Research On The Effect Of Mud In Aggregate On Mortar Performance

With the increasing demand for engineering construction,the demand for aggregates is increasing.At the same time,due to environmental development factors,the cost of sand and gravel is increasing,and the quality of sand and gravel is decreasing.The instability of aggregate quality is currently the main problem,the most obvious of which is the increase in mud content,and the mud in the aggregate has an adverse effect on the quality of mortar and concrete.The main performance of the project is the influence of workability and strength.Therefore,the problem of mud in the aggregate is valued by people.The current research focuses on the single factor of mud content,but lacks a systematic analysis of the negative effects of mud composition mineral composition and clay.At the same time,there is no clear conclusion on whether the clay in the mud has an effect on the cement hydration process.In this paper,the clay in the mud is taken as the research object,and the influence of clay on the performance of water reducing agent,cement and mortar is studied.At the same time,the influence of clay in the process of cement hydration is explored.Clay in the mud is the main component of the mud's negative adverse effects on mortar performance.The clay adsorbs the water reducing agent and the water,so that the effective water reducing agent content in the mixing slurry is reduced,and the free water which can fully contact the cement and the hydration reaction is correspondingly reduced,thereby reducing the work performance of the cement paste and the mortar..There are differences in the adsorption properties of different clays in the mud for water reducing agents and water.The main mineral composition of clay is montmorillonite,kaolin,and illite.In the study,three main clays were used as research objects,and the mud contained in the aggregates in the engineering application in Chongqing was simulated.The performance of clay on the hydration heat release rate,cement paste and mortar of different water reducers was studied.The effect of clay on the effect of water reducer in cement paste and mortar,research shows that:Under the condition of no water reducing agent,5% montmorillonite reduced the hydration heat release rate by 10% and the total heat release by 12%.Under the condition of polycarboxylate superplasticizer,5% montmorillonite will make the maximum exothermic peak 3 h ahead;kaolin will make the exothermic peak delay 2.5 h.In the early stage of hydration,clay has a certain degree of influence on the total amount of heat release from cement hydration.At 5% dosage,montmorillonite reduced the total amount of hydration heat by 12%,and kaolin increased the total amount of cement hydration heat slightly.Clay has no effect on the type of cement hydration products,but it will affect the crystallization of hydration products and affect the composition of hydration products.Montmorillonite has a significant negative impact on cement;montmorillonite has a significant adverse effect on polycarboxylate superplasticizer,5% content leads to a 50% reduction in fluidity of cement slurry and a 20% reduction in strength;kaolin and illite There is also a certain degree of influence on the fluidity of the cement system,but the kaolin has no adverse effect on the strength of the cement mortar in the 5% content,and even favors the development of the early strength at a lower content.In ultra-fine sand mortar,the amount of kaolin and illite is less than 5%,and the strength will increase by about 20%.Combined with the test of simulated clay,it is shown that the content of montmorillonite in the mud is the main factor affecting the fluidity and strength of the cement paste and mortar.