Reinforcing the properties of self-compacting mortar based on agro-waste fine (walnut shell) aggregates by alkaline treatment

The globe is now seeing a fast increase in urbanisation and civilisation, which is accompanied by excessive non-renewable resource exploitation, energy consumption during building, and the need for adequate thermal insulation to guarantee user comfort (heating and cooling). As a result, we must move towards creative and sustainable methods to reduce our environmental effect. On the other hand, agricultural activity leads to abundant generation and agglomeration of agro-wastes, which are alternative biosourced eco-materials for construction. This paper aims to reinforce the properties of self-compacting mortar (SCM) containing untreated walnut shell (UWS) (agro-waste) aggregates as fine aggregates, with alkaline pre-treatment using a solution concentration of 6% NaOH to obtain NWS aggregates. A partial volumetric sand substitution was adopted by a variation from 5 to 40%, with an increment rate of 5%. Some physical properties were evaluated in the fresh and hardened state; compressive and thermal performances of SCMs were measured at 90 days. Based on the obtained results, alkaline treatment of WS surfaces improves their morphological properties, SCMs density, compressive strength, and durability properties (water absorption) and slightly decreases thermal performance.