Properties of alkali-activated clinoptilolite

Materials made by hydrating the natural zeolite clinoptilolite with calcium hydroxide (Ca(OH)(2)) have been characterised and compared to other alkali -activated waste-derived and naturally occurring pozzolana. Compressive str ength is dependent on the Ca(OH)(2) content, clinoptilolite particle size, and curing conditions. Optimising each of these factors has produced compac ted materials containing 20 wt.% Ca(OH)(2) with average compressive strengt hs of 38.7 MPa. Capillary rise tests have been used to determine sorptivity coefficients of dry samples that range from 0.027 to 0.087 cm min(-1/2) de pending on the alkali addition and the clinoptilolite particle size. Sorpti vity depends on the Ca(OH)(2) content and reducing the clinoptilolite parti cle size reduces sorptivity but increases the level of water accessible por osity. X-ray diffraction (XRD) confirms that Ca(OH)(2) is consumed during c uring and that it is not present in high strength, fully cured materials. S canning electron microscopy combined with energy dispersive X-ray (SEM-EDX) analysis indicates the formation of hydration products with Ca/Si ratio in the range 0.8-1.2 and that a significant amount of unreacted clinoptilolit e remains in optimised materials. (C) 2000 Elsevier Science Ltd. All rights reserved.