Concrete self healing 3D printed and powder mix agent capsules desing for longer lasting and sustainability improvement

Concrete is the most used and produced material in the world, the high compressive resistance, and notable stability to traction efforts due to the reinforcement with steel bars, has made of it one of the best solutions for construction in history, revolutionizing architecture and engineering. Nowadays, is well known that the environment is facing a dramatic climatic crisis due to the excessive CO2 emissions, water pollution, waste, and many other factors; it is important to use wisely a material that requires such an important amount of natural resources, fuels for its production, and non totally renewable waste generation. The purpose of this research is to contribute in a field of study focused on the extension of concrete lifespan by introducing a determined amount of capsules, with the objective of producing a self healing effect able enough to fill the possible cracks originated during its use, preventing an exposition of steel bars to environmental conditions that could produce erosion or oxidation in the reinforcement, that limits or annul its tensile strength properties, giving as result the collapse of a structure. In this study, will be considered one of the most common crack cause in concrete, as it is the water and elevated presence of humidity; filtrations and waterproofing grind down, that are a frequent origin of fissures, permitting the water to access by an eroding gradually this material until having direct contact with steel bars and catalyze its oxidation transforming them into a powder with no mechanical resistance. By all this reasons, arises the idea of producing water activated capsules; small containers filled up with two possible healing agents: 1) a liquid agent: such as polyurethane, able to reunite both parts with a certain resistance gain, already developed in other studies but updated in this research by the use of a more efficient 3D printed cover with a higher humidity insulation; or 2) with an innovative powder agent developed in the present study as a blocking system to prevent the passage of water into the core of concrete; this powder, that contains cement, a petrous origin material, can be compacted by applying pressure in presence of elevated temperature to create a self standing cylindric element named "virtual capsule", setting aside the necessity of a container and presenting a longer lasting expected period, compared to liquid filling agents. This gives as result a total of 3 types of capsules: 1) 3D printed liquid filled, 2) 3D printed powder filled, 3) virtual capsule. This research includes all of the methodology, design process, variables and its solutions, development of molds and capsules, mixture design, productive process, verification tests, results, comparison between the three capsule types, suggestions for use, sustainable criteria evaluation, and recommendations for future studies.