Abstract
Fast setting and high viscosity are the two main obstacles to obtain desired rheological properties of alkali-activated materials (AAMs). This work aims to remove these obstacles by using a simple yet effective approach via introducing ultra fines with different characteristics. Here in the systems of alkali-activated slag-waste ceramic powder, the mechanism behind the effect of various ultra fines on rheological and hardened properties is studied. Results show that the introduction of ultrafine fly ash (UFFA) is beneficial to maintain good rheological properties and control setting, yet adding silica fume (SF) harms fresh performance due to the extremely low liquid film thickness. By 1H NMR and interstitial solution analysis, the large water demand for wetting SF rather than its dissolution, has been demonstrated to cause the insufficient dissolution of slag, which leads to lower Al3+ and Ca2+ concentrations and less precipitation of early gels. However, once gels start to precipitate, shorter particle spacing favors the rapid formation of percolation network in SF-systems, thus resulting in higher yield stress, viscosity and setting rate, as well as a faster decrease in mobile water. Furthermore, the incorporation of 5 %-10 % UFFA provides superior fresh performance and hardened properties. The results and relevant mechanisms of this study are essential towards better development of high-performance AAMs.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
