Study of the performance of waterproofing additives capable of promoting self-healing in concrete

Over time, the world of Civil Engineering has turned its attention to create structures under the concepts of sustainability and durability by reducing the consumption of raw materials and avoiding the emission of toxic gases that harm the environment. In addition, the scientific research community has focused on the study of resilient and intelligent materials capable of promoting multiple benefits, both economic and ecological, promoting sustainability. One of the most used materials in the construction world is concrete due to its multiple benefits, versatility in its use, excellent mechanical properties. However, with the pass of time, the works carried out with concrete require maintenance to ensure the superb condition of its design; this means using time and resources. Therefore, if one could guarantee that concrete works could heal themselves when required, not only would large amounts of resources be saved, but it would also change the way construction has been perceived so far. Self-healing concrete is a mechanism that is naturally or artificially induced. For example, concrete with damage can activate these mechanisms and initiate a self-healing process, the cracks will close, and mechanical properties lost are partially recovered. This work proposes the study of the influence of two crystallizing additives in promoting self-healing concrete, such as Admixplus and Multiseal, products of the company Supershield Srl. This experimental campaign has three phases which can be summarized as: pre-damage, where the specimens to be studied are created, the control specimens are distinguished from those where the respective additives are added and are kept in different conditions of exposure to the samples, submerged in water or exposed to air; damage, where the damage is created employing a compressive strength test, in displacement controlled mode; post-damage, whereafter the procedure of making the cracks, the specimens are kept for a certain period in different exposure conditions (submerged in water, exposed to air or with sprayed water). At each stage, measurements are made using the ultrasonic pulse velocity test, which provides us with knowledge regarding cracked specimens in each campaign phase. The compressive strength test results, the influence of the test setups, the exposure conditions, the additives used, and the visual evaluation of self-healing are analyzed and discussed. The present study results show, regarding the initial exposure conditions, more significant percentage increases in the samples compressive strength exposed in air, the specimens immersed in water show higher values of resistance to compression. Therefore, Admixplus is more beneficial in terms of the increase in compression resistance values. Likewise, the force-controlled test setup influences the results, incrementing compressive strength values compared with the specimens under displacement-controlled setup. As part of the UPV results obtained, it is evidenced the presence of water is essential to promote Self-Healing, the more water the specimens are exposed, the better the results obtained from the Self-healing.