Study On Compressive Strength And Working Performance Of Geopolymer Cementitious Materials And Recycled Concrete

With the rapid development of the times economy,large-scale construction projects are being carried out,and lead to the use of ordinary Portland cement increased year by year,but the cement production releases a lot of CO2.On the other hand,China produces a large amount of urban construction waste and industrial solid waste such as fly ash and slag every year,which causes environmental pollution and resource waste.In order to save energy and realize the value and economic benefit of construction waste,this paper studied the working performance and compressive strength of alkali-activated slag metakaolin geopolymer net slurry,mortar and recycled concrete under different influence factors.The specific research contents and conclusions are as follows:(1)In the net slury of geopolymer,the effects of alkali activator concentration,modulus and liquid-solid ratio on the fluidity,rheological properties and compressive strength of the net slurry were investigated with 40%slag and 60%metakaolin as the research object.The results show that the plastic viscosity of the net slurry decreases with the increase of modulus and liquid-solid ratio,and increases with the increase of concentration.The yield stress of the net slurry decreases with the increase of modulus,concentration and liquid-solid ratio;Conpared with the concentration and modulus of alkali activator,the liquid-solid ratio is the key factor affecting the fluidity of net slurry.The compressive strength increases with the increase of concentration,but decreases with the increase of liquid-solid ratio.(2)The effect of sand volume fraction on workability,rheological property and compressive strength of geopolymer mortar was considered with different grade of net mortar mix ratio.The results show that the yield stress and plastic viscosity mortar increase with the increase of sand volume fraction.The consistency and fluidity of mortar decrease with the increase of sand volume fraction;Mortar has a high early strength,more than 95%of geopolymer mortar 7d compressive strength can reach more than 80%of 28d compressive strength;The mortar has better workability and higher compressive strength when the volume fraction of sand is 45%.(3)The influence of volume fraction of coarse aggregate and replacement rate of recycled aggregate on working performance and compressive strength of concrete was studied in the recycled concrete.The results show that the working performance of concrete decreases with the increase of the volume fraction of coarse aggregate and the replacement rate of recycled coarse aggregate,and the volume fraction of coarse aggregate has a greater effect on the woking performance of concrete;The compressive strength of concrete increases firstly and then decreases with the increase of the volume fraction of coarse aggregate,and reaches the maximum value when the volume fraction of coarse aggregate is 35%,the compressive strength decreases with the increase of the replacement rate of reclaimed aggregate,and the replacement rate of reclaimed aggregate has a more obvious effect on the strength;Geopolmer recycled concrete has higher early strength.The ratio of 7d compressive strength to 28d compressive strength of 50MPa concrete is 91.5%-98.3%.It is suggested that the replacement rate of reclaimed coarse aggregate should not exceed 50%,and the volume fraction of coarse aggregate should be between 32.5%and 37.5%.