M. C. S. Ribeiro

Creep behaviour of FRP-reinforced polymer concrete

Polymer concrete is a kind of concrete where natural aggregates such as silica sand or gravel are binded together with a thermoset resin, such as epoxy. Although polymer concretes are stronger in compression than cementitious concrete, its tension behaviour is still weak. The reinforcement of polymer concrete beams in the tension zone with pultruded profiles made of epoxy resin and glass fibers are a good compromise between stiffness and strength. In this paper it is reported an investigation of the creep behaviour of polymer concrete beams reinforced with fiber-reinforced plastics (pultruded) rebars. Four-point bending creep test were performed. An analytical model was applied to verify the experimental results.

Bending characteristics of resin concretes

In this research work the influence of composition and curing conditions in bending strength of polyester and epoxy concrete is analyzed. Various mixtures of resin and aggregates were considered in view of an optimal combination. The Taguchi methodology was applied in order to reduce the number of tests, and in order to evaluate the influence of various parameters in concrete properties. This methodology is very useful for the planning of experiments. Test results, analyzed by this methodology, shown that the most significant factors affecting bending strength properties of resin concretes are the type of resin, resin content and charge content. An optimal formulation leading to a maximum bending strength was achieved in terms of material parameters.

Thermal expansion of epoxy and polyester polymer mortars: plain mortars and fibre-reinforced mortars

Abstract The study was conducted in order to determine the coefficient of thermal expansion of two specific binder formulations of epoxy and unsaturated polyester polymer mortars. The variation of this parameter with temperature was also analysed. Polymer concrete and mortars have been observed to have lower coefficients of thermal expansion at lower temperatures than at higher temperatures. Plots of strains vs. temperature are often bilinear, indicating a sharp change in the coefficient of thermal expansion (International Congress on Polymers in Concrete, July 1995). To determine how this discontinuity varies for these two materials, specimens of both formulations were tested for several temperature ranges between −20 and 60 °C. In addition, to determine the influence of fibre reinforcements on thermal expansion of polymer mortars, epoxy polymer mortars reinforced with both carbon and glass chopped fibres were also tested for thermal expansion. It was concluded that, for both formulations, the variation of thermal expansion with temperature follows a parabolic law rather than a bilinear law. The reinforcement of chopped glass fibres (1%) has no significant effect on thermal expansion of epoxy polymer mortar, while the inclusion of carbon fibres (2%) on the same mortar formulation has a reducing effect on thermal expansion of this composite material for temperatures above room temperature.

Chemical resistance of epoxy and polyester polymer concrete to acids and salts

The aim of this work is to analyse the chemical resistance of epoxy and polyester concretes when exposed to acids and salts. The chemical resistance is evaluated through the variation of bending strength and variation of mass, after exposure in acid and salted solutions, for various periods of time. Aqueous solutions of sulphuric acid and sodium chloride were chosen as test solutions. The increasing use of polymer concrete structures near seawater and residual waters is the main motivation for this research work.

Recycling of pultrusion production waste into innovative concrete-polymer composite solutions

In this study, the added value resultant from the incorporation of pultrusion production waste into polymer based concretes was assessed. For this purpose, different types of thermoset composite scrap material, proceeding from GFRP pultrusion manufacturing process, were mechanical shredded and milled into a fibrous-powdered material. Resultant GFRP recyclates, with two different size gradings, were added to polyester based mortars as fine aggregate and filler replacements, at various load contents between 4% up to 12% in weight of total mass. Flexural and compressive loading capacities were evaluated and found better than those of unmodified polymer mortars. Obtained results highlight the high potential of recycled GFRP pultrusion waste materials as efficient and sustainable admixtures for concrete and mortar-polymer composites, constituting an emergent waste management solution.

Fire Reaction and Mechanical Performance Analyses of Polymer Concrete Materials Modified with Micro and Nano Alumina Particles

In the present study, fire reaction and mechanical behaviour improvements of an epoxy polymer mortar (PM) formulation, induced by binder modification with alumina particles at micro and nano-size levels, were analysed and quantified. For this purpose, several series of PM specimens, modified with different types of microparticles, nanoparticles and nanodispersion of aluminium oxide were manufactured and tested for fire reaction, flexural and compressive load carrying capacities. Obtained results were compared with those obtained for plain epoxy polymer mortars. Fire reaction properties, such as time to ignition, heat release rate, smoke extinction area, carbon monoxide and carbon dioxide yield rates were assessed by means of cone calorimeter test. Test results revealed that the addition of alumina particles to binder matrix of polymer mortars, even in small amounts (3.9 % in weight of total mass), are effective in improving flexural and compressive behaviours of resultant polymer mortars, especially in the case of alumina nanoparticles. However larger amounts of aluminium oxide nanoparticles will be required to attain effective levels of fire retardancy.

Polymer Composite Materials modified with Nano-Oxides and Phosphinates Hybrid Flame Retardant Systems

Unsaturated polyester based composites materials present several improved properties over conventional materials. However, these composites show great sensitivity to high temperatures and poor fire behaviour. In the present study, an effort is undertaken to develop new unsaturated polyester composites with improved fire reaction behaviour by matrix modification with hybrid flame retardant systems based on nanooxides and phosphinates. For this purpose, a series of composite formulations containing different contents and types of both metal oxide nano/micro particles and organic phosphinates were manufactured, with basis on the Taguchi L9 orthogonal array, and tested for fire reaction and mechanical properties. The data treatment was carried out through analyses of variance. Fire reaction properties were analysed and quantified by the vertical flammability test (UL-94), and the mechanical properties were studied by flexural, Shore D, and Charpy impact tests. The results were compared with those obtained for plain resin specimens. Test results revealed that the addition of hybrid flame retardant systems introduced reasonable improvements in at least one fire reaction property. However, it was verified that the filler addition led to a decrease in mechanical properties, probably due to poor matrix-filler adhesion. Further studies are required in order to improve the mix design formulations.

PLSR Models for Mechanical Strengths of Concrete Composite Materials Reinforced with Pultrusion Wastes

Risk assessment is one of the main pillars of the framework directive and other directives in respect of health and safety. It is also the basis of an effective management of safety and health as it is essential to reduce work-related accidents and occupational diseases. To survey the hazards eventually present in the workplaces the usual procedures are i) gathering information about tasks/activities, employees, equipment, legislation and standards; ii) observation of the tasks and; iii) quantification of respective risks through the most adequate risk assessment among the methodologies available. From this preliminary evaluation of a welding plant and, from the different measurable parameters, noise was considered the most critical. This paper focus not only the usual way of risk assessment for noise but also another approach that may allow us to identify the technique with which a weld is being performed.In this paper, we present two Partial Least Squares Regression (PLSR) models for compressive and flexural strength responses of a concrete composite material reinforced with pultrusion wastes. The main objective is to characterize this cost-effective waste management solution for glass fiber reinforced polymer (GFRP) pultrusion wastes and end-of-life products that will lead, thereby, to a more sustainable composite materials industry. The experiments took into account formulations with the incorporation of three different weight contents of GFRP waste materials into polyester based mortars, as sand aggregate and filler replacements, two waste particle size grades and the incorporation of silane adhesion promoter into the polyester resin matrix in order to improve binder aggregates interfaces. The regression models were achieved for these data and two latent variables were identified as suitable, with a 95% confidence level. This technological option, for improving the quality of GFRP filled polymer mortars, is viable thus opening a door to selective recycling of GFRP waste and its use in the production of concrete-polymer based products. However, further and complementary studies will be necessary to confirm the technical and economic viability of the process.

Analysis and experiments on FRP-polymer concrete hybrid beams

This paper deals with a preliminary research undertaken in hybrid beams, where GFRP pultruded profiles are assembled, in an innovative way, with a layer of polymer concrete. Various beams were designed considering a pultrusion profile that will work in tension, and a polymer concrete filling that will work mainly in compression, in order to take benefit from the best mechanical properties of both materials. Several beams, with four different hybrid designs, were tested in four-point bending, and the flexural behavior of such structures was studied. A numeric model implemented in a finite element code was also developed in order to predict the experimental results. Model designs produced a highly optimised flexural behavior, with a pronounced synergetic effect.

Assessment of Thermal Degradation on Polymer Mortars

An investigation on the influence of thermal effects on flexural strength of two different binder formulations of polymer mortars was performed, by considering specimens of polyester and epoxy polymer mortars, and a wide range of temperatures. The strength degradation process occurring in the material, as a consequence of positive thermal fatigue cycles (+20°C / +100°C) and freezethaw cycles (-10°C / +10°C), was also quantified and analysed.