The Influence Of Different Admixtures On Properties Of Alkali-activated Materials

Alkali-activated cementitious materials are defined by the use of alkaline activators to stimulate the latent pozzolanic or hydraulic properties of materials which are classified as natural materials and industrial solid waste. It is reported that alkali-activated fly ash/slag cement or motor has many advantages, such as broad raw materials, green environmental protection,non-pollution to the environment,good corrosion resistance, heat tolerance and so on. But in the alkali-activation fly ash/slag system, the setting time is short and the fluidity of paste is poor. And the reaction intensity of slag and activators can account for this phenomenon.So its applications is restricted by above shortcomings in the engineering. In order to improve the early drawbacks of alkali-activation ash/slag system, we have to find a potential admixture.This research study some admixtures, including inorganic additive(calcium nitrate,trisodium phosphate,barium chloride),organic retarder(saaccharose,sodium pluconnate),organic water reducing agent(polycarboxylie acid,sodium lignin sulfonate) and organic air entrained agent(lauryl polyoxyethylene,dodecyl trimethyl ammonium chloride) added to pastes by standards, such as the setting time, fluidity, rheological behavior and consistence of fresh pastes or motors.The results obtianed are showed as follow:Traditional Portland cement admixtures did not play a greater effect, only barium chloride and air-entraining agent(lauryl polyoxyethylene,dodecyl trimethyl ammonium chloride) can significantly increase Alkali-activation fly ash/slag setting time, but adding air-entraining agent in activation fly ash/slag indecline in compressive strength of alkali-activated fly ash/slag.In the study of alkali-activated fly ash/slag mortar, It is found that the consistency of alkali-activated mortar can be greatly improved by adding additives,such as the barium chloride,lauryl polyoxyethylene,dodecyl trimethyl ammonium chloride.But when adding lauryl polyoxyethylene,dodecyl trimethyl ammonium chloride in the alkali-activated mortar,The compressive strength of the alkali activated mortar decreased,the same as the case of paste without the sand.Alkali-activation fly ash/slag added barium chloride also can slightly improve its liquidity and significantly reduced the yield strength of the slurry. Other admixtures did not produce significant results, where adding entraining agent(lauryl polyoxyethylene,dodecyl trimethyl ammonium chloride) become the fluidity of the alkali-activation fly ash/slag worse.While adding the barium chloride additive in the alkali-activated fly ash / slag system, the gel structure is not changed greatly, and resulted in the enrichment of.While adding the lauryl polyoxyethylene or dodecyl trimethyl ammonium chloride,it formed a mutual penetration of the bubble, and occured the obvious carbonization reaction.Analysis by X-ray diffraction(XRD), after adding the barium chloride, the lauryl polyoxyethylene,dodecyl trimethyl ammonium chloride,there is no new crystal formation in the alkali-alkali-activated fly ash/slag system.