Synthesis And Properties Of Geopolymer Containing Calcium

This thesis studies the early setting performance of high calcium fly ashgeopolymer paste, mechanical peoperties, durability and microstructure of geopolymercontaining calcium are investigated.High calcium fly ash, or low calcium fly ashmixxing with Ca （OH）₂or slag were used to prepare geopolymers. The curing techniqueof geopolymer was mastered and the effects of the curing technique, the water fly ashratio, the calcium content and the variety of calcium additives on the properties ofgeopolymer were investigated.The condensation process and the setting time of geopolymer paste were measuredby Vicat in the different conditions. The main factors were temperature, water fly ashratio and the surface with or without the covered film, in which the factors,thetemperature has the greatest effect on the condensation. The experimental data showsthat the setting time is between1410min and1485min at25℃and the setting time isbetween80min and90min at60℃. The more temperature increase, the faster thecondensation speed of geopolymer is.In the slag-low calcium fly ash geopolymer mortar, with the slag content increases,the fluidity decreases and the bulk density increases. The strength of high calcium flyash geopolymer mortars are growing faster in the standard curing conditions, but thestrength is dropping at the early days and the growth rate of the strength is slow in thesteam curing and oven curing, and the compressive strength at28d is almost equal inthe different curing system as the water-fly ash ratio increase, its strength graduallydecrease. It means that high calcium fly ash geopolymer mortar should choose the littlewater fly ash ratio in standard curing system for conservation. In the slag-low calciumfly ash geopolymer mortar when the slag content increases, the strength also increases.However, in the two curing conditions, low calcium fly ash mixed with Ca （OH）₂orslag, its strength of the geopolymer mortar was not high.Steam curing is good for the frost resistance in high calcium fly ash geopolymermortar, when the freeze-thaw cycles were up to300times, the specimen has not yetdestroyed. Using the MIP for pore structure analysis, after the freeze-thaw cycle, theporosity almost unchanged and the median pore size decreases, so the freeze-thawcycles can even reach more, but for the slag-low calcium fly ash geopolymer mortar,they should choose the standard curing system.For different materials, the carbonation resistance at steam curing system superiorsto standard curing system; In the standard curing conditions, the carbonation resistanceof the same calcium content of the high calcium fly ash and slag-low calcium fly ashgeopolymer mortar almost equals, but in the steam curing conditions slag-low calciumfly ash geopolymer has the better anti-carbonation properties, in standard curing and steam curing,the low calcium fly ash mixed with Ca （OH）₂geopolymer has the bettercarbonization resistance than mixxing with the slag.