Study Of The Low Temperature Hardening And Durability Performance Of Recycled Fine Aggregate Based Alkali-activated Slag Concrete

As one of the main materials in the construction industry,cement consumes a lot of natural resources in the production process,and will cause pollution to the environment.Alkali activated cementitious material is a kind of cementitious material with gelling and hydraulic properties after being mixed with industrial waste residue,tailings and alkali containing substances and a certain amount of water.Recycled concrete refers to a new type of concrete,which is made by crushing and grading the discarded concrete blocks,mixing with the grading according to a certain proportion,replacing natural aggregates such as sand and stone,and then adding cementitious materials.Using solid waste instead of traditional materials to prepare concrete can reduce environmental pollution,save resources,reduce costs and improve concrete performance.The purpose of this paper is to combine recycled fine aggregate with alkali activated concrete,to replace quartz sand with recycled fine aggregate,cement with alkali activated cementitious material,air entraining agent in concrete,to study the performance of alkali activated recycled concrete under different mix proportion,to balance the strength of concrete,and to construct in winter The optimum mixture ratio was found under the condition of the properties of anti freezing and anti freezing.The main work is as follows:(1)The effects of air entraining agent on the basic mechanical properties and durability of alkali activated concrete were studied.The effects of air entraining agent on the basic mechanical properties of alkali activated concrete,the law of improving the frost resistance and the negative effects on the decline of other durability were found.Through the study,it can be found that the addition of air entraining agent can reduce the mechanical properties of alkali activated concrete,as well as the anti acid,anti carbonation and anti chloride ion erosion ability,but it can greatly improve the anti freezing performance of alkali activated concrete with high replacement rate of recycled fine aggregate.(2)To study the influence of different replacement rate of recycled fine aggregate on the basic mechanical properties and durability of alkali activated concrete,it is found that the alkaline characteristics of recycled fine aggregate can accelerate the rapid setting effect of alkali activated concrete,improve the early setting strength of alkali activated concrete,benefit the low-temperature setting effect of concrete,and confirm the feasibility of the research direction.At the same time,with the increase of the replacement rate of recycled fine aggregate,the change rule of various properties of concrete is studied.It is found that with the increase of the replacement rate of recycled fine aggregate,the performance of concrete decreases.The performance of concrete with small replacement rate of recycled fine aggregate decreases very little.With the increase of replacement rate of recycled fine aggregate,the influence increases gradually.(3)Study the low-temperature setting effect of different air entraining agent,antifreeze,material temperature,heat preservation measures and replacement rate of recycled fine aggregate in alkali activated concrete under different alkali excitation concentration,and find that alkali excitation concentration has significant influence on the early setting effect of alkali activated concrete under low temperature,and find the initial temperature of raw material and concrete It is found that recycled fine aggregate can promote the early setting effect of alkali activated concrete.