The Study On The Application Technology Of Cellulose Ethers And Mineral Admixtures In Mortar

With the continuous development of construction industry in our country and the deeper research of construction materials, the commercialization of mortar has become an unstoppable trend. The use of the commercial mortar has been relatively common in most large and medium-sized cities in our country because it is of many advantages which traditional mortar does not have. However commercial mortar is also full of many technical problems.Due to the heavy usage of water reducer in highly flowable mortar, such as strengthening mortar, cementitious grouting materials, the bleeding can be very serious and the overall performance of cement mortar would be affected. The workability would easily get bad in a short period after mixing due to moisture loss because plastic mortar is always sensitive to the moisture loss, that is to say, the operation time can be very short. What’s more, for adhesive mortar, partial mortar would be lack of water because a lot of water would be absorbed by the matrix when the water retention of mortar is poor. That could lead to insufficient hydration, strength reduction and the the decline in cohesive force.Due to all those problems above, a kind of important additives, cellulose ether, is now widely used in cement mortar. As a kind of etherified cellulose, cellulose ether is of hydrophilicity. And this kind of high molecular compound has got excellent ability of absorbing and retaining water, so it can well solve many other problems, such as the bleeding of mortar, the short operational time, poor cohesive force.In addition, as a partial replacement of cement, admixtures, such as fly ash (FA), ground granulated blast furnace slag (GGBFS) and silica fume (SF), are drawing more and more attention. As industrial by-products and waste, the admixtures will occupy and destroy a lot of land, and will cause serious environmental pollution if we can’t fully make use of those admixtures. By reasonable application, mineral admixtures can improve some properties of concrete and mortar, and also some technical problems in engineering applications of concrete and mortar could be easily solved. Therefore, the wide application of mineral admixtures is beneficial to the both environment and industry.The influence of cellulose ethers and mineral admixtures on mortar have been respectively studied a lot both at home and abroad, but their composite using effect is still lack of discussion.This paper focused on the compounding use in mortar of the important additive, cellulose ethers, and mineral admixtures. The influence of the two components in fluidity and strength of mortar were summarized based on the test results. By changing the type and dosage of cellulose ethers and mineral admixtures in the testing process, we observed its effect on the mortar fluidity and strength (the cementing system was a binary system). Compared with HPMC, CMC should not be used for the cementitious materials to thicken mortar and to improve its water retention. HPMC under low dosage (0.2%) can significantly decrease the fluidity of slurry, increase the time-loss of fluidity, and reduce mortar strength and the ratio of compressive to bending strength. Considering fluidity and strength requirements, HPMC content in0.1%is comparatively appropriate. In terms of admixture, fly ash can increase the fluidity of slurry. The effect of GGBFS is not obvious. And silica fume can effectively reduce bleeding, but it can make the loss of fluidity serious in the dosage of3%. Above all, in the case of fly ash, the adding proportion should be under10%when used in structural or strenthening mortar which is required of rapid hardening or early strength, while20%could meet the requirements roughly when used in adhesive mortar. Considering poor volume stability because of GGBFS and silica fume, the dosage should be controlled under10%and3%respectively. And the correlation between the influences of cellulose ethers and mineral admixtures is not obvious, so they can be treated independently.And from the reference of Feret strength theory and the active coefficient of mineral admixtures, a new prediction model of compressive strength of cementitious materials was presented. On the premise that the interaction between different admixtures should have been ignored, through the method from the perspective of the volume, multiple influencing factors including the admixture, water consumption and aggregate components have been obtained on the strength of concrete (mortar), based on the activity coefficient of mineral admixtures and Feret strength theory. It has a good guiding significance.Through the work above, some conclusions of reference value were obtained both in theory and practice.