Durability and Self-Sealing Examination of Concretes Modified with Crystalline Waterproofing Admixtures

Abstract

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered to play a significant role in its durability, Permeability Reducing Admixtures (PRA) is one of the ideal solutions for protecting structures exposed to water and waterborne chemicals. Different products have been developed to protect concrete structures against water penetration, which, based on their chemistry, performance, and functionality, have been categorized into PRA. As it has previously been tested by authors and proven to be a promising solution, a hydrophilic Crystalline Waterproofing Admixtures (CWA) has been considered for this study. This paper aims to investigate how this product affects concrete’s overall freeze–thaw resistance, self-sealing, and corrosion resistance. Various testing methods have been utilized to examine the performance of CWA mixtures, including the linear polarization resistance, resonance frequency testing, half-cell potential, and self-sealing test. The reinforcement corrosion potential and rate measurements indicated superior performance for CWA-treated samples. After being exposed to 300 freeze–thaw cycles, concrete mixes containing CWA—even non-air-entrained ones—showed a Durability Factor (DF) of more than 80% with no signs of failure, while non-air-entrained control samples indicated the lowest DF (below 60%) but the greatest mass loss. The major causes are a reduction in solution permeability and lack of water availability in the concrete matrix—due to the presence of CWA crystals. Furthermore, evidence from the self-sealing test suggests that CWA-treated specimens can seal wider cracks and at a faster rate.

Effect of a Crystalline Admixture on the Permeability Properties of Concrete and the Resistance to Corrosion of Embedded Steel

“…The obtained results of electrochemical measurements seem to indicate that the presence of the admixture CCADM in concrete could reduce the scattering of the corrosion initiation period and could delay the corrosion initiation (from 110 to 170 days, according to Figure 13), in the experimental conditions of this work. This outcome is in fairly good agreement with findings of previous works [16,19]. However, the small number of tested specimens (from a statistical point of view) does not allow for unequivocal acceptance of this conclusion.…”

“…There is also some evidence that CAs can increase the resistance of concrete to water capillary absorption [15]. Hence, it seems that CAs can be considered as PRAH and PRAN [16]. Regarding the resistance of concrete to Cl − ion penetration, the reported results seem to be inconclusive: some authors found that the incorporation of an admixture characterized by crystallization activity had no detectable effect on the Cl − diffusion coefficient (natural diffusion test) of a Portland cement concrete incorporating fly ash [17], while other researchers detected some reduction in the Cl − diffusion coefficient (natural diffusion through ponding test) when incorporating a CA to a Portland cement and a Portland-Limestone cement [14].…”

“…Very few publications [16,19] have addressed the effect of CA on the corrosion of steel reinforcement embedded in concrete. Both mentioned articles have concluded that the incorporation of CAs to reinforced concrete specimens can delay the onset of the steel corrosion [16,19].…”

Avaliação do desempenho mecânico e absorção capilar de concretos com incorporação de aditivos cristalizante submetidos a danos nas primeiras idades

“…Após essa interação, o CA forma cristais insolúveis em água (compostos por sais inorgânicos, como o silicato de sódio e o silicato de potássio), obstruindo poros e trincas, assim aprimorando a eficácia do processo de cura do concreto. Adicionalmente, o CA intensifica a densidade do gel de C-S-H, reforçando a resistência do concreto à entrada de íons agressivos [18]. Para à formação de cristais minerais na presença de água, conforme relatado no estudo de HU et al [19], esses produtos químicos ativos como 2nCa (O -R -OH) 2 na equação (1) continham tanto o componente hidrofílico (-OH) quanto o componente hidrofóbico (-R), essas reações dos cristalizantes estão descritas pelas equações (1) e (2): 2 (1)…”

Research and Development of Self-Waterproofing Concrete for Tunnel Lining Structure and Its Impermeability and Crack Resistance Characteristics

“…In conclusion, numerous researchers have confirmed the beneficial effects of various concrete-reinforcing materials [ 28 , 29 , 30 , 31 ], analyzing and elaborating on the reinforcement materials’ mechanisms based on extensive experimentation. The previous research has laid a solid foundation for the further studying of the impermeability of concrete [ 32 , 33 ] and has achieved good results in the development of self-waterproofing concrete [ 34 ], such as the addition of waterproofing admixtures [ 35 ] and crushed ceramic jars [ 36 ] in concrete. However, previous studies have mainly focused on the addition of admixtures, but there are still many shortcomings, such as relatively few studies on the co-blending of different types of admixtures.…”