Andrés Juan Valdés

Influence of Moisture States of Recycled Coarse Aggregates on the Slump Test

The use of recycled aggregate to produce new concretes has become increasingly widespread, and numerous studies have demonstrated that the final product performs similarly to traditional concrete. However, construction and demolition waste (CDW) presents certain characteristics which could limit its acceptance in the construction sector due to worse performance than natural aggregates. One example of this is water absorption, which in recycled aggregates reaches such high values that the amount of free water calculated for mixing the concrete is affected, consequently impacting on the concretes properties, especially consistency. This paper reports the possibility of solving this problem with a simple and inexpensive method; pre-saturation of recycled aggregates prior to adding them to the mix. The results of two different pre-treatments are compared; one consisted of immersing the aggregates in water for 10 minutes and the other, in addition to the above procedure, included a brief period of air drying and subsequent elimination of surface water from the aggregate. Both pre-treatments were found to solve the problem of consistency.

Characterization of Colliery Spoils in León: Potential Uses in Rural Infrastructures

One of the bases of sustainable development is the responsible management of natural resources, and this is the approach which has been adopted by developed countries as regards management of all kinds of waste, through the establishment of management strategies based on prevention, reuse and recycling. This article present the results of a physical, chemical and geotechnical characterization of colliery spoils stored in slag heaps in the Ciñera-Matallana coal mining area in León, Spain. The primary objectives of this research were to determine the suitability of this mining waste for use as granular material in rural and civil engineering infrastructures and to classify it according to national and international road construction standards. On the basis of the results obtained, they are proposed several possible uses (foundation and core layers in track and road embankments, granular sub-base for light traffic and top layers of embankments), although it should be noted the need for mechanical treatments as crushing or sieving and the recommendation of use of sulphate resistant cement to avoid the possible problems.

Standardization as a Driving Force of the use of Recycled Coarse Aggregate in Concrete

When recycled aggregates are used appropriately, it is possible to obtain good quality, economic and environmentally friendly building materials. The emergence in recent years of the use of recycled materials in the construction industry, specifically in the production of concrete, has met with varying degrees of success due to the barriers that the market for recycled products has still to overcome. Scientific studies have focused on the good properties presented by the coarse fraction of construction and demolition waste (CDW), leading to the formulation of various international recommendations which, although still insufficient, provide a stimulus to the use of recycled aggregates in concrete.

Limitaciones del eurocódigo 1,parte 4, en la determinación de las acciones de materiales agrícolas ensilados

New Eurocode 1, part 4, supposes a great advance in the calculation methods of actions of silaged materials in Europe and Spain. Nevertheless, it still displays limitations that must corrected, for which is essential to incorporate the findings made by the different research groups, which work for a better understanding of the behavior of silaged materials and their influence on the silo structure