An Experimental Investigation on M-30 Grade Concrete Prepared by Partial Replacement of Cement with Polypropylene Fiber, Coconut Shell Ash and Colloidal Nano Silica: A Review

Abstract

The reviewed literature collectively highlights the potential of agricultural and industrial by-products—such as coconut shell ash, nano silica, polypropylene fibers, and glass powder—as partial cement replacements to produce sustainable concrete. Studies consistently show that coconut shell ash (CSA) possesses pozzolanic reactivity due to its high silica content, contributing to strength gain when used up to 10–15% replacement, beyond which dilution effects reduce performance. Nano silica (NS) accelerates hydration and refines the pore structure, significantly improving early-age compressive and tensile strengths, with optimal dosages generally in the range of 1–3% by weight of cement. Polypropylene fibers (PPF) are widely reported to enhance ductility, crack resistance, and post-cracking behaviour, though they tend to reduce workability at higher volumes. Combined use of CSA and NS achieves synergistic effects on mechanical properties and durability, while PPF further improves flexural toughness and resistance to chemically aggressive environments. Several researchers have noted that careful proportioning is crucial, as excessive amounts of any of these materials lead to strength reduction and workability loss. This review confirms that a hybrid blend of CSA, NS, and PPF is a promising pathway for developing sustainable, high-performance M-30 grade concrete.