp palm fiber and saturated hemp palm fiber)and early strength agents on the compressive strength,drying shrinkage,self-shrinkage and pore structure of foamed concrete.On this basis,a better mix proportion is selected to prepare foamed concrete slabs.Plate method is used to test the crack resistance of foamed concrete and explore the impact of different mix proportion and constraints on the crack resistance of foamed concrete,aiming to produce foamed concrete interior partition wallboard with low shrinkage,high crack resistance and long service life.In this study,P·II 52.5 cement and nano-synthetic foaming agent was adopted.By studying the effects of density grade,water-cement ratio,and curing system on the fluidity,compressive strength and water absorption of foamed concrete,the optimal preparation process was determined.On the basis of the best preparation process,the effects of the types and contents of fine aggregates,the types and contents of fibers and the contents of early strength agents on the compressive strength,drying shrinkage and self-shrinkage of foamed concrete were studied.The micro-testing methods of X-CT and SEM were used to characterize the pore structure of foamed concrete,and then the relationship between pore structure and other properties was established.Studies have shown that: 10% rubber particles have the most obvious effect on reducing the drying shrinkage of foamed concrete while significantly reduce the compressive strength;0.75% saturated hemp palm fiber can increase the compressive strength of foamed concrete and significantly reduce dry shrinkage and self-shrinkage of foamed concrete at the same time;the addition of early strength agent is unfavorable to the compressive strength enhancement and shrinkage deformation diminution of foamed concrete.The foamed concrete slabs were prepared using machine-made sand,rubber particles,PP fibers and saturated hemp palm fibers respectively.The crack resistance properties of foamed concrete of different groups were tested by the plate method.Studies have shown that: 20% machine-made sand can significantly improve the crack resistance of foamed concrete slab;compared with PP fiber,the crack resistance of foamed concrete is better when the same volume fraction of saturated hemp palm fiber is added;the anti-cracking level of foamed concrete slab is Ⅰ when 0.75% saturated brown hemp fiber is added. |
