| Building energy consumption is high in China,building energy conservation is urgent.The heat consumption of the envelope occupies a large proportion in the total heat consumption of the building,and the wall occupies 70% of the heat consumption of the envelope.Therefore,improving the thermal performance of the building wall is a key measure to achieve the goal of building energy conservation.Self-insulating concrete compound block is a new type of self-insulating wall material,which has many advantages: low cost,convenient materials,good thermal performance and easy masonry,etc.And filling materials directly determine the thermal performance of self-insulating concrete compound block(Ⅱ)is good or bad,which affects its practical value and economic benefit,therefore it is very necessary for filling materials to carry on a special experimental research.Based on the construction technology and requirements of Chongqing area,this paper integrates straw resources and waste polystyrene foam plastic for building materials,optimizes the pretreatment technology of rice straw,molding technology and material ratio of straw insulation blocks,according to the preparation technology of straw insulation blocks for self-insulating concrete compound blocks studied by the tutor’s team in the early stage.The main research contents and conclusions are as follows:(1)The influence of “NaOH solution mass fraction” and “soaking time” on softening effect was quantitatively studied by means of “mass loss rate”,and the concept of “comprehensive cost index” was proposed to select the optimal scheme of NaOH solution pretreatment for rice straw.The results show that the mass loss rate of rice straw increases with the increase of soaking time(the change rate is large),and increases with the increase of NaOH solution mass fraction(the change rate is small),but it decreases locally and finally tends to be flat.The optimal scheme is “NaOH solution mass fraction of 1% and straw soaking time of 6h”,but the soaking time is still long,which leads to more time for straw insulation block forming.(2)In order to study the rapid forming technology of straw insulation block,mechanical stirring was introduced,and the rapid pretreatment of rice straw was carried out by combining NaOH solution and lime slurry respectively.On this basis,the rapid pretreatment of rice straw by mechanical mixing of NaOH solution and lime slurry was studied.The results show that the mass ratio of NaOH solution to rice straw is 5:1,which can guarantee that rice straw can be fully soaked,and at the same time,no excess waste liquid will be generated after soaking.By mechanical stirring,rice straw fibers become thinner and softer,the shaped shape of the specimen is more regular and the surface is more flat,and the soaking time of rice straw can be further shortened from 6h to 3h.The softening effect of lime slurry pretreatment on rice straw is poor,which can’t meet the requirements of pretreatment.However,lime slurry can be used as a cementing material to help rice straw bonding.(3)The problems existing in the existing molding technology of straw insulation block have been summarized,and the corresponding optimization scheme has been given in combination with the previous research conclusions,the rapid molding technology of straw insulation block has been put forward,and the maintenance technology of straw insulation block has been studied.The results show that the straw insulation block prepared by rapid prototyping technology has better shape regularity,surface flatness and material bonding condition.The natural curing condition of straw insulation block: the temperature range is 15 ~ 30℃,the relative humidity range is 40 ~ 75%.The curing time is 28 d after stripping.(4)The influence of EPS particle content on the molding effect,dry apparent density and thermal performance of straw insulation block was studied,and the reasonable range of EPS particle content was determined to obtain the optimal scheme.The results show that the apparent dry density of straw insulation block decreases with the increase of EPS particle content,and the linear negative correlation was obvious.The thermal conductivity of straw insulation blocks without EPS particles is about 0.049W/(m·K),which meets the requirements of relevant specifications.Moreover,the increase of EPS particles can reduce the thermal conductivity of straw insulation blocks and improve their thermal performance.The optimization scheme of EPS particle content is that EPS particle content should not exceed 3%.(5)The influence of the mass ratio of rice straw to hydrated lime powder(referred to as the mass ratio)on the dry apparent density,hygroscopicity,volumetric water absorption,mechanical properties and size changes of straw insulation blocks were studied.The results show that the dry apparent density of straw insulation blocks decreases with the increase of the mass ratio.Both equilibrium moisture content and volumetric water absorption show a “wavy” relationship with the mass ratio.Its cube compressive strength is small,and the relation with the mass ratio is not significant.After natural curing for 48 h,the outer dimension of straw insulation blocks tends to be stable.The primary deformation and secondary deformation in the direction of height are much larger than that in the direction of length and width,and both of them are linearly positively correlated with the mass ratio.The optimization scheme of the mass ratio is that the mass ratio is 7.5. |
