Experimental Study On Acid Erosion Durability Of Thermal Insulation Glazed Hollow Bead Mortar

As a major breakthrough in the field of inorganic heat preservation material,thermal insulation glazed hollow bead mortar is now in the retaining structurehas been widely used on internal and external insulation of building envelope,and its performance study has caused attention of many people.Durability is one of the important indices for evaluation of buildingstructures. Energy conservation failure and structure degradation problems hasbeen found in the building energy conservation practice in recent years, itpushed the durability basic research to the critical position.But its durability research has not been paid enough attention because of theshort history of thermal insulation mortar and the function features of theunstructured material. Domestic and foreign scholars has made a lot of progressabout the structural material of concrete durability research, but the theories andhypothesis which were put forward to research concrete durability cannotexplain mortar damage mechanism without coarse aggregate correctly, it is alsodifficult to apply to a new type of inorganic insulation mortar.At present, our country has no reasonable detection and experimentalmethod to determine and evaluate thermal insulation glazed hollow bead mortardurability and weather ability, the study of material degradation mechanism,thermal insulation system durability and the impact on the structure arerelatively lacked. This article carries on the national natural science fund project: thermal insulation glazed hollow bead mortar degradation mechanism andimpact on structural durability research (51308371). By combining micro andmacro methods, the changes of physical and mechanical performance and phasecharacteristics were studied under the action of corrosive medium. It aimed atrevealing influence regularity about such thermal insulation material underaggressive medium, which provides the basis for performance optimization ofinorganic thermal insulation system, durability design and life prediction.The main contents of this paper are as followed:1.According to heat preservation system working environment and thermalinsulation material properties, combining with the physical and mechanicalproperties and durability test methods of cement-based materials, the durabilitytest methods of inorganic thermal insulation material are analyzed.2.Experience laws on thermal mortar physical performances of pH value,age and other factors were studied through tests. The results showed that withthe increase of erosion age, mass loss rate and relative dynamic elastic modulusdecline extent of thermal mortar was not significant, the linear expansioncoefficient increased with the decrease of the first, then thermal conductivityincreased; under the same age of erosion, the relative dynamic elastic modulusdecreased with the decrease of the pH value, the coefficient of thermalconductivity increased gradually, linear expansion coefficient of test block with14d erosion age decreased, and increased with28d and56d in turn.3.The mechanical properties change laws of the thermal insulation mortarunder different pH after cycle of erosion were studied through tests. The resultsshowed that with the increase of erosion cycles, thermal mortar compressivestrength, elastic modulus, flexural strength, tensile strength and tensile bondstrength are declining after increase first, ratio of compressive strengthdecreased and then increased. It is related to the mortar early hydration degreeand chemical composition of the erosion solution, swelling material of hydrationreaction and chemical reaction will reduce mortar porosity and increase density, its early strength increased. With the deepening of erosion, erosion is greaterthan the hydration gradually. Peeling phenomenon was appeared on themacroscopic, intensity gradually declined. In the early stage of erosion cycles,the change of the mechanical properties about thermal insulation mortarimproved anti-crack capacity of the thermal mortar system.4.The phase change law of thermal insulation mortar after erosion cycleswere studied by electron microscopic scanning and X-Ray diffraction analysis.The research results showed that the thermal mortar aperture decreased and thenincreased within erosion cycles, glazed hollow bead particle breakage becamemore serious. Erosion destroy of thermal insulation glazed hollow bead mortar isthe result of combined action about H+and SO42-. In the process of erosion, thehydration products of Ca (OH)2, C-S-H and AFt content were greatly reduced,some swelling materials was generated, such as gypsum, etc. As a result itcaused damage.5.Combining with the change rule of macroscopic properties andmicroscopic image after insulation mortar erosion cycles, erosion mechanism ofthermal insulation glazed hollow bead mortar was preliminarily summarized.Erosion process of thermal insulation mortar is mainly in the process ofhydration and erosion chemical substances in turn. In the early, hydration andthe expansion of the chemical reaction effect made the mortar densityincreasing, acid chemical erosion was given priority to in the late period, whichcaused the destroy of mortar surface spalling and porosity increasing.