Characterisation of sugar cane straw waste as pozzolanic material for construction: Calcining temperature and kinetic parameters Moise ´s Frı ´as a, * , E. Villar-Cocin ˜a b , E. Valencia-Morales b a Eduardo Torroja Institute (CSIC), c/ Serrano Galvache 4, 28033 Madrid, Spain b Department of Physics, Central University of Las Villas, Santa Clara 54830, Cuba Accepted 28 February 2006 Available online 22 May 2006 Abstract This paper reports on the influence of calcining temperature (800 and 1000 °C) on the pozzolanic activation of sugar cane straw (SCS). The reaction kinetics of SCS ash–lime mixtures were inferred from physicochemical characteristics (X-ray diffraction patterns and ther- mogravimetry analysis. The fitting of a kinetic–diffusive model to the experimental data (fixed lime versus time) allowed the computing of the kinetic parameters (reaction rate constant) of the pozzolanic reaction. Results obtained confirm that the sugar cane straw ash (SCSA) calcined at 800 and 1000 °C have properties indicative of very high pozzolanic activity. No influence of calcining temperature on the pozzolanic activity was observed. Also, no crystalline compounds during the pozzolanic reaction were identified up to 90 days of reac- tion. Environmental durability and strength of the consequential mortars remain to be assessed. Ó 2006 Elsevier Ltd. All rights reserved. 1. Introduction Pozzolans are siliceous or siliceous and aluminous mate- rials which alone possess little or no cementitious value but which will, in finely divided form in the presence of mois- ture, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties (ASTM-C618). Natural pozzolans have been used since antiquity with excellent results for the produc- tion of durable mortars and concretes. Nowadays, indus- trial by-products including clays and wastes with an elevated silica content are used as pozzolans in Portland cement. This is due to their capacity for reacting with cal- cium hydroxide (CH), produced during the hydration of the Portland cement. Hydrated compounds formed during pozzolanic reactions commonly improve the performance of new cements (Massazza, 1976; Taylor, 1997; Metha, 1998; Frı ´as et al., 2002; Frı ´as and Sa ´nchez de Rojas, 2004). The recycling of industrial wastes from the agriculture sector is increasingly encouraged, particularly in develop- ing countries. In Cuba, approximately 15 million tons of sugar cane are processed that generate high volumes of lig- nocellulose-rich by-products including cane trash and bagasse. The sugar cane straw is burnt in open landfills, contributing to air and water pollution. Also, there is a growing shortage of landfills in most countries (Sasao, 2004). The amount of ashes generated in the process repre- sents 3–5% of the initial residues, which constitutes a con- siderable volume of ashes. For these reasons, there needed to be better knowledge of the composition and physico- chemical properties of lignocellulose-rich by-products of the local sugar industry. It was already known (Kantinaris, 2004) that sugar cane bagasse and sugar cane straw (sugar cane leaves) can be recycled in the manufacture of commercial cements and other composites, either as raw material or as pozzolanic material. For use as pozzolans, the agricultural wastes need prior calcination but pozzolanic activation can vary sub- stantially as a result of the calcining conditions and the nat- ure of the source materials. However, there are contradictory reports about the pozzolanic effectiveness 0956-053X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2006.02.017 * Corresponding author. Tel.: +34 91 30 20 440x220; fax: +34 91 30 20 700. E-mail address: mfrias@ietcc.csic.es (M. Frı ´as). www.elsevier.com/locate/wasman Waste Management 27 (2007) 533–538