Drying Shrinkage Of Alkali-Activated Slag-Fly Ash Foamed Concrete

Alkali-activated foamed concrete combines the advantages of both foamed concrete and alkali-activated materials,and is a new green,low-carbon and energy-saving building material developed in recent years.In this paper,through a large number of systematic experiments,the factors that affect the drying shrinkage of alkali-activated foamed concrete and the relationship between each factor and drying shrinkage are studied,and the measures and methods to inhibit the shrinkage are put forward,so as to provide data and theoretical reference for the wider application of alkali-activated foamed concrete and the green low-carbon development.This article main research content is as follows:（1）The optimum ratio of alkali-activated slag-fly ash slurry system was determined and the relationship between different pore structures and drying shrinkage in the slurry was investigated.Too low and too high water-powder ratio will lead to the increase of drying shrinkage,with the lowest drying shrinkage at 0.47(2818×10^-6at 90 d).The increase of fly ash replacement slag content can significantly reduce dry shrinkage and open porosity,and the lowest value is 2733×10^-6when the fly ash slag ratio is 5:5.When the modulus of sodium silicate increases,the drying shrinkage increases.The 90 d shrinkage value is 3058×10^-6when the modulus is 2.0.The drying shrinkage value increases with the increase of alkali equivalent,and the 90 d shrinkage value of 8%alkali equivalent is 3072×10^-6.In summary,the optimal ratio of water to powder is 0.47,fly ash to slag ratio is 4:6,sodium silicate modulus is 1.5,and alkali equivalent is 6%.（2）Through the preparation of 400 kg/m³,600 kg/m³,800 kg/m³,1000 kg/m³dry density alkali-activated foamed concrete,explore water powder ratio,dosage of fly ash and slag ratio and modulus of sodium silicate,alkali equivalent of these factors in different dry density of strength,bibulous rate,dry shrinkage and the effect of pore connectivity.In the research part of foamed concrete,the optimal proportion is different from the net slurry,which needs to be selected appropriately according to the different amount of foamed concrete.Water-powder0.47 or 0.49 for G1000,800 and 600,and 0.47 for G400 is more suitable.The water-powder ratio of 0.47 or 0.49 for G1000,G800 and G600 and 0.47 for G400 are the best ratios.The fly ash slag ratio is 4:6,the sodium silicate modulus is 1.5,and the alkali equivalent is 6%.In the test of pore size distribution,the peak value shifts to the right with the increase of fly ash slag ratio,the pore size of 10～100μm decreases with the increase of sodium silicate modulus,and the pore size of 0.1～1μm increases with the increase of alkali equivalent.Therefore,it is concluded that pores with a pore size distribution of 0.1～1μm have a greater impact on drying shrinkage than pores with a pore size distribution of 10～100μm or more.（3）The relationship between the effect of two shrinkage methods of aggregate and fiber on pore structure and drying shrinkage was explored.With the increase of quartz sand content,the strength increases obviously,the dry density increases,the total porosity decreases,and the inhibition effect on drying shrinkage is obvious,and the best is when the sand to cement ratio is 3/4.The increase of polypropylene fiber content has little effect on the strength and dry density,and the strength will decrease at low density.The increase of polypropylene fiber content has an obvious inhibition effect on dry shrinkage,resulting in the increase of open porosity,and the correlation coefficient between open porosity and dry shrinkage is higher.In combination with the drying shrinkage value of G400 and G600,0.10%was selected,while0.15%was selected for G800 and G1000.