Study On Preparation And Properties Of Geopolymer Foam Materials

Geopolymer is mainly composed of [Si O4],[AlO4] tetrahedron, which is one kind of new inorganic silica-alumina gel material with three-dimensional network structure. Geopolymer not only has advantages of rich in raw materials, low power consumption and virtually no CO2, etc, but also has excellent mechanical performance and high temperature resistance property, which has a wide foreground of application in engineering. This paper aimed to obtain geopolymer foam materials with excellent performance through mixing preformed foam with geopolymer formed by alkaline activation of metakaolin, and studied the effects of various additives and curing conditionsons on dry density, strengths and strengths/dry density of geopolymer foam materials. In summary, the majority of contents of this paper are as below:In the geopolymer preparation technology, by measuring compressive strengths, XRD,SEM and FT-IR analysis, the effects of kaolin calcining temperature, calcining time, modulus of water glass and alkali content on geopolymer phase composition, morphology, structure and polymerization hardening behavior were researched. The result indicates that: the crystal structure of kaolin is transition into amorphous metakaolin after calcination.Atoms produce large dislocation. Metakaolin has high activity. The metakaolin has higher activity when calcined kaolin at 800℃ for 2h. When smodulus of water glass is 1.3 and the alkali content is 15%, the specimen has the best mechanical properties, whose strengths of 3d,7d and 28 d are 56.80 MPa, 64.30 MPa and 72.10 MPa, respectively. Metakaolin amorphous phase is transition into amorphous inorganic polymer gel through XRD analysis. Through SEM analysis, hydration products are mainly irregular gel. Through FT-IR analysis, there maybe appear network structure of amorphous Si-Al like zeolite phase.To improve foaming agents’ properties, the compounds of different proportions of tea saponin and sodium lauryl sulfate on foam properties were researched. The results show that:when the quality ratio of tea saponin and sodium dodecyl sulfate is 1:1, the foaming agents have optimal properties, namely the settlement and the bleeding water are minimum, and the foaming multiple and foaming height are maximum.In the geopolymer foam materials preparation technology. This thesis researched theinfluences of coagulant dosage, curing temperature on dry density, strengths and strengths/dry density of specimens. The effects of water/cement ratio, dosage of foaming agents and tackifier on bending strength/dry density, compressive strength/dry density and water absorption of specimens by orthogonal experiment were researched; Then the effects of curing humidity, waterproof agent dosage on strengths/dry density and water absorption were researched, too. Using XRD and SEM methods to study the hydrate phase composition and morphology of geopolymer foam materials. The results show that: the optimum experimental conditions of geopolymer foam material are as follows: the coagulant dosage: 2.2wt%,tackifer: 0.24wt%, foaming agents: 0.45wt%, water/cement ratio: 0.67, waterproof agent:3.5wt%, curing at 40℃ for 24 h and then 60℃ for 24 h in the fast curing box. The dry density of optimum specimen is 506kg/m3, the bending and compressive strength are 0.51 MPa and1.66 MPa, the water absorption is 13.4% and the thermal conductivity is 0.071W/(m·K),which deligates the characteristics of high-strength, light-weight, low water absorption and low thermal conductivity. The prolonged conservation at high temperature makes amorphous gel change into zeolite phase through XRD analysis. Through SEM analysis, the holes which are regular and distribute evenly, then holes size are small that can enhance mechanical performance, waterproof property and thermal insulation performance of geopolymer foam materials. Through analysis of spectrum, hydration products of geopolymer foam materials are composed of like zeolite phases, C-S-H gel and unhydrated metakaolin and silica, which form three-dimensional network structure by vertical and horizontal cross-linking.