Experimental Research Of Modified Rice Husk Mortar Self-insulating Assembled External Wallboard

Due to the advantages of light weight and strong corrosion resistance of agricultural waste rice husk,a certain proportion of rice husk can effectively solve the problems of self-weight,crack resistance and impermeability of assembled wallboard,but the polysaccharide,waxy layer and hemicellulose on the surface of rice husk are not conducive to the hydration reaction of cement.In this paper,the raw materials of rice husk was soaked and modified with tap water,saturated lime water and 3%sodium hydroxide solution.The physical and mechanical properties and durability of the modified rice husk mortar samples were studied.The modification mechanism of the rice husk mortar was analyzed by scanning electron microscope,infrared spectrum and X-ray diffractometer.The bending,seismic behavior and fracture development law of the modified rice husk mortar external wall board under load was obtained.This provides a theoretical basis for the application of rice husk mortar composites in the prefabricated construction.The main research results of this paper are as follows:(1)The rice husk was modified with tap water,saturated lime water,3%sodium hydroxide solution and different treatment time as variables.When the volume of rice husk was 45%,the mechanical properties of modified rice husk mortar were studied by 7 d,28 d compressive strength test and flexural strength test.Compared with the untreated rice husk specimen,the compressive strength and the flexural strength of the rice husk specimen soaked in saturated lime-water solution for 24 hours increased 10.8%and 29.7%respectively.(2)The impermeability,freeze-thaw resistance and sulfate resistance wet-dry cycling of modified rice husk mortar were tested.Compared with the raw rice husk mortar specimen,the durability of rice husk mortar made by soaking with tap water improved obviously.The maximum seepage pressure increased by 26.9%.The mass loss rate and strength loss rate of the specimen after 45 cycles of freezing and thawing were1.2%and12.6%,respectively.The maximum seepage pressure of rice husk mortar treated by saturated lime water soaking increased by 53.8%.The mass loss rate and strength loss rate of the specimen after 45 cycles of freezing and thawing were 0.9%and 10.9%,respectively.The corrosion resistance coefficient was 78.5%after 45 times sulfate wet and dry cycles.The durability of the rice husk mortar treated with 3%sodium hydroxide solution has been reduced,and the decrease was greater with the increase of treatment time.(3)The microcosmic of the modified rice husk mortar were analyzed by scanning electron microscope,infrared spectroscopy and X-ray diffractometer.The SEM showed that the uniform bulges of the modified rice husk on the outer surface of the rice husk were more obvious and improved the interface between the rice husk and the cement paste.The hollow composite grid structure of rice husk cross section has the function of storing moisture and heat insulation.The infrared spectrum showed that the modified technology could remove hemicellulose,polysaccharide and waxy layer on the surface of rice husk,which was helpful to cement hydration and cement paste bonding with rice husk.The XRD showed that the cement paste perform better cement hydration in the modified rice husk,high degree of crystallization of hydration products and increase the compactness of the sample.(4)The flexural performance and seismic performance of modified rice husk mortar full-scale external wall board was prepared.The results showed that:the uniformly distributed load of the external wall board under bending failure was 10.08kN/m~2,much higher than the most unfavorable wind load-2.955kN/m~2 in the whole country.The load-displacement curve showed that the rice husk mortar has strong flexural bearing capacity.The hysteretic curve showed that the specimen has elastic and plastic development stage,and the stiffness curve showed that the stiffness of the wall board was gradually decreasing and degenerating under the action of push-pull load.The area surrounded by the hysteretic curve indicated that the structure has good ductility,plastic deformation capacity,seismic performance and energy dissipation capacity.