Experimental Study On The Key Properties Of Cement Mortar

Ready-mixed mortar industry has enjoyed a rapid development for the reasons that construction industry itself becomes increasingly strict with mortar quality and performance, that people pay more and more attention to environmental problems, and that the variety of mortar becomes diversified. In China, a host of ready-mixed mortar enterprises with considerable scale of production has been established in some developed cities. Except traditionally used as a bond or for covering walls, mortar has been given the special functions such as heat preservation, thermal insulation, sound absorption, water resistance, crack resistance, repair, etc. and has been widely used in the civil engineering field.This thesis mainly studied cement mortar’s water-retaining property, dry shrinkage, early-stage cracking, adhesion to the base, and the conventional compressive property and fracture resistance, and the main factors influencing these properties, and provides some necessary information and means for developing various kinds of functional mortar. First, it decided the mix ratio of basic mortar and studied the water-retaining property of cement mortar. Through tests, it found that the water-retaining property of cement mortar can be improved to some extent by adding cellulose ether, starch ether, or dispersible emulsion powder, and cellulose ether produces the best water-retaining effect; however, with more and more cellulose ether being added, the mortar will get more and more viscous and its working performance will go bad. Adding starch ether can improve cement mortar’s working performance very well, so by adding cellulose ether and starch ether in combination, both the mortar’s water-retaining property and working performance can be improved. Second, by adding polypropylene fiber, expanding agent, cellulose ether, starch ether, or adding cellulose ether and starch ether together to the selected basic mortar, it studied these substances’ effect on the mortar’s dry shrinkage and early-stage cracking. Through tests, it found that adding polypropylene fiber or cellulose ether to the basic mortar can alleviate the mortar’s dry shrinkage and restrain the early-stage cracking, while expanding agent and starch ether has no such effect on the mortar. Third, it studied mortar’s adhesion to the base. Through tests, it found that curing condition, property of base material, surface roughness of base material, interface agent, and mortar’s own properties all the above have effect on mortar’s adhesion to the base. Of them, curing condition has the most obvious effect. With same temperature, the cohesive strength of the mortar under wet curing condition is much higher than that under dry curing condition. Fourth, it studied the compressive strength and fracture resistance of the mortar added with the above-mentioned functional additives. Through tests, it found that adding polypropylene fiber, expanding agent, fly ash, granulated blast furnace slag, or other additives to adhesive mortar, or changing water-binder ratio can influence the mortar’s compressive strength and fracture resistance. Of these influencing factors, water-binder ratio’s effect is more significant. At last, it applied the functional mortar developed in the study to actual engineering and achieved good results.