material wastage and simplifying logistics) via the adoption of a modern wet-mix shotcrete system. Ultimately, the goal was to demonstrate that a carefully engineered shotcrete mix, and application method could yield quantifiable productivity gains while meeting the mine’s geotechnical support requirements. In the following sections, we describe the ICS implementation strategy, present key results from the trial, and discuss the broader implications for mine development practices. The role of a collaborative approach between partners (e.g, Sika, Hochschild, UNICON) is highlighted as a critical factor in the successful outcome. ICS IMPLEMENTATION AT INMACULADA 2.1 Fast-cycle shotcrete mix design At the core of the ICS approach was the development of a shotcrete mix that could gain strength very rapidly without compromising long-term quality. A wet-mix fiber-reinforced shotcrete was designed in collaboration between the mine’s engineering team and Sika’s concrete specialists. The mix incorporated: (a) Ordinary Portland cement (OPC), (b) A high-range water reducer (superplasticizer) to attain the required flow for pumping at low water: binder ratio, (c) A high-dose alkali-free set accelerator, added at the nozzle, to induce immediate setting and rapid stiffening, and (d) Macro-synthetic fibers (polypropylenebased, 40 mm length, ~4-7 kg/m³ dosage) to provide post-crack toughness and reduce reliance on steel mesh. These components were selected to work in synergy: the admixture chemistry was optimized so that the accelerator’s quick-setting action did not cause excessive slump loss in the plastic stage, and the superplasticizer maintained pumpability up to the point of spraying. Laboratory tests of the proposed mix indicated it could reach ≥1 MPa compressive strength in about 60 minutes (measured by UNE EN 14488-2), meeting the mine’s re-entry criteria which were based on empirical guidelines and local experience (e.g, EFNARC, 2009). The 1-hour strength target corresponds to the industryrecognized requirement for immediate support in freshly blasted rock to be effective against loosening and fallout (Garcia et al., 2018). By 2 hours, the mix achieved around ≥2.5Mpa and 4 hours ≥ 4.5Mpa, providing a substantial safety margin before the next blast. Table 1 summarizes the key properties of the ICS shotcrete mix versus the prior standard mix used at the mine. Table 2 shows physical properties of washed sand for shotcrete mix used at the mine.
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