1 ice | science The increasing focus on global climate change, the public and consumer preferences for “green” products and the associated markets in carbon credits have promoted the use of alternate cements in place of pure Portland cement binders. Using alkali activation method, waste materials such as fly ash and slag can be modified to replace ordinary Portland cement. In the present study, a combination of sodium hydroxide pellets and sodium silicate solution is used for the alkali activation of fly ash to prepare geopolymer cement. In the same way, a mixture of KOH (pellets) and K-silicate solution has been used with fly ash and slag (used in British Columbia, Canada) for comparison. Ambient temperature curing has been considered in addition to oven curing. Compressive strength tests indicate that both duration and intensity of the temperature affect the properties of the geopolymer. Higher intensity of the temperature accelerates the polymerization process much faster and gives higher compressive strength for the same duration of curing. On the other hand, longer duration of curing leads to improved hardened properties compared to shorter span at the same intensity. This paper presents data for curing done at ambient temperatures and the effectiveness of using potassium- and sodium-based solutions for geopolymer cement. Further recommendations for future work are also included. 1. Introduction The production of 1 ton of cement, which directly generates 0·55 tons of chemical-CO 2 , requires the combustion of carbon-fuel to yield an additional 0·40 tons of carbon dioxide. Two traditional methods may help to offset chemical-CO 2 emissions from cement manufacturing: (a) reabsorption of atmospheric carbon dioxide during the carbonation of concrete and (b) blending of Portland cement with industrial by-products. One other alternative is to replace ordinary Portland cement with geopolymeric cements. 1 Palomo et al. 2 have classifed the different alkali-activated cements as alkali-activated slag-based cements, alkali-activated pozzolan cements, alkali-activated lime pozzolan/slag cements, alkali- activated calcium aluminate blended cement and alkali-activated Portland blended cement: hybrid cements. Palamo et al. discussed the environmental issues surrounding binders used in construction as a whole and provided a certain amount of preliminary information on alkaline activation technology and alkaline cements. Davidovits 3 has compared Portland cement chemistry with geopolymer chemistry and classifed geopolymer cement into four catagories: (a) slag-based geopolymer cement, (b) rock-based geopolymer cement, (c) fy ash–based geopolymer cements and (d) ferro sialate–based geopolymer cement. The source of fy ash for use as a source material for geopolymer is an important parameter. Although silica and alumina are the main precursors for the geopolymeric reaction, other factors also seem to play a signifcant role in the resultant compressive strength of fy ash–based geopolymers. Other factors such as CaO content and fneness of fy ash affect the compressive strength of the geopolymer. The fner the particle, the greater is the surface area and the more reactive is the fy ash. Although increasing CaO content in fy ash appears to have a positive infuence on the compressive strength of the resulting geopolymer, fy ash stockpiles with Current state of K-based geopolymer cements cured at ambient temperature Gupta and Rathod ICE Publishing: All rights reserved Keywords: mechanical properties\sustainable materials\waste reduction 1 2 *Corresponding author e-mail address: guptar@uvic.ca 1 Rishi Gupta PhD, PEng* Assistant Professor, Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia, Canada 2 Harsh M. Rathod BTech MTech Student, Institute of Technology, Nirma University, Ahmedabad, Gujarat, India Current state of K-based geopolymer cements cured at ambient temperature Emerging Materials Research http://dx.doi.org/10.1680/emr.14.00037 Research Article Received 29/01/2015 Accepted 09/04/2015 Published online 21/04/2015