Ultrasonic Monitoring of the Interaction between Cement Matrix and Alkaline Silicate Solution in Self-Healing Systems

Abstract

Alkaline solutions, such as sodium, potassium or lithium silicates, appear to be very promising as healing agents for the development of encapsulated self-healing concretes. However, the evolution of their mechanical and acoustic properties in time has not yet been completely clarified, especially regarding their behavior and related kinetics when they are used in the form of a thin layer in contact with a hardened cement matrix. This study aims to monitor, using linear and nonlinear ultrasonic methods, the evolution of a sodium silicate solution interacting with a cement matrix in the presence of localized cracks. The ultrasonic inspection via linear methods revealed that an almost complete recovery of the elastic and acoustic properties occurred within a few days of healing. The nonlinear ultrasonic measurements contributed to provide further insight into the kinetics of the recovery due to the presence of the healing agent. A good regain of mechanical performance was ascertained through flexural tests at the end of the healing process, confirming the suitability of sodium silicate as a healing agent for self-healing cementitious systems.

Ultrasonic Pulse Velocity—Compressive Strength Relationship for Portland Cement Mortars Cured at Different Conditions

“…In addition, NDT-UPV has been successfully used investigating the corrosion of mortar and concrete reinforcement [16,17], and in the study of durability of these construction materials [18][19][20][21][22][23][24]. For instance, non-destructive ultrasonic test methods have been used to monitor microcracking in concrete [24,25].…”

“…For instance, non-destructive ultrasonic test methods have been used to monitor microcracking in concrete [24,25]. Ouarabi et al used ultrasonic measurements in self-healing systems to study the kinetics of the recovery thanks to the healing agent performance [21]. They validated the capacity of the ultrasonic techniques to assess microstructural changes in concretes.…”

Impact Damage Detection in Composite Beams by Analysis of Non-Linearity under Pulse Excitation

“…To overcome the need of a preliminary modal analysis and to address the issue of a proper selection of the excitation frequency, a broadband impulsive excitation could be exploited. Rectangular pulse excitations at various amplitudes were used in [25] when applying the SSM to analyze the behavior of a cracked cementitious mortar in the presence of a thin layer of sodium silicate solution. The damage indicators adopted in [25] were the classical ones of the method, defined in the time domain.…”

Performance of Epoxy Resin Polymer as Self-Healing Cementitious Materials Agent in Mortar

“…However, the previous research indicated that the crack width that can be healed in such technique is limited to a maximum of 0.1 mm, which is not enough for practical application [ 6 ]. In addition to autogenous healing, cracks may also be automatically closed using a specific healing agent in the cement matrix [ 7 , 8 , 9 ].…”