Preparation And Properties Of Fully Recycled Aggregate Concrete

Due to the relatively poor performance of recycled aggregate prepared from construction waste,the performance of fully recycled aggregate concrete is comparatively weaker than that of natural aggregate concrete.At present,the research on fully recycled aggregate concrete focuses on recycled coarse aggregate,and there is less research on the simultaneous use of recycled coarse and fine aggregate,resulting in insufficient research and utilization of recycled aggregate.Therefore,it is necessary to study the recycled concrete with recycled coarse and fine aggregate.On the premise of meeting the design strength of fully recycled aggregate concrete,Explore the influence of the preparation process of fully recycled aggregate concrete on the performance,study the methods to improve the performance of fully recycled aggregate concrete,and summarize the corresponding laws and conclusions.This thesis studies the mix proportion design method of fully recycled aggregate concrete,compares and tests with the current standard and recycled concrete design method,obtains the more suitable mix proportion design method of fully recycled aggregate concrete,and studies the influence of different dosage of water reducing agent and fly ash on the compressive performance and workability of fully recycled aggregate concrete;By studying the composition of recycled aggregate and adopting different aggregate performance optimization methods,this thesis explores the impact on the performance of recycled aggregate;Then the influence of recycled powder on cement hydration is studied,and the performance changes of fully recycled concrete mixed with recycled powder are explored.The main conclusions are as follows:1.The mix proportion design method of saturated surface dry method should be adopted for fully recycled aggregate concrete to obtain better working performance;The water reducing efficiency of fully recycled aggregate concrete using polycarboxylic acid water reducing agent is lower than that of traditional concrete,and the role of water reducing agent gradually weakens with the increase of dosage:the advantages of two-stage mixing method and net slurry stone wrapping method have also been verified in fully recycled aggregate concrete.The fully recycled aggregate concrete using these two methods has better working and mechanical properties.2.The parts with weak performance in recycled aggregate are hardened mortar and brick.The recycled aggregate can be strengthened by heating grinding method and cementitious slurry wrapping method.The performance of the strengthened recycled aggregate can be greatly improved,which can effectively improve the performance of fully recycled aggregate concrete;Nano-SiO₂and polyacrylonitrile fiber with strong alkaline resistance are ideal reinforcement materials for fully recycled concrete.The addition of appropriate amount of nano-SiO₂and polyacrylonitrile fiber can effectively improve the compressive strength of fully recycled aggregate concrete.3.During the preparation of fully recycled aggregate concrete,more recycled aggregate waste will be produced.The research and utilization of recycled aggregate powder is a method to improve the utilization rate of recycled aggregate.After screening the recycled aggregate powder,the experiment shows that it can promote the hydration of cement.Adding the recycled aggregate powder to the concrete shows that a certain amount of recycled aggregate powder can improve the performance of concrete.