Study On Preparation And Properties Of Coal Gangue-based Geopolymer And Its Porous Materials

Geopolymer is a kind of inorganic macromolecule material,which is made of aluminosilicate material and stimulated by alkali.It is a three-dimensional reticulated solid structure consisting of tetrahedral structural units of silicon and aluminium.The material has good mechanical properties,acid and alkali resistance,fire resistance and high temperature resistance,high strength,fast hardening and other characteristics.In addition,it is a green and sustainable material with simple preparation process,wide source of raw materials,low energy consumption and low pollution,which conforms to the purpose of maximizing the use of resources advocated by the state.In this paper,coal gangue-based geopolymer materials were prepared by alkali activation process with coal gangue powder,sodium hydroxide and sodium silicate as main raw materials.The effects of sodium silicate modulus and solid content of alkali activator on the strength of geopolymer were studied.The results show that the optimum ratio of compressive strength of coal gangue-based geopolymer is sodium silicate modulus 1.2,alkali activator solid content 42%,liquid-solid ratio 85%,and its compressive strength can reach 67.5 MPa.The optimum ratio of flexural strength is sodium silicate modulus 1.0,alkali activator solid content 46%,liquid-solid ratio 100%,and its flexural strength can reach about 9.4MPa.On this basis,the effects of four factors on the strength of geopolymer porous materials were studied,including the content of hydrogen peroxide,curing temperature,sodium carboxymethyl cellulose and water.The experimental results show that the optimum ratio of the compressive strength of coal gangue-based geopolymer porous materials is curing temperature 30℃,water content 40%,hydrogen peroxide content 1%,sodium carboxymethyl cellulose content 1.5%.The compressive strength of coal gangue-based geopolymer porous materials can reach 12.3 MPa,and the content of hydrogen peroxide is the main factor affecting the compressive strength.The pore structure,pore size distribution,roundness and Ferect diameter of porous materials based on coal gangue with different content of hydrogen peroxide were analyzed,and the relationship between pore size distribution,porosity and thermal conductivity was studied.The results show that the content of hydrogen peroxide has the most significant effect on the pore structure of the porous material.With the increase of the content of hydrogen peroxide,the porosity increases,the pore size distribution increases,the number of connected pore increases,the capillary water absorption ability of the sample decreases,and the thermal conductivity decreases.The electrochemical analysis of various factors(liquid-solid ratio,activator solid content,sodium silicate modulus)affecting the properties of coal gangue-based Geopolymer Materials was carried out.The experimental results show that when the optimum ratio of coal gangue-based geopolymer material is 85% liquid-solid ratio,the modulus of sodium silicate is 1.2,and the solid content of activator is 46%,the impedance of the sample reaches the maximum.This is basically consistent with the test results of mechanical properties of geological polymer based on coal gangue.