| How to improve the mechanical properties of alkali-activated materials economically and conveniently,Meanwhile,how to improve their efflorescence has become the key to promote the engineering application of alkali-activated materials.Based on this,alkali-activated materials were modified and strengthened by acid treatment and membrane curing.Through acid-alkali synergistic activation measures to further stimulate the potential activity of solid waste in the material preparation process,and through coating treatment to make sure the activation effect of the activator during the curing process,so as to improve and enhance the properties of alkali-activated materials.This paper is of great significance to promote the utilization of solid waste and the engineering application of alkali-activated materials.(1)The influence of membrane curing on the compressive strength of alkali-activated materialsThe alkaline activator used to prepare alkali-activated materials is easily soluble in water,and is easy to be dissolved and lost in the curing process,resulting in a decreased activation effect on the potential activity of solid wastes.In this paper,the effect of membrane curing on compressive strength of specimen with different water glass modulus and different water glass content were studied.The application scope of membrane curing was determined,and the mechanism was analyzed.The results show that the membrane curing can effectively promote the development of the mechanical strength of alkali-activated materials,especially when the water glass modulus is high or the water glass content is low,the membrane curing can promote the compressive strength of specimens more significantly.However,when the water glass modulus is lower than 1.0,or the water glass content is more than 26.66%,the membrane curing will affect the continuous development of the mechanical strength of specimens.In general,the best modulus of water glass is1.25,and the best content is 16.66%.(2)The influence of acid treatment on the compressive strength of alkali-activated materialsThe activity of most industrial solid wastes is poor,so the mechanical of alkali-activated materials prepared is often not high.Moreover,the effect of activator on the mechanical strength of alkali-activated materials is only obvious when the amount of it is relatively low,but it will be greatly weakened when the amount of it isrelatively high,even brings adverse effects.This paper proposes the acid-alkali synergistic activation measures,and studies the effect of different kinds of acids on the mechanical strength of alkali-activated materials.The application scope of acid-alkali synergistic activation was determined,and the mechanism of acid treatment in different raw materials was analyzed.The results show that the synergistic activation effect of acid before alkali is better than that of alkali before acid.The steel slag treated with strong acid is beneficial to the development of the compressive strength of alkali-activated steel slag,with the best sulfuric acid content of 4%,and the best hydrochloric acid content of 3%.The incineration bottom residue treated with strong acid is also beneficial to the development of the compressive strength,with the best sulfuric acid content of 3%,and the best hydrochloric acid content of 3%.The red mud treated with sulfuric acid is also beneficial to the development of the compressive strength,and the best content is 2%.The fly ash treated with sulfuric acid is also beneficial to the development of the compressive strength.However,the slag treated with acid will lead to a decrease of the compressive strength of alkali-activated slag.(3)The influence of acid treatment and membrane curing on the efflorescence of alkali-activated materialsDue to the addition of more alkali activators in the process of preparation of alkali-activated materials,the content of soluble saline and alkali in the materials is higher,which leads to more serious efflorescence.Therefore,in order to promote the application of alkali-activated materials,we should pay attention to their mechanical properties as well as their serious efflorescence.So this paper studies the influence of acid treatment on the efflorescence of alkali-activated materials and analyzes whether acid treatment can improve the serious efflorescence of alkali-activated materials.The results show that the membrane curing is more conducive to improving the efflorescence of alkali-activated materials than the conventional curing,when the water glass modulus is more than 1.0 and the water glass content is no more than26.66%.The slag,steel slag and incineration bottom residue treated with acid is also beneficial to improve the efflorescence of alkali-activated materials,but the red mud and fly ash treated with acid cannot improve the efflorescence.There are 52 figures,31 tables and 81 references in this paper. |
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