Self-healing concrete has the potential to optimise traditional design approaches; however, commercial uptake requires the ability to harmonize against standardized frameworks. Within EU SARCOS COST Action, different interlaboratory tests were executed on different self-healing techniques. This paper reports on the evaluation of the effectiveness of proposed experimental methodologies suited for self-healing concrete with expansive mineral additions. Concrete prisms and discs with MgO-based healing agents were produced and precracked. Water absorption and water flow tests were executed over a healing period spanning 6 months to assess the sealing efficiency, and the crack width reduction with time was monitored. High variability was reported for both reference (REF) and healing-addition (ADD) series affecting the reproducibility of cracking. However, within each lab, the crack width creation was repeatable. ADD reported larger crack widths. The latter influenced the observed healing making direct comparisons across labs prone to errors. Water absorption tests highlighted were susceptible to application errors. Concurrently, the potential of water flow tests as a facile method for assessment of healing performance was shown across all labs. Overall, the importance of repeatability and reproducibility of testing methods is highlighted in providing a sound basis for incorporation of self-healing concepts in practical applications.

This work studies the polymerization process of four different commercially available silicon-based polymers and their consequent effect on surface tension and water transport properties of natural stones used in architectural monuments, essential for modeling and predicting the durability of natural stones against weathering action of aqueous solutions. The four products studied consisted of two ethyl-silicate based materials, an alkyl-alkoxy siloxane oligomer with hydrophobic agents and finally, a silane/siloxane emulsion. In all cases, the morphology of the amorphous material deposited into the pore network of stones was examined by electron microscopy (SEM). The polymerization process was studied by infrared spectroscopy (FTIR) on both inert surface and porous stone substrate. The treated stone specimens were further tested after polymerization in terms of determination and comparison of water absorption coefficient, open porosity, pore size distribution (mercury intrusion porosimetry) and surface tension (contact angle measurements) properties. According to the analysis, the modification of the wetting properties of the stone surface should be related rather with the chemistry than the microstructure of the xerogels alone.

A methodological approach, followed for the development of compatible repair mortars, for joining archaeological stone fragments of marl limestones, is presented. The development of compatible mortars for joining archaeological stone fragments requires an in-depth study of mechanical and microstructural properties of both stone substrate and mortar mixtures. Therefore, this work focuses on the evaluation of the stone-repair mortar interface, based on the interpretation of mechanical properties of both individual stone and mortar specimens as well as, of joined stone specimens with different types of adhesive mortar mixtures. The cementing material used in the different repair mixtures was: white cement, natural hydraulic lime and lime-metakaolin mixed binder. The binders were further modified with metakaolin to adjust hydraulicity and mechanical strength. The evaluation of adhesion strength and compatibility parameters was based on unconfined compression, three-point flexural bending and four point bending tests. It was shown that mechanical properties of join mortars can be adjusted by modifying the binder chemistry. Moreover, it was proved that adhesion strength is more relevant to the total surface area and porosity of the binder rather than compressive strength of the mortar.

In the present study the strength recovery of Ordinary Portland Cement (OPC) mortars due to the autogenic self‐healing mechanism was examined following two experimental approaches: compression tests and Ultrasonic Pulse Velocity (UPV) measurements. The focus was given on a quantitative approach for the evaluation of the inflicted damage degree and the healing capacity using experimental data. It is noteworthy that for the calculation of the healing capacity, the damage degree was taken into consideration. The results have shown that the compressive strength values can be correlated with the UPV measurements by an exponential relationship, which suggests that the use of a non‐destructive technique, such as UPV, can be a fast and reliable method for the evaluation of damage degree as well as the quantification of healing capacity. Overall, it was shown that controlled damage and self‐healing capacity of cementitious materials can be measured and quantified.