Showing papers in "Materiales De Construccion in 2013"

Rice husk ash as a source of silica in alkali-activated fly ash and granulated blast furnace slag systems

Abstract: This study assesses the viability of using an agro-industrial by-product, rice husk ash (RHA) from a Colombian rice company’s combustion facility, as a total replacement for the commercial sodium silicate ordinarily used in alkaliactivated binders. Fly ash (FA), granulated blast furnace slag (GBFS) and binary 50FA:50GBFS blended pastes were activated with a mix of sodium hydroxide and either sodium silicate or one of two types of RHA. The pastes were characterised for strength, mineralogy and microstructure. The findings showed that the agro-industrial by-product can be used to yield alkali-activated materials with 7-day mechanical strengths on the order of 42 MPa. The study confirmed that both amorphous silica and part of the crystalline silica present in RHA participate in the alkaline activation process, providing the alkalinity is suitably adjusted.

Durabilidad del hormigón armado expuesto a condiciones agresivas

Abstract: Reinforced concrete is the most widely used construction material in the world. The combination of high compressive strength, afforded by concrete and, and the excellent mechanical properties that characterise steel make it an ideal composite for all manner of structures. One of the main weaknesses of this material, however, is that when the concrete is exposed to aggressive environments, in particular high concentrations of chloride ions or carbon dioxide, reinforcing steel corrodes, shortening service life. This article reviews the state of the art on concrete durability, along with the conditions that affect its useful life by inducing reinforcing steel corrosion. It also discusses the prevention and control methods, in particular electrochemical prevention and rehabilitation techniques, that have been developed to mitigate the problem.

Effect of mixes made of coal bottom ash and fly ash on the mechanical strength and porosity of portland cement

Abstract: New additions to the cement are needed to achieve a more sustainable and durable construction material. Within this context, bottom ashes can be used as a main constituent of Portland cements when it is mixed in an optimized proportion with fly ashes. The mechanical characteristics of standarized mortars made of mixes of pulverized coal combustion bottom and fly ashes are studied. The mortars were made of ordinary Portland cement (CEM I 42.5 N) and mixes of bottom ashes with fly ashes in similar proportions to those of CEM II/A-V, CEM II/B-V and CEM IV/A (V). Summing up, it can be said that the utilization of bottom ashes mixed with fly ashes in replacement levels from 0% to 100% do not affect significantively on the mechanical caracteristics of the mortars considered in the present study which had an addition maximum content of 35%.

Influencia de diferentes condiciones de curado en la estructura porosa y en las propiedades a edades tempranas de morteros que contienen ceniza volante y escoria de alto horno

Abstract: In this work, the evolution of the microstructure, durability properties and mechanical strength of mortars made with commercial cements, which contain fly ash (between 21% and 35%) and ground granulated blast-furnace slag (between 66% and 80%), were studied These mortars were exposed to three different environments during their hardening, an optimum laboratory condition, and two environments representing a mild Atlantic climate and a Mediterranean climate, respectively As a reference, ordinary Portland cement mortars were also tested The microstructure was characterized using mercury intrusion porosimetry Regarding durability, the capillary suction coefficient and non-steady-state chloride migration coefficient were determined Compressive strength was studied too The tests were performed at 7, 28 and 90 days The main conclusion of this work is that cements with slag and fly ash hardened under environmental conditions of Atlantic and Mediterranean climates, can develop good service properties after three months of hardening

Comportamiento mecánico de columnas de hormigón armado reforzadas con mortero reoplástico

Abstract: The present research fits in the general thematic of the renovation of existing building with special attention to concrete structures. A series of tests have been performed with the aim to define the best solution in strengthening a deteriorated structure with a rheoplastic mortar reinforcement. Three types of possible structural reinforcing renovation on reinforced concrete pillars have been considered, with special attention to adhesion between materials with different chemical-physical and mechanical characteristics. The crack patterns obtained on the specimens have been analyzed to demonstrate the relevance of an appropriate thickness of the reinforcement to obtain an effective mechanical behavior of the reinforced concrete element over time.

Influencia del número de llaves en la resistencia a cortante de juntas secas postensadas

Abstract: The shear strength of dry joints plays an important role in the design of prestressed segmental structures. However, the formulations of different design codes do not conform to the behavior of multiple-keyed joints. This paper ana - lyzes the fracture behavior of dry keyed joints under shear loading, focusing on the influence of the number of keys on the joint capacity and its average shear stress. It has been developed a finite element model of four different types of joints, with a number of keys varying between one and seven. The results show that the average shear stress transferred across the joint decreases with the number of keys but this effect is less appreciated as the prestressing stress increases. In this paper it is presented a formula of adjustment of the obtained numerical results including a factor with the dependence on the number of keys.

Ariadne´s house (Pompeii, Italy) wall paintings: A multidisciplinary study of its present state focused on a future restoration and preventive conservation

Abstract: This paper deals with the development of a multidisciplinary study on the current state of conservation of Ariadne's house (Pompeii, Italy), a domus of great archaeological value. The aim of this study is to undertake the preventive conservation actions required and increase the knowledge about its conservation and to generate discussions and points of view for a future restoration. Environmental studies, electromagnetic radiation measurements, study of materials and a photographical study were carried out. Those studies revealed that the rooftops covering the analyzed rooms resulting in adverse weather conditions causing grave damage to the conservation of the wall paintings. Thus, between 2009-2010 the rooftops were changed and new environmental studies were conducted. Studies of materials showed that the paintings match in execution and composition with those reported by other authors. The salts from modern mortars from previous restorations were affecting frescoes, also it is described a thin grayish surface layer from environmental contaminants.

Effect of different forms of silica on the physical and mechanical properties of gypsum plaster composites

Abstract: Gypsum plaster/silica composites prepared by dry blending (0.2-10 %) natural sand, silica fume or silica gel and subsequently hydrated. Their physical and mechanical properties, including normal consistency, setting time, apparent porosity, bulk density and compressive strength, were determined after hydration for 7- and 28-days. The results indicated that adding different forms of silica lowered the bulk density and increased the normal consistency, setting time, apparent porosity and, to some limited extent, compressive strength of the composites. This improvement in properties can be attributed to the existence of silica in the interstitial pores in the hardened plaster matrices. While most of the composites revealed only scant rises in compressive strength, their composition was beneficial in so far as it included either a readily available low-cost constituent (sand) or industrial by-products. Consequently, the formed plaster-silica composites are of economic value, contribute to a cleaner environment by minimizing waste and can be used for applications where high porosity, lightweight units are required or recommended for low-cost buildings.

Diseño de mezclas de hormigón reciclado mediante el método Volumen de Mortero Equivalente (EMV): Validación bajo el contexto español y su adaptación al método de diseño de Bolomey

Abstract: A new method for proportioning recycled aggregates concrete (RAC) is used to check its feasibility under the Spanish context. First, an extensive experimental campaign has been done, with the purpose of check and analyze the applicability of the EMV method with two Spanish recycled concrete aggregates (RCA). The aim of the second part of the investigation, was to elaborate an adaptation of the EMV method to Bolomey methodology (1), using a 20% weight replacement of coarse natural aggregates (NA) for RCA, and so, with this, comply with the Spanish Instruction for Structural Concrete (EHE 2008). Slump, air content, fresh and hardened densities, compressive strength and modulus of elasticity were determined and analyzed, in order to check the concrete properties. Finally, it was observed that, the EMV method is viable, and its adaptation, results in concrete mixes with similar or better properties than the natural aggregate concrete and RAC conventionally prepared.

Shear strengthening of reinforced concrete members with CFRP sheets

Abstract: In light of their excellent mechanical properties and other advantages over conventional systems for repairing and rehabilitating structures, fibre-reinforced polymers (FRPs) are commonly used to enhance the shear strength of RC members. Because of the relatively recent application of the technique in civil engineering, however, it is addressed in very few recommendations or guides. While the design guides in place contain a single, well defined and generally accepted procedure for calculating bending moments, they collectively propose a wide variety of numerical models for shear, none of which is universally acknowledged. The present article focuses on the calculation of ultimate shear strength and describes an experimental study in that context conducted on reinforced concrete beams retrofitted with unidirectional carbon fibre reinforced polymer (CFRP) fabric.

Análisis de Ciclo de Vida para el ecodiseño del sistema Intemper TF de cubierta ecológica aljibe

Abstract: The construction industry is one of the less sustainable activities on the planet: with a consumption of 40% of the materials entering the global economy and the generation of 40–50% of the global output of greenhouse gases. The biggest environmental impact caused by buildings is generated during their use phase due to the energy consumption for thermal conditioning. Addition of green elements to buildings is used to improve energy efficiency of buildings. In this study Life Cycle Assessment (LCA) methodology has been applied to quantify the environmental impact of the green roofs materials to analyze its environmental profile. The identification of hot spots of the system permits an ecodesign strategy that effectively reduces environmental burdens associated with roof construction, optimizing the environmental performance. The results identify the high environmental impact associated to the structure, the important contribution of the felt wick irrigation system and the extruded polystyrene thermal insulation.

Utilización de nuevas materias primas y residuos industriales para mejorar las posibilidades de uso de los materiales cerámicos del área de Bailén (Jaén)

Abstract: Raw materials used by the ceramic industry in Jaen (southern Spain) consist of mixtures of carbonated clays from the Guadalquivir Basin and red clays from the Iberian Massif. The mixtures formulation usually obeys empirical experience developed by this industry for many generations. This work evaluates different possibilities of using these raw materials to manufacture new ceramic products on the basis of clay physical-chemical properties and analyzes limitations to produce high added value products. As an alternative to overcome these limitations, the mixture of these clays with raw materials from near regions (pyrophyllite clay) and with different industrial wastes is proposed. These wastes are screen glass from monitors and oil impregnated diatomaceous earth. The study of the technological properties shows that the new mixtures are suitable for the processing of ceramic products in which structural and thermal insulating properties are improved or kept.

Viabilidad de utilización de una pasta de cemento con nanofibras de carbono como ánodo en la extracción electroquímica de cloruros en hormigón

Abstract: In the application of the electrochemical chloride extraction (ECE) technique, traditionally, the Ti-RuO2 wire netting has been used as the external anode. This article provides the results of the research based on the use of conductive cement paste with addition of carbon nanofibers (CNF) as anodes and its application in ECE. The tests were developed in concrete specimens previously contaminated with chloride. The efficiencies achieved were compared with those obtained using a traditional anode (Ti-RuO2) and cement pastes with the addition of other carbonaceous materials. The results show the feasibility of using conductive cement paste with CNF as the anode in the electrochemical extraction of chlorides in concrete, finding similar efficiencies to those obtained with traditional Ti-RuO2 wire netting but with the added advantage that it can be adapted to complex structural geometries as it can be applied as a paste.

Lightweight concrete with EVA recycled aggregate for impact noise attenuation

Abstract: The purpose of this study is to evaluate the acoustic performance of lightweight concrete with ethylene vinyl acetate copolymer (EVA) residues to reduce impact noise on floors. Three types of concrete with three different mix proportions were evaluated. The method adopted includes the characterization of water absorption, voids and density of the samples. The experimental study of noise impact followed the procedures of ISO 140. The results indicate that the lightweight concrete with EVA recycled aggregate can reduce impact noise levels by up to 15 dB and the highest percentage of coarse aggregate EVA does not entail a higher acoustic performance.

Study about the capillary absorption and the sorptivity of concretes with Cuban limestone aggregates

Abstract: The objective of this study was to demonstrate the possibility to obtain concretes in Cuba with values of effective porosity below of 10%, using limestone aggregates with high levels of absorption (higher than 1% in many cases), and values of Sorptivity below of 5 x 10-5 m/s1/2 as is established in the document prepared by the DURAR Latin Working Group, for structures exposed to very aggressive environments. The experimental results showed that the use of the trial method of capillary absorption of Goran Fagerlund, were obtained concretes with effective porosity below of the 10%, for water/cement ratios of 0.4 and 0.45, but the values of sorptivities were very high. Nevertheless the subsequent use of the trial method of the ASTM C1585, that use cylinders probes with bigger depth and different processing, permits to obtain the desired sorptivity values for water/cement ratios of 0.4 and 0.45 whenever would be fulfilled the Good Practices of the Construction.

The acoustic absorption of textile curtains on the function of the fullness

Abstract: Acoustic absorbing materials are applied to reduce noise levels in a room. They are also used to adjust the reverberation time an acoustic enclosure to use for which it´s designed. There are multi-purpose rooms for conferences, concerts, cinemas, etc. In this case, the acoustic absorbent materials should be changed according to use. Curtains can be an easy way to modify the acoustics of a room based on usage. This paper presents a study of the acoustic absorption of different curtains under actual placement. The study was performed in a reverberant chamber. It takes into account different textiles. It also takes into account different air plenums and different fullness to pucker. It can be seen in the results, good acoustic behavior of such systems. The acoustic absorption of different fabrics, air plenums and plicate of textiles (fullness) are compared in this work. The good acoustic behaviour of these systems is observed in the results.

Experimental and analytical study about the compressive behavior of eps sandwich panels

Abstract: This study presents a detailed characterization of the behavior of EPS sandwich panels subject to normal load taking into account several variables. For that, two experimental programs were performed, leading to the proposal of an analytical formulation to estimate the maximum load resisted. The results obtained show how the height of the panel, the material properties, the position and configuration of the reinforcement may affect the resistance of panels. Special attention should be given to the eccentric position of the reinforcement, which may reduce considerably the maximum load resisted. Some recommendations about the optimum placement of the reinforcement are proposed.

Estudio de la fluencia de una calcarenita: la Piedra de San Julián (Alicante)

Abstract: Este trabajo ha sido financiado por la Universidad de Alicante bajo los proyectos uausti11–11 y gre09–40 y por la Generalitat Valenciana bajo el proyecto gv/2011/044.

Estudio de laboratorio sobre utilización de zeolita natural versus zeolita sintética en la fabricación de mezclas semicalientes

Abstract: Zeolite can be used as an ingredient in warm bituminous mixes to reduce manufacturing temperatures. The zeolite for this purpose is usually synthetic, but natural zeolite can also be used. The research presented in this paper analyzed the use of natural zeolite from Cuba in the form of sand and filler as an additive in warm asphalt mixes and compared it to asphalt mixes with synthetic zeolite. The mixes were given the Marshall tests, and their moisture sensitivity and stiffness modulus values were also obtained. The results showed that both types of mix had a similar performance, which was only slightly lower than that of the reference mix. The use of different dosages of natural zeolite in the mixes gave the best results when the zeolite was incorporated as filler. This study demonstrated that the use of natural zeolite is an effective way of reducing the temperature of bituminous mixes.

Bloques de hormigón ligero con áridos reciclados de EVA: una contribución a la eficiencia térmica de paredes exteriores de edificios

Abstract: The regions with lots of shoe production suffer environmental impacts from waste generation during manufacturing of insoles and outsoles. Research conducted in Brazil has demonstrated the technical feasibility to recycle these wastes, especially Ethylene Vinyl Acetate (EVA), as lightweight aggregate, in the production of non-structural cement blocks. This article presents an evaluation of thermal performance with measurements of temperature variation in mini walls (1 m2) built with different materials, including various kinds of EVA block and ceramic bricks. Tests have shown efficient thermal performance for masonry blocks with EVA. These results and supplementary estimates contribute to add value to the EVA block, considering that there are good expectations that the component, with the new geometry proposed, can contribute to the energy efficiency of buildings, highlighting its suitability to most Brazilian bioclimatic regions.

Comportamiento de Sistemas Provisionales de Protección de Borde de polietileno de alta densidad frente a cargas estáticas y de impacto

Abstract: We have tested under static and dynamic load temporary edge protection systems (TEPS) formed by a continuous fence, some are made of high density polyethylene (HDPE) and others have been manufactured using a composite material, adding glass fiber at a matrix of HDPE at a rate of 4%. Tests under static and impact have been performed according to standard UNE-EN 13374, class systems A and B. It has been found the influence of aging on TEPS and samples of the same materials as the TEPS. All tested TEPS exceed the strength requirements and accidental load and requirements compared to dynamic loads. The incorporation of glass fibers results in a composite material with a modulus of elasticity higher and significantly less creep. We haven’t seen dependence on the results with the degree of aging or in SPPB or in the samples.

Influence of different technological-environmental parameters on the evolution of resistance of concrete, produced in the Province of Valencia

Abstract: In this article on the basis of analysis of the influence of different technological-environmental parameters, such as the type of cement, water/cement ratio, initial curing temperature, time of conservation work, content of cement, additions, additives and consistency in the evolution of the concrete compressive strength, obtained a calculation equations and some graphs to estimate the resistance evolution of the concrete HA-25/B/20/IIa and HA-30/B/20/IIa from 3 to 28 days for each initial temperature curing interval specified and for the sample of concrete. So are based on 67.782 data of different compressive strength of prepared concrete in the province of Valencia during the years 1996 to 2011, that has allowed to compare the equations obtained from regression with a significant database.

Métodos granulométricos en la caracterización del árido reciclado para su uso en hormigón estructural

Abstract: Recycled aggregate produced at construction and demolition waste plants is frequently used as an ingredient in structural concrete Nevertheless, the physical, chemical and mechanical properties of this aggregate must be supervised in order to ensure the quality of the final product Of these properties, one of the most important is particle size which depends to a great extend on the process used to manufacture the aggregate and it directly affects the consistency, workability, uniformity, and mechanical strength of concrete as well as its density, compactness, permeability and resistance to wear This paper analyzes recycled aggregate samples with various size grading methods to determine their potential use in concrete On the one hand, results have showed that some differences between different methods existed; on the other hand the manufacturing process should be modified so that the particle size of the recycled aggregate complied with the guidelines in the EHE-08 Code

Evaluación del dispositivo Pavement Quality Indicator (PQI) en la determinación de la densidad in situ de mezclas fabricadas con emulsión bituminosa

Abstract: The Pavement Quality Indicator (PQI) is a non-nuclear gauge used for the on-site density measurement of asphalt pavements without the need to extract core samples. Previous studies of hot asphalt mixes found that PQI density readings were very similar to laboratory density measurements of pavement cores. This paper describes the first stage of a research project whose objective is to analyze PQI density measurements of mixes manufactured with an asphalt emulsion binder. The PQI density variability for such mixes was verified and compared with the results obtained with other on-site methods for measuring pavement density.

‘Materiales de Construcción’ Journal, 2003-2012: a bibliometric analysis

Abstract: The aim of the present work was to make a bibliometric analysis of research articles and technical notes published in the journal ‘Materiales de Construccion’ between 2003 and 2012. Authors’ productivity and collaboration, affiliation and nationality of authors, collaboration amongst institutions using techniques of social networks analysis, and the impact factor of the journal were analyzed. The results show high levels in authors’ diversification and collaboration; high number of institutions but a low level of collaboration among them; and a big increase of impact factor during all the period. The main conclusion of this work is that ‘Materiales de Construccion’ has evolved positively since 2003 to 2012, becoming a quality journal in its area.

Polished Stone Value Test and its relationship with petrographic parameters (hardness contrast and modal composition) and surface micro-roughness in natural and artificial aggregates

Abstract: El objetivo de este trabajo es establecer, por un lado, las relaciones existentes del CPA con las caracteristicas petrograficas de los aridos, asi como su microrrugosidad superficial y, por otro, las diferencias de comportamiento entre aridos naturales y artificiales. Los resultados indican que en los aridos naturales la microrrugosidad superficial y el diferente valor del CPA estan determinados, en gran medida, por las diferencias de dureza de sus minerales y tambien por la proporcion en la que estos minerales se encuentran en las distintas litologias. Sin embargo, en los aridos artificiales (escorias de fundicion) su elevada porosidad es la responsable de su marcada microrrugosidad superficial y su elevado valor del CPA. Finalmente, se relaciona el CPA con un parametro petrografico (Contraste de Dureza Global, ?H) mediante una curva exponencial, cuyo excelente indice de regresion hace que sea factible estimar mediante el estudio petrografico de un arido su valor del CPA (CPA=39,726?H0,057).

Castillo-palacio de La Calahorra, Granada: influencia de los factores climáticos y arquitectónicos en el deterioro diferencial de sus fábricas pétreas

Abstract: The castle-palace of La Calahorra is a historical building (6th century ) with a dual-function. The exterior is a castle-fortress of late-medieval style, built with rubbles and rough ashlars of a crystalline limestone of great hardness and strength. The interior is a Renaissance palace, made of micritic limestone and dolomitic sandstone ashlars, both stone materials are porous, soft and low strength. The entire building has an orangey colored due to an iron patina that stains its stone masonries as a result of wind action. There is a differential deterioration among its external and internal, depending on the type of stone used factories, the rainwater and wind action and the building defects detected. While the exterior stone is in good state of conservation, the interior stones shows some important deterioration processes , mainly the micritic limestone present in the ornamental and decorative areas of the central courtyard.

Performance of silicic pozzolans and Portland cements in their behavior in front of gypsum attack as determined by ASTM C 452-68

Abstract: For this study, ASTM C 452-68 testing was conducted for two years on 54 POZC-silica fume (SF) or diatomites (D and N) (=Z pozzolans), were tested for 2 years, by ASTM C 452-68 method, having determined to their specimens their Vcl(=ΔL(%)/day) The results have borne out that the pozzolanic reactions from SiO 2 r- of these Z pozzolans, in a sulfatic environment, had prevailed sooner (with D and N) or later (with SF) over the sulfatic hydration of their POZC, reaching completion in the first 28 days Therefore, after positive result is obtained in the Frattini test, as well as in other equivalent tests standardized, the ASTM C 452- 68 test can be validly used to differentiate 28-day POZC-Z pozzolan or with any other from natural or artificial origin, which may or may not give rise to the development of low, moderate or high SR The only requisite would be to establish suitable standard physical-chemical requirements and specifications

Variación del módulo de Young de un elemento de fábrica de ladrillo sometido a altas temperaturas

Abstract: In order to understand the thermal behavior of the masonry elements submitted to high temperatures we need to know the variation of their thermal properties with regard to the temperature. Submitted to high temperatures clay brick masonry presents thermomechanical effects (as the variation of Young's modulus, the thermal expansion of the unit and the mortar, spalling, losses of resistance …) as well as variation of the properties of the material as result of its degradation. In this article the variation of the module of elasticity of the unit and the mortar is described with regard to high temperatures according to the state of the knowledge. In this article is also exposed the results obtained from the experimental program carried out on elements of clay brick masonry submitted to high temperatures in order to observe the variation of Young's module related to temperature.

Comparación entre el comportamiento mecánico a tracción, fractura y fatiga de armaduras de refuerzo fabricadas con distintos tipos de acero

Abstract: The use of austenitic stainless steels as rebar is an option increasingly used in reinforced concrete structures exposed to aggressive environments and especially those that have to work in marine environments. The same is true for duplex stainless steel rebars, although nowadays they have a lower use, mainly due to the fact that their inclusion in the reinforced concrete standards was delayed 10 years compared to austenitic stainless steel ones, and consequently their in-service behavior is not as well known. A study of the mechanical properties, including fracture toughness, fatigue behaviour and corrosion resistance in saline alkaline environments of austenitic (AISI 304LN and 316LN) and duplex (D2205) stainless steel reinforcing bars was performed in this work. Bars made on a high ductility carbon steel (B500SD) that are normally used to reinforce concrete were also characterized and used as a comparison. Stainless steel reinforcing bars show mechanical properties at least similar but usually higher than one of the best carbon steel re-bars (B500SD), along with a significantly higher ductility and, of course, much better corrosion behaviour in saline alkaline environments.