On the use of fine dune sand in Reactive Powder Concrete: Effect on resistance, water absorption and UPV properties

In this paper is presented an experimental study investigating the impact of dune sand inclusion in engineered Reactive Powder Concretes (RPC). RPCs are built upon specifically proportioned materials such as very fine sand particles and high amounts of cement and mineral admixtures, while maintaining a very low water content through superplasticizer usage. Fibers, whether metallic or synthetic, are a key component of these concretes, as they procure higher mechanical strengths and ductility. The purpose of this experimental work is two-fold. Firstly, to find out the potential positive impact of using dune sand (DS) as a partial substitute for river (allu-vial) sand in RPCs. Secondly, to quantify for various substitution rates, to what extent the mechanical, water absorption and ultrasonic pulse velocity (UPV) properties are altered. The results of the experiments point out the positive effect of river sand replacement by dune sand on the compressive strength of both the fiberless and fibered RPC mixtures, with improvement reaching up to +104.43% and +83.91% respectively when high DS proportions are used. The study also reveals the necessity of fibers usage, as the fibers seem to counteract the lesser flexural tensile strengths observed on high dune sand content concretes. Water absorption, porosity, and UPV test results showed improved values as DS proportions increase, revealing a densification of the cement matrix and hence, improved durability properties.