Luis M. López-González

Study of the Technical Feasibility of Increasing the Amount of Recycled Concrete Waste Used in Ready-Mix Concrete Production

The construction industry generates a considerable amount of waste. Faced with this undesirable situation, the ready-mix concrete sector, in particular, has invested energy and resources into reusing its own waste in its production process as it works towards the goal of more sustainable construction. This study examines the feasibility of incorporating two types of concrete waste, which currently end up in landfill, into the production process of ready-mix concrete: the waste generated during the initial production stage (ready-mix concrete waste), and waste created when demolition waste is treated to obtain artificial aggregate. The first phase of the study’s methodology corroborates the suitability of the recycled aggregate through characterization tests. After this phase, the impact of incorporating different percentages of recycled coarse aggregate is evaluated by examining the performance of the produced concrete. The replacement rate varied between 15% and 50%. The results indicate that recycled aggregates are, indeed, suitable to be incorporated into ready-mix concrete production. The impact on the final product’s performance is different for the two cases examined herein. Incorporating aggregates from generic concrete blocks led to a 20% decrease in the produced concrete’s strength performance. On the other hand, using recycled aggregates made from the demolition waste led to a smaller decrease in the concrete’s performance: about 8%. The results indicate that with adequate management and prior treatment, the waste from these plants can be re-incorporated into their production processes. If concrete waste is re-used, concrete production, in general, becomes more sustainable for two reasons: less waste ends up as landfill and the consumption of natural aggregates is also reduced.

Exhaust Emissions from Diesel, LPG, and Gasoline Low-power Engines

Abstract In a way similar to the automotive industry, outboard emissions limits are being constantly revised, which strongly effects the development of the new engines and their compliance. During the last ten years, conventional two-stroke outboard engines, which are used for fishing and recreational boats, have thus been replaced by four-stroke engines or direct-injection two-stroke engines. The objective of this article is to compare various outboard engines and the technical solutions developed for the reduction of exhaust emissions, with special emphasis being placed on the low-power gasoline and diesel outboard engine range. A gasoline outboard engine was also transformed to allow the use of liquefied petroleum gas (LPG) and showed that this technique could be an alternative solution for the future emission limit compliance.

Adapting Buildings to the Current CTE-DB-HE: A Single-Family Housing Development in Logroño (La Rioja)

The main innovation introduced by the new CTE-DB-HE 2013 regulation for private residential housing is the mandatory limitation of energy demand and non-renewable energy consumption; such buildings, therefore, need to be simulated with official or authorised computer tools. The previous CTE-DB-HE 2009 limited energy demand, but the resulting energy demand figures were far higher than those stipulated by the current Code. A decrease in energy demand translates into final energy savings. If more efficient technologies are used, those savings can be increased. Overarching priorities include the following: a proportion of the energy used must come from renewable sources, and consumption of primary energy and CO2 emissions must be reduced. A study has been conducted on how these parameters are affected by five different building envelopes used in single-family housing developments in Logrono (La Rioja), considering prior and current regulations. The thermal transmittance figures utilised in the study are as follows: the limit values established under the CTE-DB-HE1 2009; compliant with the CTE-DB-HE 2009; the limit values established under the CTE-DB-HE1 2013; the recommended values listed in Appendix E of the CTE-DB-HE1 2013; and compliant with the current CTE-DB-HE 2013.