Caracterização de estéril de mineração e sua utilização em argamassas e em compósitos cimentícios reforçados com fibras de PVA

Abstract

Waste rock from the extraction of iron ore is waste generated during mining that is disposed of in geotechnical structures such as piles, dams or pits, which require adequate monitoring to ensure the safety of these structures. The mining sector produces large quantities of this material, ensuring its availability for application in cementitious materials, however, in the literature, there are few studies on this application. The use of waste rock as a mineral addition in mortars and cementitious composites with high strain capacity is an innovative topic, which has not yet been reported in the literature. The use of waste rock represents a way of making this type of composite more sustainable, mitigating the consumption of cement and enabling the use of mining waste. The present study aimed to develop an experimental program for the physical-chemical, morphological, mineralogical and thermal characterization of waste rock and its application in mortars and ECC. According to the results of this work, waste rock is a crystalline silico-aluminous material with lamellar-shaped grains and high surface area. The characterization results were promising for its application as a filler in mortars and ECC. To produce waste rock mortars, three levels of cement replacement by waste rock were used (10%, 20% and 30%) and tests were carried out in the fresh and hardened state. In the fresh state, the waste rock did not affect the mortar mixtures, meaning there was no need to use superplasticizer. In the hardened state, the waste rock influenced the physical properties of specific mass, water absorption and void index, and the mechanical properties of compressive strength, toughness and fracture energy. Regarding to ECC mixtures, two waste rock contents (20% and 30%) and two water/(cement + waste rock) contents of 0.40 and 0.32 were evaluated. The ECCs mixtures showed strain and deflection hardening behavior, with multiple cracks formation. The specific mass of fresh ECC mixtures were little affected by the use of waste rock and the workability of the mixtures was adequate. In the hardened state, the physical properties of specific mass, water absorption and void index were affected by using waste rock, as well as the mechanical properties of compressive strength, modulus of elasticity, tensile strength, flexural strength and strain capacity. The reduction of water in the ECC mixture reduced the void index, water absorption and strain capacity of the ECC, as well as increased the compressive strength, elastic modulus, tensile strength and flexural strength. Therefore, the test results confirmed its application as a mineral addition in cementitious materials, being promising for the waste rock contents evaluated in this research (up to 30% waste).