Civil Engineering and Architecture 8(5): 1028-1038, 2020 http://www.hrpub.org DOI: 10.13189/cea.2020.080529 Evaluation of Mechanical and Durability Performance of Coir Pith Ash Blended Cement Concrete Balagopal V, Viswanathan T. S * Department of Structural and Geo-technical Engineering, School of Civil Engineering, Vellore Institute of Technology, Vellore, India Received August 5, 2020; Revised September 22, 2020; Accepted October 19, 2020 Cite This Paper in the following Citation Styles (a): [1] Balagopal V, Viswanathan T.S , "Evaluation of Mechanical and Durability Performance of Coir Pith Ash Blended Cement Concrete," Civil Engineering and Architecture, Vol. 8, No. 5, pp. 1028 - 1038, 2020. DOI: 10.13189/cea.2020.080529. (b): Balagopal V, Viswanathan T.S (2020). Evaluation of Mechanical and Durability Performance of Coir Pith Ash Blended Cement Concrete. Civil Engineering and Architecture, 8(5), 1028 - 1038. DOI: 10.13189/cea.2020.080529. Copyright©2020 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract India is one of the prominent producers of coconuts in the world. Along with the desired products, many undesirable by-products are also generated from the coconut and coir industry. Among the various by-products, coir pith and short coir fibres are the major ones and are obtained during the extraction of long coconut fibres. Raw coir pith was heated in a metallic vessel at 450 o C to obtain coir pith ash. In this study, the impact of the presence of CPA as a supplementary cementitious material, on the various mechanical and durability parameters are taken into consideration. The various parameters considered for assessing the mechanical performance include compressive strength, split tensile strength, flexural strength and Ultrasonic pulse velocity. Water absorption and resistance to sulphuric acid environments were considered to evaluate the durability of CPA blended concrete. The resistance of CPA blended concrete against sulphuric acid environment was evaluated by considering the variation in weight, water absorption and percentage loss in compressive strength. Five concrete mixes were used for the study with CPA content ranging from 0% to 20%. Indian standard method of concrete mix design with water-cement ratio 0.45 was adopted. To understand the effect of change in water-cement ratio on the durability parameters of concrete, the study also considered other water-cement ratios like 0.40 and 0.50. Results indicated that the mechanical and durability performance improves when CPA is used as supplementary cementitious material. Also, the specimens with water-cement ratio 0.40 performed better than other ratios. Keywords Concrete, Supplementary Cementitious Materials, Coir Pith Ash, Durability, Acid Attack 1. Introduction The utilization of by-products from industrial and agricultural sectors as supplementary cementitious materials (SCMs) are gaining popularity among numerous researchers across the globe. The use of SCMs not only improve the product quality of blended concrete but also reduces the cost and adverse impacts of concrete production. The most prominent and popular SCMs include fly ash, GGBS, metakaolin, sugarcane bagasse ash, wheat straw ash rice straw ash, rice husk ash, etc. [1-7]. These materials possess pozzolanic property due to the presence of amorphous silicon dioxide which undergoes secondary reaction with lime (Calcium hydroxide) present in the concrete matrix to form cementitious materials. Concrete was considered to be a durable material and due to this consideration, concrete constructions were common even in areas of severe industrial pollution, harmful subsoil conditions and other circumstances where usage of alternate construction materials was not feasible. However, exposure conditions can have a tremendous impact on the life of concrete members. Though the durability of concrete can be assessed by compressive strength to some extent, it may not be entirely true that a strong concrete specimen or member is always durable since damage can occur due the harsh environmental conditions [8]. As per the definition given by the ACI committee, “Durability is the ability to resist weathering