Fracture energy of natural fibre reinforced concrete

This paper reports on an experimental study of the fracture energy of concrete reinforced with natural fibres of hemp, elephant grass, and wheat straw. Concrete specimens containing 0.19% of fibres by weight and of 40 mm of length were uniaxially tested with the wedge splitting test (WST) method. The addition of fibres was found to improve the fracture toughness of plane concrete. The most distinctive increase in the fracture energy has been observed by hemp reinforced concrete, up to 70%, when comparing with non reinforced concrete, whereas for straw and elephant grass reinforced concrete this increase was moderate, up to 2% and 5%, respectively. The beneficial effect of hemp fibres is believed to be the result of the fibre’s high tensile strength and the fibre’s fineness, resulting in a better bonding between fibres and concrete matrix. The presence of fibres in concrete decreased minimally the tensile strength of concrete, for 4%, 7%, and 8% for hemp, straw and elephant grass reinforced specimens, respectively.