F. Hernández-Olivares

Static and dynamic behaviour of recycled tyre rubber-filled concrete

Abstract The paper summarises the experimental results of mechanical behaviour under static and dynamic loads of specimens made of concrete filled with small volumetric fractions of crushed tyre rubber and polypropylene short fibres, at 7 and 28 days. The experimental results are compared with results of concrete specimens of similar features without fibres or tyre. The results of a microscopic study (SEM) of the interface cement–rubber fiber are included in order to analyze their compatibility. Compression, indirect tension and bending static tests and compression dynamic tests have been performed. The results of the dynamic tests have been used to calculate the complex modulus and the capacity of this material to dissipate elastic energy due to low-frequency dynamic actions.

Fire performance of recycled rubber-filled high-strength concrete

Abstract The paper presents the behavior of a high-strength concrete (HSC) with silica fume (SF) modified with different amounts of solid particles recycled from crumbed used truck tires. The aims of including elastomeric materials in a cementitious matrix are reducing the stiffness of HSC in order to make it compatible with other materials and elements of the building, unexpected displacement of foundations and shrinkage, recycling of solid wastes and improving fire performance. The inclusion of low volumetric fractions of rubber reduces the risk of explosive spalling of HSC at high temperatures because water vapor can exit through the channels left as the polymeric particles get burnt. The temperature reached at a fixed depth of the fire-tested specimens is reduced as the percentage of rubber increase. A set of mechanical, destructive and nondestructive tests were accomplished in order to obtain optimum quantities of crumbed used tires rubber in the composition, taking into account workability, stiffness and, obviously, strength. The results obtained show that a relatively high-volume fraction of rubber (3%) does not reduce significantly the strength, although it reduces the stiffness. Higher values of rubber produce a progressive reduction of strength and stiffness but might improve the dynamic behavior.

Development of cork–gypsum composites for building applications

Abstract This paper presents an experimental analysis on a new composite material, cork–gypsum composite. It is shown that cork and plaster are mutually compatible and that a lot of new building materials can be made by mixing those materials in different volume fractions. Mechanical properties of the cork–gypsum composite have been measured. The acoustic absorption coefficient and thermal conductivity of this new composite have also been experimentally obtained and those values are reported for design purposes. Concerning the acoustical insulation characteristics, this composite is not a sound-absorbing material but a reflecting one, and it needs some kind of perforations to behave as an absorbing construction material for sound and noise. The thermal insulation properties are quite good as a result of the thermal conductivity tests. This new composite material is suggested for use in building applications as partitions.

Rubber-modified hot-mix asphalt pavement by dry process

This paper focuses on tyre rubber-modified hot-mix asphalt for traffic pavements fabricated by dry process. Fine granulated crumbed rubber from discarded tyres was mixed with heat aggregates and after a short delay time, an ordinary bitumen binder was added to the mixture in the plug mill. The research was partially carried out in the laboratory (designing the optimum mixture composition) and on site, constructing an experimental road segment, 2.5 km length, in a secondary traffic road located between Salamanca and Ciudad Rodrigo (Spain). The rubber-modified hot-mix asphalt (RMHMA) was placed on site and compacted after a controlled time of maturation (ageing) of the warm rubber-modified hot-mix asphalt, which promotes a close interaction between the rubber particles and the binder.

Interfacial Transition Zone (ITZ) Analysis in Hydraulic Lime Restoration Mortars for Grouting of Historical Masonries

In this study, binder-aggregate interfacial transition zone (ITZ) of some hydraulic lime based mortars is analyzed in order to determine the way in which their morphological and compositional structure is related to strength and durability development. To achieve this determination, using a lime mortar as a starting point, several hydraulic mixes were prepared with metakaolin (MK), sepiolite, and Portland cement additions. Lime mortar ITZ was compared with hydraulic mortars, obtained both from a natural hydraulic lime (NHL) and from the mentioned artificial hydraulic lime mixes. Scanning electron microscopy (SEM) and energy dispersion X-ray analysis (EDX) microanalysis techniques in combination with stress tests were carried out. Results showed the most radical behavior with the MK addition to mortar rather than with the Portland cement addition, even at 1:1 ratio. Continual transition zones together with higher strengths correspond to mortars with smaller aluminate phases and hydrogarnets. Thus, a small contribution of the latter to binder-aggregate bonding and mechanical resistance can be considered. Finally, sepiolite addition does not affect mechanical behavior under these work conditions.

Study of Fine Mortar Powder from Different Waste Sources for Recycled Concrete Production

Searching new options to exploit crushing concrete waste or recycled mortar powder fines (RMF) has lead the development of new processes for recycling concrete. By heat treatments allow reincorporates concrete waste material into new concrete manufacturing process. The current research determines chemical composition of burned recycled mortar powder fines (BRMF) obtained from different sources. Also, this experimental research, analyzes how BRMF in addition to cement, affects to compressive strength of composite. Using a 30% BRMF ratio for replacing Ordinary Portland Cement (OPC), the study determined that the direct use of this material, decreases compressive strength of composite, reaching 21–54% of normal strength in most specimens. Based in Ca/Si ratio study, is observed how compressive strength is related to Ca/Si balance of the mixture, where the specimens with Ca/Si higher radio reach at 72% of normal compressive strength, compared to mixtures using only cement. Thus, experimental study noticed that the main criterion for assessing the use of RMF is the concentration of CaO, there are no significant differences between RFM from concrete or mortar prepared and put in work, unlike waste or special premixed mortars.

Sandstone Adherence in Building Construction

This study analyzes bonding properties of porous sandstone to conclude that adherence between porous sandstone panels and their background supports, in building construction, can be substantially improved by applying adhesive primers at the rear of the panels. Two types of primers have been studied: styrene-butadiene latex and epoxy-resin. Laboratory tests have shown a bonding strength increase by applying both products. However, styrene-butadiene latex primers have shown better performance than epoxy-resins, mainly after accelerated ageing cycles. Bonding joints based on styrene-butadiene present higher strength than natural sandstone under tensile pull-off and shear tests; this higher strength was retained after ageing cycles of wet-dry and cold-heat on the samples. This new technique offers an innovative use of natural porous sandstone in building construction and in architectural heritage restoration, allowing for thinner veneers, substituting todays heavy thick panels. Commonly used epoxy-based mortars and latex-based mortars were discarded in this research as described in text.

Assessment of the Relationship Between Diameter and Tensile Strength of Piassaba (Aphandra natalia) Fibers

Sustainable development of materials is a triangle between the ecological, economic and social that aims to reduce the extraction and use of conventional materials, through the use of regenerable natural materials that cause minimal impact or like the incorporation of waste and by-products that can be recycled . Natural fibers have characteristics of technical and economic solution, an important source for its use are the palms, considered one of the most economically important plants group. Of this variety, piassaba is the name of the hard fibers brown, considered as a non-timber forest product, which can be obtained from three species of palm: Leopoldinia piassaba Wallace, Attalea funifera and Aphandra natalia . Piassaba of Aphandra natalia displays mechanical properties similar to Leopoldinia piassaba and Attalea Funifera already tested of composite materials . Like any other natural fiber, the Aphandra natalia fibers have different diameters even in each fiber. In several lignocellulosic fibers has been found that the dimension of the diameter it affect value of the tensile strength . In this work a Weibull analysis of sisal fibers tensile strength was performed to find a correlation with the diameter. It was determined that a smaller diameter of the largest fiber tensile strength, indicating a hyperbolic equation between average strength and diameter.

A New Cladding System Using Low Strength Sandstone in Precast Concrete Panels for Building Façades

Most monumental architectures are based on the use of the stone with the idea of giving solidity and durability to the constructions. Usually, the stone used is supplied by the natural environment in which the buildings are located. In those cases, the preservation of the urban ensemble requires that the new constructions align with the ancient building not by imitating the architectural forms but, perhaps, by using the same materials in a new way. This is the case, of Salamanca (Spain). The monumental architecture of this town is directly related to sandstone obtained in the neighbouring quarries. This stone has a particular golden colour that is one of the characteristics of the urban ensemble of Salamanca. The particular characteristics of this stone, such as high porosity, poor adherence with mortars, and low strength, that decreases when the stone water absorption increases, prevent the use of thin plates simply adhered to the brickwork and make its use with ventilated facades not possible. To solve this question, decades ago a particular construction system was developed. It consists in the use of nails partially hammered in the back side of plates joined to the brickwork by mortar. With this technique, the head of the nails remain inserted in the mortar working as anchors between the stone and the mortar. To improve it, a new use of this traditional construction system is described in this communication. The idea is to make precast concrete panels cladding with stone plates by using the nails technique. An experimental assessment of this system and their safety against wind suction is discussed.