Mine tailings (MTs) that are rich in aluminosilicates can be reused to create geopolymer via alkaline activation as an alternative to portland cement concrete for construction and building applications. However, pure MTs may lack sufficient aluminum or amorphous aluminosilicates to facilitate geopolymerization that competes with traditional concrete. It is essential, therefore, to add supplemental aluminum source materials and amorphous aluminosilicates to adjust the $\mathrm{Si}:\mathrm{Al}$ ratio to change the geopolymeric cell structures of MTs. The study presented in this paper utilized Class F fly ash (FA) as the amorphous supplement for better reactivity or aluminum source to alter the $\mathrm{Si}:\mathrm{Al}$ ratio that can be reacted through alkali activation to facilitate better geopolymerization. First, a series of laboratory tests was conducted to obtain the characterizations of the FA. Then geopolymer samples using different amounts of FA were produced by activating the $\mathrm{MTs}+\mathrm{FA}$ mixtures with 10 M NaOH solutions at a moisture ratio of 16% cured for 7 days with a slightly elevated temperature. Finally, uniaxial compression tests (UCTs) were applied to evaluate the influence of the addition of different amounts of FA (5%, 10%, 15%, and 20%) on the compressive behaviors. In addition, microscopic insights with different FA additions were evaluated regarding morphology, chemical bonds, and mineralogy. Results show that adding FA supplements based on the initial moisture content and curing conditions increased the mechanical behavior of the geopolymer specimens, followed by a decrease due to insufficient water for a chemical reaction. However, due to the water loss during the curing process, improvement in mechanical properties began to decrease when the FA was increased to 20%.

Precipitation estimate is important for earth science studies and applications, and it is one of the most difficult meteorological quantities to estimate accurately. For regions such as Peru, reliable gridded precipitation products are lacking due to complex terrains and large portions of remote lands that limit the accuracy of satellite precipitation estimation and in situ measurement density. This study evaluates and cross-examines two high-resolution satellite-based precipitation products, a global rain-gauge interpolated precipitation product, and a Weather Research and Forecast (WRF) model that simulated precipitation for a ten-year period from 2010 to 2019 in the Peruvian Andes region across the Pacific coast, Andes, and in the Amazon. The precipitation estimates examined in this study are the Integrated Multi-SatellitE Retrievals for GPM (IMERG), Multi-Source Weighted-Ensemble Precipitation (MSWEP), Global Precipitation Climatology Center product (GPCC), and a 3 km grid spacing WRF-based regional climate model (RCM) simulation. The evaluation and cross-examination were performed at sub-daily (6 h), daily, and monthly time scales, and at various spatial resolutions. The results show that the WRF simulation performs as well as, if not better than, GPM IMERG in the low precipitation and dry regions but becomes inaccurate in wet regions. GPM IMERG is more suitable for higher precipitation and wet regions, and MSWEP shows a systematic overestimation over the study area. It is therefore important to choose the most suitable precipitation product based on research needs and climate condition of the study for the challenging Peruvian Andes region.

Beneficiation of industrial wastes, such as mine tailings (MTs), through development of alternative eco-friendly geopolymer binders for construction composites offers a twofold environmental benefit, as it reduces the demand for cement and it increases the sustainability of industrial processes by creating a value-added product from an industrial byproduct. While MTs have the requisite composition for use as a geopolymer precursor, they are often low-reactive. This study explored the effect of Class C Fly Ash (FAc) on the geopolymerization of low-reactive gold MTs. A 10 M sodium hydroxide (NaOH) solution was used as the alkaline activator with four different concentrations of FAc (5, 10, 15 and 20 wt.%). The results indicated that the combination of FAc with the low-reactive gold MTs improved the physicochemical stability of the final geopolymerized samples, with a 95–120% increase in compressive strength, compared to the geopolymer samples of only low-reactive gold MTs. Although some of the strength improvement could be attributed to geopolymerization of the FAc itself, the presence of the FAc also improved the reactivity of the MTs, increasing the geopolymer production of the MTs. This study documents the positive effects of the FAc on gold MTs with low-calcium content and their conversion into sustainable inorganic composite geopolymers for the construction field.