The document discusses the effects of adding natural fibers like coir and kenaf to concrete mixtures on the strength properties of the concrete. It describes an experimental study where concrete mixtures were prepared with different volume fractions of coir fiber, kenaf fiber, and hybrid mixtures of both. The results showed that concrete with 0.3% coir fiber content exhibited the highest compressive strength of 38.12 MPa, over 70% greater than the control mixture. Concrete with 0.75% kenaf fiber content showed the best mechanical properties overall. Additionally, a hybrid mixture with 0.45% kenaf and 0.3% coir fibers increased flexural strength by 36%, split tensile strength by 27%,