Investigation on characteristics of blended cements containing pumice Hayati Ulusu a , Huseyin Yilmaz Aruntas b , Osman Gencel c,⇑ a Construction Department, Vocational School, Erzincan University, 24100 Erzincan, Turkey b Civil Engineering Department, Technology Faculty, Gazi University, 06500 Ankara, Turkey c Civil Engineering Department, Faculty of Engineering, Bartin University, 74100 Bartin, Turkey highlights  We studied effect of pumice on properties of blended cement pastes and mortars.  Pumice usage decreases mechanical properties of mortar while increasing durability.  Specific gravity is decreased by the usage of pumice.  Pumice decreases shrinkage strains of mortars. article info Article history: Received 4 September 2015 Received in revised form 27 April 2016 Accepted 4 May 2016 Keywords: Blended cement Pumice Durability Natural pozzolan Microstructure Mechanical properties abstract In this experimental study, the effects of 10, 20, 25, 30 and 40 wt.% pumice addition on properties of blended cement pastes and mortars were investigated. Pumice blended cements with a high fineness were produced by intergrinding Portland cement clinker, pumice and gypsum. Characteristics such as particle size distribution, soundness, setting times, chemical analysis, compressive and bending strengths, drying shrinkage, autoclave expansion and sulfate resistance were determined. In addition, the microstructures of some samples scanned by scanning electron microscopy were photographed. Compressive strengths of mortars produced with pumice blended cements were lower than that of Portland cement tested ages up to 360 days. Pumice blended cements increase durability, sulfate expan- sion, shrinkage and autoclave expansion. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Concrete and mortar are most widely used construction materi- als in civil engineering applications such as building, road, dam, flooring, precast elements etc. Their consumption has increased due to new developments in construction technologies, population growing, increasing of living standard and urban transformation of residence causing more building construction. Although polymer concretes and mortars have been used for strengthening structures and repair applications, their high cost restricts usage of them. In this respect, cement based concretes and mortars are most widely used. Thus, cement consumption increases. Since the cement industry demands vast amount of energy, any increase in cement manufacturing increases it. And this causes environmental pollu- tion. Cement production is responsible for 8% CO 2 emision in the world. Significant part of cement production cost is due to energy consumption during the clinker production. 1.6 ton raw materials are used to produce 1 ton cement. Therefore, the attempts to decrease clinker production have been done. Manufacturing of cement with additive is an economic and feasible method due to the decreasing of clinker ratio in cement. For this purpose, poz- zolans can be used in the cement production. Amorphous silicates in pozzolanic materials react with Ca(OH) 2 during the hydration of cement and form new CSH gels. Productions of cements containing fly ash, silica fume and blast furnace slag are common worldwide. Pumice is a natural pozzolan of volcanic origin produced by release of gases during cooling and solidification of lava. Porous structure of pumice is formed by the bubbles or air voids when gases in molten lava is trapped during cooling. Air voids are elon- gated and parallel to one another. They are sometimes intercon- nected. Pumice has been used as aggregate in lightweight concrete. Structural concrete which is two to three times lighter than normal concrete with high thermal performance can be man- ufactured. Pozzolans improve durability and strength while reduc- ing hydration heat. http://dx.doi.org/10.1016/j.conbuildmat.2016.05.030 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: osmangencel@gmail.com (O. Gencel). Construction and Building Materials 118 (2016) 11–19 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat