Influência da substituição de agregado fino e água de amassamento por resíduos industriais na produção de argamassa e concreto alternativo

Abstract

The increasing demand for more spaces in industrial sanitary landfills and the correct management for final disposal of waste require new technological alternatives for its reuse. In this sense, aiming to reduce the consumption of drinking water and river sand in civil construction, mortars and concrete were produced with river sand replaced by 0, 25 and 50% of Waste Foundry Sand (ADF) contaminated with phenolic resin, as well as mixing water by sugarcane vinasse (0, 20, 40, 60, 80 and 100% replacement). Three ADFs were used, being named by the amount of resin present, being ADF1 (low resin content), ADF2 (high resin content) and ADF2T (high resin content treated). Initially these residues were studied separately, in mortar (smaller scale), in order to evaluate their influence on the morphological and physical-mechanical properties of the mortars and later, the proportions with the best performances were applied in the production of a new alternative concrete. The results showed that sugarcane vinasse, due to the presence of sucrose in its composition, resulted in a delay in hardening when used in up to 20% for water replacement, in addition to increased workability, in proportions higher than 60 %. In addition, the mechanical results of the mortars with up to 60% replacement showed similar performances to the control mortar in the periods of 28 and 91 days of curing. Durability tests showed that sucrose contributes to the reduction of water loss in the hydration process, reducing accessible pores and penetration susceptible to weathering, resulting in more durable materials. The substitution of river sand for different ADF showed that the greater amount of chemical contaminant in the ADF2 particle was the main factor for the marked reduction of the mechanical resistance (up to 50%), since the sand particles involved with resin present low adhesion with the cement matrix. Leaching tests showed that the phenolic resin present in the ADF presents levels above the normative limits for ADF2 and ADF2T. However, when analyzing the broken and crushed mortars, it was observed that the alkaline cement matrix contributed to an even greater release of total phenols. Finally, concretes were developed with both residues for structural application. Using 60% vinasse replacing water and 25% of ADF2T replacing natural sand, according to previous results, a concrete with 94% of the mechanical strength compared to the control concrete was obtained, with workability between 10 and 16 cm and low porosity, being able to have structural application with conventional concrete (ABNT NBR 8953:2015), as well as some types of pavements and elements of foundations. It is concluded that these industrial residues present satisfactory mechanical properties for application in mortars and alternative concretes. However, more efficient treatments should be studied for the total removal of the phenolic resin from the ADF, allowing its application in cementitious materials.