Key Factors Determining the Self-Healing Ability of Cement-Based Composites with Mineral Additives

Abstract

This paper reveals the relationships between key factors that determine the ability of cementitious composites to self-heal autogenously and specific measures for quantifying the effects of this process. The following material factors: water-to-binder ratio (w/b), uniaxial compressive strength and age of the composite at the time of defect formation were considered, as well as the method and degree of damage to the tested material. The subjects of this study were mortars and concretes in which Portland cement was partially replaced, to varying degrees, with mechanically activated fluidized bed combustion fly ash (MAFBC fly ash) and siliceous fly ash. The samples were subjected to three-point bending or cyclic compression tests after 14 or 28 days of aging, in order to induce defects and then cured in water for 122 days. Microscopic (MO) and high-resolution scanning (HRS) observations along with computer image processing techniques were used to visualize and quantify the changes occurring in the macro-crack region near the outer surface of the material during the self-sealing process. Techniques based on the measurement of the ultrasonic pulse velocity (UPV) allowed the quantification of the changes occurring inside the damaged materials. Mechanical testing of the composites allowed quantification of the effects of the activity of the binder-supplementary cementitious materials (SCMs) systems. The analysis of the results indicates a significant influence of the initial crack width on the ability to completely close the cracks; however, there are repeated deviations from this rule and local variability of the self-sealing process. It has been shown that the compressive strength of a material is an important indicator of binder activity concerning crack width reduction due to self-sealing. Regardless of the crack induction method, the internal material changes caused by self-sealing are dependent on the degree of material damage.

Enhancement of Autogenous Healing on Pre-Cracked PFA Concrete Using Response Surface Methodology (RSM)

“…Recently, the ability of cementitious composites with mineral additives, such as fly ash, silica fume, limestone, and others has the capacity to self-heal autogenously crack in the concrete. As well documented in Tomczak et al [11], the mineral additives improve autogenous self-healing in concrete because cementitious composites can restore the material's original integrity through a spontaneous self-healing process. Numerous researchers have proven that the presence of a newly created calcium silicate hydrate (C-S-H) phase was found to boost the selfhealing potential in cracked concrete [12,13].…”

“…Numerous studies have been conducted on the self-healing property of concrete utilizing pulverized fuel ash (PFA), commonly known as fly ash. Researchers discovered that concrete made from fly ash improves the properties of concrete due to pozzolanic activity, resulting in the sealing of small cracks in the concrete being healed as well as better results in terms of self-healing properties [9,11,15]. Depaa and Kala [20] reported on the same study on the effect of pre-cracked fly ash concrete on self-healing.…”

“…This is because the strength of concrete containing PFA has more contribution to the pozzolanic effect. Therefore, the autogenous healing in the PFA concretes was improved with the high compressive strength of concrete and dense microstructure[11]. The correlation coefficient (R 2 ) between the experimental and model-predicted values of the response variable was used to assess the goodness of the fit model.Fig.…”

A Systematic Review of the Research Development on the Application of Machine Learning for Concrete

“…Some supplementary elements such as fly ash, silica fume, or chemical combinations have been utilized to enhance the performance and strength of concrete [32][33][34][35][36]. The literature indicates that researchers are concentrating increasingly on these supplementary materials, since they are often waste materials created as a result of industrial, agricultural, and municipal processes [37][38][39][40][41]. The recycling and the widespread stockpiling of these leftovers for bulk use raise serious social and environmental problems on a global scale [42].…”

Implementation of Alternative Mineral Additives in Low-Emission Sustainable Cement Composites

“…The already tested, non-standard alternative mineral additives include i.a. ground waste expanded perlite [ 15 , 16 ], waste glass powder [ 17 , 18 ], fluidized bed combustion fly ashes [ 19 , 20 ] or alkali-activated waste or synthetic glasses [ 21 , 22 ].…”