Field application of self-healing concrete with natural fibres as linings for irrigation canals in Ecuador

Abstract

This paper describes the first field application of self-healing concrete with alkaliphilic spore-forming bacteria and reinforced with natural fibres. The application took place in the highlands in Ecuador in July 2014. The concrete was cast as linings for an irrigation canal that transports water from glaciers in the Andean mountains to agricultural fields. This canal has been used for over a century by the local farmers. Until not long ago the walls and bottom of the canals were simply made out of compressed soil without any concrete. The yield of the canal was therefore very low: about 70% of the water was lost due to evaporation and infiltration into the soil. In order to improve the functionality of the canal it was then decided to line it with concrete. Unfortunately within one year the concrete cracked so that water was now wasted through the cracks. Self-healing concrete reinforced with natural fibres was proposed as a solution to this problem. The use of fibres in concrete increases the tensile capacity of concrete and assures a controlled crack width. Abaca fibres were selected due to their mechanical properties and availability as they are a fibre indigenous to Ecuador. Additionally, Abaca fibres have already been studied as reinforcement for mortar to improve the structural behaviour of houses in Ecuador under seismic loads. The bacteria are included in the concrete in order to seal possible cracks. The mechanical properties of the concrete with fibres and bacteria were first evaluated in the laboratory by means of flexural and compression tests. The compressive strength fulfilled the requirements for the intended application in irrigation canals. The selfhealing capacity of the concrete with and without bacteria was studied by monitoring the crack-healing. The concrete was designed to favour the use of locally available materials and following mixing procedure that could be replicate by the local communities. The self-healing concrete was mixed and cast in-place. Following this successful application, new sites in Ecuador are being evaluated by the local authorities for more field applications of this material.