J.A. Polanco

Maturity Approach Applied to Concrete by Means of Vicat Tests

Contractors would be aided in planning a pavements texturing and finishing times through better knowledge of initial concrete setting time. The authors present a straightforward temperature influence on setting time evaluation method with this in mind. The Freiesleben-Hansen and Pedersen maturity function was used to accomplish this. A Vicat test series was carried out at different temperatures for cement apparent activation energy determination usage in this equation. To determine the correctness of any activation energy found, there was application to the times for a specific penetration resistance to be attained with various water-cement (w/c) ratios and at different temperatures with three different cement types. When equivalent concrete setting time ages were calculated, w/c and setting time linear relationships were obtained at the reference temperature. The authors concluded that temperature influence on concrete setting time evaluation could be performed through the apparent activation energy this method obtained.

Abrasive wear evolution in concrete pavements

Abrasion of a concrete pavement is habitually due to the continued movement of wheels on the concrete surface. Starting from the theoretical model developed by Horszczaruk, this paper proposes the development of a new model, which expresses the material volume loss as a function of the work done by the wheel and the total abrasion time, as well as the composition of the concrete. For the verification of the model, samples of an experimental pavement were used, in which a dry shaking treatment with corundum had been applied. Finally, with this model an engineer could predict the concrete pavement lifetime from the parameters of the concrete and its traffic characteristics.

Mechanical Behavior of Anchorages for Reinforcing Marine Stone Structures Subjected to Sea Waves

This study shows the results of a research project conducted to study the technical feasibility of the reconstruction of a real marine structure of natural rock. The experimental campaign enables the analysis of the behavior of stainless steel anchorages adhered with polymeric adhesives for strengthening the stone structure. To this end, mechanical tests were carried out to characterize the adhesive-steel-stone system and to verify the static effectiveness of anchorages, both in situations of nonimmersion and immersion in seawater. Tensile tests in anchorages under cyclic loading were performed in addition to other trials to estimate the bond stress under shear of epoxy polymer adhesive with the stone substrate and bending tests to evaluate the performance of stones reinforced with epoxy polymer mortar and stainless steel. The results obtained provide for an advance in the difficult field of the selection of materials potentially applied to the reinforcement of structures subjected to complex and varied mechanical actions, particularly in highly aggressive environments, such as seawater.

Characterization of Materials with Repellents and Consolidants from a Historic Building

AbstractIn order to study the feasibility of the rehabilitation of the building of the Palace of Riva Herrera (sixteenth century), in Santander, Spain, four types of natural stone found in the building have been characterized. The chemical, microstructural, physical, and mechanical properties have been obtained. Also, in order to evaluate the durability of the stones, a program of freeze-thaw aging has been completed. In parallel, the effect of four commercial water repellents and consolidants was analyzed by means of capillary absorption tests. The results showed relations between the durability and the open porosity of the different stones. The capillarity absorption coefficient can be applied as an indicator of durability. Also, all of the waterproofing treatments were shown to be effective, reducing the capillary absorption of the treated stones with respect to the stones not subjected to protective treatments by virtue of a delay in the capillarity process, this effect being greater in more porous ma...

Evolution of mechanical behaviour in a structural steel subjected to high temperatures

Abstract In this work a study of how exposure to high temperatures can affect the mechanical properties of a structural steel is presented. To this end, several mechanical tests such as tensile, impact and microhardness tests have been carried out in order to compare the properties of the heat-exposed steel with those of an unaffected reference steel. Complementary compositional, metallographic and fractographic analyses have also been performed to try to cast some light on the problem. The results obtained allow us to extract some conclusions on the reutilization of the steel for structural applications.

Quasidistributed fiber sensor for precast concrete structures monitoring

The prestressing force is transferred to the concrete during the slack period of precast concrete structures fabrication. To contribute to a better understanding of the armor compliant behaviors during the mentioned process, a custom quasidistributed Bragg Grating optical fiber sensor system is designed, fabricated and embedded into a prestressed concrete prismatic beam. The experimental works, the results, their discussion and finally the obtained conclusions are presented in this paper.

Predicting Crack Arrest Behaviour of Structural Steels Using New Procedures

The crack arrest philosophy, based on the concept that a brittle crack can be arrested when it emerges from a critical region, is especially useful for such situations where additional safety against unforeseen circumstances is needed. This criterion is included in the R6 procedure [1] as a complementary method against fracture toughness criterion for the assessment of the structural integrity of components containing defects.

Experimental validation of fiber Bragg grating sensors for steel girder strain characterization

Although several Fiber Bragg Grating (FBG) based transducers have been successfully applied to the measurement of strain and temperature on civil engineering applications, important research work must be done to obtain transducers able to be used out of the laboratory. One of these research topics are the study of good interfaces between the optical fiber and the structural part to be measured. In this work a wide range of fixing techniques and interfaces have been investigated for fiber Bragg grating based transducers. Several transducers were constructed and fixed to a steel girder. Conventional strain gauges and professional displacement metering devices was added to the test specimen to make comparisons. A complete characterization setup using a laboratory test machine to test the transducers was designed. The test included several static and dynamic cycles and was applied to the steel girder while all the transducers were monitorized simultaneously. Results obtained with traditional and with the optical fiber mentioned technologies show a very good agreement.

Cracking diagnostics of brake pedals during press forming operations

Abstract In this work a study of the cracking problems arising in manufacturing of steel brake pedals by press forming is presented. Cracks were detected in critical zones of the part revealing a possible lack of ductility in the constitutive material. In order to overcome this problem, a detailed study of the behaviour of the steel used has been carried out. In this way, mechanical characterization as well as microstructural analysis were performed over both cracked and uncracked pedals. The results obtained from this comparative analysis showed different microstructural features and, consequently, the dissimilar mechanical behaviour can be justified.