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.
Highlights
Due to their attractive potential and practical value, self-healing materials have been extensively investigated over the last ten years, and significant advances have been achieved [1]
The interaction between a cracked cementitious matrix and a solution of sodium silicate was analyzed in terms of acoustic behavior by means of linear and nonlinear ultrasonic techniques
The linear ultrasonic analysis investigated the resonance modes and the acoustic transmission properties of the prisms in their intact, cracked and progressively repaired states, revealing that some changes were induced in time by the presence of the sodium silicate and that the healing mechanism created was able to virtually turn the acoustic behavior of the prisms back to their initial state, prior to crack formation
Summary
Due to their attractive potential and practical value, self-healing materials have been extensively investigated over the last ten years, and significant advances have been achieved [1]. Attention is focused on mono-component encapsulated systems using an alkaline silicate solution as a healing agent Such alkaline solutions as sodium, potassium or lithium silicates are considered to be very promising for the purpose of developing successful self-healing cementitious systems because of their low viscosity, which enables them to effectively diffuse through the cracks once released at the damage site, and owing to their chemical affinity with the cement matrix. Their good compatibility with cementitious composites is well known by the construction industry, where soluble silicates, in particular sodium silicate ( referred to as “water-glass”), already have several applications
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