Experimental Investigation On Partial Replacement Of Cement And Additives To Concrete With Sawdust Ash And Coffee Husk Ash

Abstract

Concrete, as the world's most used construction material, is increasingly being used because of the rapid development of industrialization and urbanization. Limited resources and progressive depravation of the environment is forcing scientific efforts to seek alternative and effective materials from large amounts of natural resources as additives in the partial replacement of cement and continuous generation of wastes arising from industrial by-products and agricultural residue, create acute environmental problems both in terms of their treatment and disposal. The country has enormous amount of coffee husk and sawdust ash. However, the utilization of this coffee husk ash and sawdust ash waste in concrete production provides significant benefits in terms of reducing construction costs as well as greenhouse gas emissions. This research was therefore, aimed to examine the potential of combination of coffee husk ash (CHA) and sawdust ash (SDA) as partial replacement and additive for ordinary Portland cement (OPC) in C-20/25. Control and four different concrete mixes were prepared for 25MPa concrete, 5%, 10%, 15% and 20% hybrid of CHA&SDA replacement of cement and 2% additive separately. Workability of fresh concrete using slump test and compressive test, split tensile strength test and flexural test were performed. From the experimental results, it was found that the replacement of coffee husk ash and sawdust ash reduces workability of wet concrete. The results of the hardened concrete have shown that, up to 12% replacement of the hybrid of CHA&SDA achieved a higher compressive strength, split tensile strength and flexural strength at all test ages i.e. 7, and 28 days of age by test. It can therefore, be concluded that 12% replacement of cement by hybrid of coffee husk ash sawdust ash results in a similar concrete property with control test and it is the optimum replacement. This experimental investigation also aims to evaluate the impact of using sawdust ash and coffee husk ash as additives (plasticizers) in concrete at a maximum dosage of 2%. The study focuses on assessing the effect of these agricultural waste materials on the workability, mechanical properties, and durability characteristics of the resulting concrete mixtures. The results indicated that the inclusion of sawdust ash and coffee husk ash as additives of 2% had a positive influence on the tensile strength of the concrete and setting time of concrete without significantly compromising its mechanical properties. The slump values remained within an acceptable range, indicating good workability. Moreover, compressive strength and flexural strength were maintained at satisfactory levels. A detailed study on the source of SWDA & CHA on concrete mineralogy and properties must be performed to fill the potential research gap.