Abstract
Abstract 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.
Highlights
IntroductionExposure environment, cement chemical reactions are common sources of cracks in cement-based matrices
External loading, exposure environment, cement chemical reactions are common sources of cracks in cement-based matrices
Crack repairs may occur through different approaches: (a) external actions, such as surface treatments, which consist of filling the crack and repair of other existing damage (LI et al, 2019; SÁNCHEZ et al, 2018); and (b) through repairing itself by materials inserted into the matrix (ARAÚJO et al, 2018; BORG et al, 2018; ERŞAN et al, 2018; VAN BELLEGHEM et al, 2018; SELVARAJOO et al, 2020), either by the further cement anhydrous grains hydration and carbonation of Portlandite, a product of these hydration reactions (ANGLANI; TULLIANI; ANTONACI, 2020; MOSTAVI et al, 2015)
Summary
Exposure environment, cement chemical reactions are common sources of cracks in cement-based matrices. (a) external actions, such as surface treatments, which consist of filling the crack and repair of other existing damage (LI et al, 2019; SÁNCHEZ et al, 2018); and (b) through repairing itself by materials inserted into the matrix (ARAÚJO et al, 2018; BORG et al, 2018; ERŞAN et al, 2018; VAN BELLEGHEM et al, 2018; SELVARAJOO et al, 2020), either by the further cement anhydrous grains hydration and carbonation of Portlandite, a product of these hydration reactions (ANGLANI; TULLIANI; ANTONACI, 2020; MOSTAVI et al, 2015). Self-healing phenomenon is affected, as described by Reinhardt et al, (2013) by physical factors, such as particles swelling, chemicals and mechanical, for example from the deposition of small particles in the cracks from the matrix itself or impurities present in the water from the exposure environment. Regarding the calcium ionstransport, Huang et al (2016) asserted that the crack region with the highest ionic concentration is responsible for the deposition of calcium carbonate, crystalline material with shallow solubility water, and largely responsible for autogenous self-healing
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