Experimental Study On Influence Of Ultra-fine Brick And Limestone Powder On The Performance Of Cement-fly Ash Mortar

At present,our country as a whole is in the middle of ongoing urbanization.The human are confronted with lack of building materials and mineral admixtures and serious environmental pollution caused by construction waste.Sorting and crushing construction waste for recycling,which is an important way for the sustainable development of the construction industry,meets the basic national policy of green,environmental protection and energy conservation as well.In this paper,the reference of cement-fly ash mortar was prepared according to the test method for basic properties of building mortar,on the basis of the reference mortar,three trials were designed in which fly ash replaced by superfine brick powder or ultra-fine limestone powder,and fly ash replaced by brick powder on the basis of replacing 5%cement with limestone powder,to study the influence of different dosages of brick and limestone powder on the performance,mechanical properties and durability of cement-fly ash mortar.Whendesigning test,three kinds of strength grades of M7.5,M10 and M15 were used in the three tests,and six replacement rates of 0%,20%,40%,60%,80%and 100%were designed for each strength grade,so as to calculate the actual mix ratio of mortar,besides,810 standard cubic test blocks were prepared.The actual water consumption,apparent density and water retention of the mortar were studied according to the test,and the cube compressive strength and frost resistance of cement-fly ash mortar were explored.The main conclusions are as follows:(1)Fly ash replaced by Ultra-fine brick powder.The actual water consumption of mortar increased with the increase of replacement rate;The apparent density did not change too much;Water retention had been greatly improved;When the best performance o f cement-fly ash mortar was achieved,the replacement rate of ultra-fine brick powder was 40%～60%.The compressive strength of mortar cube increased first and then decreased with the increase of replacement ratio.The frost resistance index decreased with the increase of substitution rate.The replacement rate to achieve the best mechanical properties and durability was 40%.(2)Fly ash replaced by ultra-fine stone powder.The actual water consumption of the mortar was higher than that of the reference mortar and rose slowly with the increase of replacement rate.It had little effect on the apparent density.Water retention had been improved to some extent;The best performance was achieved when the replacement rate of ultra-fine limestone powder was around 60%.On the whole,the cube compressive strength of mortar showed a trend of first rising and then falling.The frost resistance decreases with the increase of substitution rate.The replacement rate to achieve the best mechanical properties and durability was 60%.(3)Fly ash replaced by brick powder on the basis of replacing 5%cement with limestone powder.The actual water consumption of mortar increased with the increase of replacement ratio.The range of apparent density varied little.Water retention was improved to some extent.The best performance was achieved when the replacement rate of 5%cement with limestone powder was near 40%.The cube compressive strength of mortar increased first and then decreased with the increase of replacement rate,and decreased with the increase of strength grade.The frost resistance index decreased gradually;The mechanical properties and durability of mortar were the best when the replacement rate of brick powder was 40%after the replacement of 5%cement by limestone powder.(4)The actual water consumption of mortar was increased in all the three admixture tests.On the basis of limestone powder replacing 5%cement,fly ash replaced by brick powder increased the most,followed by single-mixed brick powder,and the single-mixed limestone powder was the least.It had little effect on the apparent density.The water retention of the mortar was improved with each ad mixture,which first increased and then decreased with the increase of the replacement rate.The cube compressive strength of mortar was improved on the whole,but with the increase of strength grade,the strengthening effect was weakened.All the three admixtures had adverse effects on the antifreeze performance of mortar,but they met the requirements within the allowable scope of the specification.