Steam curing effect on the properties of fly ash high performance recycled aggregates concrete

The aim of this study is to encourage the use of Recycled Concrete Aggregate (RCA) in High Performance Concrete (HPC) with fly ash. Three types of coarse RCA sourced from medium to high strength concretes were employed in 100% replacement. In order to boost their mechanical performance at early age, steam curing was assessed. The physical, mechanical and durability properties of Recycled Aggregate Concretes (RAC) were compared to those from Natural Aggregate Concrete (NAC). According to the results, natural aggregates could be completely replaced by RCA if they are sourced from similar parent HPC. Lower quality RCAs decreased the mechanical and durability behavior of HPC. However, the properties of RAC had higher long-term improvements than those from NAC due to the influence of fly ash. Despite steam curing produced higher early-age compressive strength, it had longterm negative effects. Nevertheless, RACs were less affected by long term effects of steam curing.Postprint (published version

Properties of plain concrete produced employing recycled aggregates and sea water

The final publication is available at Springer via http://dx.doi.org/10.1007/s40999-017-0229-0The generation of construction and demolition waste (C&DW) is a noteworthy environmental and economic concern. The development of new applications in which Recycled Mixed Aggregates (RMA) can be used will lead to a reduction of landfills growth. Moreover, the use of seawater shall represent another advance in sustainability due to the consequent reduction of fresh water consumption, which can be a limited resource in certain areas. Although seawater is not generally recommended for concrete production, especially in reinforced concretes, seawater could be a viable replacement for fresh water in the production of plain concretes. This study intends to analyse the possibility of using RMA and seawater in the production of concrete to be used in port sites. This study is based on three different parameters: cement class, water source and RMA content. The results highlighted the beneficial effects of using type III cement, especially with regard to durability properties. The concretes produced employing RMA and type III cement achieved lower value of sorptivity coefficient and higher values of ultrasonic pulse velocity (UPV), chloride ion penetration resistance and electrical resistivity than those produced with natural aggregates and type I cement. Moreover, the use of seawater in concretes with type III cement not only produced higher density and lower absorption capacity but also higher mechanical properties by creating a denser cement matrix, which proved to suffer low decrease by RMA addition.Peer ReviewedPostprint (author's final draft

Inertial measurent units and their application to mobile robot localization

Resumen del trabajo presentado al seminario celebrado en el Instituto de Robótica e Informática Industrial (IRII-CSIC-UPC) el 6 de marzo de 2014.Peer Reviewe

Aigua i sanejament

Es tracta d'una extensa publicació que en el seu subtítol, “Accions locals per a aconseguir objectius mundials”, concreta el seu objectiu principal: fer difusió d'experiències concretes locals en zones urbanes d'ingressos mitjans i baixos, amb l'adaptació de les qual a altres circumstàncies locals ajuden a la consecució de dos de les fites de l'Objectiu de Desenvolupament del Mil·lenni núm. 7 de “Garantir la sostenibilitat ambiental”.Esta extensa publicación concreta en su subtítulo -“Acciones locales para alcanzar objetivos mundiales”- su objetivo principal: hacer difusión de experiencias concretas locales en zonas urbanas de ingresos medios y bajos, con cuya adaptación a otras circunstancias locales ayuden a la consecución de dos de las metas del Objetivo de Desarrollo del Milenio nº 7 de “Garantizar la sostenibilidad ambiental”.Peer Reviewe

Map-based localization for urban service mobile robotics

Mobile robotics research is currently interested on exporting autonomous navigation results achieved in indoor environments, to more challenging environments, such as, for instance, urban pedestrian areas. Developing mobile robots with autonomous navigation capabilities in such urban environments supposes a basic requirement for a upperlevel service set that could be provided to an users community. However, exporting indoor techniques to outdoor urban pedestrian scenarios is not evident due to the larger size of the environment, the dynamism of the scene due to pedestrians and other moving obstacles, the sunlight conditions, and the high presence of three dimensional elements such as ramps, steps, curbs or holes. Moreover, GPS-based mobile robot localization has demonstrated insufficient performance for robust long-term navigation in urban environments. One of the key modules within autonomous navigation is localization. If localization supposes an a priori map, even if it is not a complete model of the environment, localization is called map-based. This assumption is realistic since current trends of city councils are on building precise maps of their cities, specially of the most interesting places such as city downtowns. Having robots localized within a map allows for a high-level planning and monitoring, so that robots can achieve goal points expressed on the map, by following in a deliberative way a previously planned route. This thesis deals with the mobile robot map-based localization issue in urban pedestrian areas. The thesis approach uses the particle filter algorithm, a well-known and widely used probabilistic and recursive method for data fusion and state estimation. The main contributions of the thesis are divided on four aspects: (1) long-term experiments of mobile robot 2D and 3D position tracking in real urban pedestrian scenarios within a full autonomous navigation framework, (2) developing a fast and accurate technique to compute on-line range observation models in 3D environments, a basic step required by the real-time performance of the developed particle filter, (3) formulation of a particle filter that integrates asynchronous data streams and (4) a theoretical proposal to solve the global localization problem in an active and cooperative way, defining cooperation as either information sharing among the robots or planning joint actions to solve a common goal.Actualment, la recerca en robòtica mòbil té un interés creixent en exportar els resultats de navegació autònoma aconseguits en entorns interiors cap a d'altres tipus d'entorns més exigents, com, per exemple, les àrees urbanes peatonals. Desenvolupar capacitats de navegació autònoma en aquests entorns urbans és un requisit bàsic per poder proporcionar un conjunt de serveis de més alt nivell a una comunitat d'usuaris. Malgrat tot, exportar les tècniques d'interiors cap a entorns exteriors peatonals no és evident, a causa de la major dimensió de l'entorn, del dinamisme de l'escena provocada pels peatons i per altres obstacles en moviment, de la resposta de certs sensors a la il.luminació natural, i de la constant presència d'elements tridimensionals tals com rampes, escales, voreres o forats. D'altra banda, la localització de robots mòbils basada en GPS ha demostrat uns resultats insuficients de cara a una navegació robusta i de llarga durada en entorns urbans. Una de les peces clau en la navegació autònoma és la localització. En el cas que la localització consideri un mapa conegut a priori, encara que no sigui un model complet de l'entorn, parlem d'una localització basada en un mapa. Aquesta assumpció és realista ja que la tendència actual de les administracions locals és de construir mapes precisos de les ciutats, especialment dels llocs d'interés tals com les zones més cèntriques. El fet de tenir els robots localitzats en un mapa permet una planificació i una monitorització d'alt nivell, i així els robots poden arribar a destinacions indicades sobre el mapa, tot seguint de forma deliberativa una ruta prèviament planificada. Aquesta tesi tracta el tema de la localització de robots mòbils, basada en un mapa i per entorns urbans peatonals. La proposta de la tesi utilitza el filtre de partícules, un mètode probabilístic i recursiu, ben conegut i àmpliament utilitzat per la fusió de dades i l'estimació d'estats. Les principals contribucions de la tesi queden dividides en quatre aspectes: (1) experimentació de llarga durada del seguiment de la posició, tant en 2D com en 3D, d'un robot mòbil en entorns urbans reals, en el context de la navegació autònoma, (2) desenvolupament d'una tècnica ràpida i precisa per calcular en temps d'execució els models d'observació de distàncies en entorns 3D, un requisit bàsic pel rendiment del filtre de partícules a temps real, (3) formulació d'un filtre de partícules que integra conjunts de dades asíncrones i (4) proposta teòrica per solucionar la localització global d'una manera activa i cooperativa, entenent la cooperació com el fet de compartir informació, o bé com el de planificar accions conjuntes per solucionar un objectiu comú

Influence of the quality of recycled aggregates on the mechanical and durability properties of high performance concrete

The final publication is available at Springer via http://dx.doi.org/10.1007/s12649-016-9637-7The main objective of this experimental work is to analyse the effect of recycled aggregates (RA), on the basis of the study of the various qualities, of the physical, mechanical and durability properties of high performance concrete (HPC). Five types of recycled aggregates: three coarse RA sourced from parent concretes of 100, 60 and 40 MPa, as well as one coarse mixed recycled aggregate and one fine ceramic waste aggregate were used as replacement for natural aggregates (NA). Two types of coarse NA and two types of river sands were employed for concrete production. On the basis of the findings of our research it was determined that the reduction in quality and the increase in the amount of RA substitution produced a decline in the properties of HPC. According to our analysis of the mechanical properties, a 100 % replacement of coarse NA for recycled concrete aggregates can be employed, providing the RA has been sourced from a 60 MPa minimum-strength concrete. Nevertheless, durability behaviour was greatly influenced by the use of RA, and consequently replacement ratios of high quality RA should be reduced to 50 % to achieve similar behaviour patterns to those of NA concrete. Moreover, severe reductions of RA qualities (sourced from 40 MPa strength concretes or mixed waste) only permitted 20 % replacement ratios on HPC production. However, those concretes containing fine ceramic RA (up to 30 %) reached higher compressive strength, higher chloride-ion penetration resistance and higher improvements of durability properties at longer ages than those concretes produced using NA concrete.Peer ReviewedPostprint (author's final draft

Structural behaviour of prestressed concrete sleepers produced with high performance recycled aggregate concrete

The final publication is available at Springer via http://dx.doi.org/10.1617/s11527-016-0966-6A comparative analysis of the structural behaviour of prestressed concrete sleepers made with high performance concrete (HPC) and high performance recycled aggregate concrete (HPRAC) is presented in this study. Two types of HPRAC sleepers were tested, using 50 and 100% of recycled concrete aggregate (RCA) in replacement of coarse natural aggregates. The RCA employed in this research was sourced from crushing rejected HPC sleepers. The aim of this study was to determine through analysis if the HPRAC sleepers’ behaviour fulfilled the European minimum requirements standards for prestressed concrete sleepers and compare their experimental behaviour with that of the HPC sleepers. The three types of prestressed concrete sleepers were subjected to static load tests at rail-seat and centre section (positive and negative load). In the centre section tests a comparative study between the experimental results and the proposed values of four assessment methods of ultimate capacity was carried out. Dynamic load and fatigue tests were also performed at the rail-seat section. The HPRACs and HPC sleepers met all the structural requirements for prestressed concrete sleepers. The experimental results determined the satisfactory performance of the HPRAC-50 and the HPRAC-100, which was very similar to that of the HPC sleepers. The load–strain behaviour recorded via the use of strain gauges on the prestressing bars revealed slightly higher stiffness of the HPC sleepers. The values obtained from the four assessment methods of ultimate capacity were also accurate when applied to HPRAC.Peer ReviewedPostprint (author's final draft

Some Formal Considerations on the Generation of Hierarchically Structured Expressions

In this note we define a machine that generates nests. The basic relations commonly attributed to linguistic expressions in configurational syntactic models as well as the device of chains postulated in current transformational grammar to represent distance relations can be naturally derived from the assumption that the combinatorial syntactic procedure is a nesting machine. Accordingly, the core of the transformational generative syntactic theory of language can be solidly constructed on the basis of nests, in the same terms as the general theory of order, an important methodological step that provides a rigorization of Chomsky's minimalist intuition that the simplest way to generate hierarchically organized linguistic expressions is by postulating a combinatorial operation called Merge, which can be internal or external. Importantly, there is reason to think that nests are a useful representative tool in other domains besides language where either some recursive algorithm or evolutionary process is at work, which suggests the unifying force of the mathematical abstraction this note is based on

The assessment of ceramic and mixed recycled aggregates for high strength and low shrinkage concretes

The final publication is available at Springer via http://dx.doi.org/10.1617/s11527-018-1244-6Very few studies on recycled aggregate concretes (RC) have been extended to the use of recycled ceramic and mixed aggregates in relation with high strength concretes. In the main they concentrate only on the analysis of the physical and mechanical properties. This study deals with the investigation of the influence that different percentages (up to 30% substitution for natural aggregates) of high porous ceramic and mixed recycled aggregates have over the plastic, autogenous and drying shrinkage of the concretes. The physical and mechanical properties as well as the chloride resistance were also determine in order to assess the viability of the use of ceramic and mixed recycled aggregates in high strength concretes. The results revealed that the employment of highly porous recycled aggregates reduced the plastic and autogenous shrinkage values of the concrete with respect to those obtained by conventional concrete (CC). Although the total drying shrinkage of the recycled concrete proved to be 25% higher than that of the CC concrete, the CC concrete had in fact a higher shrinkage value than that of the RCfrom7 to 150 days of drying. It can be concluded that the RC concrete produced employing up to 30% of fine ceramic aggregates (FCA, with 12% of absorption capacity) achieved the lowest shrinkage values and higher mechanical and chloride ion resistance. In addition, the concrete produced with low percentage (10–15%) of recycledmixed aggregates also had similar properties to conventional concrete.Peer ReviewedPostprint (author's final draft