Sustainable Recycling of High-Strength Concrete as an Alternative to Natural Aggregates in Building Structures

Abstract

The application of recycled coarse aggregates (RCA) in high-performance concrete (HPC) was analyzed in the article. In the paper, the behavior of HPC with coarse recycled aggregate and natural coarse aggregate (NCA) was compared. Short-term experiments were conducted, including concrete deformation, deflection, load bearing capacity, and cracking of beams. The analysis involved reinforced concrete T-beams made in 100% of RCA or NCA. The studies indicated that the beams with recycled aggregate are characterized by greater deflection and 7.6% lower load bearing capacity in comparison to the beams with NCA. Substitution of coarse natural aggregate with RCA reduced the compressive and tensile strengths by 20 and 26 (%), whereas and the modulus of elasticity was decreased by 15%.

Behavior of Reinforced Concrete Beams Containing Waste Crushed Concrete and Bricks

“…Cracking pattern and deflection response of beams containing waste aggregate are similar to those of natural aggregate concrete beams as reported by Malešev et al 2010 [14]; Seara-Paz et al 2018 [18]; Wang et al 2019 [21]; Oad et al 2019 [4]. However, some researchers indicated that deflection is greater and cracks are more and closer in waste aggregate beams due to lower modulus of elasticity and higher shrinkage, respectively [5,11,12,17,19].…”

“…On the other hand, demolition waste is increasing and has become one of the most serious concerns worldwide [1][2][3]. So, recycling waste materials in constructions offers environmental as well as economic benefits such as reducing extraction of virgin materials and overall projects costs [2,[4][5][6].Since concrete is the most common construction material and about 75 % of concrete volume is occupied by aggregate, waste materials like crushed concrete and/or crushed bricks have successfully used as coarse and/or fine aggregate in various percentages to produce new concretes even though they, generally; give lower strength and stiffness than conventional concrete [7][8][9][10][11][12]. However, studies show that less or no negative effect is observed when the ratio of waste aggregate is about 50 % or less [1,8,13].…”

“…Since concrete is the most common construction material and about 75 % of concrete volume is occupied by aggregate, waste materials like crushed concrete and/or crushed bricks have successfully used as coarse and/or fine aggregate in various percentages to produce new concretes even though they, generally; give lower strength and stiffness than conventional concrete [7][8][9][10][11][12]. However, studies show that less or no negative effect is observed when the ratio of waste aggregate is about 50 % or less [1,8,13].…”

“…Many researchers found that the flexural strength of reinforced concrete beams with different replacement ratios of waste aggregate is equivalent to or even greater than that of natural aggregate beams where failure is still governed by main steel yielding [10,15,[17][18][19][20]. Other researchers recorded lower capacity for beams with waste aggregate compared to natural aggregate beams [3,5,11,12,21].…”

Studying the usability of recycled aggregate to produce new concrete

“…Wang Q et al [29] reported that one of the characteristics of the concrete that was investigated in this examination is autogenous shrinkage, as the results proved that it is possible to reduce shrinkage by using recycled aggregates, as the researchers studied many ratios of aggregate with different ratios of (w/c). Sadowska B. and Małgorzata G. 's [30] study demonstrates that substituting recycled aggregate for conventional aggregate in high-performance concrete results in a loss of concrete strength, modulus of elasticity, and tensile resistance. Salgado F. and Silva F. [31] in this one, three types of recycled aggregate were used: construction aggregate, concrete aggregate, aggregate, and a mixture of the two types.…”