Effect of pine needle fibre reinforcement on the mechanical properties of concrete

Abstract

To meet the requirements of energy savings, green environmental protection and sustainable development in engineering construction, the use of natural biomasses as raw materials for engineering construction has become a focus of research in recent years. Pinaceae plants are widely distributed worldwide. The leaves (pine needles) of Pinaceae plants are renewable, numerous and have a low utilization rate, and they have the potential tobe developed into natural plant fibre materials. Therefore, this paper selects Masson pine needle fibre (MPNF) to study the influence of this plant fibre on the mechanical properties of concrete, demonstrates the feasibility of adding MPNF to concrete, and provides a theoretical basis for the promotion of pine needle fibre-reinforced concrete composite materials. The MPNF was processed to a length of 30 mm and soaked in 2% NaOH solution, boiling water, or unheated water. After treatment, each type of MPNF was mixed with concrete at volumefractions of 0.5%, 1%, 1.5% and 2%, and then the mechanical properties were tested. Extract tests, industrial computer tomography (ICT), and scanning electron microscopy (SEM) were used to observe the extractive content, three-dimensional distribution, and surface structure of the MPNF for each pretreatment. The test results show that after pretreatment, MPNF can increase the compressive strength, splitting strength and modulus of rupture of concrete, as well as increase its ductility and toughness. This shows that it is feasible to incorporate MPNF into concrete, resulting in a new type of plant fibre-reinforced concrete composite material.