Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high “N50” and moderately high “92-200”) of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92-200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 μm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).The support of the Islamic Development Bank (IDB) scholarship, collaborating with the Cambridge Commonwealth, European and International Trust (CCEIT) for the first author’s PhD research, is highly appreciated. The authors also thank Wai Yuk Lau for his assistance and suggestions in the shrinkage measuring experiments.This is the author accepted manuscript. The final version is available from the Institute of Physics via http://dx.doi.org/10.1088/0964-1726/25/8/08400