Technical Feasibility of the Reuse of Dry Concrete Slurry Waste in Concrete Fabrication.

Concrete slurry waste (CSW) is an industrial by-product retrieved in large quantities from ready-mix concrete plants. The present work aims to study the feasibility of the incorporation of this residue in the production of concrete to reduce the dilemma of its disposal on huge amounts, decrease the quantities of natural materials used in concrete assembly and produce a lower carbon footprint concrete. Hence, the CSW were divided into three parts, the first part contains the fraction of fine particles (< 80 µm) (residue 1), the second part contains the entire CSW (residue 2) and the third part contains the rest of CSW after the elimination of residue 1 by sieving (residue 3). Then, the introduction of CSW into concrete was achieved, on one hand, by replacing 2, 4, 6, 8 and 10% of cement by residue 1 and, on the other hand, by substituting 5, 10, 15, 20 and 25% of river sand and crushed sand by residues 2 and 3, separately. In order to qualify and analyze the behavior of this residues in the company of other components of concrete, several chemical and physical characteristics of CSW were evaluated. In addition, CSW were characterized by x-ray fluorescence (XRF), x-ray diffraction (XRD), fourier transform infrared spectrometer (FTIR) and scanning electron microscopy (SEM). The various constituents used in the manufacturing of concrete were characterized physically including particle size distribution, fineness modulus, cleanliness of the sand, flattening coefficient, hardness, apparent density and actual density to conclude the formulation used for the development of the specimens. In addition, the properties of fresh and hardened concretes were also investigated, including Abrams cone subsidence, density and compressive strength. The outcome of this study concludes that modest amounts of CSW improve the physical properties of concretes and consequently their compressive strength, especially at 90 days, whatever the type of martial being substituted. Thus, the introduction of residue 1 into the cement must not exceed 2%, the replacement of residue 2 by river and crushed sands can be done at rates up to 5 and 10%, respectively, while the residue 3 can only substitute river sand at a rate up to 10%. [ABSTRACT FROM AUTHOR]