# Performance of Ore Sand as Aggregate for Interlocking Blocks
## 1 Introduction  
The construction industry continues to grow due to housing shortages, the need for modern infrastructure and urbanization, and other factors. Its activity is responsible for a large demand for natural resources, contributing to the consumption of 4.27 billion tons of cement [1] and 50 billion tons of aggregates (gravel and sand) per year worldwide [2]. Sand and gravels are mined worldwide, with aggregates accounting for the largest volume of solid material extracted globally [3]. In Brazil, approximately 500 million tons of aggregates are consumed annually. These aggregates are mostly employed in cementitious materials used for construction and civil-engineering applications [4]. As a result, the search for alternative raw materials is essential to creating a more sustainable construction industry. Mine tailings can be a promising source of substitutes for natural raw materials, with a worldwide availability that can reach up to 60 billion tons [5]. All countries that conduct ore extraction generate mining waste. Brazil, India, China, and Australia are major producers of iron ore in the world and are consequently the largest sources of iron ore tailings [6]. It is estimated that in Western Australia, 632 million tons of iron ore tailings are produced per year [7]; in China, approximately 600 million tons are generated [8]; and in India, the data are not precise, but the amount is up to 20 million tons [9]. Around the world, this resource has been usually stockpiled behind dams, withattendant latent environmental and social risks [10; 11]. In the state of Minas Gerais (Brazil) alone, 290 million tons per year of tailings are generated from mining activity [12]. Iron ore mining generates large amounts of tailings (on the order of 0.48 tons for each 1.0 ton of iron ore concentrate), and this amount tends to increase with the depletion of the metal concentration in the deposits [13]. Studies have shown that iron ore tailings (IOTs), also called ore sand (OS), have characteristics that can enable them to be effectively used in construction as a substitute for natural sand [14]. Mine tailings have been studied in terms of their use as a fine aggregate for the production of concrete [15; 16], geopolymers [17; 18] ceramic materials [19; 20], and pigments [21]. Along the same lines, mine tailings can be used for the production of interlocked blocks, which have been utilized on a large scale for paving in Brazil. The growth in the production of interlocked blocks is due to their reduced repair cost, easy installation and reusability; more than 90% of the blocks are reused. [PERSON] et al. [13] systematized the recovery of iron ore tailings using the criteria of classification, potential, quantity/viability, and applicability for four possible uses: asphalt pavement; aggregate for pavers; aggregate for mortar; and aggregate for ceramic products. Through the critical index developed by the author, the use in block pavers allows for IOTs to be valued and used in symbiosis with industry. [PERSON] et al. [22] investigated the properties of interlocking concrete block paver mixed with IOT as a partial replacement for cement. For M25 concrete, the addition of varying levels of iron ore tailings resulted in an increase in compressive strength with IOT levels from 5% to 15% and decrease in compressive strength for IOT levels from 15% to 25%. [PERSON] et al. [23] studied the use of IOTs as a fine aggregate in the production of interlocking concrete blocks, replacing natural aggregate in proportions from 10 to 80%. Physical analyses, environmental analyses (leaching and dissolution), and mechanical tests were performed. The authors concluded that IOTs can be technically and environmentally used for the production of precast concrete blocks. According to Brazilian standards (NBR 9781 [24]), the fundamental materials for the manufacture of interlocking blocks are binders, aggregates, and water, with the use of additives and pigments being allowed.