Study On Mechanism And Preparation Of Artificial Sand Anti-crack Dry Mortar

Artificial sands are the all crushed sands and mixed sands in addition to the natural sands.In recent years, the rapid development of China's infrastructure construction and the attention of environmental protection has made the natural sand resources increasingly scarce and exploiting artificial sands which adapt for the engineering application seems inevitable.Although there are some examples about artificial sand in the application of engineering successfully, they are basically limited to the research on concrete and ordinary mortar, rarely on the dry-mixed mortar. For this reason, the steel-slag sand and crushed sand (granite, sandstone and limestone) anti-crack mortar were studied in this paper, mainly about the mix porportion design and performance.The basic physicochemical characteristics of steel-slag sand and three different lithologies of crushed sands were analyzied from the microscopic viewpoint by the modern test analysis tools such as X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), and the macro rules of the effects of them on the performance of mortar were understood deeply by combining the microstructure with porperties.The preparation of steel-slag anti-crack mortar:First, with contrast experiments, the proper addition content of steel-slag sand, mineral admixtures, the variety of water-reducer agent and the addition content of water-proofing agent are determined by the study on the workability and the normal mechanical properties (the water absorbing content, cohesive strength, compressive and flexural strength ratio) of the steel-slag sand anti-crack mortar. Then it is through the tests of related durability of the steel-slag mortar such as water resistance and freezing resistance, heat and alkali resistance, volume stability, and weatherability, etc to satisfy the project need, and through the comparison of cohesive strength in different curing systems to establish appropriate curing system of the steel-slag mortar. The tests on performrances showed that when the addition content of steel-slag sand is between 50% and 70%, the comprehensive performance of mortar is better.Proper addition of grounded furnace slag(GFS) and fly ash can decrease the water absorbing content and dry shrinkage. Melamine and polycarboxylate water-reducer agents have better water reducing effects.The water-proofing agent can effectively reduce the water absorbing content of anti-crack mortar, but it should be controlled in 2‰around.The preparation of crushed sand anti-crack mortar:Comparative study on the workability, normal mechanical properties and related endurability of three different lithologic crushed sand anti-crack mortar, and on the comprehensive properties of the natural sand mortar and steel-slag sand mortar.The results showed that the water absorbing content of crushed sand mortar was a little more than natural sand mortar, but much less than steel-slag sand mortar.The cohesive strength of limestone and granite mortar is a bit low than natural sand mortar, but sandstone mortar slightly improved the cohesive strength. Overall, mortar prepared by crushed sand has its characteristics such as small water absorbing content, high cohesive strength, good resistance to water, small dry shrinkage rate etcFinally, it was analyzed the mechanism of artificial sand anti-crack mortar in this paper, understanding its anti-cracking mechanism, and perfecting the theoretical basis of artificial sand anti-crack mortar.