Experimental Study On Frost Resistance Of Recycled Fine Powder Concrete

With the rapid development of China's construction industry,sand and stone raw materials are increasingly scarce,recycled concrete has become an indispensable new building materials in the construction industry.In this paper,the recycled fine powder concrete is taken as the research object,the mechanical grinding method is used to activate the recycled fine powder,the mechanical properties and antifreeze properties of recycled fine powder concrete are compared with fly ash and slag,and the antifreeze properties of recycled fine powder concrete are improved by adding mineral admixture and air-entraining agent.The concrete results are as following:(1)the compressive strength of recycled fine powder concrete decreases with the increase of the content of recycled fine powder and increases with the increase of water-cement ratio.When the water-cement ratio was 0.35 and the content of recycled fine powder was 10%,the compressive strength of the recycled micro powder reached 60.7mpa,which was close to the compressive strength of natural concrete(65.9mpa).(2)when the water-cement ratio is 0.35,the compressive strength of fly ash concrete at different ages is similar to that of recycled fine powder concrete at different ages;At the same water-cement ratio,the compressive strength of slag concrete at all ages is lower than that of recycled micro-powder concrete,with a difference of about 10 MPa.(3)when the mineral admixture is mixed with only recycled fine powder,when the content of recycled fine powder is 30% and the water-cement ratio is 0.35,the frost-resistance of recycled fine powder concrete reaches 175 times at most.With the increase of the content of recycled fine powder,the frost resistance of recycled fine powder concrete increases first and then decreases.When only fly ash and slag are added,the frost resistance of concrete is poor,up to about 75 times.(4)the mineral admixture is conducive to improving the antifreeze performance of the recycled fine powder concrete.When the water-binder ratio is 0.35,the total mineral admixture content is 30%,and the regenerated powder content is 21%,the regenerated powder concrete has the best frost resistance of 200 times.When only adding regenerated powder and adding 0.01% air entraining agent,the anti-freezing performance can reach 250 times when the content of regenerated powder is 30%.The antifreeze performance of the regenerated powder was higher than that of the regenerated powder when the regenerated powder content was 30%.(5)the compressive strength of concrete is relatively low when aerating agent is added on the basis of mineral admixtures.The 28 d compressive strength is close to 40 MPa.When the air entraining agent dose is 0.03%,the relative dynamic elastic modulus of concrete decreases slowly,and the recycled fine powder concrete has the best frost resistance,up to 300 times.