The paper addresses several options to improve the reaction kinetics of alkali-activated low-calcium fly ash binders for soil stabilisation in road platforms. For that purpose, an experimental programme was established to assess the strength evolution, with time, of different binders, based on ash, lime, sodium chloride and alkali solutions, applied in the stabilisation of a silty sand. The tests included unconfined compression strength tests, triaxial tests and seismic wave measurements performed at different curing periods. The results were compared with a binder made of Portland cement and a commercial additive specifically designed for soil stabilisation in road applications. The activated ash mixtures with lime were the most performing producing a significant increase in the reactions development and, consequently, in the strength gain rate. The sodium chloride significantly improved the lime and lime-ash mixtures, but provided only a slight improvement in the activated ash mixtures.

With the current tendency to gradually increase the contribution of renewable energy to achieve significant proportions of the entire production, the wind farm construction rate is actually high. Because the location of the wind turbines (WTs) is dictated by factors usually independent of the foundation soil conditions, which are mostly based on energy production and consumption efficiency (e.g., average wind speeds, possibility of connecting to existing electrical networks, approval of authorities and local population, etc.), it is not uncommon for the construction sites to be unfavorable in terms of geotechnical demands. In these circumstances, the choice of the optimal foundation system is an important aspect in the design phase of a WT. The aim of this paper is to analyze, using three-dimensional (3D) numerical models and the suitability of currently available foundation solutions (based on a shallow foundation on the natural or improved ground), and compare the overall behavior with solutions based on rigid inclusions (RIs). The parametric study developed was based on a real soil profile, and all the foundation solutions are analyzed for realistic static WT loads. The assessment of the efficiency of each foundation system, as well as the subsequent comparative analysis, was performed in terms of the surface settlement on the foundation soil and the axial force and bending moment on the vertical reinforcements.

Mining is a primary sector for the national economy of many countries, but exploiting these natural resources causes negative impacts on the environment. Tailings produced during mining, called mine tailings, have to be disposed of, and for that purpose, they are often mixed with Portland cement to control environmental toxicity and improve their mechanical properties. However, the high environmental impacts of producing Portland cement are well known. In this sense, sustainable binders based on the alkaline activation of industrial wastes have been studied as an alternative to using Portland cement. This study focused on applying a sustainable binder based on the alkaline activation of fly ash to improve the mechanical performance of a mine tailing from a mine located in Portugal. Geotechnical tests and chemical analysis were conducted to characterize the mine tailing and fly ash used in the alkaline activation process. In addition, triaxial tests were performed to evaluate the mechanical performance of the specimens, with both natural and stabilized tailings. The developed study proved that stabilized tailing with activated fly ash shows promising mechanical performance showing that this approach can be an excellent alternative to using Portland cement.