Materials Science Forum Vols. 587-588

Abstract: Copper slag is a copper industry waste that is essentially used as an abrasive for metals to remove coatings or paintings, due to its hardness, sieve distribution and rough surface, mainly in the naval industry. After the wearing process, copper slag retains most of its original properties, and remaining an environmental problem. Chemical composition of copper slag presents a high Fe, Si and Al oxide content what makes it a pozzolanic material. Thus, it is possible to use it as a partial replacement for sand and after triturating it into very small particles as a replacement for cement. After a chemical, physical, mineralogical, and environmental characterization of copper slag, its use as a partial replacement of sand on mortars was investigated. The experimental program was developed to evaluate the effect of several percentages of sand substitution in mortars. For mortars 25, 50 and 75 % of sand replacement by volume was studied. A standard 1/3 cement/sand ratio, by weight, with cement type CEM 42.5 I, was used. The type of sand and the effect of washing the slag were also investigated. Strength was measured at 7, 28, 60 and 90 days. Results obtained until now indicate that a reduction of strength occurs when the slag content increases. Additionally, it was observed a delay of the hardening process by the addition of the copper slag. As a conclusion, the use of copper slag as a sand replacement seemed to be a practical option.

Abstract: This work concerns with the study of coatings to inhibit the ingress of water and also the use of lithium nitrate to modify the swelling properties of the ASR reaction products. In order to accomplish these objectives concrete samples extracted from a Portuguese structure affected by internal expansive reactions were treated with six different coatings and subjected to natural and accelerated environments. In order to study the modifications produced by lithium nitrate in the expansive properties of ASR products, different test conditions were used namely the application of lithium by immersion and electrical migration. In this work we present the results of the application of these treatments namely by the evaluation of the mechanical, physical, microstructural and electrical properties.

Abstract: One of the key characteristics of fresh mortars is their rheological behaviour since it determines the material workability and has a clear influence on the hardened product final properties. Indeed, mortars rheological properties are extremely important since several factors, related with placement, consolidation, durability and strength depend on the flow properties of the mortar paste. In this work, the effect of ageing time on the rheological properties of fresh aerial lime-based mortars was investigated. Mortars having a 1/3 binder/aggregate volume ratio were studied as a function of ageing time. The influence of a water retaining agent (0.1 wt. %) addition in these mortars was also analysed. Mixing and ageing have a clear influence in the water intake process ruling over the rheological behaviour of this type of mortars.

Abstract: The experimental results of hooked-end steel fibers pullout tests on a self-compacting concrete medium are presented and discussed in this work. The influence of fiber embedment length on the fiber pullout behavior is studied. The role of the end hook of the fiber on the overall pullout behavior is also investigated by carrying out tests with fibers without its end hook, in order to separate the contribution of the frictional bond component from those derived from the mechanisms provided by the end hook of the fiber. Finally, the experimental bond-slip relationships are modeled by an analytical model.

Abstract: To study the fracture energy of materials, the stable crack propagation must be observed during the test. To this end, an appropriate method, particularly in the case of large samples, is the wedge splitting method. By this method, the test machine stores less elastic energy, facilitating stable propagation. The materials tested in this study were mortars with sand:cement ratios of 2:1 and 3:1. Two types of samples were prepared: one with a notch and grooves produced with a diamond disk and the other with notch and grooves produced directly during molding of the mortar. The crack moved easily along an imaginary vertical plane defined by the grooves. The methodology proved sensitive to the material’s microstructure, modified here by varying its formulation. High sensitivity was also found in relation to the shape of the tip of the notch, whether V-shaped or square. In the material studied here, the values of fracture energy varied from 23 to 56 J.m-2.

Abstract: The available research has evidenced that discrete steel fibers can increase significantly the shear resistance of High Strength Concrete (HSC) structural elements when High Strength Fiber Reinforced Concrete (HSFRC) is designed in such way that fiber reinforcing mechanisms are optimized. In general, the increase of the concrete compressive strength is associated to an increase of its compactness, resulting benefits in terms of durability, but a strong concern emerges related to the integrity of this material, since it fails in a too brittle mode when submitted to high temperatures. To contribute for the knowledge about the benefits provided by discrete steel fibers when added to HSC applied to laminar structures, an experimental program composed of slab strips submitted to shear loading configuration was carried out. Uniaxial compression tests with cylinders of 150 mm diameter and 300 mm height, and bending tests with 600×150×150 mm3 beams were executed to assess the compression and bending behavior of the developed HSFRC. To evaluate the influence of the percentage of fibers in the shear resistance of laminar structures, three point loading tests with slab strips of 800×170×150 mm3 dimensions were performed. Taking the obtained experimental results, the applicability of the formulation proposed by RILEM TC 162-TDF was evaluated. Test results showed that, even with relative low dosages of steel fibers, the increment in shear resistance was significantly increased. The main obtained results in the research program are presented and discussed in this paper.

Abstract: In real engineering components and structures, many accidental failures are due to unexpected or additional loadings, such as additional bending or torsion, etc. Therefore, it has attracted more research attentions to study the mechanical behavior of materials under complex loading conditions. Two typical structural materials are studied and compared in this paper: AISI 303 stainless steel and 6060-T5 Aluminum alloy. The objective is to study the effects of multiaxial loading paths on the crack initiation and orientation of the two materials studied. Fatigue tests were conducted in a biaxial testing machine. Fractographic analyses of the fracture surface were carried out by optical microscope and SEM approaches. In addition to the experimental studies, theoretical predictions of the damage plane were made using critical plane approaches. Comparisons of the predicted orientation of the damage plane with the experimental observations are shown. The applicability of the multiaxial fatigue criteria for the two materials is discussed. It was shown that the two materials studied have different crack orientations under the same loading path. This observation appears to show that the applicability of the fatigue models is dependent on the material type and multiaxial microstructure characteristics.

Abstract: There exists an increasing concern about the dangers originated in a building in case of fire. In this work the behaviour of vermiculite as aggregate in fireproof mortars was compared with mortars formulated with two magnesium by-products aggregates which undergo an endothermic decomposition. Fire resistance and mechanical properties were evaluated. An optimal mixture of both magnesium by-products as aggregates allows formulating mortars that improve fire resistance at temperatures greater than 450 °C compared with vermiculite mortars. It would be interesting to obtain mortars formulated with magnesium by products and vermiculite to study possible synergic effects.

Abstract: In the present study, fire reaction improvement of an epoxy polymer mortar (PM) formulation, induced by polymer modification with three different flame retardant (FR) systems, was analyzed and quantified. For this purpose, several epoxy PM formulations, modified with different contents and/or types of phosphate, metal hydroxide and brominated based FR systems, were manufactured and tested for both, fire reaction and flexural strength. The results were compared with those of plain epoxy PMs. Fire reaction of PM formulations was assessed by means of the Oxygen Consumption Calorimeter test, also known as Cone Calorimeter test. This test allows the determination of the main parameters that assess fire reaction behaviour of combustible materials: heat release rate, smoke extinction area, carbon dioxide and monoxide release rates, and ignitability. Test results revealed that all FR systems, in particular the phosphate based one, are effective in improving fire reaction performance of epoxy PMs. Moreover, this improvement is attained without significant losses of bearing carrying capacity of PM materials.

Abstract: The sustainable world’s economic growth and people’s life improvement greatly depend on the use of alternative products in the architecture and construction, such as industrial wastes conventionally called “green materials”. This paper concerns the main results of an experimental work carried out with the objective of developing new composite materials based on gypsum and incorporating waste material as granulated cork, a by-product of cork industry, and cellulose fibres, a waste of paper industry. Such materials are intended to be used as composite boards for non structural elements of construction, such as dry walls and ceiling. Cork (bark of the plant Quercus Suber L), a substance largely produced in Portugal, is a material whose characteristics are of considerable interest for the construction industry. It is regarded as a strategic material with enormous potential by its reduced density, elasticity, compressibility, waterproof, vibration absorption, thermal and acoustic insulation efficiency [1]. During the first stage of this research work the gypsum binder and its properties were studied. Then, composites with mineral additions (added to increase the waterproofing and resistance) were also developed and submitted to tests to determine their physical and mechanical properties. In last stage, reinforced composites using different industrial by-products have been developed. This paper will present the properties and the manufacture methods used to produce the above mentioned eco-friendly composites that can ease ways for using industrial wastes as new construction materials, with excellent inherent thermal and acoustic properties.