Study On The Influence Of Silane-treated Zeolite Powder On The Performance Of Cement Mortar

Zeolite is a kind of silica-aluminate mineral with rich reserves,which has certain volcanic ash activity and micro-aggregate filling effect.Because of the porous structure of zeolite,the zeolite powder admixture prepared with it will absorb a large amount of mixing water and admixture in the concrete mixing process,which makes the fresh concrete fluidity drop rapidly and makes the concrete,especially the pumped concrete,difficult to be constructed.In order to reduce the high water absorption of zeolite powder,this study was carried out based on mortar,in which isobutyltriethoxysilane was used to impregnate natural zeolite to prepare silane-treated zeolite powder to reduce the high water absorption of zeolite powder,and its mechanism of action was studied by testing the water absorption and pore structure of zeolite before and after silane treatment.Then the prepared silane-treated zeolite powder was mixed into mortar to study its effect on the flow and mechanical properties of mortar.Finally,SEM and XRD characterization were used to study the mixture of natural zeolite powder and Ca（OH）₂and the mixture of silane-treated zeolite powder and Ca（OH）₂,respectively,to compare the difference of the reaction process between the two materials and Ca（OH）₂and to provide theoretical support for their effects on the mechanical properties of the mortar.The main contents and results of the experiments are as follows:1.Preparation of silane-treated zeolite powder:It was found that if the natural zeolite powder was directly impregnated with silane,the mixture of the two was sticky and difficult to dry in a short time.Therefore,the impregnation treatment of 6-10 mm zeolite particles was adopted in this study.Zeolite particles were impregnated in liquid isobutyltriethoxysilane for 12 h,then filtered,dried（100℃,12 h）and ball milling（45 min）,and finally silane treated zeolite powder was obtained.2.Effect of silane-treated zeolite powder on fluidity of cement mortar:after impregnated with silane,the water absorption rate of zeolite is significantly reduced,and fluidity of cement mortar can be significantly increased.When the content（mass fraction）is 10%,the fluidity of cement mortar is 11.5%and 8.6%higher than that of natural zeolite powder and fly ash.3.Effect of silane-treated zeolite powder on mechanical properties of cement mortar:when the dosage is less than 15%,the strength of cement mortar only decreases slightly,and increases with the curing age,and the strength of cement mortar gradually approaches or even exceeds the reference group.Adding natural zeolite powder and silane treatment zeolite powder can reduce the fold-pressure ratio of cement mortar,but the fold-pressure ratio of natural zeolite powder to cement mortar decreases more obviously.4.Effect of silane impregnation on activity of volcanic ash from zeolite powder:in the same reaction time,natural zeolite powder consumes more Ca（OH）₂than silane treated zeolite powder.In addition,the micromorphology of C-S-H gel produced by the reaction of natural zeolite powder with Ca（OH）₂and silane treated zeolite powder with Ca（OH）₂is different.The C-S-H gel in the samples containing natural zeolite powder showed a network shape and filled between the particle pores,forming a good overall spatial network structure.However,the samples containing silane treated zeolite powder have high calcium-silicate ratio,resulting in the decrease of the C-S-H layer spacing.Therefore,the C-S-H gel generated in such samples are mostly clustered and only adsorbed on the particle surface,resulting in poor spatial integrity of the system.