Investigating the effect of the foundry sand and waste foundry sand on the fracture toughness of concrete

The use of recycled or waste materials in the composition of concrete materials is one of the most applicable solutions for compensating for the lack of initial sources. The effect of waste materials on the mechanical properties of concrete should be assessed before utilizing them in mix design of practical projects such as dam construction and tunneling. The aim of this paper is to use the foundry sand (FS) and waste foundry sand (WFS) as fine aggregate ingredients in the mixture of ordinary cement concrete and then evaluate the influence such particles on the corresponding fracture toughness value. A number of fracture tests were conducted on single-edge notched beam (SENB) samples constructed by normal sand (as control sample) and three different combinations of FS and WFS compounds. The experimental results revealed that replacing 20% FS can reduce slightly (up to 2%) the fracture toughness of concrete, while its value decreases nearly 25% by substituting 20% WFS. Such a reduction trend can also be interpreted by scanning electron microscopy (SEM) pictures of the fracture surface. The SEM pictures show that the heat treatment results in reducing the adhesion of aggregate and increasing the porosity of mixture. © 2021, Saudi Society for Geosciences.