Understanding the carbonation of concrete with supplementary cementitious materials: a critical review by RILEM TC 281-CCC

Abstract

Blended cements, where Portland cement clinker is partially replaced by supplementary cementitious materials (SCMs), provide the most feasible route for reducing carbon dioxide emissions associated with concrete production. However, lowering the clinker content can lead to an increasing risk of neutralisation of the concrete pore solution and potential reinforcement corrosion due to carbonation. carbonation of concrete with SCMs differs from carbonation of concrete solely based on Portland cement (PC). This is a consequence of the differences in the hydrate phase assemblage and pore solution chemistry, as well as the pore structure and transport properties, when varying the binder composition, age and curing conditions of the concretes. The carbonation mechanism and kinetics also depend on the saturation degree of the concrete and CO2 partial pressure which in turn depends on exposure conditions (e.g. relative humidity, volume, and duration of water in contact with the concrete surface and temperature conditions). This in turn influence the microstructural changes identified upon carbonation. This literature review, prepared by members of RILEM technical committee 281-CCC carbonation of concrete with supplementary cementitious materials, working groups 1 and 2, elucidates the effect of numerous SCM characteristics, exposure environments and curing conditions on the carbonation mechanism, kinetics and structural alterations in cementitious systems containing SCMs.

Hydration and Carbonation of Alternative Binders

“…In the process of carbonation of OPC-based mortars and concretes, the CO 2 from the air diffuses into the pore structure of the material and dissolves in the alkaline pore solution, forming weak acidic ionic species [5]. The dissolved carbonates react in a multistage process with the calcium ions from the hydrate phases of the cement matrix, summarized by [6] as:…”

Previsão da vida útil de estruturas de concreto com base em modelos para avanço da frente de carbonatação

“…In the first situation, the concrete pores would be filled with water, hindering the penetration of CO2 for H2CO3 formation. On the other hand, in low RH conditions, the water in the concrete pores would be insufficient to generate more accelerated natural carbonation rates since water is required to generate H2CO3 (Félix et al, 2017;POSSAN et al, 2017;Elsalamawy et al, 2019;Dierfeld et al, 2020). Considering Scenario C, results of Possan ( 2010) and Bob and Affana (1993) show a reduction in carbonation depths due to the RH increase from 50 to 70%, which suggests that the pore saturation is predicted in these ranges of ambient RH.…”

Optical fiber sensors based on sol–gel materials: design, fabrication and application in concrete structures

“…These changes depend on the cement chemistry and may have impact on the porosity and therefore on the transport properties of the carbonated concrete. 221 Moreover, exposure conditions such as the CO 2 concentration, RH and temperature strongly influence the carbonation kinetics of concrete as well as the amount of carbonation products.…”