Study On The Properties Of Polymer Modified Cement Mortar

Lots of buildings and structures in service urgently need repairing and strengthing for the much existing hidden disease trouble, which are caused by human factors such as unreasonable design, incorrect construction and improper curing etc., and natural factors including aging, freeze-thaw damage and so on.Common cement-based repair materials have many disadvantages, such as low bond strength and high brittleness etc. Traditional cement-based modified polymers have poor construction performance, high cost and causing environment pollution etc. Polymer modified cement-based composites were widely used in dams, highway bridges and culverts, ports, parking lots, waterproof and anticorrosion projects and so on, for their excellent workability, high mechanical properties, good impermeability and super corrosion resistance etc, and they have already become an important sort of non-structural reinforcing materials. In this paper, in order to provide some help for the application, many properties of polymer modified cement mortar were experimentally studied.For the close relationship between the effect of repairing and strengthing and the bond strength of the rapair material to the structure need rapairing, a systemic research on the bond strength of the polymer modified cement mortar to the old concrete was studied. Considering the more widespread application of PP fiber in engineering for its many advantages, the influence of PP fiber on polymer modified cement mortar is investigated in this paper. The influence of admixtures and active mineral mixture on the properties of polymer modified cement mortar is investigated too.The reseach thinking and the main contents of this paper are as follows:1. Selection experiment on the polymer modifider. Five kinds of products from the two main sorts of cement-based modified polymer emulsions at present are experimentally studied with recommended mix proportion respectively. By comparing the mechanical properties of the five modified cement mortar each other, simultaneously considering convenient construction, environment propection and safety etc, the waterborne epoxy resin emulsion producted by Shanghai Jiangtian Polymer Materials Co., Ltd. is selected as the further studied object.2. The properties of polymer modified cement mortar and the main investigation factors are studied through orthogonal experiment. Water-binder ratio(A), polymer-binder ratio(B), sand-binder ratio(C) and active mineral mixture replacement rate(D) with four levels respectively, are arranged in the orthogonal table L₁₆(4⁵). The results indicated that there is a significant effect of B, C and D on the properties of polymer modified cement mortar. CMPI is regarded as a focus of investigation, considering convenient construction and cost etc, the optium levels of the factors are A(3)B(2)C(2)D(3), and the engineering averages of the corresponding compression strength, bending strength, bonding strength and CMPI of the polymer modified cement mortar are 11.23MPa, 62.67MPa, 1.714MPa and 2.03MPa respectively.3. An experimental study on the relativity between polymer-cement ratio, silence coupling agent, defoamer, shrinkage-reducing admixture and the setting time of polymer modified cement mortar was carried out, the results show that there is a significant positive correlation between them. 4. The influence of silence coupling agent, defoamer and active mineral mixture on the mechanical properties of polymer modified cement mortar is investigated. The compatibility problem of defoamer and polymer modified cement mortar is revealed. The bond strength between polymer modified cement mortar and old concrete is enhanced when silence coupling agent is used as the interfacial agent. The surface submicro-roughness of old concrete has an important effect on the bond strength. A reasonable evaluation mechanism for estimating the submicro-roughness of the old surface should be proposed, which could give a scientific effective guidance for the bond between concrete and polymer modified cement mortar. The addition method determines the effect of mixed mineral filler. The results show that external addition is better than internal addition. The results show that the addition of silica fume can increase the brittleness of polymer modified cement mortar.5. The influence of PP fiber on polymer modified cement mortar is investigated. The results indicate that the addition of PP fiber enhances the bending strength, the compressive strength ,the CMPI and the touhness of polymer modified cement mortar, but reduces the apparent density. The results of the influence of different length of PP fiber on the polymer modified cement mortar show that the longer PP fiber is, the better the whole performance of polymer modified cement mortar is. It was found that the apparent density of PP fiber reinforced polymer modified cement mortar increases along with the blast furnace slag replacement rate increasing, but it reduces with the silica fume replacement rate increasing. Comparing with the blast furnace slag incorporation, the addition of silica fume has a more significant enhancement on the bending strength, the compressive strength and the CMPI of the PP fiber reinforced polymer modified cement mortar.