A Study of Concrete Made with Fine and Coarse Aggregates Recycled from Fresh Concrete Waste

Abstract

This paper deals with the possibility of using fresh concrete waste as recycled aggregates in concrete. An experimental program based on two variables (proportion of fine aggregates replacement and proportion of coarse aggregates replacement) was implemented. The proportions of replacement were 0%, 50%, and 100% by mass of aggregates. Several mechanical properties were tested as compressive and tensile strengths. The results show a good correlation between aggregates replacement percentage and concrete properties. Concerning mechanical properties, a gradual decrease in compressive, splitting, and flexural strengthn with the increase in recycled aggregate percentage is shown.

Mechanical properties of steel fiber reinforced recycled aggregate concrete

“…The split‐tensile strengths of the SFRRAC mixes are observed to decrease with RA content. This is consistent with the observations made by previous researchers . Figure shows the variation of split‐tensile strength of SFRRAC with SF content.…”

“…However, the usage of recycled aggregate concrete (RAC) has been mainly restricted to construction of pavements and tunnel linings, because of its inferior mechanical properties, compared to those of natural aggregate concrete (NAC). RA negatively affects the shrinkage strain, the compressive strength, the flexural strength, the split‐tensile strength, the elastic modulus and the modulus of rupture of RAC . Such inferior mechanical properties of RAC compared to those of NAC are due to the greater porosity and water absorption of RA compared to that of NA, which affect the cement hydration process and the subsequent strength development in RAC…”

Recycling fresh concrete waste: A review

“…For both fine and coarse aggregates, the water absorption of slurry waste particles has a wide range of 4.3–15.8%, which is several times larger than that of the natural aggregates which has a value around 0.9–2.2%. This is attributed to the angular shape of the particles with well‐defined edges and the porous structure mentioned above . To reach the SSD condition, more water is needed for processing the slurry waste particles.…”

“…Furthermore, the recycled fine aggregate tends to have more severe effect than the recycled coarse aggregate because of its higher water absorption. In another study, natural aggregates were replaced by both recycled fine and coarse aggregates in combination modes . Concerning the size effects, concrete with 100% recycled fine aggregates required 42.2 more liters of water than that with coarse aggregates for adjustment.…”

“…The negative effects of recycled coarse aggregates were weakened with time as the 90‐day compressive strength of the concrete mixtures with 15, 30, and 50% recycle coarse aggregate decreased by 25.0, 34.8, and 51.4% of the compressive strength of the normal concrete, respectively. Similar conclusions on compression strength of concrete with recycled aggregates were acquired at 1, 14, and 28 days . It was concluded that both recycled fine and coarse aggregates were adverse to the concrete under compression, especially for concrete after 1‐day curing.…”