Research On Preparation And Performance Of High Specific Strength EPS Lightweight Concrete

With the continuous development of economy and building technology,the greening of buildings and the continuous improvement of functional requirements,Start from the material body,it is of great significance to research and develop the prefabricated building basic materials which integrates lightweight insulation,energy saving and green environmental protection.Waste expanded Polystyrene(EPS)particles are introduced into high-performance cement-based materials in the form of recycled light aggregates,which can give concrete structural and functional coupling characteristics such as high specific strength and excellent thermal insulation.In view of this,in order to meet the functional composite requirements of prefabricated building envelopes component for lightweight concrete,high specific strength and energy saving,this paper systematically studied the preparation technology of EPS lightweight concrete,and based on its bulk density,mechanical properties,Influencing factors such as thermal and durability,through the experiment to determine the structural and functional comprehensive optimization parameters,to prepare a new type of assembled light-weight envelope structure material with early strength,high specific strength and excellent insulation characteristics,provide a reference for the development of EPS lightweight concrete and its application in new building envelope system.The main contents and results are as follows:Firstly,the high-fluidity and early-strength modification of cement-based cementitious materials are studied.Portland cement(PC)is used as the main cementing material,sulfoaluminate cement,silica fume,and fly ash are modified materials.Based on the early single factor test to determine the range of the three modified materials,the response surface method is used Test design and model analysis were carried out,and based on the prediction model,the optimal ratio of Portland cement-sulfoaluminate cement-silica fume-fly ash quaternary system was predicted to be 65.77%: 12.84%: 9.28%: 12.11%.The optimal ratio of the predicted cementitious material system was tested and verified,and it was found that the 1d and 28 d compressive strengths of the modified cementitious material system were 47.8MPa and 101.3MPa,respectively,which were higher than the 1d and 28 d compressive strengths of the control PC cement.After 47.08% and 29.71%,the fluidity of the slurry is 161 mm,and the initial setting and final setting time are 29 min and 42 min respectively.The deviation between the actual measured value and the predicted value is small,and the prediction model accuracy is high.It is feasible to predict the basic ratio of high-flow early-strength cementing material system.In order to meet the requirements of convenient pouring,rapid demoulding and high specific strength of prefabricated envelopes for prefabricated buildings,the above-mentioned basic proportion cementitious material system was further optimized and adjusted for high fluidity,early strength and high strength.The effects of water binder ratio,type and content of water reducing agent,fineness and surface activity of cementing materials on the properties of the modified cementitious materials were studied.The results show that the water binder ratio has a significant effect on the workability and strength of the slurry.When the water binder ratio is 0.23,the fluidity of the slurry drops to 147 mm,but the specimens have the highest compressive strength at 1d and 28 d,respectively reaching 53.7MPa and 109.9MPa,and the 28 d flexural strength is 9.2MPa,which has good mechanical properties.The water reducer test results show that compared with melamine water reducer,the polycarboxylic acid water reducer has better compatibility with the high-fluid early-strength cementitious material system,and its saturated amount is 0.31%.At this time,the slurry performance Good,the slump flow is 195 mm,the initial setting time and final setting time of the slurry are extended to 36 min and 54 min respectively,It can meet the requirements of construction pouring operation time and rapid demoulding;Using mechanical activation,the fineness and surface activity of the cementing material are improved by grinding the cement and other cementing material powder.The results show that: when the grinding time is 10 min,the specimen has the highest compressive strength,and its 1d and 28 d compressive strength are 65.3MPa and 114.6MPa respectively,and the high expansion of 185 mm can be maintained.Based on the above tests,the optimal parameters of high fluidity early strength cementitious material system meeting the working performance,setting time and strength are obtained as follows: water binder ratio 0.23,polycarboxylic acid water-reducing agent content 0.31%,powder grinding time 10 min.Recycled EPS particles are used as light aggregate,compounded with high fluidity early strength cementitious material system,high specific strength EPS concrete is prepared and its performance is optimized.The results of surface modification of EPS particles show that the bonding between EPS particles and cement paste interface transition zone is more dense,which can effectively restrain the "weak connection" defect of the EPS-cement-stone interface transition area;By blending Hydroxypropyl Methyl Cellulose(HPMC)and quantitatively characterizing with Image-Pro Plus,the homogeneity of EPS concrete can be controlled.The results show that when the content of HPMC is more than 0.05%,the viscosity of the slurry is greater than 0.47Pa·s,and the EPS particles below 5mm will not float in the slurry,and the uniformity of concrete can meet the requirements.The effect of EPS particle size,gradation and dosage on concrete bulk density,mechanical properties,thermal conductivity,dry shrinkage and frost resistance was studied.The results show that when the EPS particle size is 3～5mm and the dosage is 70%,EPS concrete has the best comprehensive performance.On this basis,the effect of PVA fiber content on the performance of EPS concrete was studied.The results show that when the PVA fiber content is 0.8%,the flexural strength and splitting tensile strength of EPS concrete are greatly improved,which effectively inhibits the performance of EPS concrete.Shrinkage deformation prevents the generation of micro-cracks,improves its frost resistance,and also inhibits the floating effect of EPS particles to a certain extent.This paper systematically studied the preparation and performance control methods of EPS lightweight concrete.The apparent density was 850kg/m3～1350kg/m3,the 28 d compressive strength was 15MPa～30MPa,and the specific strength was 0.018 N·m/kg ～0.022 N·m/kg,thermal conductivity of 0.16W/m·K～0.35W/m·K,EPS lightweight concrete with high specific strength and excellent thermal insulation,which is 63.6% higher than LC15 ordinary lightweight aggregate concrete,and compared with C30 ordinary concrete An increase of 76%.At the same time,EPS lightweight concrete shows good resistance to shrinkage deformation and frost resistance,which provides a reference for the recycling of waste EPS resources and the application of high-performance new wall materials in prefabricated building enclosure systems.