Miren Etxeberria

Properties of concrete blocks prepared with low grade recycled aggregates

Low grade recycled aggregates obtained from a construction waste sorting facility were tested to assess the feasibility of using these in the production of concrete blocks. The characteristics of the sorted construction waste are significantly different from that of crushed concrete rubbles that are mostly derived from demolition waste streams. This is due to the presence of higher percentages of non-concrete components (e.g. >10% soil, brick, tiles etc.) in the sorted construction waste. In the study reported in this paper, three series of concrete block mixtures were prepared by using the low grade recycled aggregates to replace (i) natural coarse granite (10mm), and (ii) 0, 25, 50, 75 and 100% replacement levels of crushed stone fine (crushed natural granite <5mm) in the concrete blocks. Test results on properties such as density, compressive strength, transverse strength and drying shrinkage as well as strength reduction after exposure to 800 degrees C are presented below. The results show that the soil content in the recycled fine aggregate was an important factor in affecting the properties of the blocks produced and the mechanical strength deceased with increasing low grade recycled fine aggregate content. But the higher soil content in the recycled aggregates reduced the reduction of compressive strength of the blocks after exposure to high temperature due probably to the formation of a new crystalline phase. The results show that the low grade recycled aggregates obtained from the construction waste sorting facility has potential to be used as aggregates for making non-structural pre-cast concrete blocks.

Dredged marine sand as construction material

Dredging works are usually required to maintenance activities in many ports all over the world and represents a huge volume of disposal material. The use of dredged aggregates can be considered in several applications as erosive process control, coastal stabilization, beach replenishment, production of construction materials (clay, bricks, aggregates) or construction works (foundation fill, dikes, etc.). Researches revealed the feasibility of dredged marine sand (DMS) in the construction of base and sub-base harbour pavements incorporating this material to hydraulic binder mixes (cement or lime) in order to improve the grading of aggregates and correct the granular skeleton. Its main objective is to improve the packing and to obtain the compressive properties required for geotechnical applications. In this work the study of DMS from the Port of Sant Carles de la Rapita (Tarragona, Spain) as construction material is presented. The analysis of its influence on paste, mortar and concrete production is described. Two experimental phases were carried out once chemical and physical characteristics of DMS were determined. At first, pastes and mortars were made using CEM II/A-M 42,5R cement, different percentages of DMS on replacement of raw sand and plasticizer additive in order to obtain fresh and hardened properties of the mixes studied. After that, DMS was used in the production of concretes as fine aggregates. A pilot experience was carried out with concrete port pavements produced in industrial scale. Fresh and hardened properties of the concretes were determined and compared to the control mix. Results show satisfactory behaviour of DMS as construction material when incorporated in concrete as fine corrective sand.This work deals with the study of dredged marine sand (DMS) from the Port of Sant Carles de la Ràpita (Tarragona, Spain) as construction material. The analysis of its influence on paste, mortar and concrete production is described. Two experimental phases were carried out after the chemical and physical characteristics of DMS were determined. Firstly, pastes and mortars were made using CEM II/A-M 42.5R cement, different percentages of DMS in replacement of raw sand and plasticiser additive in order to obtain the fresh and hardened properties of the mixes studied. After that, DMS was used for the production of concretes as fine aggregates. A pilot study was carried out with harbour concrete pavements produced at industrial scale. The results were compared to those of the control mixes and proved the satisfactory behaviour of DMS as construction material when incorporated into concrete as granular corrector Dans ce travail, l’étude d’un sable marin dragué DMS originaire du port de Sant Carles de la Ràpita (Tarragone, Espagne) comme matériau de construction est présenté. L’analyse de son influence sur des pâtes, mortiers et bétons est décrite. Deux phases expérimentales ont été effectuées après avoir déterminées les caractéristiques chimiques et physiques du DMS. Tout d’abord, des pâtes et des mortiers ont été réalisés en utilisant un ciment CEM II / AM 42.5R, avec différents pourcentages de remplacement du sable naturel par le DMS. L’utilisation des additifs plastifiants a été envisagée afin d’obtenir les propriétés requises aux états frais et durci des mélanges étudiés. Ensuite, le DMS a été utilisé comme granulats fins dans la fabrication de bétons. Une expérience pilote a été réalisée avec des pavements portuaires en béton produits à une échelle industrielle. Les résultats ont été comparés aux mélanges de contrôle et ont montré un comportement satisfaisant du DMS comme matériau de construction lorsqu’il est incorporé dans le béton comme correcteur granulaire.

Propiedades del hormigón de árido reciclado fabricado con adiciones, activa e inerte

El trabajo de investigacion presentado en este articulo describe las propiedades fisicas, mecanicas y de durabilidad de los hormigones fabricados con el 25% y 100% de arido grueso reciclado utilizando adiciones activa e inerte (microsilice y filler de escoria de arco electrico). La fase experimental realizada consta de dos etapas: En la etapa 1 se realizo un estudio fisico-mecanico (resistencia a compresion y velocidad de ultrasonido); En la etapa 2 se evaluo la durabilidad de los hormigones reciclados fabricados con adiciones mediante los ensayos de difusion de cloruros, resistividad, absorcion y porosidad, lo que permitio comparar los resultados con el hormigon convencional fabricado con similar dosificacion. Los resultados demuestran que los hormigones reci-clados obtienen propiedades fisicas y mecanicas inferiores al hormigon convencional. Sin embargo, la durabilidad del hormigon reciclado fabricado con adiciones activas mejora las propiedades del hormigon convencional.