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The objective of this work was to develop a chemical admixture to make concrete capable to heal its fissures autonomously and, consequently, mitigate the concrete’s reinforcement corrosion due to the ingress of aggressive agents. For that, polymeric microcapsules built by a shell of urea-formaldehyde-melamine (UFM) and a core of methylmethacrylate were developed and added to the concrete to further evaluation. The concrete specimens containing 0%, 3% and 6% of the proposed microcapsules (mass of microcapsules / mass of cement) were subjected to destructive and non-destructive tests. The water absorption and the mechanical tests i.e., compressive strength and indirect tensile strength (Brazilian test) were carried out to characterize concrete, while the electrochemical impedance spectroscopy (EIS) and the non-destructive ultrasonic pulse velocity (UPV) tests were conducted to evaluate the concrete self-healing ability. These tests showed that the proposed admixture was able to heal the concrete’s fissures partially. In addition, it was concluded that the samples with 3% of microcapsules presented higher self-repairing rates. Despite the microcapsules developed in this work have presented a satisfactory self-healing efficiency, their effectiveness looks to be affected by the mixing procedure once part of them is broken during the process.

La arañita roja (Oligonychus yothersi) ha sido catalogada como una plaga de poca importancia en los cafetales de Costa Rica, lo cual afecta levemente solo en la época seca en los bordes del cultivo. El único ataque fuerte de O. yothersi se reportó entre 1963 y 1965 en el Valle Central, relacionado con la caída de ceniza del volcán Irazú. Durante el año 2017 el volcán Poás lanzó cantidades importantes de ceniza que fueron llevadas por el viento en dirección suroeste y se relacionó con un fuerte ataque de arañita roja entre noviembre de 2017 y marzo de 2018, en un área de 4155 ha ubicadas sobre 1200 m de altura entre los cantones de Poás y Naranjo de Alajuela. La población decreció por efectos del combate biológico natural lo cual se relaciona con una población abundante de 5 especies de depredadores. Se evaluó el control con acaricidas químicos con buenos resultados al aplicar productos a base de propargite y azufre.