Feasibility of using olive biomass bottom ash in the sub-bases of roads and rural paths M. Cabrera a,⇑ , J. Rosales a , J. Ayuso a , J. Estaire b , F. Agrela a a Area of Construction Engineering, University of Cordoba, Cordoba, Spain b Geotechnical Laboratory (CEDEX), Madrid, Spain highlights  We show the use of biomass bottom ash for soil treatments.  Different mixtures of expansive soils were applied, with different BBA rates.  The use of BBA as stabilizer material in road was proved.  The addition of BBA in all the mixtures improved the bearing capacity.  BBA reduces the expansion same as treatment whit lime. article info Article history: Received 5 December 2017 Received in revised form 14 May 2018 Accepted 5 June 2018 Keywords: Soil stabilization Biomass bottom ash Expansive soil Clay soils abstract Clay soils are widely distributed throughout the world and are the source of multiple technical problems in their application for the construction of sub-grade and sub-road bases. These types of soils are found in areas where civilian infrastructure such as roads and rural roads must be built. Therefore, in many situ- ations it is necessary to use stabilized expansive soils, in the formation of the foundation and structural layers of linear infrastructures. Soil stabilization is used to increase the load capacity of the soil, and mixtures of lime and cement are generally used as binders. In recent years, interest in the recycling of industrial products and by-products has increased. One example of this is the use of biomass combustion in power plants. The management of significant amounts of waste (biomass bottom ash) from biomass power plants remains a problem. This paper presents the results of an experimental study for stabilizing expansive soil to determine its bearing capacity and mechanical properties via a triaxial test of the addition of biomass bottom ash. A double objective was targeted: reduction of the problems in using this type of soil and provision of a use for this type of waste. The results showed significant improvements in the mechanical. Therefore, herein is proposed the use of biomass bottom ash as a stabilizing agent for expansive soils, to improve the efficiency of the construction process by incorporating this product into a second life cycle as road bases. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction In road and rural-path construction, it is essential to minimize the use of additional materials, and eliminate earth moving as much as possible, for environmental and technical considerations. The soil treatment techniques contribute to the competitive- ness and sustainability of road engineering [1]. The engineering properties of construction materials determine their potential use and application in civil works. The material characteristics must satisfy the engineering functions that contribute to the durability and quality of the entire road structure [2]. Previous works have proved the feasibility of reusing industrial residues from different origin which have been applied in road construction [3,4]. Soil stabilization is the process of alteration of geotechnical properties to satisfy engineering requirements [5]. Extensive stud- ies have been carried out regarding the treatment of expansive soils using various additives, such as lime, cement, fly ash, indus- trial waste products, potassium nitrate, calcium chloride and phos- phoric acid [6–13]. Traditional techniques of soil stabilization are https://doi.org/10.1016/j.conbuildmat.2018.06.035 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: manuel.cabrera@uco.es (M. Cabrera). Construction and Building Materials 181 (2018) 266–275 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat