Preparation And Optimization Of Sulfoaluminate Green Energy-saving Insulation Materials Derived From Industrial Solid Wastes

The two problems have been brought with the acceleration of industrialization and urbanization in China.On the one hand,the sharp increase in energy consumption and carbon emissions in the construction industry had made the sustainable development of the environment face significant challenges.On the other hand,many industrial solid wastes were produced and stored,resulting in severe environmental pollution.Given the above problems,this paper proposes a "two-step method" to realize the preparation of sulfoaluminate green energy-saving insulation materials derived from industrial solid wastes without the application of heat or pressure.Firstly,sulfoaluminate high-activity material(SHAM)was prepared using desulfurization gypsum,red mud,aluminum ash,and carbide slag as raw materials.Then use this as a cementitious material to prepare green energy-saving insulation material(GEIM)based on physical foaming.This technical route can realize the large-scale,high-value,and resource utilization of industrial solid wastes and help promote the technological innovation of GEIM.Ultimately,it is conducive to realizing the green,low-carbon,and circular development of society.This subject first determined the physicochemical properties of the SHAM based on industrial solid wastes.And based on this cementitious material slurry,mixed with preform foam,successfully prepared low-density energy-saving insulation materials.The relationship between the different dry densities of energy-saving insulation materials and their compressive strength,thermal conductivity,water absorption,and pore structure were explored.At the same time,the correlation between macroscopic properties and microscopic morphology of materials was summarized.Furthermore,this article systematically studies the optimization strategies of energy-saving insulation materials from the perspectives of thickening and stabilizing foam,reducing water resistance,fiber reinforcement,and tailings utilization,and finally gives corresponding economic analysis.To further reduce the energy consumption and cost of material preparation,this paper puts forward the technical route of large-scale desulfurized gypsum synergistically with SHAM to prepare energy-saving insulation materials.And its feasibility has been verified.In short,this research provides the necessary theoretical basis and data support for the promotion of sulfoaluminate green energy-saving insulation materials derived from industrial solid wastes in practical applications.The main conclusions of this paper are as follows:(1)The SHAM has the characteristics of early strength,high strength,rapid hardening,and its mechanical properties meet the strength requirements of 52.5 rapid-hardening sulphoaluminate cement.And its hydration characteristics are similar to those of sulphoaluminate cement.There was a positive linear correlation between the dosage of foam and the dry density of GEIM,while the compressive strength,thermal conductivity,water absorption and dry density showed a power function,a quadratic polynomial,a power function fitting relationship.The dry density,7 d compressive strength,thermal conductivity,and water absorption of GEIM were obtained as 615 kg/m3,4.10 MPa,0.164 W/m·K and 46.57%,respectively.The slender hexagonal prismatic ettringite grew inwardly from the pore wall staggered extension by analyzing the microscopic pore structure.The clusters of Al(OH)3 gels were dispersed in the gap,and a stable spatial structure was formed in the interfacial transition zone.And its unique three-dimensional pore wall self-extending microscopic configuration directly affects its macro performance(2)The addition of hydroxypropyl methylcellulose(HPMC)can effectively improve the viscosity of SHAM slurry.And the optimal dosage of HPMC in the slurry is 0.2 wt%.With this content,the compressive strength of GEIM increased by 27.22%to 5.22 MPa.At the same time,the internal pore structure and the pore walls’micromorphology were improved.The addition of methanesiliconic acid sodium salt can significantly reduce the water absorption of GEIM.When content is 0.4 wt%,the water absorption of GEIM was reduced by 42.38%compared with that of the sample without addition.An appropriate amount of polypropylene fiber is helpful to enhance the compressive strength of GEIM,and the optimal content of 4 mm length is 1.5 wt%.The mechanical properties of porous materials are susceptible to the particle size of tailings.Mixing 10 wt%of ground limestone tailings into the material,the compressive strength of GEIM was most similar to that of the blank sample.With the increase of the original state of gold tailings and iron tailings content,the compressive strength of GEIM gradually decreases.And the maximum acceptance of the two tailings by SHAM slurry was 40 and 50 wt%,respectively.The economic analysis determined that the cost of SHAM was 264-306 RMB/t,and the minimum charge of GEIM was 106-137 RMB/m3.Finally,it proved that the process route is extremely economical.(3)The water loss of desulfurized gypsum is affected by the stoving temperature and soaking time at the same time.And the change process is reversible.It is found that the hydration process of hemihydrate gypsum is faster than that of SHAM by studying the hydration of large proportion desulfurization gypsum and SHAM composite material.And part of the resulting dehydrated gypsum was involved in the hydration of SHAM.The slender prismatic ettringite skeleton and gel clusters generated by SHAM hydration can effectively improve gypsum-based materials’ strength and water resistance.Finally,GEIM was successfully prepared with a matching ratio of 70 wt%pretreated desulfurization gypsum and 30 wt%SHAM.Its dry density,compressive strength,thermal conductivity,and water absorption were 567.6 kg/m3,1.73 MPa,0.156 W/(m·K)and 19.49%,respectively.It was proved that the feasibility of composite materials used in the preparation of GEIM.