Antonio Aguado

Fatigue behavior of polymer-modified porous concretes

Abstract Highly permeable materials provide drainage and noise-absorption properties that are useful in pavement top layers. In such porous concretes, the voids reduce the mechanical integrity, which may have to be compensated for with the incorporation of nonconventional components, such as polymers. A basic property needed for the design of pavements is the fatigue behavior of the material, which has not been studied thoroughly for polymer-modified porous concretes. This paper presents experimental results of fatigue tests in compression in terms of Wohler curves for four porous concretes (two of them with polymer). It is seen that the polymer-modified porous concretes exhibit better fatigue behavior than those without polymer. However, the improvement decreases for low values of the stress level, S , and appears to be negligible for the case of traffic loads in main roads or highways (number of load cycles, N > 10 6 ). Additionally, the deformation and internal temperature evolutions have been monitored, and it is concluded that their trends are similar to those of conventional concrete, with temperature increases significantly higher than in conventional concretes.

Sustainability Assessment of Concrete Structures within the Spanish Structural Concrete Code

Since 2008, the Spanish Structural Concrete Code (EHE in Spanish) has generally focused on respecting the environment; as a result, it has become a support tool for designing sustainable concrete structures. The Ministry of Public Works took charge of the initiative and a wide range of professionals and researchers, encompassing various points of view in this sector, carried it through. It is a pioneering initiative, opening up an avenue for the future of sustainable structural design. The purpose of this paper is to summarize the procedure used in drafting the sustainability appendix for the EHE and to present the EHE model for assessing the sustainability of concrete structures. Although the project has had its problems, the model that it produced is very thorough. It includes practically all the main criteria, taking into account the current state of the art and the fact that this was the first time a sustainability assessment technique has been included in a structural code.

Estimation of the modulus of elasticity for dam concrete

Abstract The modulus of elasticity of dam concrete is difficult to determine directly from tests, due to the necessity for large specimens and testing machines. In order to study the applicability of simple elastic models for predicting the modulus from standard size specimens, tests were conducted on prisms of 45 × 45 × 90 cm fabricated with dam concrete (maximum aggregate of 120 mm). The tests on standard 15 × 30 cm cylinders were made with the mortar and wet-screened components of this concrete. It is seen that the use of the data from these components together with estimated values of the modulus of the aggregates gives reasonable predictions of the moduli of the dam concrete. This has been verified for a range of ages, from 7 to 180 days.

Application of constitutive models in European codes to RC-FRC

Abstract The recent publication of codes for the design of FRC is a major step towards extending the use of the material. An in depth analysis indicates several differences between the constitutive models proposed in the existing codes. In this study, these models are compared and a numerical simulation is performed to evaluate their differences in terms of the structural behavior predicted and measured in an experimental program of RC–FRC elements. The predictions provided by the models fit satisfactorily the experimental results for elements with steel fibers and with plastic fibers.

New analytical model to generalize the barcelona test using axial displacement

The Barcelona Test has proved to be very suitable for the systematic control of the tensile properties of Fibre Reinforced Concrete (FRC). Nevertheless, the need to measure the total circumferential opening displacement (TCOD) of the specimen entails the use of an expensive circumferential extensometer. In order to simplify the test, studies from the literature propose the use of the axial displacement of the press (δ) instead of the TCOD, obtaining empirical equations to correlate the energy estimated with both measurements. However, these equations are only valid for δ ranging from 1 to 4 mm and were adjusted based on the test results of just a few types of FRC. The verification of this formulation for other types of FRC shows an average error of 51.1%, thus limiting the simplification proposed for the test. In this paper, a new analytical model to convert the δ into the TCOD is developed and validated for a wide range of FRC. Besides being applicable to the whole range of δ, the new model provides a clear physical understanding of the main mechanism observed during the test and shows an average error of only 6.7%, making it possible to simplify the Barcelona test.

Effect of Aging on the Fracture Characteristics and Brittleness of a High-Strength Concrete

Results of notched beam (fracture) tests on a 60-MPa silica fume concrete at the ages of 4, 10, 31, and 232 days are presented. Fracture parameters at the different ages were obtained using the size effect and cohesive crack models, which indicate that the fracture resistance (toughness and energy) decreases and the brittleness increases with the age of the concrete. This trend is attributed to the increase in the strength of the hardened cement paste and the interfaces that leads to less bond cracking and more aggregate rupture, and, consequently, to more brittle failure and lower toughening.

Bioreceptivity evaluation of cementitious materials designed to stimulate biological growth

Ordinary Portland cement (OPC), the most used binder in construction, presents some disadvantages in terms of pollution (CO2 emissions) and visual impact. For this reason, green roofs and façades have gain considerable attention in the last decade as a way to integrate nature in cities. These systems, however, suffer from high initial and maintenance costs. An alternative strategy to obtain green facades is the direct natural colonisation of the cementitious construction materials constituting the wall, a phenomenon governed by the bioreceptivity of such material. This work aims at assessing the suitability of magnesium phosphate cement (MPC) materials to allow a rapid natural colonisation taking carbonated OPC samples as a reference material. For that, the aggregate size, the w/c ratio and the amount of cement paste of mortars made of both binders were modified. The assessment of the different bioreceptivities was conducted by means of an accelerated algal fouling test. MPC samples exhibited a faster fouling compared to OPC samples, which could be mainly attributed to the lower pH of the MPC binder. In addition to the binder, the fouling rate was governed by the roughness and the porosity of the material. MPC mortar with moderate porosity and roughness appears to be the most feasible material to be used for the development of green concrete walls.

Damage in High-Strength Concrete Due toMonotonic and Cyclic Compression-A StudyBased on Splitting Tensile Strength

The splitting tension test is used to determine an engineering measure of the damage induced by uniaxial compressive loading. The method is applied to monotonic and cyclic loading. Tests results indicate that damage in high-strength concrete evolves at a much lower rate than in normal concretes. Also, it is observed that tensile strength could be reduced by 25 percent due to compressive stresses applied in a transverse direction.

Investment priorities for the management of hydraulic structures

Maintenance management of the hydraulic structures requires the selection of the most necessary maintenance intervention to ensure their proper operation and structural safety. Given the characteristics of these structures, many types of damage may appear, so it is not easy to take a decision. The purpose of this paper is to present the Prioritisation Index for the Management of Hydraulic Structures (PIMHS), a multi-criteria decision-making system based on the three axioms of sustainability (social, environmental and economic), which orders and prioritises non-similar maintenance investments in hydraulic structures. The results obtained show that PIMHS can be used by decision-makers to prioritise, in hydraulic structures, all kinds of maintenance interventions where the damages cannot lead to dam break.

Multi-criteria decision-making model for assessing the sustainability index of wind-turbine support systems: application to a new precast concrete alternative

AbstractA multi-criteria decision-making system based on the MIVES method is presented as a model for assessing the global sustainability index scores of existing wind-turbine support systems. This model is specifically designed to discriminate between tower systems in order to minimize the subjectivity of the decision and, thus, facilitate the task of deciding which system is best for a given set of boundary conditions (e.g., height, turbine power, soil conditions) and economic, social and environmental requirements. The model’s versatility is proven by assessing the sustainability index of an innovative new precast concrete tower alternative also described in this paper. As a result of this analysis, some points of improvement in the new system have been detected.