Experimental Investigation of a Novel Formulation of a Cyanoacrylate-Based Adhesive for Self-Healing Concrete Technologies

Abstract

The selection of an appropriate healing agent is critical to the success of vascular and mini-vascular networks. In self-healing concrete technology, commercially available cyanoacrylate (CA) adhesives have been shown to produce good strength recoveries; however, their rapid curing rate and short shelf-life make them unsuitable for site application. The aim of this study was to develop a modified cyanoacrylate (n-CA) with an extended shelf-life suitable for incorporation in a self-healing system. A series of n-CAs were formed from a commercial Ethyl Cyanoacrylate adhesive mixed with acrylic acid (AA) and nitro-anthraquinone (nAq) in varying ratios. When encapsulated within 3D printed mini-vascular networks (MVNs), the n-CAs remained dormant in liquid form for up to 5 days. The contact angle between the n-CAs and the cement mortar substrate, as measured via the sessile drop technique, decreased significantly with increasing AA content. The mechanical properties (bond strength) and the polymerization hardening of the n-CAs were evaluated over a curing period of 7–21 days, via a series of pull-off tests using cement mortar cubes. The 4:1:02 (CA:AA:nAq) n-CA formulation showed a significant increase in bond strength from 14 to 21 days, with a ceiling value of 2.6 MPa, while the 2:1 (CA:AA) n-CA formulation exhibited a good bond strength after 21 days (1 MPa). Nuclear Magnetic Resonance (NMR) conducted on the n-CAs suggested the formation of several new polymeric species, whilst differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) on the pre- and post-printed MVN material confirmed no significant changes in chemistry with no evidence of polymer degradation. Considered together, the experimental results show the potential for different n-CA formulations to act efficiently as a healing agent.

A Comparative Study of the Applications and Prospects of Self-healing Concrete / Biocrete and Self-Sensing Concrete

“…Stiffness recovery of approximately 40% is achieved by sodium silicate-based healing agent. This highlights the efficiency of the d-TETs concept as a system that enables stiffness and strength regaining with little use of the healing agent [16].…”

“…To address the challenge of the limited shelf life of single-component healing agents and enhance the healing effectiveness of the concrete-TET system, modifications were made to the TETs design. Specifically, co-axial hollow ligament TETs (d-TETs) were manufactured, enabling the storage of bicomponent healing agents [16].…”

“…The d-TETs proved successful in storing these bi-component agents which helps in healing without premature mixing and curing. Additionally, the d-TETs effectively busting and released the healing agents when the crack width reached 0.35 mm [16].The incorporation of superabsorbent polymers (SAPs) has gained popularity as an effective means to enhance the self-healing capability of cementbased materials, leading to potential cost savings associated with manual repairs.It is essential to evaluate their self-healing capacity, ensuring infrastructure's structural integrity and safetyto promote the widespread adoption of SAP additives (in large-scale construction projects), [18]. Following one cycle of damage and healing, significant recovery in both strength and stiffness was observed.…”

Computational Fracture Modeling for Effects of Healed Crack Length and Interfacial Cohesive Properties in Self-Healing Concrete Using XFEM and Cohesive Surface Technique

“…The idea of sustainable composite materials has gained popularity recently, including self-healing concrete (SHC) which became a hot topic due to its ability of automatic crack repairing without human intervention to prolong the service life and reduce the maintenance cost of structures [1]. Many laboratory studies and experiments have been conducted to investigate the fracture of the capsules and the bonding interaction between capsules and the concrete matrix, as well as the healing efficiency and fracture mechanism, such as in [2,3]. However, computational modeling has shown advantages in modeling physical phenomena that are challenging and difficult to investigate experimentally, such as capsular clustering [4].…”

Research on the production of cement composites with autonomous self-healing performance

“…The self-healing mechanism is produced because of chemical reactions of a self-healing agent embedded directly, embedded in capsules or introduced through vascular networks when designing and making the concrete mixture. Among the most used systems are superabsorbent polymers [9], [10], crystalline mixtures [11], [12], microencapsulated sodium silicate [13], tubes with adhesives [14][15][16] and bacteria [17][18][19][20].…”