Preparation Technology Of Foam Concrete With A Large Mixing Amount Of Wet Fly Ash

Foam concrete has the characteristics of low density,low thermal conductivity,high flowability,and self-compacting etc.It was mainly used as a building insulation material in the early stage of development,and then was widely used in other fields such as backfill engineering.Adding a certain amount of fly ash when preparing foamed concrete can further improve the utilization rate of fly ash and reduce economic cost.However,there are certain requirements for the quality,dosage of fly ash and other cementitious materials.This paper mainly studies the preparation of foamed concrete using low-quality wet fly ash with the appropriate activator and ordinary Portland cement for backfilling engineering.The experiment was carried out in three directions:the excitation of the wet fly ash,the compatibility of the foaming agent and the preparation of the foamed concrete.The results show:The four activators of Na₂SO₄,Na₂SO₄&CaO,CaSO4&NaOH and Na₂O·?SiO₂?_1.5 have obvious stimulating effects on wet fly ash.All four kinds of activators can increase the strength of the mortars with 80%wet fly ash at 56 days to above 15 MPa,which is over 200%higher than that of the mortars without excitation.In addition,the first three kinds of excitation methods are mainly to promote the formation of Aft,and the result of Na₂O·?SiO₂?_1.5 excitation is mainly the formation of C-S-H gel.Stabilizing agents such as SDS and thickeners such as PVA can greatly increase the foaming performance of the plant protein foaming agent.Considering the comprehensive performance and economic benefits,the experiment achieves the best effect after adding 0.3%SDS and 0.1%PVA to plant protein foaming agent.The water-binder ratio of the foamed concrete slurry will affect the uniformity of the mixing of the foam and the slurry,but has little effect on the overall trend of the internal pore size distribution.The different proportions of the slurry and the type of the wet fly ash activator can affect the pore diameter distribution of the pores in the foamed concrete,resulting in significant changes in the proportion of pores in different sizes.Finally,through reasonable design,foam concrete with 80%wet fly ash and a surface dry weight of 800 kg·m^-3 can be prepared.Its 56-day compressive strength reaches 1.84MPa.It was demonstrated that the wet fly ash has a good potential activity,and has the possibility of being applied to other concrete projects after further treatment.And the performance of foamed concrete prepared can be further improved by reducing the amount of wet fly ash or increasing the bulk density of foamed concrete,which provides the possibility for the application of the foamed concrete in other fields.