Valorisation of Dune Sand Treated with Lime and Scrap Tyre Rubber Powder as a Road Foundation Material.

The purpose of the work presented in this paper is the treatment of dune sand; which is abundant in the region of  Djelfa (Algeria), with different lime and tyre rubber powder in order to valorise them in road construction. Several steps were considered in this research. A method of blend formulation has been proposed which is based on stabilization of the studied sand using a hydraulic binder (lime) and scrap tyre rubber powder with different percentages. For each mixture, the optimum Proctor, shear strength, immediate and immersion CBR index, compressive strength and tensile strength were determined. After that, an analysis of the results was made to examine the influence of treatment agents on the characteristics of the mixtures. The results show that the replacement of lime and tyre rubber powder at optimum content has a positive impact on the physical and mechanical behaviours of the treated dune sand mixtures; increases its compressive and tensile strengths, improves its cohesion and increases its immediate and immersion CBR indexes. The selected optimum formulation has sufficient performances to be used as road material

Optimization of High-Performance-Concrete properties containing fine recycled aggregates using mixture design modeling

This investigation means to predict and modeling the fresh and hardened concrete behavior containing fine aggregates from concrete and brick wastes, for different recycled aggregates substitution rates. To succeed this, the design of experiments DOE method was used. It is observed that slump of recycled concrete is significantly influenced by the content in recycled concrete aggregates (RCA), natural sand (NS) and recycled brick aggregates (RBA), respectively.The compressive strength (CS) reaches a maximum value of 83.48 MPa with factors values of 25% RBA, and 75% RCA. And HPC’s based on RBA sand presented greater values of flexural strength at 7 days than HPC’s based on RCA sand, it was revealed that this is due to the RBA fines pozzolanic reaction and the production of new CSHs, which leads to better cement matrix densification.Under optimal conditions, themaximum desirability is 0.65, who has given HPC no added natural sand, by mixing recycled sands RBA (9.5%) with RCA (90.5%).The statistical terms result show that the expected models are very well correlated with the experimental data and have shown good accuracy

Physicomechanical Behavior of High-Performance Concrete Reinforced with Recycled Steel Fibers from Twisted Cables in the Brittle State—Experimentation and Statistics

This research studied the effect of recycled steel fibers extracted from twisted cable waste on the fresh and hardened states of high-performance concretes. Accordingly, slump, water absorption (WA), compressive strength (CS), flexural strength (FS), and split tensile strength (STS) were measured in the laboratory using mixtures generated by the response surface methodology (RSM). The RSM-based central composite design (CCD) was used to assess the influence of water-to-binder (W/B) ratios from 0.27 to 0.31, length-to-diameter (L/d = 46 to 80) and steel fiber content (SFC) in the range of 19 to 29 kg/m3 on the behavior of high-performance fiber-reinforced concrete (HPFRC). The accuracy and validation of the generated models were evaluated by employing analysis of variance (ANOVA) and optimal parameters. The experimental findings revealed that the use of an L/d ratio of 63, a W/B ratio of approximately 0.28, and an SFC of around 22 kg/m3 resulted in high workability in terms of slump. While a notable increase in compressive strength was observed when employing an L/d ratio of approximately 70, a W/B ratio of around 0.28, and the maximum SFC of 29 kg/m3, as confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis