Utilization of coconut fibres and ropes as concrete reinforcement in mortar-free construction with novel interlocking blocks: Considering its application in earthquake resistant housing

Abstract

Safe housing in earthquake prone regions is a priority for all. No one wants to compromise on this, but at the same time, there arises a question of ability to finance. Many people, particularly those who live in rural areas of developing and underdeveloped countries, cannot afford expensive houses. The overall aim of the research is to develop natural fibre reinforced concrete structures, which can not only withstand earthquakes, but also are low cost and easy to construct. Natural fibres are cheap and locally available in many countries. For this study, coconut fibres were selected because of their highest toughness amongst all natural fibres. Coconut fibre is extracted from the husk of coconut fruit. The material characterization of coconut fibre reinforced concrete (CFRC) was carried out because limited information was available about it. Fibre properties like fibre length and content were optimised for obtaining the best properties of CFRC. During the standard static testing, cracks were produced in CFRC cylinders (unlike the spalling/splitting of plain concrete) while performing compressive and splitting tensile strength tests. CFRC beamlets did not break into two pieces after a crack was produced, reflecting the advantage of coconut fibres. While performing dynamic testing, it was observed that the damping of CFRC increased with increasing fibre content, and this increment was considerable after cracking at different damage stages. These observations confirmed that CFRC can be utilized as a construction material. The investigations on bond strength between (i) fibres and concrete and (ii) rope and CFRC were also studied. The considered parameters include embedded length, diameter, pre-treatment and matrix strength. The results of both bond strength tests provided insightful information about the influential variables to be taken care of for increasing the structural stability at local and global levels. Mortar-free construction can lead to energy dissipation during strong ground motions. Therefore, interlocking blocks were invented to facilitate the construction of mortar-less walls. The blocks were prepared with CFRC. The blocks can move relative to each other during an earthquake, and also have self-centring ability during and after the ground motion. The shear and compressive capacities of the interlocking blocks were experimentally determined. Mortar-free structures using these blocks and rope reinforcement were tested under harmonic and earthquake loadings. The dynamic performance was analysed and it was found that the damping increased with increasing load amplitude because of block uplift. Finally, future recommendations are provided for achieving the overall goal of the research, i.e. affordable earthquake-resistant housing.