Study On The Water Resistance Properties Of Wheat Straw-Magnesium Oxychloride Cement Composite Insulation Mortar

With the rapid development of economic and social society, there has been a sharp increase in energy consumption, the shortage of coal, natural gas and other non-renewable resources is becoming more and more notable. Therefore, the state proposed requirements to the energy-saving, low-carbon, environmental functions of buildings. In the construction industry, there is a large building energy consumption, a large proportion of high energy consumption buildings, and the condition of energy saving in city buildings is far more to be improved, so it’s urge to speed up the process in the construction of building energy saving. Improved wall insulation performance is an important part to get a better building energy efficiency, and research on wall insulation materials will be a new trend in the development of building materials.The wheat straw- magnesium oxychloride cement composite insulation mortar has a poor water resistance when used in wet condition, in this paper, modification experiments on the water resistance properties of the mortar are carried out by using mixtures of four different additives. The effects of the composite additive on the strength and water resistance properties are discussed from the perspective of macroscopic properties, the stability of hydration products and microscopic pore structure. This paper provides theoretical basis and data support for the further research of the mortar.First of all, choose proper additives and dosage range and select evaluate indexes of water resistance properties by reading reference articles, understand the hydration mechanism of the mortar, learn the related information of pore structure in cement-based materials and grasp the test and analysis method of pore aperture.Secondly, the composite additive contains sodium pyrophosphate, ferrous sulfate, organic acids and silica fume, orthogonal test based on the dosage of additives is designed to determine the effects and optimal dosage of additives.Thirdly, the macroscopic properties of the reference group and optimal group specimens are compared, and XRD diffraction patterns and microscopic pore structure are analyzed in order to study the effects of additives on the hydration products and microscopic pore structure.Finally, the reasons for the deliquescence and dehalogenation phenomenon that happens on the surface of mortar specimens are analyzed, and according to these reasons, some measures are put forward to improve its properties of resistance to deliquescence and dehalogenation, and enhance the performance of the mortar in actual engineering applications.The results of the research show that these additives can apparently improve the strength of wheat straw- magnesium oxychloride cement composite insulation mortar specimens along the whole experiment process, which also means a better property of water resistance. The results of XRD diffraction and mercury intrusion experiment show that the composite additive can improve the stability of 5·1·8 phase, it can also reduce the total porosity of mortar and change the distribution of pore aperture, so that the strength and water resistance properties are improved.