Effect of relative humidity on the carbonation rate of portlandite, calcium silicate hydrates and ettringite

Steiner, Sarah; Lothenbach, Barbara; Proske, Tilo; Borgschulte, Andreas; Winnefeld, Frank

doi:10.1016/j.cemconres.2020.106116

Cited by 155 publications

(76 citation statements)

References 93 publications

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“…Given the above, Figure 5 shows wet/dry exposure conditions, both with renewal (CC) and without renewal (CS), the Ca(OH)2 content tends to be constant earlier when compared to the submerged conditions (SS and SC) and this can be explained by the lower humidity present in these exposure environments. Steiner et al (2020) stated that portlandite in environments with lower relative humidity and a source of CO2 can produce a layer of CaCO3 around its particle, making its solubilization impossible. After evaluating renewal water wet/dry cycles, Figure 5 (CC), in the second cycle, a Ca(OH)2 content is below the significance level for all cement types and remains constant up to the end of the test.…”

Section: Resultsmentioning

confidence: 99%

Calcium hydroxide influence in autogenous self-healing of cement-based materials in various environmental conditions

et al. 2021

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Several factors, such as chemical shrinkage or environmental attack can produce concrete cracks. Calcium hydroxide content from the environment or cement hydration can promote the self-healing phenomenon (SHP). This study evaluates the calcium hydroxide concentration influence on the self-healing phenomenon of cement-based materials. Cracked mortars with different types of cement, such as a filler, pozzolanic, and high initial strength, were exposed to four environmental conditions. Titration was the method proposed to determine the amount of calcium hydroxide content leached in the water, and the cracks closure were analyzed by optical microscopy. CPII F (Portland Cement, type II, compound with limestone) samples showed no trend to Ca(OH)2 leached, and to superficial cracking closure. Regarding CPV (Portland cement, type V, high initial strength cement) samples, their behavior showed the highest Ca(OH)2 content to all environmental exposure, and cracking closure to samples in submerged condition. Thus, a significant influence in the cracks´ closure regarding the presence of Ca2+ leached to the exposure environments, and a water source related to this behavior seems to be a primary factor to improve the SHP.

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Section: Resultsmentioning

confidence: 99%

Calcium hydroxide influence in autogenous self-healing of cement-based materials in various environmental conditions

et al. 2021

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“…Like NL, the combination of nanoparticles (NSL) led to higher carbonated species content ( Figure 4 ). The shifted peak temperature from 720 °C to 752 °C could indicate crystallinity modification of carbonates or the presence of additional carbonated species [ 28 ]. After 28 days of wetting-drying cycles, the portlandite content was found reduced compared to the reference, and the carbonates of NC-cement pastes were found increased ( Figure 4 ).…”

Section: Resultsmentioning

confidence: 99%

The Influence of Curing Regimes in Self-Healing of Nano-Modified Cement Pastes

2020

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The present study proposes nano-calcium oxide (NC) and nano-silica (NS) particles as healing agents in cement pastes, taking into account the curing conditions. Two series of specimens were treated in water and under wetting-drying cycles. The addition of NC (1.5%wt of binder) triggered early healing since cracks were healed within 14 days in underwater immersion and before 28 days at wetting-drying cycles. Attenuated Total Reflectance (ATR) spectroscopy and SEM analysis revealed that the healing products were mainly aragonite and calcite in water conditions and more amorphous carbonates under wetting-drying cycles. The combination of NS and NC (3.0%wt in total) offered healing under both curing conditions before 28 days. The presence of NS assisted toward porosity refinement and NC increased the carbonates’ content. The newly formed material was dense, and its elemental analysis by SEM revealed the C-S-H compounds that were also verified by ATR.

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“…As a result, the phenolphthalein concentration can change, which may affect the concrete colouration [ 22 ]. Time plays an important role in this type of test because of the individual phases of the cement matrix of concrete colour at different rates [ 66 ]. Phenolphthalein changes the concrete surface colour at a pH range from 8.5 up to 9.5.…”

Section: Methodsmentioning

confidence: 99%

“…Carbonated cement paste in concrete is characterised by reduced compactness and/or evident absence of portlandite. In this pastes in the place of portlandite various calcium carbonates are formed [ 28 , 66 , 72 , 73 , 74 , 75 ]. As a result of carbonation on the surface of the portlandite, amorphous calcium carbonates are formed, which over time turn into vaterite, from which aragonite can be formed.…”

Section: Methodsmentioning

confidence: 99%

Diagnostics of Concrete and Steel in Elements of an Historic Reinforced Concrete Structure

et al. 2021

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Existing buildings, especially historical buildings, require periodic or situational diagnostic tests. If a building is in use, advanced non-destructive or semi-destructive methods should be used. In the diagnosis of reinforced concrete structures, tests allowing to assess the condition of the reinforcement and concrete cover are particularly important. The article presents non-destructive and semi-destructive research methods that are used for such tests, as well as the results of tests performed for selected elements of a historic water tower structure. The assessment of the corrosion risk of the reinforcement was carried out with the use of a semi-destructive galvanostatic pulse method. The protective properties of the concrete cover were checked by the carbonation test and the phase analysis of the concrete. X-ray diffractometry and thermal analysis methods were used for this. In order to determine the position of the reinforcement and to estimate the concrete cover thickness distribution, a ferromagnetic detection system was used. The comprehensive application of several test methods allowed mutual verification of the results and the drawing of reliable conclusions. The results indicated a very poor state of the reinforcement, loss in the depth of cover and sulphate corrosion.

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Effect of relative humidity on the carbonation rate of portlandite, calcium silicate hydrates and ettringite

Cited by 155 publications

References 93 publications

Calcium hydroxide influence in autogenous self-healing of cement-based materials in various environmental conditions

Calcium hydroxide influence in autogenous self-healing of cement-based materials in various environmental conditions

The Influence of Curing Regimes in Self-Healing of Nano-Modified Cement Pastes

Diagnostics of Concrete and Steel in Elements of an Historic Reinforced Concrete Structure

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