Development of sandwich panels combining sisal fiber-cement composites and fiber-reinforced lightweight concrete

Abstract

This research proposes the development of innovative structural sandwich panels composed of thin outer wythes of Sisal Fiber-Cement Composites (SiFCC) and a core layer of Polypropylene FiberReinforced Lightweight Concrete (PFRLC). Sisal fibers were used in two different lengths, short sisal fibers (50 mm) randomly distributed in the matrix; and long unidirectional aligned sisal fibers (700 mm) applied by a cast hand layup technique. Lightweight aggregates and polypropylene fibers were used in the concrete core to reduce panel’s density, to improve its thermal insulation and energy absorption, and to assure the required shear capacity. The behavior of the sandwich panels in four-point bending test is described and the various failure mechanisms are reported. Pull-off tests were performed to evaluate the bond strength between SiFCC and PFRLC layers. The results revealed that the long sisal fibers were more effective in terms of increasing the ultimate flexural capacity, exhibiting a deflection hardening and multiple cracking behavior, comparing with the SiFCC laminates reinforced with short sisal fibers, which presented a deflection softening response after first cracking. The panels with short sisal fibers (SSiFCC) revealed higher bond strength between the layers in comparison to the panels with long sisal fibers (LSiFCC).The study reported in this paper is part of the activities carried out by the Authors within the International Cooperation Project “EnCoRe - Environmentally-friendly solutions for Concrete with Recycled and Natural components” (www.encore-fp7.unisa.it), funded by the European Union within the International Research Staff Exchange Scheme (IRSES) of the 7th Framework Programme (FP7PEOPLE-2011-IRSES, n.º 295283). The first author acknowledges the research grant under this project