Inﬂuence of duration of heat curing and extra rest period after heat curing on the strength and transport characteristic of alkali activated class F ﬂy ash geopolymer mortar S. _ Ilkentapar a,⇑ , C.D. Atis ß a , O. Karahan a , E.B. Görür Avs ßarog ˘lu b a Erciyes University, Civil Engineering Department, Kayseri, Turkey b KSU, Vocational School, Kahramanmaras ß, Turkey highlights  Inﬂuence of rest period after heat curing on property of AAFA mortar was evaluated.  Heat and extra rest period of curing increased transport properties value of mortar.  Heat and extra rest period of curing improved mechanical properties of AAFA mortar.  High strength and abrasion resistant ﬂy ash geopolymer mortar mixture was developed. article info Article history: Received 14 December 2016 Received in revised form 18 May 2017 Accepted 7 June 2017 Keywords: Sodium hydroxide Fly ash Geopolymer Heat curing Rest period abstract In the study, the inﬂuence of heat curing duration and rest period after heat curing duration on the strength and transport characteristics of alkali activated ﬂy ash (AAFA) mortar were investigated. A local class F type ﬂy ash, CEN reference sand, sodium hydroxide and potable water were used in preparation of cement-less fresh geopolymer mortar mixture. Mixture ratios (in mass basis) were 3, 1, 0.29, and 0.1 for sand, ﬂy ash, water and sodium hydroxide, respectively. Some samples were cured at 75 °C temperature for 4 h, 1, 2, 3 and 7 days; then, they were tested after heat curing period. Additionally, some of the equiv- alent samples were kept in the laboratory at 23 ± 2 °C temperature with 50 ± 5% relative humidity, until 28 days after their initial heat curing period. Then, they were tested at 28 days for combined curing con- ditions. The measured properties of AAFA mortar were unit weight, porosity, capillary water absorption, water absorption capacity, ﬂexural-bending and split tension strength, compressive strengths and abra- sion resistance. It was observed that the strengths of mortar were signiﬁcantly increased with the increase in heat curing duration. A signiﬁcant strength development was also observed after rest period. As a result of the study, high strength and abrasion resistant AAFA geopolymer mortar was produced. However, transport properties of AAFA geopolymer mortar found to be not as good as mechanical properties. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Cement production is not a green process, since it consumes large energy; also sintering of calcareous and clayey materials in cement production is responsible for CO 2 emission at about 10% into atmosphere. Equivalent of total CO 2 emission of energy con- sumed for cement production as well as CO 2 emission due to dis- integrating CaCO 3 rock is known to be at about 7% [1,2]. Pressure of green peace movements, savings energy and cement cost lead researchers to ﬁnd a way for manufacturing cheaper cement and binder. One of the way to obtain green and cheaper cementing materials is employing industrial waste and by- products (for example; ground granulated slag, ﬂy ash, rice husk ash and silica fume) in concrete as a partial replacement of Port- land cement [3]. Some researchers [3–5] investigated utilisation of a vast quan- tity of ﬂy ash as cement substitution in concrete mixture. They par- tially substituted Class F type ﬂy ash with cement and prepared high volume ﬂy ash concrete mixture with proper water content. http://dx.doi.org/10.1016/j.conbuildmat.2017.06.041 0950-0618/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: serhan@erciyes.edu.tr (S. _ Ilkentapar). Construction and Building Materials 151 (2017) 363–369 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat