Study On The Influence Of Natural And High-temperature Activated Bentonite On The Mechanical Properties Of Concrete

As an indispensable building material for modern civil engineering,concrete is one of the most used materials in the world,and cement is the decisive component of concrete in terms of its cost and environmental impact.Cement production will produce a large amount of carbon dioxide and heat energy emissions,which will cause environmental problems.In order to reduce the negative environmental impact and cost in cement production,using pozzolanic materials is one of the best solutions to reduce greenhouse gas emissions and energy and cement consumption.In this paper,different content of natural and high-temperature activated bentonite is used to replace the cement in the mix proportion of ordinary and high-strength concrete.Through experiments,the influence law and mechanism of different content of natural and activated bentonite on short-term and long-term mechanical properties of concrete are explored.The test results of mechanical properties of natural sodium-based and calcium-based bentonite concrete show that the early contribution of bentonite is small,which leads to the slow development of early strength of concrete,but with the increase of age,the later strength is improved.When the cement substitution rate of bentonite is5%,the loss rate of concrete strength decreases with the increase of concrete strength grade,while when the substitution rate exceeds 10%,the influence law is opposite.XRD test shows that the montmorillonite content of sodium bentonite is high,and the strength of sodium bentonite concrete is higher than that of calcium bentonite concrete at the same content,and the optimal content of natural bentonite is 5%.Through the electric flux and water absorption test,it can be seen that the improvement effect of bentonite content on concrete pore structure increases firstly and then decreases,and reaches the best when the bentonite content is 5%.The characteristic parameters of bentonite concrete pore structure are obtained through mercury injection test.Strength activity index(SAI)analysis shows that the critical content of sodium bentonite is 15% and that of calcium bentonite is 10%.The activity of high-temperature activated sodium bentonite increases with the increase of temperature,reaching a certain critical point and starting secondary activation,thus reducing the activity.The best treatment temperature in this experiment is 800℃.Compared with natural bentonite,sodium bentonite activated at high temperature obviously improves the mechanical properties of concrete,and the critical content of bentonite activated at high temperature can be increased to more than 20%,showing better engineering applicability.