In this work, the effects of replacing the aggregates of self-compacting concrete by air-cooled blast furnace slag have been analysed. Different mixes have been manufactured by substituting the fine and coarse natural aggregates by air-cooled blast furnace slag. The fracture energy and the tensile and compressive strength have been determined for each mix. The self-compacting properties of the mixes, or the absence of them, have been observed. The main goals of this research are the decrease of the price of aggregates, reduction of the industrial waste, and attenuation the rate of consumption of natural resources. The results show that the self-compactability of the concrete is gradually lost as the slag content is increased, thus, when the ratio of replacement is low, the concrete keeps the self-compacting properties. Nevertheless, the loss of self-compaction affects the mechanical properties by increasing its strength. An air-cooled blast furnace slag did not present problems of heavy metals leaching.

The aim of this study is twofold. First, to assess the effect of the sonication process on the optimal dispersion of GO sheets for nanostructural reinforcement of cement pastes, as there is currently no clear criterion on this effect in the literature. For this purpose, in the first stage, the GO content in distilled water was fixed at 0.03% by weight, and the sheets were dispersed using different levels of ultrasonic energy, ranging from 0 J/mL to 2582 J/mL. In the second stage, to analyze the modification of pore structure due to the addition of GO sheets in different ratios (0–0.06% by weight) and its relationship with the mechanical and fracture properties of reinforced cement pastes. According to the results, it has been determined that the incorporation of GO sheets into the matrix alters the mechanical and fracture behavior, varying depending on matrix pore size and GO particle size. The addition of GO leads to a reduction in the average size of macropores (greater than 8 µm) of 13% for a dosage of 0.45% in weight and micropores (between 8 and 0.5 µm) in a 64% for the same composition with non-sonicated GO, although the total volume of pores in these ranges only decreased slightly. This reduction is more pronounced when the GO has not been sonicated and has larger particle size. Sonicated GO primarily modifies the range of capillary pores (<0.5 µm). The addition of GO with the highest degree of dispersion (465 nm) did not show significant improvements in compressive strength or Young’s modulus, as the cement used contains a significant volume of macropores that are not substantially reduced in any composition. Adding 0.030% ultrasonicated GO achieved a 7.8% increase in fracture energy, while an addition of 0.045% resulted in a 13.3% decrease in characteristic length, primarily due to the effect of capillary and micropores.

This paper analyzes the dynamic soil–structure interaction (SSI) of a railway bridge under the load transmitted by high-speed trains using the finite element method (FEM). In this type of bridges, the correct analysis of SSI requires proper modeling of the soil; however, this task is one of the most difficult to achieve with the FEM method. In this study, we explored the influence of SSI on the dynamic properties of the structure and the structure's response to high-speed train traffic using commercial finite element software with direct integration and modal superposition methods. High-speed trains are characterized by the high-speed load model (HSLM) in the Eurocode. We performed sensitivity analyses of the influence of several parameters on the model, such as the size and stiffness of the discretized soil, mesh size, and the influence of the dynamic behavior of the excitation. Based on the results, we make some important and reliable recommendations for building an efficient and simple model that includes SSI. We conducted a dynamic analysis of a full model of a general multispan bridge including the piers, abutments, and soil and identified the impact factors that affected the design of the bridge. The analysis revealed that the methodology we propose allows for a more accurate determination of the dynamic effects of the passage of a train over the bridge, compared to the simpler and more widely used analysis of a directly supported isolated deck, which tends to overestimate the impact factors.