Research On Thermal Stability Of Steel Slag Thermal Storage Mortar

Xinjiang has abundant solar energy resources and low land prices in the desert Gobi,which is suitable for the development of solar thermal power generation technology.However,this technology is easily affected by natural factors such as day and night alternation and weather changes,which makes the power supply fluctuate and intermittently insufficient.The coupling of solar thermal power generation technology and heat storage technology can better solve this problem.The heat storage material in the heat storage system is the key to solar thermal power generation technology.The heat storage concrete,which is a sensible heat storage material,has good heat storage capacity and low cost,and has a good development prospect.At this stage,the working temperature of thermal storage concrete for solar thermal power generation is mostly around 300℃.With the expansion of power plants and the improvement of efficiency,as well as the application of thermal storage concrete in other areas,its working temperature will further increase.High temperature can easily cause the uneven deformation of concrete materials and cause structural damage,which affects its work efficiency and service life.Good thermal stability is a prerequisite for other performances of heat storage materials.How to improve the thermal stability of cement-based heat storage materials becomes the key The key issues that the industry urgently solves.In response to the above problems,this paper uses cement and mineral admixtures as the matrix,uses waste slag aggregates,casts mortar products,and uses the thermal expansion coefficient and strength loss rate as the evaluation index to carry out research: the thermal deformation and compatibility of the aggregate and the cementitious system The performance problem;the thermal fatigue damage problem of the thermal storage mortar under the condition of periodic temperature change;and the optimization problem of the preparation process of the thermal storage mortar.The above work has practical significance for broadening the utilization of solid waste materials and promoting the application and development of steel slag thermal storage concrete in solar thermal power generation.The main research results are as follows:(1)The length measurement method is used to test and evaluate the thermal expansion performance of the cementitious system and cement mortar,and the mortar mix ratio is optimized through the thermal expansion performance and high-temperature mechanical properties.The test results show that the incorporation of mineral admixtures is beneficial to improve the thermal expansion performance of the cementitious system and cement mortar,among which the effect of fly ash is relatively significant.There are big differences in the thermal stability of mortars with different ratios.(2)Test the thermal expansion performance and high temperature mechanical properties of mortar with different fly ash content.The test results show that a certain amount of fly ash can improve the thermal expansion performance of steel slag cement mortar and stabilize the thermal expansion coefficient of the mortar.With the increase of fly ash content,the high temperature mechanical properties of the mortar show a law that the compressive strength loss rate gradually decreases,and the flexural strength loss rate first decreases and then increases.(3)The deformation performance and mechanical properties of steel slag thermal storage cement mortars of different cementing systems under periodic temperature changes are tested.The test results show that the thermal fatigue damage of the steel slag thermal storage cement mortar mainly occurs during the first thermal cycle.After the cycle reaches five times,the deformation performance and mechanical properties are basically stable.Among them,the fly ash and steel slag thermal storage mortar has strong resistance to thermal fatigue damage,and the steel slag thermal storage mortar can withstand multiple thermal cycles when used in solar thermal power generation.(4)The response surface optimization analysis method is used to optimize the preparation process of thermal storage mortar and seek the best process parameters for thermal stability.The test results show that the optimal process parameters of thermal storage mortar are: mortar-sand ratio 1:3,fly ash content 65%,and molding temperature 70℃.The thermal expansion coefficient of the product prepared under this process parameter after five thermal cycles is 13.02×10-6m/℃,and the compressive strength loss rate is 11.50%.