Study On The Mechanical Properties Of Fly Ash Geopolymer Concrete

Geopolymer was prepared by coal fly ash from industrial wastes and sand and stone as aggregate under the alkaline excitation of mixture of sodium silicate and sodium hydroxide in this thesis.Analysis the best preparation conditions and the the level factors affection with sodium silicate modulus, water-cement ratio and curing temperature for three factors three levels by orthogonal test.And geopolymer concrete was analyzed micro structure by using SEM.In the end, geopolymer concrete was studied the air content and elastic modulus.The main conclusions of this study are as follows:(1) Through orthogonal test, concluded the best preparation conditions of compressive strength of geopolymer concrete is A2B2C3, namely the sodium silicate modulus is 1.5, water/cement ratio is 0.35, the curing temperature is 80℃.The influence factors of important order by range and variance analysis is C>A>B.(2) Concluded the best preparation conditions of splitting tensile strength of geopolymer concrete is A2B2C3, namely the sodium silicate modulus is 1.5, water/cement ratio is 0.35, the curing temperature is 80℃.The influence factors of important order by range and variance analysis is C>B> A.(3) Concluded the best preparation conditions of Tension-compression ratio of geopolymer concrete is A3B2C3, namely the sodium silicate modulus is 1.8, water/cement ratio is 0.35, the curing temperature is 80℃.The influence factors of important order by range and variance analysis is C>B> A.(4) Observation of different mixing proportion of morphology by SEM,C-S-H gel was made in continuous chemical reaction in geopolymer concrete,The strength of the concrete was decided the gel.(5) The air content test:Because of the geopolymer concrete reaction in the mixing process,The gas was left inside the concrete,So the air content slightly higher than the ordinary Portland concrete.(6) Elastic modulus test:compressive strength of geopolymer concrete is low in early age lead to low elastic modulus,However,with the development of age, the compressive strength increases gradually,the elastic modulus increases too,Up to the age of 56 d,the increases is less than before.