Mechanical Properties And Microstructure Analysis Of Recycled Mortar

With the development of urbanization process in China,there is a large number of construction waste and concrete wastes up to about 80%.If there is no way to reuse,it not only has a certain impact on the environment,but also causes a waste of resource.On the basis of previous studies,this experiment made use of the waste concrete blocks to crush as recycled fine particles in mortar to replace cement and natural sand,respectively.The effect on the mechanical properties of recycled mortar and microstructure was studied.The experiment applied three sets of water/cement ratios of 0.55,0.60 and 0.65.The main contents of this paper are as follows:(1)When using the recycled paticles of 0-0.32 mm and 0-0.16 mm respectively replace cement by 10% and 20%.The results show that with the replacement increasing,the strength of recycled mortar decreases;as the grain size of recycled particle becomes small,the strength of the recycled mortar becomes great.(2)When the water/cement ratio was 0.60 and recycled particle’s replacement of cement is 20%,fly ash dosage to replace cement was 20% and 40% respectively.The experimental results show that with the the increasing of fly ash,the bending strength of recycled mortar decreases and compressive strength increases firstly and then decreases.(3)Based on the sieving results of natural sand,the experiment used recycled fine aggregate to replace the natural sand with the dimension of 0-0.32 mm,0-0.63 mm,0-1.25 mm,0-2.5 mm and 0-5 mm respectively.It appears that with the size range of recycled fine aggregate increasing,the strength of recycled mortar gradually increases.(4)When the water/cement ratio is 0.60,of the recycled particles 0-0.16 mm and 0-0.32 mm were added as filler into the recycled mortar by 5%,10% and 25% of cement.We can see that with the increasing of recycled particles,the strength of recycled mortar increases.(5)Compared with the four different methods,using recycled fine aggregate to replace the nature sand has the greatest impact on the strength of recycled mortar.When using the scanning electron microscopy technique to analyze recycled mortar microstructure,it shows the internal structure of recycled mortar is more dense and the pores are filled with a lot of hydration products.What’s more,there are some glass spherical fly ash particles found in the recycled mortar and it makes the strength of recycled mortar which mixed with recycled fine aggregate higher.