No abstract

No abstract

No abstract

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.

No abstract

No abstract

Although numerous studies have proven the effectiveness of self-healing technologies in concrete, its practical application is limited to only few trials. One of the reasons lies in the lack of self-healing in-situ non-destructive evaluation methods as opposed to invasive and extensive laboratory testing. In this study, a novel Terahertz (THz) wave imaging technique is proposed as a simple, non-destructive, and non-contact measurement methodology to quantitatively evaluate the selfhealing effectiveness of cementitious materials. Experiments were conducted in fiber-reinforced cementitious composites (FRCC), which confirmed self-healing performance based on a combination of stimulated autogenous and autonomous healing by using supplementary cementitious materials (FRCC), and PVA fibers; the self-healing index was also calculated by using novel THz wave measurement and compared with existing evaluation methods. Simultaneously, sorptivity test and microstructural characterization on damaged and healed specimens were conducted as the conventional methods. As a result, the proposed THz imaging successfully quantified the self-healing performance on cementitious samples. Also, a correlation between the recovery rate (cracked/healed) measured by sorptivity test and THz wave imaging was defined.

The durability of building materials is related to the presence of cracks as they provide a fast pathway to the transport of liquid and gases through the structure. Restoration and preservation of historic buildings has been investigated through the application of novel cementitious materials, using nanoparticles such as nano-silica and silica fume. The small particle size range and the high reactivity of nanoparticles allow them to interact with calcium sources naturally present in construction materials, forming binding and strengthening compounds such as calcium silicate hydrate. Nanoparticles act as a crack-filling agent, reducing the porosity and increasing the durability of existing materials. In this study we describe the injection of nano-silica using low water pressure in hydrated cement paste. This novel technique can tailor mechanical and hydraulic properties of existing building materials using a simple and non-destructive procedure