Pre-Wetting of Recycled Concrete as Alternative of Chemical, Natural and Industrial Waste Additives

Abstract

Destructive infrastructure is increasing day by day due to the successive wars in the Arab region and this led to the formation of large volumes of demolished concrete, which produces a lot of waste materials and visual pollution in the spaces. Meanwhile, environmental protection has become a challenge, not an option. As well as, reusing of demolished concrete in new structures is necessary to preserve the raw resources of aggregate away from attrition. Seventy-two specimens of ( 100 x 100 x 100 mm ) were prepared with water to cement ( W/C ) ratio of 0.4, where have replaced the different proportions of natural aggregate ( NA ) ( 0%, 30%, 45%, and 60% ) by recycled concrete aggregate ( RCA ), and then were added 2.5% super plasticizer ( SP ) in place of cement to other specimens according to previous replacement proportion of RCA to determine the optimum percentage of RCA and to investigate the effectiveness of using Super Plasticizer. The replacement proportion of RCA were 45% of NA. sixty six cubes of 45% - RCA were prepared with a different proportions of 0, 10, 15, and 20 % of instead of a fine aggregate for each the Iron Filler ( IF ) and Al-Qawirah Silica Sand (QSS), it is natural Silica was got from the quarry of AL-Qawirah, Jordan. The use of this type of silica as a substitute for fine aggregate with RCA is the first use in Jordan. The final stage of research was the pre-wetting of RCA by 0%, 2.5%, 5%, and 7.5% as percentage of W/C, it is an extra water added to the 45%-RCA mixtures before an hour from mix process, thirty-six cubes were casted with different proportions of extra water. The results displayed that the workability was reduced by increasing the RCA, while the workability was increase as ratios of W/C increase. The analytical study shows a considerable enhancement of the compressive strength of 2.5% pre-wetting of RCA with 45%-RCA relative to the SP, IF, and NA, where the increase in the compressive strength was 64% and 28% at 2.5% pre-wetting of RCA relative to SP-45% RCA and NA, respectively