Mechanical And High Temperature Resistance Properties Of Fly Ash Geopolymer

The cement industry has become the focus of the low-carbon reform due to the huge CO₂ emissions.With the development of the times,low-carbon economy will become a new model for the future development of cement industry.The Fly Ash Geopolymer can not only realize the resource recycling of solid waste,but also can replace part of cement.It is of great significance for China,which has serious energy shortage and environmental pollution.This paper is based on the theory of alkali activated and the physical and chemical properties of raw materials.By analyzing the influence factors of the strength,the best ratio is obtained,and the qualitative prediction model of strength development is established.The hydration mechanism of Fly Ash Geopolymer was analyzed by means of microscopic and hydration heat tests.On the basis of the above research,the influence of water glass modulus,water glass content and slag content on the high temperature resistance and the influence mechanism of Fly Ash Geopolymer are analyzed.The study on the mechanical properties of Fly Ash Geopolymer showed that the compressive strength of Fly Ash Geopolymer was greatly affected by the modulus of water glass,the content of water glass and the content of slag.Fly Ash Geopolymer with 1.2 modulus of water glass,20% content of water glass,40% content of slag and 3%¹0% content of slaked lime,the highest 28 days compressive strength is up to 72.66 MPa,meeting the requirements of P·O52.5 for compressive strength.The Fly Ash Geopolymer strength model is composed of linear growth stage and platform stage,and the factors such as the slag content,the modulus and content of water glass are variables.The Fly Ash Geopolymer hydration mechanism research shows that the hydration products including flocculent polymer gel with-Si-O-Al-O-bond,C-S-H gel and ferritealuminate four calcium crystals.In Fly Ash Geopolymer,the C-S-H gel,which is produced by the reaction of Ca2+ and reactive SiO₂ in the water glass micelle,is bonded with the products of the adjacent micelles to form a whole.Oligomers are formed by breaking the bonds between Si-O and Al-O in fly ash and slag.Under the condition of dehydration,the oligomer and the core are polymerized.The polymer expands and forms a complete spatial network structure with the adjacent core.The results of the study on the high temperature resistance of Fly Ash Geopolymer show that the cracking of specimen with high content and low modulus of water glass and high content of slag is more serious under high temperature,and the compressive strength increased slightly espically after 800℃,the strength decreased significantly.Under high temperature,the structure of the slurry is more compact due to the loss of water.Under high temperature,the slurry melt and form a solid vitreous body after cooling to establish a higher strength.Water loss of specimen causes cracking and mass loss,and the deformation of the aggregate is inconsistent with the slurry,which results in the separation of the slurry from the aggregate and the overall strength decreases.