Preparation And Performance Of Na-Geo Polyler Cementitious Material Based On Fly Ash

Geopolymer is a kind of new green inorganic polymer cementitious materials, which has a 3D network of silico-aluminate structures. Geopolymer can be synthesized from calcined clays, industrial waste(such as fly ash, coal gangue and slag, etc) or other alumino-silicate containing source materials under strongly alkaline conditions. Geopolymer have excellent performance in setting time, early mechanical properties, fire resistance, durability and other aspects, which is a low cost,high performance, environmentally friendlymaterials of.Na-geopolymer cementitious material based fly ash is made of Shanxi Yahua fly ash,metakaolin, slag and silica fume under the effect of on-demand alkali activator which produced by water, Na OH and nano-Si O2, fly ash is main raw materials, metakaolin, slag and silica fume are the auxiliary mareials. Study on the basic mixture ratio of the geopolymer cementitious material by orthogonal experiment, optimized the perparation. Study on the mechanical properties, thermal stability, durability and the application in the cement pavement repair of the geopolymer binder by XRD, IR, SEM, etc.The properties of geopolymer are best and the geopolymerization is full when the molar ratio of Si/Al was 2.5, the content of Na OH(MNa OH/M solid ash%) was 7.5%, the content of soluble Si O2(MSi O2/M solid ash%)was 7.5%, the ratio of the number of Si O4 and Al O4 groups,the system alkalinity and the content of soluble Si O2 are in the range of the most appropriate.The results of IR show that Al O4 terahedron bonded in Si O4 tetrahedron in the geopolymerization, formed a three-dimensional network structure. The results of XRD show that there was no new crystalline phased in the geopolymerization, the mainly reaction producst are amorphous aluminosilicate gel phase. The activity of fly ash were improved by activation pretreatment, the fineness reaches the minimum after 2 hours, activity was highest after 3 hours. Stir for a long time would disrupt the formation of aluminosilicate gel continuous network structure. Increasing the curing temperature is helpful to the geopolymerization rate, but there is little influence on the later strength of geopolymer.Adding appropriate amount water is helpful to the geopolymerization.Adding appropriate amount calcium rich raw materials(slag) is helpful to rapidcondensation and strength growth.The durability of geopolymer cementitious material is better than OPC, after 50 freezingand thawing cycles, mass loss was 2%, strength loss was 8.2%. Geopolymer exposed to 5%wt solution of hydrochloric acid, sulfuric acid, sodium sulfate, magnesium chloride 28 days, the mass loss was 4.2%, 3.5%,-0.2%, 1.6%, the strength loss was 30%, 20%, 5%, 10%. The thermal stability of geopolymer cementitious material is better than OPC, sintering reaction would be happening at high temperature, calcined at 1000℃ for 2 hours, the mass loss was2.4%, strength loss was 8%. Geopolymer cement concrete has the characteristics of quick setting early strength, setting time is 105 min, compressive strength of 7 days is 45.4Mpa,adhesive strength, and shrinkage of geopolymer concrete meet the technical requirments of repair cement.