Enhancement of Recycled Aggregate Concrete Properties by a New Treatment Method

Abstract

ABSTRACT:Recently, decreasing natural sources of aggregate accompanied by increasing large quantities of construction and demolition waste (CDW) cause challenges for environment and construction industry. A significant solution for this is to recycle CDW as a new aggregate source for concrete. However, using recycled concrete aggregate (RCA) in concrete involves various obstacles and controversial issues in controlling the quality of recycled aggregate concrete (RAC). This study is an effort to improve the quality of RAC containing 100% coarse RCA by using pozzolanic and sodium silicate solution as new treatment solutions. This study examined performance abilities of RAC after being treated with new treatment solutions and a new mixing procedure. The mechanical properties of RAC were evaluated based on testing of concrete under various conditions. The significant results indicated that sodium silicate combined with pozzolanic materials can improve mechanical properties of RAC containing 100% coarse RCA. At 20% concentration of sodium silicate and silica fume, the compressive strength of RAC could improve up to 36%. Achievements of this approach demonstrated its effectiveness in enhancing the strength of RAC, which is potentially applied to treating RCA for concrete in the future.

Enhancing Sustainable Concrete: A Study on Mechanical Properties and Durability of Concrete with Treated Recycled Aggregates and Marble Dust

“…Figure 5 depicts the treatment procedure in detail. For the SS + FA treatment, 10% and 20% concentration solutions were prepared according to (Bui, Satomi and Takahashi, 2018) guidelines. The RCA were immersed in these treatment solutions for 24 hours at 20 degrees Celsius.…”

Methods of strengthening the grains of recycled aggregates

“…These SCM´s include fly ash, silica fume, ground granulated blast furnace slag [21,22,23]. However, less common materials are also tested as the effective pozzolanic component of the coating slurry, like Fe2O3 [7], nano-silica [24,25], calcium metasilicate -wollastonite [25], geopolymer paste [20,26], metakaolin [27] or RCA fines [28].…”

The Chemical-Mineralogical Characterization of Recycled Concrete Aggregates from Different Sources and Their Potential Reactions in Asphalt Mixtures

“…Reactions with some complex compounds in organic matter (especially fulvic and humic acids) and soil clays cause the mercury to remain for some time. These compounds can reach the RCAs by the exploitation of river sands or soils contaminated with mercury [34]. In the atmosphere, mercury can be found due to natural causes (such as volcanic eruptions, volatilization of aquatic and marine environments) or anthropogenic factors (industrial processes).…”

“…Thus, depending on the location of the RCA's origin, the aggregates may contain mercury. In the case of RCAB, the proximity to the sea and industrial zone means that the concrete had been exposed to the mercury present in the atmosphere and absorbed the mercury in its base matrix [34]. Another important indicator is iron (Fe) found in natural aggregates, and its value in RCA decreases to approximately 50%.…”