Strength characteristics and microstructural properties of cement mortars incorporating synthetic wollastonite produced with a new technique Hasan Erhan Yücel a,⇑ , Sümeyye Özcan b a Department of Civil Engineering, Nigde Omer Halisdemir University, Nigde, Turkey b Construction Technology, Nigde Technical Sciences Vocational School, Nigde Omer Halisdemir University, Nigde, Turkey highlights  Synthetic wollastonite (SW) mineral was produced by using a new production technique.  It was proved that the produced SW is wollastonite by using SEM, XRF and XRD analysis.  The CMs were produced by using SW with five different ratios instead of cement.  The mechanical performance of CMs improved up to 9% SW content.  Acicular particle structure of SW is effective on strength improvement of CMs. article info Article history: Received 2 December 2018 Received in revised form 2 June 2019 Accepted 24 June 2019 Keywords: Microstructure Synthetic wollastonite Cement mortar Compressive strength Flexural strength abstract In this study, synthetic wollastonite (SW) mineral was produced by using a new production method. This method which quartz and calcite minerals are used as raw materials, is 3-step wollastonite production method consisting of mechanochemical process, hydrothermal process and solid state reaction process. It was proved that the material (SW) produced with the help of this new method is wollastonite by using SEM, XRF and XRD analysis. The effect of SW on the mechanical and microstructural properties of cement mortar (CM) were experimentally investigated. The CMs were produced without SW as control mortar and by using SW with the ratios of 3%, 6%, 9%, 12% and 15% instead of cement. Compressive and flexural strength tests were conducted at 7 and 28 days. In addition, SEM/EDX, TGA/DTA and FTIR analysis were applied to mixtures incorporating SW in the ratios of 0%, 3%, 9% and 15% at 28 days. Test results indicate that mechanical performance of CMs improved up to 9% SW content. However, CMs with 12% and 15% SW had higher compressive and flexural strength than the control mortar. Microstructural analysis demonstrated that improvement in the strength characteristics of CMs incorporating SW can be explained with the acicular particle structure of SW. In addition, according to TGA/DTA and FTIR analysis, it is observed that CaCO 3 in CMs decreased with the increase of SW. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, cement based composites have generally been produced by using puzzolonic and/or inert minerals containing high amounts of CaO and SiO 2 in chemical compositions. [1,2]. Cement, which is widely used in the construction industry, is the main material in the constituents of cement based composites. However, harmful formations of cement production such as high temperature, dustiness, allergic matter, CO 2 emissions, waste gases in chimney emissions, and the separation of toxic chemicals nega- tively affect the environment and human health [3]. Therefore, the pozzolanic materials such as fly ash, silica fume, blast furnace slag, and inert materials such as wollastonite are used instead of cement to produce economic and environmental friendly cement based composites [4]. A large part of the pozzolans used in cement based composites are self-generated waste products during the production of steel, thermal energy, etc. in the industry. The use of these materials in cement based composites has an important effect in terms of preventing environmental pollution and providing economic efficiency [5–7]. In addition, the reactions occured as a result of https://doi.org/10.1016/j.conbuildmat.2019.06.195 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: heyucel@ohu.edu.tr (H.E. Yücel). Construction and Building Materials 223 (2019) 165–176 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat