The Preparation And High Temperature Performance Research Of Alkali Slag Base Geopolymer Materials

Geopolymer is a type of aluminosilicate inorganic polymer material consists of tetrahedral [SiO4]4- and [AlO4]5- units, which is of amorphous to semicrystalline. Due to the geopolymer material has excellent performance such as high strength, simple production process, less pollution, energy conservation, good compactness, high temperature resistant and anti-corrosion performance, it is widely used in a range of areas including civil engineering materials and rapid repair materials, geological polymer matrix composites, high quality geopolymer coating, toxic waste and waste solid sealing materials, porous materials, and so on.In this paper, considering mechanical properties and setting time as the main evaluation index, the slag and liquid water glass which was added by KOH to adjust the modulus were used as the main raw materials to prepare the alkali slag base geopolymer material of excellent mechanical properties and workability, with KH2PO4 as the retarder. By single factor experiments, this paper discussed how the exciting agent dosage, water cement ratio and modified waterglass modulus affected the performance of the alkali slag base geopolymer material, on the basis above, the retarder KH2PO4 was introduced to improve the workability of alkali slag base geopolymer material. And the optimum parameter of the alkali slag geopolymer material which were cured at different temperature was determined:the modified waterglass modulus at 2.0, water cement ratio at 0.24, exciting agent content at 22%, KH2PO4 content at 6%, the curing temperature at 60℃.When the alkali slag base geopolymer material obtained by the optimum parameters was calcined at different temperature (300℃,600℃,700℃,800℃, 1100℃、1300℃、1400℃), the paper discussed its changes of macroscopic performance and microstructure to lay the foundation for the application of the geopolymer material further, with supplementing the related research about the performance of geopolymer at high temperature. By compressive strength, shrinkage, XRD, SEM, BET aperture analysis, TG and other analysis, the study founded that the compressive strength of the alkali slag base geopolymer material decreased, linear shrinkage rate increased, with the increase of the calcination temperature, the phase transited from amorphous to crystalline, and the crystal phase by SEM at 1100℃ could be observed easily. Also with the increase of the calcination temperature, the average pore size of the alkali slag base geopolymer material first increased then decreased. At 600℃, the alkali slag base geopolymer material had the largest average pore size of 18.31 nm; at about 200℃, it lost mass fastest; at about 800℃, its quality remained unchanged. When the calcination temperature was 1100℃, the compressive strength of the alkali slag base geopolymer material was 51.1 MPa, linear shrinkage of 7.64%, pore size of 5.69 nm, crystalline phase of mainly melilite, the crystal phase could be observed easily by the SEM at the same time. When the calcination temperature was 1400 ℃, its compressive strength was 77.2 MPa, linear shrinkage of about 10%, average pore size of 3.24 nm.On the whole, the alkali slag base polymer material had excellent high temperature performance, which could still maintain sufficient strength at high temperature, the disadvantage was that the high temperature shrinkage rate was relatively large, which needed to be further explored.