The investigations on properties of self-healing concrete with crystalline admixture and recycled concrete waste

Abstract

The concept of self-healing concrete is becoming more necessary as sustainability in construction is more desirable. Amongst the current solutions in this technology are autogenous, chemical, and bacterial self-healing. It is paramount that secondary raw materials be used in the production of selfhealing concrete as a form of a sustainable solution. Therefore, in this paper, the admixture “Betocrete-CP-360-WP”, which is a crystallizing waterproofing admixture with hydrophobic effect and is 100% recyclable, has been used and its effect on the physical, chemical, and mechanical properties of concrete, as well as selfhealing capabilities of concrete, have been determined. According to the obtained results, the crystalline additive “Betocrete-CP-360-WP” has no effect on density and slightly increases the amount of entrained air in the concrete mix. However, it does decrease the workability of the concrete mixture which could prove problematic in transportation to the construction site or in concreting in general. Also, with the crystalline admixture in the concrete mix, a 60% reduction in concrete compressive strength after one day of hardening has been estimated, but after 7 and 28 days, the strength attained is within the ranges of the control samples. In addition, concrete containing Betocrete-CP360-WP was 30% less water permeable as compared to control samples. The self-healing efficiency of the concrete was determined by a water flow test through a formed crack (approximately 0.35 mm wide). This was done by gluing a plastic pipe to the top of the cracked concrete specimens and maintaining a constant pressure of the water in the pipe. The experiment was continued for 28 days, and the crack self-healing efficiency of the concrete was calculated from the differences in the amount of water passed through the crack before healing and after 7, 14, 21 and 28 days of the healing process. After 28 days of the water flow test, the cracks in the concrete with the crystalline admixture and recycled concrete dust were completely healed, while the control specimens were not.

Resistance of Concrete with Crystalline Hydrophilic Additives to Freeze–Thaw Cycles

“…When it comes to surface damage due to freeze/thaw cycles, the air-entraining agent is evidently the most effective additive for preventing damage, almost equally effective regardless of whether freezing/thawing occurs with or without salt presence, while the negative effect of the crystalline hydrophilic additive is significantly more pronounced during freezing/thawing in the presence of salt. Such research findings on the impact of the crystalline hydrophilic additive are even worse than the results presented in [51]. Specifically, Manhanga et al [51] concluded in part of their study addressing the scaling of concrete exposed to a 3% sodium chloride solution that the crystalline hydrophilic additive (in amount of 0.8% per cement weight) does not affect this type of damage caused by freeze-thaw cycles.…”

“…Such research findings on the impact of the crystalline hydrophilic additive are even worse than the results presented in [51]. Specifically, Manhanga et al [51] concluded in part of their study addressing the scaling of concrete exposed to a 3% sodium chloride solution that the crystalline hydrophilic additive (in amount of 0.8% per cement weight) does not affect this type of damage caused by freeze-thaw cycles.…”

“…Figure 10a,b confirm the conclusions regarding Figure 8a,b, namely that regarding internal damage, the air-entraining agent has shown the highest effectiveness in protecting concrete from damages caused by freeze/thaw cycles, but the crystalline hydrophilic additive at a 1% dosage (M3) has shown potential to improve concrete's resistance to freeze/thaw cycles. Furthermore, regarding internal damages, the crystalline hydrophilic additive used in this study achieved better performance in enhancing the concrete's resistance to freeze/thaw cycles compared to the crystalline hydrophilic additive used in [51]. Specifically, Manhanga et al [51] concluded, in part of their research focusing on the impact of the crystalline hydrophilic additive on the strength of cubic specimens exposed to freeze/thaw cycles in the presence of water, that the crystalline hydrophilic additive does not affect this type of damage caused by freeze-thaw cycles.…”

“…Furthermore, regarding internal damages, the crystalline hydrophilic additive used in this study achieved better performance in enhancing the concrete's resistance to freeze/thaw cycles compared to the crystalline hydrophilic additive used in [51]. Specifically, Manhanga et al [51] concluded, in part of their research focusing on the impact of the crystalline hydrophilic additive on the strength of cubic specimens exposed to freeze/thaw cycles in the presence of water, that the crystalline hydrophilic additive does not affect this type of damage caused by freeze-thaw cycles. On the other hand, Ferrara et al [55] have indeed confirmed that the velocity of the ultrasonic wave passage is higher in concrete with a crystalline hydrophilic additive compared to reference concrete during the self-healing process of cracks in concrete, leading to the conclusion that the crystalline hydrophilic additive promotes crack healing.…”

Influence of consumer motivations and perception on the adoption of smart, green, and sustainable building materials

“…Self-healing concreate is another widely discussed smart building material in the literature. Numerous techniques, including autogenous, chemical, and bacterial self-healing, are used in self-healing concrete to repair the material's structural integrity (Manhanga et al, 2022). Cracks and other damage on the building can be self-healed, thus enhancing the building's lifespan and reducing the need for expensive repairs (Chen et al, 2023).…”