Synergistic Effect Of Superplasticizers And Tourmaline Powder On Properties Of Water Glass-activated Slag Binder Paste

Alkali-activated slag binder(AAS),which is a clinker-free,green and low carbon binder significantly differing from traditional Portland cement,meets the requirement of energy saving and omission reducing strategy.The widely application of AAS is restricted by the high viscosity,however,traditional superplasticizers lose efficacy or has very low work efficiency in AASC system,which become one of the technical obstacles.To solve this challenge,one of the most significant ways is to find plasticizer technology which is suitable for AASC.Negatively charged mineral(Tourmaline powder,TP)combined with superplasticizer(Liquid naphthalene-based superplasticizer,LN)were introduced into this study to investigate the synergistic plasticizer efficiency in tourmaline-naphthaleneAAS(T-N-AAS)system,the effects of preparation parameters,such as the quality of slag,the modulus of water glass,the content of alkali and the addition methods of alkali on the rheological properties were considered,the heat release of hydration of T-N-AAS was studied by using isothermal calorimetry method,the development of compressive strength of T-N-AAS concretes were tested and the microstructural evolution was determined by scanning electron microscope(SEM)observation,the main results can be summarized as follows:(1)The synergistic effects of TP and LN showed remarkable plasticizer efficiency,for a given water to binder ratio 0.30,the AAS pastes combined with 20% TP and 2.5% LN could reach a water-reducing rate of 13.36%,the suitable rheological model changed from Herschel-Bulkley model to Bingham model.(2)For a given water to binder ratio 0.30,the rheological properties of AAS pastes prepared with different slags were significantly different,the synergistic plasticizer efficiency were also different,the Herschel-Bulkley model were not suitable for all the pastes made with different slags.A general linear relationship between setting time and fluidity of AAS pastes were found and the setting time could be predicted by the sum of activity coefficient and alkali coefficient.The modulus of water glass in a range of 1.0-2.0,the alkali content in a range of 3%-6%,the TP and LN should a remarkable synergistic plasticizer efficiency,which changed the rheological models from Herschel-Bulkley model into Bingham model.(3)The LN delayed the second heat-released peak of AAS paste and decreased the heat-released values.There was no obvious reaction between TP and alkali solution.the AAS pastes combined with 20% TP and 2.5% LN could delay the hydration of AAS paste,however increased the heat-released values in 3 d.The synergistic effect of TP and LN decreased the compressive strength of AAS concretes and had a larger drop at the early ages.(4)The regular hexagonal plates with a diameter around 5?m were found in the samples with LN,and confirmed as Naphthalene-Layer double hydroxides.TP could exist stably in AAS pastes with a compacted internal transition zone.