Study On The Application Of High Adsorption Machine-made Sand And Stone Powder In Waterproof Mortar

At present,machine-made sand has rapidly replaced natural sand as the main source of sand.However,due to the application of high adsorption machine-made sand,such as gneiss machine-made sand,in the ready mixed concrete,the amount of water reducing agent will increase significantly,and the workability is poor,which leads to great limitations in the application of concrete engineering.A large amount of rock powder is accumulated in the mine site,and the resources are not fully utilized.As soon as possible to form a solution for the application of high adsorption machine-made sand and stone powder,it can absorb a large amount of stone powder.It can not only alleviate the current situation that the supply of highquality machine-made sand and admixture is in short supply,but also reduce the production order and environmental protection problems caused by the discharge of waste stone powder,which has significant social and economic benefits.This project uses gneiss machine-made sand and stone powder to prepare waterproof mortar.The admixture(fly ash)accounts for 40% of the cementitious material system,and stone powder 0%,25%,50%,75%,100% substitute powder.Preparation of waterproof mortar from coal ash.The influence of stone powder replacement rate on the performance of the "cementfly ash-stone powder" ternary composite cementitious material system was explored,and the mechanism was explained and analyzed from the aspects of hydration heat,hydration products and micro-morphology.The effect of stone powder replacement rate on the performance of waterproof mortar was studied,and the internal structural changes of waterproof mortar were analyzed by SEM and MIP observation.The main conclusions are as follows:(1)The impact of stone powder replacement rate on the ternary composite cementitious material system: With the increase of stone powder replacement rate,the standard consistency water consumption of the cementitious material system gradually increases,and the initial setting and final setting time gradually decrease;when the substitution rate of stone powder is about 25% ~ 75%,the yield stress,plastic viscosity and lag ring area of the paste are all lower,the rheological property of the paste is better,and the best substitution rate of stone powder is 50%,and the compatibility of the cementitious material system and polycarboxylic acid water reducer is better when the substitution rate of stone powder is less than 50%;the addition of stone powder has no great influence on the types of hydration products,but it will reduce the total hydration heat release of the cementitious material system.(2)The influence of substitution rate of stone powder on workability and mechanical properties of waterproof mortar: With the increase of substitution rate of stone powder,the loss rate of 2h consistency of waterproof mortar increases gradually,but all meet the specification requirements;the water retention of waterproof mortar is better under different stone powder replacement rate,which is far higher than the requirement of ? 88% in Ready-mixed Mortar(GB/T 25181-2010);when the substitution ratio of stone powder is 25% ~ 75%,the rheological property of mortar is better,and the rheological property of mortar with 50% substitution ratio is the best;the substitution rate of stone powder has little effect on the 28 d compressive strength,flexural strength and compressive flexural ratio of waterproof mortar.(3)Effect of stone powder substitution rate on impermeability,durability and deformation of waterproof mortar: Adding stone powder into waterproof mortar can slightly reduce its frost resistance,but all of them meet the requirements of specifications;adding stone powder can reduce the shrinkage and cracking sensitivity of waterproof mortar,and the replacement rate of stone powder is about 50% and 75%;the impermeability of waterproof mortar is good,and the impermeability pressure of each group of mortar reaches P6 impermeability grade of Readymixed Mortar,and when the replacement rate of stone powder ? 50%,it reaches P8,or even P10;reducing the water binder ratio can improve the impermeability of waterproof mortar,but it will make the workability of mortar worse;there is no obvious difference in impermeability of waterproof mortar made of limestone,gneiss and their powder.In general,it is feasible to prepare waterproof mortar with high adsorption machine-made sand powder instead of fly ash,which is conducive to the healthy development of machinemade sand industry and the construction of green mines,and has broad application prospects.