Carbon footprint is one of the most widely used tools for assessing the environmental impacts of the production and utilization of concrete as well as of the components derived from it, representing the amount of carbon dioxide and other greenhouse gases associated with this product, expressed as CO₂ equivalents. In this paper, carbon footprint was used to compare the environmental performance in the production phase of a concrete made with both recycled and crushed virgin limestone aggregates, using a life cycle analysis methodological approach. Research outcomes revealed, as expected, that carbon dioxide equivalent emissions decreased slightly as the use of recycled aggregates increased. Emissions for concrete with 0.5 w/c were between 347 and 351 kg of CO₂‐e/m³. It was also corroborated that cement is the material with the greatest influence on greenhouse gas emission generation in the concrete’s production phase, regardless of the use of recycled or virgin aggregates.

The use of recycled aggregates in structural concrete production has the inconvenience of increasing the fluid transport properties, such as porosity, sorptivity, and permeability, which reduces the resistance against penetration of environmental loads such as carbon dioxide and chloride ion. In this paper, behavior of ten concrete mixtures with different percentages of coarse aggregate replacement was studied. The recycled material was recovered by crushing of concrete rubble and had high absorption values. The results showed that it is possible to achieve good resistance to carbonation and chloride penetration with up to 50% replacement of recycled coarse aggregate for 0.5 water/cement ratio. Finally, new indexes for porosity and sorptivity were proposed to assess the quality of concrete.

In this research, the effect of the addition of zirconium oxide-synthesized nanoparticles on the microstructural development and the physical–mechanical properties of cement mortars with limestone aggregates was studied. Zirconia nanoparticles were synthesized using the co-precipitation method. According to XRD analysis, a mixture of tetragonal (t) and monoclinic (m) zirconia phases was obtained, with average crystallite sizes around 15.18 and 17.79 nm, respectively. Based on the ASTM standards, a mixture design was obtained for a coating mortar with a final sand/cement ratio of 1:2.78 and a water/cement ratio of 0.58. Control mortars and mortars with ZrO₂ additions were analyzed for two stages of curing of the mortar—7 and 28 days. According to SEM analysis, mortars with ZrO₂ revealed a microstructure with a high compaction degree and an increase in compressive strength of 9% on the control mortars. Due to the aggregates’ characteristics, adherence with the cement paste in the interface zone was increased. It is suggested that the reinforcing effect of ZrO₂ on the mortars was caused by the effect of nucleation sites in the main phase C–S–H and the inhibition of the growth of large CH crystals, and the filler effect generated by the nanometric size of the particles. This produced a greater compaction volume, suggesting that faults are probably originated in the aggregates.

Una de las fuerzas motrices del crecimiento económico es la innovación, que incrementa la productividad mediante la creación de nuevos métodos productivos, tecnologías, productos y empresas. Este artículo examina un instrumento que apoya este proceso, el capital de riesgo, y destaca la necesidad de un sistema de financiamiento para cada fase de la innovación. Comienza por ilustrar el rezago de América Latina en materia de innovación. Luego analiza en general las dificultades con que tropieza el financiamiento de la innovación, así como el aporte del capital de riesgo a su superación. Enseguida examina cómo esos obstáculos se materializan en la región y, teniendo en cuenta la experiencia de Brasil y Chile, de qué manera se les ha enfrentado. En relación con varios de los temas tratados se abordan aspectos atingentes a importantes problemas de desarrollo del sistema financiero.

Carbon nanotubes have demonstrated their versatility in the manufacture of various devices such as molecular probes, pipes, cables, fibers and springs. Recently, they have been used in cement composites to improve their physical and mechanical properties, but there are still many questions regarding the physical-mechanical behavior that can be achieved in structural concrete. In view of this, the present work aimed at the designing of concrete mixtures with multi-walled carbon nanotubes additions, in order to minimize the unfavorable conditions caused by high absorption limestone aggregates and to improve the mechanical properties compared to regular concretes. Results showed improvements in the microstructural development, compressive strength (7 -11%), splitting tensile strength (14-16%) and modulus of elasticity of the concrete (8-12%). However, some issues related to the functionalization and dispersion of the nanotubes in the mixtures remain to be solved to advance their utilization.