Substitution of Coarse Aggregates with Mollusk-Shell Waste in Acoustic-Absorbing Concrete

Abstract

Most of the aggregates in construction material come nowadays from the quarrying of natural resources, and their consumption tends to rise. The aim of this study was to evaluate the total substitution of traditional natural coarse aggregates with alternative, renewable resources, such as mollusk shell waste from the aquaculture industry, to manufacture a recycled porous concrete and its possible use in sound-absorbing barriers for road traffic. Two different shells, separately or as a mix, were used in this research work: Peruvian scallop and Mediterranean mussel. In addition, two different particle size distributions, smaller than 2 mm and between 2 and 7 mm, were used. Acoustic absorption, open porosity, density, mechanical resistance to compression and bending, and resistance to freeze-thaw cycles, along with leaching properties, were studied. The results revealed that specimens formed using any kind of mollusk shell waste with a particle size between 2 and 7 mm exhibited a 40% increase weighted acoustic absorption coefficient over porous concrete specimens made with river gravel. For particles of the same size, the acoustic absorption assessment index showed absorption over 4 dB in 12-cm thickness. In addition, the mechanical properties analyzed showed better values in all specimens made with shell waste than in conventional porous concrete specimens. In the specimens manufactured of mollusk shell waste with a particle size between 2 and 7 mm, compression strength was twice that of conventional porous concrete.