Performance evaluation of concrete made with double-processed recycled aggregate (DPRA): mechanical grinding and silica fume impregnation technique

The depletion of natural aggregate sources has increased exponentially due to the enormous demand for concrete. Therefore, the recycled aggregate (RA) extracted from old concrete structures may reduce the demand for natural aggregate (NA). This paper introduced a new double processing technique that combines mechanical grinding in the Los Angeles Abrasion Machine (LAAM) followed by silica fume (SF) impregnation technique to produce high-quality double-processed recycled aggregate (DPRA). To examine the effect of DPRA, five different types of DPRAs [viz: DPRA (0RVS), DPRA (200RVS), DPRA (300RVS), DPRA (400), and DRA (500RVS)] were utilized to replace NA in an M30 grade control mix. In this investigation, different DPRAs were employed to replace NA in each concrete mix (e.g., 0%, 25%, 50%, 75%, and 100%). In addition, experiments were carried out to examine the workability, strength, and durability of concrete made with DPRAs. The compressive strength has decreased by 7.58% compared to the control mix at a 75% replacement level of NA. Similarly, the Rapid Chloride Penetration Test (RCPT) value within the lower permeability zone is up to a 75% replacement level of NA with DPRA (400RVS). Further mechanical crushing in an LAAM with 400 revolutions followed by SF impregnation of 10% concentration is the optimum processing to produce superior quality double-processed recycled aggregate (DPRA). Based on the experimental investigations, a 75% substitution level of DPRA (400RVS) in place of NA is finally suggested for structural concrete.