Effect of crystalline admixtures on the self-healing capability of early-age concrete studied by means of permeability and crack closing tests

This paper analyzes the self-healing properties of early-age concretes, engineered using a crystalline admixture (4% by the weight of cement), by measuring the permeability of cracked specimens and their crack width. Two concrete classes (C30/37 and C45/55) and three healing exposure conditions have been investigated: water immersion at 15 °C, at 30 °C and wet/dry cycles. Specimens were pre-cracked at 2 days, to values of crack width in the range of 0.10 0.40 mm. The results show almost perfect healing capability for specimens healed under water at 30 °C, better than for specimens healed under water at 15 °C, while insufficient for the wet/dry exposure.Roig Flores, M.; Pirritano, F.; Serna Ros, P.; Ferrara, L. (2016). Effect of crystalline admixtures on the self-healing capability of early-age concrete studied by means of permeability and crack closing tests. Construction and Building Materials. 114:447-457. doi:10.1016/j.conbuildmat.2016.03.196S44745711

Evaluation of raw bagasse Ash as sand replacement for the production of engineered cementitious composites

This study aims to evaluate the possibility of using raw sugar cane bagasse ash (SCBA) as a sand replacement in engineered cementitious composites (ECC). A total of three mixtures, i.e., 0, 25%, and 50% of sand replaced with SCBA (by volume), were produced in this study. The experimental characterization of raw SCBA revealed that SCBA collected from the sugar mill consists mainly of silica and carbon with small particle size. In terms of ECC properties, the addition of SCBA caused a loss in workability and decreased the density of fresh ECC mixtures. For proper workability, higher HRWR dosages were utilized, which altered the air content of ECC mixtures (i.e., air content increased from 1.4% to 3.5%). The compressive strength of SCBA-ECC mixtures was slightly lower than the control mix. However, the tensile strength and, more markedly, the tensile ductility were enhanced compared to control. The negative effect on compressive strength was mainly attributed to the higher air content of the SCBA-ECC mixtures. The increment in ductility observed in SCBA-ECC mixtures by increasing the contents of SCBA may be attributed to the combined effect of smaller particle size of SCBA, increased air content, and the possible carbon coating of the PVA fiber

A review of self-healing concrete for damage management of structures

The increasing concern for safety and sustainability of structures is calling for the development of smart self-healing materials and preventive repair methods. The appearance of small cracks (<300 µm in width) in concrete is almost unavoidable, not necessarily causing a risk of collapse for the structure, but surely impairing its functionality, accelerating its degradation, and diminishing its service life and sustainability. This review provides the state-of-the-art of recent developments of self-healing concrete, covering autogenous or intrinsic healing of traditional concrete followed by stimulated autogenous healing via use of mineral additives, crystalline admixtures or (superabsorbent) polymers, and subsequently autonomous self-healing mechanisms, i.e. via, application of micro-, macro-, or vascular encapsulated polymers, minerals, or bacteria. The (stimulated) autogenous mechanisms are generally limited to healing crack widths of about 100–150 µm. In contrast, most autonomous self-healing mechanisms can heal cracks of 300 µm, even sometimes up to more than 1 mm, and usually act faster. After explaining the basic concept for each self-healing technique, the most recent advances are collected, explaining the progress and current limitations, to provide insights toward the future developments. This review addresses the research needs required to remove hindrances that limit market penetration of self-healing concrete technologies