Research On Properties Of Manufactured Sand Dry-mixed Masonry Mortar

Dry-mixed mortar is a new kind of mortar which has advantages of high efficiency,high quality and environmental protection and will be universalized in construction.Though dry-mixed mortar has a series of excellent performance, natural sand as onecomponent of mortar is increasingly depleted. The use of manufactured sand instead ofnatural sand is imperative. However, there are few studies on dry-mixed mortar made bymanufactured sand. The research on manufactured sand dry-mixed mortar is of greatsignificance for guiding the production and application.The influence of the maximum particle size, particle distribution, MB value andmineral admixture on workability and mechanical properties of mortar were studied.The influence of mixing process on dry powder homogeneity was studied, with methylviolet as a tracer. The rheological properties of mortar were researched based onstatistics and analysis. Research results can be concluded as following:①Stone powder in manufactured sand can improve water retention and reduce theamount of thickening material in mortar. At the appropriate mix proportion the mortareven did not need thickening material, so the kinds of mortar components were reducedand it helped enhance the homogeneity of powder and reduce production costs.②The mortar made with blastfurnace slag and limestone powder performed betterthan that made with fly ash and limestone powder. Consistency, water retention rate andstrength of the former met the specification requirements.③The content of methyl violet in different parts of stirred powder can effectivelycharacterize the degree of mixing uniformity when methyl violet was incorporated as atracer.④The curve of mixing degree with stirring time was similar to the sine functionand the maximum mixing degree was in the first peak at about3min.⑤Under different load factor(30%,50%,70%), mixing degree with stirring timealso presented the relation similar to the sine function and the difference was curveposition. There may be a more reasonable load factor between50%and70%which canmake powder mix uniformly easier under the same conditions.⑥When enhancing the mixer speed from60r/min to120r/min, the time to achievethe best mixed state reduced from3min to1min48s and the mixing uniformity gotslightly higher. ⑦The rheological equation τ=a*x^b+c of manufactured sand dry-mixedmasonry mortar can be seen as “power law fluid” having the limiting static shear stress.‘A’ can be regarded as consistency coefficient.‘X’ and ‘c’ can be regarded as shear rateand the initial limiting static shear stress.