Use of lignocellulosic liquid waste from wood hardboard manufacture as bitumen emulsion extender for cold asphalt mixtures for low traffic roads

Abstract

[Abstract:] During the wet process of manufacturing wood hardboards, a large amount of water contaminated with lignocellulosic waste is generated. With the aim of promoting the circular economy, it is interesting to find new uses for this liquid waste, rich in biopolymer lignin. The present research is a preliminary laboratory analysis of the feasibility of using this industrial waste as bitumen emulsion modifier or extender. To this purpose the lignocellulosic industrial waste was tested as partial substitute of bitumen emulsion for cold asphalt mixtures type grave emulsion. Particularly, GE-2 grave emulsions for low traffic roads have been manufactured. Substitution percentages of 0% (control), 5%, 10%, and 15% were analysed. The envelope water was visually determined. Also the optimum fluid content was obtained by means of the Modified Proctor Test. In addition, the optimum bitumen emulsion content, the compressive strength, and the water resistance of the cold asphalt mixtures were analysed conducting immersion-compression tests. All the tested percentages of lignocellulosic waste led to grave emulsions that could be used for low traffic roads, according to the Spanish specifications. Nevertheless, the results indicate decreased compressive strength with increasing liquid waste percentages. For this reason, only percentages of substitution up to 10% of liquid waste rich in lignin are considered adequate as bitumen emulsion extender.