Preliminary Study On Crack-healing And Basic Mechanical Properties Of Concrete With Expanded Perlite As Microbial Carrier

Currently,concrete is the most widely used building material.However,it is difficult to avoid small cracks on the surface and inside of concrete.Compared with the man-made repair after the cracking,the microbial-induced self-healing of concrete cracks technology do not need human control,just buried the microorganism in the concrete.When the crack is produced,the microorganism forms the mineralized product at the crack and finally repair the crack.Direct incorporation of unprotected bacteria can result in a significant reduction in the number of bacteria.In order to make the microorganism better survive and maintain the activity,the research group first proposed to use the expanded perlite to immobilizing the mineralized microorganism,and to study the self repairing effect of the crack of the cracked concrete after the cracking.In comparison with ordinary concrete,a large number of expanded perlite can reduce the mechanical properties of concrete.In order to ensure that the concrete has good self repairing effect and sufficient strength,the basic mechanical properties of the concrete are tested.The main work is as follows:(1)first of all,this paper studies the preparation of self repairing particles,and tests the basic ability of the chemical composition,particle gradation,packing density,pressure strength,water absorption(under negative pressure and atmospheric pressure)and volume floating rate of the expanded perlite and ceramsite carrier.The water absorption,accumulation density,water absorption and pressure strength of the expanded perlite wrapped in the metakaolin and wrapped cement slurry are tested and the microstructure of the surface is analyzed.The thickness of the coated layer is measured,which provides the basis for the follow-up test.The results show that the water absorption and volume floating rate of the expanded perlite treated by the polymer and the cement slurry are significantly decreased,and the compressive strength and density of the piling are significantly increased.(2)the influence of the mixing method of the mycelium,the content of the expanded perlite,the carrier package material,the addition of calcium lactate and the particle size of the expanded perlite on the self repairing effect of the concrete cracks were studied.The repair effect was characterized by the width of the fracture repair.The results showed that the repair rate of the specimen with the expanded perlite carrying bacteria was the highest and the maximum crack width of 28 d was 0.79 mm.In the later period of the fracture repair,the effect of 30%,50% and 70% of the concrete specimens with the amount of 90% of the expanded perlite was better than that of the unwrapped group.The effect of fracture repair is better than that of the parcel group.(3)the influence of mixing method,water to glue ratio,silica fume content,content of expanded perlite,carrier package material,carrier particle size,polypropylene fiber content and other factors on the physical and mechanical properties of the concrete are studied.The results showed that the adverse effects of expanded perlite loaded bacteria on the compressive strength of concrete decreased significantly compared with the direct addition of bacteria.The compressive strength,apparent density and splitting tensile strength of concrete cube decreased with the increase of expanded perlite content.The apparent density and compressive strength of the wrapped cement paste are higher than those of the unwrapped concrete.With the increase of polypropylene fiber content,the compressive strength decreases,the splitting tensile strength and the ratio of tension to compression increase,and the brittleness of concrete decreases.