Preparation And Properties Of FGD Gypsum-based Lightweight Energy Saving Thermal Insulation Materials

With the acceleration of industrialization and urbanization in China,a large number of industrial solid wastes such as desulfurized gypsum,fly ash and steel slag have caused severe environmental problems.And the proportion of building energy consumption in the total social energy consumption is gradually increasing and the application of wall insulation materials is an effective way to achieve building energy conservation.In view of the above problems,this paper takes industrial solid wastes such as flue gas desulfurized gypsum,steel slag and fly ash as composite cementitious materials,expanded polystyrene particles as light aggregate,adding various additives such as activator,retarder and water-proof agent to prepare a kind of flue gas desulfurized gypsum based light energy-saving thermal insulation material with excellent performance such as light weight,high strength,heat insulation,water resistance and fire protection by compression technology,which has reached the goal of using industrial solid waste as raw material and the transformation of industrial solid waste with high added value.Composite cementitious material system composited of flue gas desulfurized gypsum,fly ash and steel slag was designed,and the standard consistency water consumption,setting time,mechanical properties and water resistance of the samples were tested and analyzed.The optimal mix ratio of flue gas desulfurized gypsum,fly ash and steel slag was 70:15:15.The effect of retarder and water reducing agent on setting time,water consumption of standard consistency and mechanical properties of composite cementitious materials was studied by single factor experiment.The optimum dosage was 0.1%and 0.2%respectively.NaOH,sodium silicate and CaCl₂ were selected as additives to stimulate the chemical activity of fly ash and steel slag.The influence of the three on the mechanical properties of composite cementitious materials was studied by orthogonal experiment.The results showed that the mechanical properties of composite cementitious materials could be improved by adding composite activator.The optimum mixture ratio of the composite activator was 1%Na OH,1.5%sodium silicate and 2.5%CaCl₂.At this time,the flexural strength and compressive strength of the sample are 3.35 MPa and 15.6 MPa respectively,which are 55.8%and 45.1%higher than those of the blank sample.The mechanical properties and water resistance of flue gas desulphurization gypsum based lightweight energy saving thermal insulation materials hardly met the application requirements.The ultra-high molecular weight polyethylene fiber and acrylic emulsion were used to enhance the mechanical properties of the materials,and the sodium silicate waterproof agent was added to improve the water resistance of the insulation materials.Their mechanisms were analyzed.The results showed that polyethylene fiber and acrylic emulsion could obviously improve the mechanical properties of thermal insulation materials.After adding methyl sodium silicate,the water resistance of insulation materials was significantly improved.Fiber skeleton made up of polyethylene fiber in the sample could hinder the generation and propagation of microcracks and consume the energy of crack propagation,resulting in the improvement of mechanical properties of thermal insulation materials.Acrylic emulsion could improve the mechanical properties of thermal insulation products by improving the interface between expanded polystyrene particles,polyethylene fibers and composite cementitious materials.Methyl sodium silicate waterproof agent could form a layer of hydrophobic organic film in the thermal insulation material,which could block the invasion of water and reduce the dissolution rate of flue gas desulfurization gypsum.And it had a positive impact on the water resistance of the thermal insulation material.