Study of chemical and thermal activations of zeolite-lime blend

Abstract

Abstract The advantages of using zeolites are lower costs and better durability, but it requires longer setting time and slower strength development. Chemical and thermal methods have been developed to overcome these disadvantages and to enhance the reactivity of natural zeolite. This paper addressed through a parametric experimental pozzolanic reactivity, the strength and setting time by varying the cure temperature and the amount and type of chemical activators. To this end, several mixtures of natural zeolite-lime pastes were made with two concentrations of chemical activators including 4% and 8% of NaOH, NaCl, and CaSO4.2H2O. The produced pastes were cured at 20, 40, and 80 °C. The blends were also analyzed by X-ray diffraction and infrared spectroscopy. The results showed that curing at high temperatures accelerated the pozzolanic reactivity and increased the compressive strength. The use of CaSO4.2H2O led to an increase in the consumption of Ca(OH)2 and strength. Adding NaCl improved slightly the compressive strength at high curing temperatures. The addition of 8% NaOH at 40 °C significantly improved reactivity and strength. Setting time was accelerated by adding chemical activators to the blends. The raw zeolite had good pozzolanic activity, but the addition of CaSO4.2H2O enhanced it.

Keywords

• zeolite
• lime
• compressive strength
• pozzolanic activity