Manufacture of artificial reefs by 3D printing using sustainable mortars

Esta tesis presenta el desarrollo de morteros sostenibles para su aplicación en impresión 3D por extrusión. Se emplearon morteros de cemento y morteros de geopolímero incorporando materiales reciclados y provenientes de desechos industriales. Los morteros se caracterizaron física y mecánicamente. Se realizó, además, un análisis de ciclo de vida para evaluar su impacto ambiental y un análisis multicriterio para elección de las mezclas óptimas. Con las mezclas óptimas, se elaboraron arrecifes artificiales impresos en 3D que se sumergieron posteriormente en distintas costas del Atlántico Norte. Los resultados mostraron que los morteros de cemento fueron más adecuados para esta aplicación y que el empleo de arrecifes artificiales sirve para fomentar la vida marina.Este trabajo ha sido cofinanciado por el Fondo Europeo de Desarrollo Regional a través del Programa Interreg Atlantic Area, en el marco del proyecto 3DPARE (EAPA_174/2016) y refleja la opinión del autor, por lo que las autoridades del programa no son responsables del uso de la información aquí incluida. Además, la culminación de esta tesis ha sido posible gracias a la Beca de Finalización de Doctorado (RESOL-2021-143-APN-DIR#CONICET) otorgada por el Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) de la República Argentina

Assessment of the environmental acceptability of potential artificial reef materials using two ecotoxicity tests: Luminescent bacteria and sea urchin embryogenesis

Ecotoxicological analysis of construction products is a relatively unexplored area at international level. Aquatic toxicity tests on construction products has been recommended recently for freshwater environment. However, the biological effects of alternative materials on marine ecosystem are still not considered. In this study, the main aim was to assess the environmental impact of alternative mortars proposed as artificial reefs (ARs) materials. The ARs specimens were developed by 3D printing, based on cement and geopolymer mortars using recycled sands of glass and seashells. For this purpose, a leaching test and two different toxicity bioassays, luminosity reduction of marine bacteria Vibrio fischeri (Microtox®) and the success of embryo-larval development of sea-urchin Paracentrotus lividus, were conducted. From the leaching results it should be noted that the mobility of all trace elements considered in both, raw materials and mortars, meet the inert landfill limits, except As, Mo, Se or Sb in the leachates geopolymer mortars. However, the results obtained from the both bioassays show low environmental acceptability for those mortars containing shell sand, probably due to the degradation of the organic matter adhered to the shells. On the other hand, cement mortars obtain better results than geopolymer mortars, regardless of the aggregate used, showing certain consistency with the leaching behaviour, since they present the lowest mobility of trace chemical elements. Therefore, the results supporting the environmental acceptability of its potential use as alternative materials in the production of ARs.This work has been supported by a) the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund by means of the research project RTI 2018-097612-B-C22