Influência da adição no comportamento reológico da pasta autoadensável de alto desempenho

Influence of admixture on the rheological behavior of high performance self-compacting paste. This research proposes to study the influence of the specific area, mould and surface texture of admixtures on the rheological behavior of high performance self-compacting paste (HPSCP). The selected admixtures are calcareous filler and basalt filler, which are industrial residues, thus contributing to sustainable development. The paste is made up of cement, silica fume, calcareous filler or basalt filler, water and superplasticizer additive. For this study, the water/cement ratios are fixed = 0.40 L kg(-1); silica fume/cement = 0.10 kg kg(-1); the filler/cement and superplasticizer/cement ratios are determined through Marsh cone and mini-slump tests. The results show that for same filler/cement ratios, the ratios of superplasticizer to paste with calcareous filler are significantly lower than those of paste with basalt filler. The results show that the specific area, mould and surface texture of these admixtures significantly influence the rheological behavior of HPSCP.

Resistência à compressão do concreto autoadensável: Influência da atividade pozolânica do calcário e do basalto

This research studies the influence of the pozzolanic activity of the calcareous and basalt in the resistence behavior of the compressive strength of high performance self-compacting concrete (HPSCC). The selected aditives are the calcareous filler and basalt filler, for they are industrial residues helping that way the sustainable development. The paste of this concrete type is constituted of cement, silica fume, calcareous filler or basalt filler, water and superplasticizer additive. In this research the relationships water/cement are fixed in 0,40 kg/kg, silica fume/cement of 0,10 kg/kg and the relationships filler/cement and superplasticizer/cement are determined through of Marsh́s cone and mini-slump tests. The granular skeleton is gotten from a composition between quartzous sand and brita of basalt that presents the lesser index of emptinesses. The results show that the HPSCC with the addition of calcareous filler has greater compressive strength than what the HPSCC with addition of basalt filler in the ages of 7, 28 and 63 days. It is explained by the fact that the calcareous filler presents greater index of pozzolanic activity than the basalt filler. Besides that the relation water/fine for the HPSCC with calcareous filler is 0,27 l/kg whereas the HPSCC with basalt filler is of 0,29 l/kg.

Análise das propriedades reológicas de materiais cimentícios associando o conceito de empacotamento de partículas

Pós-graduação em Engenharia Mecânica - FEIS

Utilização de resíduos de concreto em concreto auto-adensável

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigação da retração plástica e da fissuração da argamassa do concreto auto-adensável

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A influência do patamar de cura térmica sobre a resistência dos concretos auto-adensáveis elaborados com diferentes tipos de cimento: avaliação pelo método da maturidade

Pós-graduação em Engenharia Mecânica - FEIS

Avaliação do comportamento reológico na retração plástica e na fissuração de argamassas de concreto auto-adensável

This paper investigated the influence of the amount of superplasticizer and mineral adding - silica fume and basaltic filer - in plastic shrinkage and cracking of self-compacting concrete (SCC) mortars. Initially analysis was performed of the rheological behavior of cement paste and mortars phases of the compositions of SCC. Then the deformations of mortars were measured by the effect of shrinkage and evaluation of cracking. On plastic shrinkage and cracking, the composition with silica fume showed superior results, independent of wind and superplasticizer content, relative to the composition with addition of basalt filler. However, the composition with silica fume showed superior results only in the tests with imposed ventilation at vertical plastic deformation. The rheological behavior affected directly the plastic shrinkage and cracking at early ages, fact confirmed by the analysis of capillary pressures of mortars tested.

Estudo da viabilidade do emprego do pó de mármore para produção de concreto autoadensável e substituição parcial dos agregados por pérolas de poliestireno expandido (EPS)

Pós-graduação em Engenharia Civil - FEIS

Concreto autoadensável utilizando cinza de casca de arroz: estudo das propriedades mecânicas

Pós-graduação em Engenharia Civil - FEIS

Prove di caratterizzazione meccanica del legame di adesione fra FRP ed acciaio

Il progresso nella tecnica di recupero e di rinforzo nelle strutture metalliche con i polimeri fibro-rinforzati FRP (fibre reinforced polymers). 1.1 Introduzione nelle problematiche ricorrenti delle strutture metalliche. Le strutture moderne di una certa importanza, come i grattacieli o i ponti, hanno tempi e costi di costruzione molto elevati ed è allora di importanza fondamentale la loro durabilità, cioè la lunga vita utile e i bassi costi di manutenzione; manutenzione intesa anche come modo di restare a livelli prestazionali predefiniti. La definizione delle prestazioni comprende la capacità portante, la durabilità, la funzionalità e l’aspetto estetico. Se il livello prestazionale diventa troppo basso, diventa allora necessario intervenire per ripristinare le caratteristiche iniziali della struttura. Strutture con una lunga vita utile, come per la maggior parte delle strutture civili ed edilizie, dovranno soddisfare esigenze nuove o modificate: i mezzi di trasporto ad esempio sono diventati più pesanti e più diffusi, la velocità dei veicoli al giorno d'oggi è aumentata e ciò comporta anche maggiori carichi di tipo dinamico.

Sul rinforzo di elementi in C.A.: confronto tra varie normative

Il documento pre-normativo italiano sul rinforzo di strutture in c.a. mediante l’uso di materiale fibrorinforzato. 1.1 INTRODUZIONE La situazione unica dell’Italia per quanto riguarda la conservazione delle costruzioni esistenti, è il risultato della combinazione di due aspetti, come primo, il medio-alto rischio sismico di una gran parte di territorio, come testimoniato dalla zonizzazione sismica recente, e come secondo aspetto, l'estrema complessità di un ambiente edilizio che non ha confronto nel mondo. Le tipologie della costruzione in Italia si distinguono a quelle stimate come patrimonio storico, che in alcuni casi risalgono a circa 2000 anni fa, a quelle che sono state costruite in ultimi cinque secoli, durante e dopo il Rinascimento, che sono considerate come patrimonio culturale ed architettonico dell' Italia (e del mondo!), infine a quelle fatte in tempi recenti, considerevolmente durante e dopo il boom economico del l960 ed ora visti come antiquate. Le due prime categorie in gran parte sono composte dalle edilizie di muratura, mentre agli ultimi principalmente appartengono le costruzioni di cemento armato.

Composite materials design, manufacture and evaluation

Fibre-Reinforced-Plastics are composite materials composed by thin fibres with high mechanical properties, made to work together with a cohesive plastic matrix. The huge advantages of fibre reinforced plastics over traditional materials are their high specific mechanical properties i.e. high stiffness and strength to weight ratios. This kind of composite materials is the most disruptive innovation in the structural materials field seen in recent years and the areas of potential application are still many. However, there are few aspects which limit their growth: on the one hand the information available about their properties and long term behaviour is still scarce, especially if compared with traditional materials for which there has been developed an extended database through years of use and research. On the other hand, the technologies of production are still not as developed as the ones available to form plastics, metals and other traditional materials. A third aspect is that the new properties presented by these materials e.g. their anisotropy, difficult the design of components. This thesis will provide several case-studies with advancements regarding the three limitations mentioned. In particular, the long term mechanical properties have been studied through an experimental analysis of the impact of seawater on GFRP. Regarding production methods, the pre-impregnated cured in autoclave process was considered: a rapid tooling method to produce moulds will be presented, and a study about the production of thick components. Also, two liquid composite moulding methods will be presented, with a case-study regarding a large component with sandwich structure that was produced with the Vacuum-Assisted-Resin-Infusion method, and a case-study regarding a thick con-rod beam that was produced with the Resin-Transfer-Moulding process. The final case-study will analyse the loads acting during the use of a particular sportive component, made with FRP layers and a sandwich structure, practical design rules will be provided.

[The stamp technique for direct composite restoration]

The indications for direct resin composite restorations are nowadays extended due to the development of modern resin materials with improved material properties. However, there are still some difficulties regarding handling of resin composite material, especially in large restorations. The reconstruction of a functional and individual occlusion is difficult to achieve with direct application techniques. The aim of the present publication was to introduce a new "stamp"-technique for placing large composite restorations. The procedure of this "stamp"-technique is presented by three typical indications: large single-tooth restoration, occlusal rehabilitation of a compromised occlusal surface due to erosions and direct fibre-reinforced fixed partial denture. A step-by-step description of the technique and clinical figures illustrates the method. Large single-tooth restorations can be built-up with individual, two- piece silicone stamps. Large occlusal abrasive and/or erosive defects can be restored by copying the wax-up from the dental technician using the "stamp"-technique. Even fiber-reinforced resin-bonded fixed partial dentures can be formed with this intraoral technique with more precision and within a shorter treatment time. The presented "stamp"-technique facilitates the placement of large restoration with composite and can be recommended for the clinical use.

Bonding shear strength in timber and GFRP glued with epoxy adhesives

The bonding quality of epoxy glued timber and glass fibre reinforced polymers (GFRP) was evaluated by means of compression loading shear test. Three timber species (Radiata pine, Laricio pine and Oak) and two kinds of GFRP (plates and rods made with polyester resin reinforced with mat and roving glass fibre) were glued and tested using three epoxy formulations. The increase in shear strength with age after the setting of epoxy formulations and the effect of surface roughness on timber and GRP gluing (the planing of the surface of timber and the previous sanding of GRP) were studied. It can be concluded that the mechanical properties of these products make them suitable for use in the reinforcement of deteriorated timber structures, and that a rough timber surface is preferable to a planed one, while the previous sanding of GRP surfaces is not advantageous.

New Courthouse at El Ejido

The courthouse at El Ejido has a trapezoid floor plan (47 m × 55/26 m) and comprises two distinct volumes that are structurally connected at the basement level and by the footbridges on the upper storeys. A third trapezoid unit featuring a glazed curtain wall facade cantilevers 8 m off the main facade of the front volume. This facade is a structural diaphragm wall, constituted by nine rows of vertical precast concrete members separated by horizontal cast-in-place, self-compacting concrete chords. The location of the courthouse in a seismic area and the small number of horizontal supports for the facade make this wall potentially vulnerable. The high risk, in particular, during construction required careful planning based on a detailed analysis of the interaction between the structure and the ancillary resources used to build it