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Tufa precipitation from Recycled Concrete Aggregate (RCA) over geotextile: Mechanism, composition, and affecting parameters
Highlights Plummer et al. set-up is suitable to study the induced RCA tufa precipitation. Garrels-Mackenzie model predicts the composition and mechanism of RCA tufa formation. Calcium sulfate compounds are dominant in evaporative RCA Tufa. Calcium carbonate compounds are dominant in artificially CO2 saturated environments. Formation of evaporative tufa is more favorable for using RCA in construction.
Abstract One of the limiting factors of using RCA as a construction material has previously been related to the generated tufa despite its acceptable mechanical properties. Studies conducted in the mid-90s seem to overestimate the potential of such formations; whereas, more recent studies tend to underestimate such depositions from RCA. However, a comprehensive study to understand the chemical mechanisms and resulting chemical composition of pure RCA tufa had not been carried out. This paper discusses the results of an analytical study that combines both the findings from experimental and theoretical geochemistry to demonstrate the conditions that result in tufa precipitation, the associated mineral compositions, and what these differences in mineral compositions may mean for the construction. The precipitation experiments were conducted using Plummer et al. reaction vessel. Based on the observations from these experiments, the findings showed that the chemical reactions and the formation of tufa depend on different precipitation mechanisms. The theoretical evaluations showed that Garrels-Mackenzie (progressive evaporation) model can be successfully used to interpret observations from the experiments. The results of this analytical study confirm that in most construction conditions calcium sulfate minerals are more likely to precipitate from RCA than calcium carbonate minerals. This finding would mean that the precipitated deposition from RCA may be seasonal due to the higher solubility constant of calcium sulfate. For practical implications in construction, a one-point leach test and geochemical analysis method is suggested to estimate the characteristics of potential tufa formations from different RCA sources.
Tufa precipitation from Recycled Concrete Aggregate (RCA) over geotextile: Mechanism, composition, and affecting parameters
Highlights Plummer et al. set-up is suitable to study the induced RCA tufa precipitation. Garrels-Mackenzie model predicts the composition and mechanism of RCA tufa formation. Calcium sulfate compounds are dominant in evaporative RCA Tufa. Calcium carbonate compounds are dominant in artificially CO2 saturated environments. Formation of evaporative tufa is more favorable for using RCA in construction.
Abstract One of the limiting factors of using RCA as a construction material has previously been related to the generated tufa despite its acceptable mechanical properties. Studies conducted in the mid-90s seem to overestimate the potential of such formations; whereas, more recent studies tend to underestimate such depositions from RCA. However, a comprehensive study to understand the chemical mechanisms and resulting chemical composition of pure RCA tufa had not been carried out. This paper discusses the results of an analytical study that combines both the findings from experimental and theoretical geochemistry to demonstrate the conditions that result in tufa precipitation, the associated mineral compositions, and what these differences in mineral compositions may mean for the construction. The precipitation experiments were conducted using Plummer et al. reaction vessel. Based on the observations from these experiments, the findings showed that the chemical reactions and the formation of tufa depend on different precipitation mechanisms. The theoretical evaluations showed that Garrels-Mackenzie (progressive evaporation) model can be successfully used to interpret observations from the experiments. The results of this analytical study confirm that in most construction conditions calcium sulfate minerals are more likely to precipitate from RCA than calcium carbonate minerals. This finding would mean that the precipitated deposition from RCA may be seasonal due to the higher solubility constant of calcium sulfate. For practical implications in construction, a one-point leach test and geochemical analysis method is suggested to estimate the characteristics of potential tufa formations from different RCA sources.
Tufa precipitation from Recycled Concrete Aggregate (RCA) over geotextile: Mechanism, composition, and affecting parameters
Abbaspour, Aiyoub (author) / Tanyu, Burak F. (author)
Construction and Building Materials ; 196 ; 317-329
2018-10-15
13 pages
Article (Journal)
Electronic Resource
English
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