Experimental Study Of The Influences Of Polypropylene-fiber And Stone Powder On Basic Properties Of Cement Mortar With Manufactured Sand

With the rapid development of our country,s infrastructure construction, natural sandresources become dwindling and the contradiction between supply and demand is increasingacutely, using manufactured sand rather than natural sand as conventional materials in theconcrete and mortar becomes the main development tendence. However, the currentspecification "Sand for Construction"(GB/T14684-2011) strictly limits the contents of stonepower in the manufactured Sand. Because of its multi-angular, rough surface and poor rollingability, manufactured Sand produced by dust moving or washing methods greatly reduces themobility of cement mortar, which makes the cement mortar into some problems such as thebleeding and poor cohesiveness.So that, experimental study should be performed toinvestigate the effects of stone powder contents on properties of cement mortar withmanufactured sand. At the same time, there are also some problems of great drying-shrinkageand easily crack at early age, it is necessary to improve cement mortar with manufacturedsand by admixing polypropylene fiber. Currently, the application of polypropylene fibers toimprove the properties of natural sand mortar is relatively mature,but the research ofpolypropylene fibers used to improve cement mortar with manufactured sand is still relativelyscarce. As the study of effects of stone power on cement mortar usually concentried on asingle strength level and without considering the influence of cement dosage on content ofstone powder, the different conclusions were given out.In addition, the relations, the relationbetween water dosage and content of stone powder is simply described, quantitativecalculation method has not been proposed. Based on cement mortar of manufactured sand infour strength grades of M5, M10, M15and M20, The main works of this paper are as follows:1）By analyzing the changes of water dosage, the quantitative calculation method relatingthe water dosage with the content of stone powder for cement mortar with manufactured sandis proposed.2）To ensure the performance of cement mortar, the content of stone power of0%,7.9%,10%,15%,20%,25%and30%mass of manufactured sand were used to research itsinfluence on the mass density, compressive strength, flexural strength, drying-shrinkage andcracking-resistance.3）On the basis of the optimal content of stone powder, the polypropylene fiber wasconsidered in mass contents of0.6kg/m3,0.8kg/m3,1.0kg/m3and1.2kg/m3, and lengths of6mm,12mm and18mm respectively, to improve compressive strength, flexural strength, bend-compresion ratio, drying-shrinkage and cracking-resistance of the cement mortar withmanufactured sand.4）The microstructure and mechanism of cement mortar were analyzed from themicroscopic viewpoint by the modern test analysis tools such as scanning electronmicroscopy(SEM).