Research On The Influence Of Modifiers On The Mechanical Properties Of Recycled Aggregate Concrete

Due to the long trial period and multiple destructions,the performance of recycled aggregates is far inferior to natural aggregates,resulting in low mechanical properties of recycled concrete.The use of modifiers to optimize the modification of recycled aggregate can improve its structure to a certain extent,thereby enhancing the strength of recycled concrete.Therefore,in this paper,two modifiers of sodium silicate and silane are selected for single modification and mixed modification of recycled aggregates.By comparing the performance indexes of each group of aggregates with the mechanical properties of modified recycled concrete,the modification rules are explored,Modification mechanism and optimal modification plan;explore the changing law of modified concrete affected by confining pressure and age under complex stress conditions,so as to provide theoretical guidance for aggregate modirication in actual engineering.The main research contents of this paper are as follows(1)Exploring the modification law of aggregate by a single modifier,and found that under the same concentration,the modification effect of sodium silicate solution on aggregate is basically better than that of silane solution,and silane solution is only superior to the modification of water absorption.Sodium silicate solution;the effect of mixed modification is mostly better than that of single modification.The mixed modification of 8%sodium silicate and 12%silane can increase the apparent density and bulk density of the aggregate the most,10%sodium silicate and 12%Silane mixing modification has the greatest increase in water absorption and crushing index of recycled aggregates.(2)The mechanical performance experiment of modified recycled concrete was carried out,and the law of single modification of recycled concrete was obtained.The compressive strength modification effect of silane and sodium silicate in the concentration range of 0%～8%is equivalent,8%～Sodium silicate is better than silane in the concentration range of 12%,and the modification effect of sodium silicate on the cleavage tensile strength is better than that of silane solution in the concentration range of 0%to 12%.(3)According to the experimental results of the mechanical properties of the modified recycled concrete,find out the optimal scheme of mixed modification.When 8%sodium silicate solution and 12%silane solution are mixed and modified,the compressive strength and splitting tensile strength of recycled concrete are 41.3MPa and 2.67MPa,respectively,which are 22.29%and 87.42%higher than RAC,reaching NAC 96.11%and 82.41%,the comprehensive modification is the best,so the mixed modification of 8%sodium silicate and 12%silane is the comprehensive best solution.(4)The triaxial compression test of modified recycled concrete was carried out,and the influence of confining pressure and age on the results of the triaxial test was obtained.The age remains unchanged.As the confining pressure increases,the axial compressive strength,axial peak strain,and elastic modulus of the modified recycled concrete all show an increasing trend;the confining pressure is fixed,and as the age increases,the modified recycled concrete The axial compressive strength and elastic modulus of concrete gradually increase,and the peak strain gradually decreases.At the same time,the optimal modification scheme under complex stress conditions was found.This scheme is the same as uniaxial compression,and is also modified by mixing 8%sodium silicate and 12%silane.(5)Develop correlation statistics between the performance indicators of modified aggregates and the mechanical properties of concrete,and the two are linearly positively correlated.The study of the modification mechanism of the modifier and the analysis of the combined state of the various materials of recycled concrete confirmed the importance and necessity of aggregate modification.The SEM scanning electron microscope was used to observe the microstructure of the modified aggregate to verify the modification mechanism of the modifier.