612 research outputs found
Chloride Ingress of Carbonated Blast Furnace Slag Cement Mortars
No full textIn the Netherlands civil engineering structures, such as overpasses, bridges and tunnels are generally built using blast furnace slag cement (BFSC, CEM III/B) concrete, because of its high resistance against chloride penetration. Although the Dutch experience regarding durability performance of BFSC concrete has been remarkably good, its resistance to carbonation is known to be sensitive, especially when the used slag percentage is high. In a field investigation on a highway overpass damage was found in sheltered elements such as abutments and intermediate supports, which was attributed to chloride induced corrosion enhanced by carbonation that occurred prior to the chloride exposure.Many structures built using BFSC could be prone to this mechanism, i.e. carbonation enhanced chloride induced corrosion, negatively affecting their durability. Focus of the research was given on the influence of carbonation on the chloride penetration resistance of BFSC mortars with varying slag content. In light of the characteristics from the overpass case, it was assumed that first there is a period of carbonation during sheltered exposure, and subsequently joint leakage causes exposure to chlorides. In order to identify the influence of slag content on carbonation, chloride penetration resistance and their coupled effect, mortars with twelve cement blends in a range of 0–70% slag were evaluated based on chloride migration coefficient, accelerated carbonation and electrical resistivity.This study shows that carbonation of BFSC mortars increases the porosity, consequently decreasing the chloride penetration resistance. Binders with 50% or more slag were found to have a significantly lower resistance after carbonation. Consequently, the chloride penetration resistance of a given concrete cover strongly depends on the duration of carbonation and the resulting carbonation depth, hence influencing its lifespan. The service life was estimated using a simplified model for the chloride penetration time of a combined carbonated and uncarbonated layer. It was found that mortar with a slag content between 35 and 50% that was carbonated before chloride exposure show the lowest influence of carbonation on the chloride penetration resistance.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen
Chloride ingress of carbonated blast furnace slag cement mortars
No full textIn the Netherlands infrastructural works, such as bridges and overpasses, are generally constructed using blast furnace slag cement (BFSC) concretes, because of the relative high resistance against chloride penetration from de-icing salts. However, sheltered elements constructed in BFSC concrete are prone to carbonation, for example abutments and support beams. From the field investigation at the Hattemerbroek overpass, concrete damages were found at the abutments and attributed to chloride induced corrosion enhanced by carbonation. This research focuses on the influence of carbonation on the chloride penetration resistance of BFSC mortars and the effect of slag content. For the influence of carbonation on chloride penetration resistance it is assumed that there is a sheltered carbonation period before exposure to chlorides, like an abutment exposed to chlorides after a joint starts to leak. This research was needed since there are up to 2000 concrete structures like Hattemerbroek, executed in BFSC and prone to carbonation enhanced chloride induced corrosion. In order to identify the influence of different slag contents (0-70%) on carbonation, chloride penetration and their coupled effect, twelve slag cement blends were tested. Chloride penetration resistance was expressed by means of electrical resistivity and chloride diffusion coefficient determined from the RCM-test in accordance with NT Built 492. Research shows that carbonation of slag cement mortars increases the porosity, consequently decreasing the chloride penetration resistance. A 70% slag sample with a relative high chloride penetration resistance before carbonation was found to have a significantly lower resistance after carbonation. The chloride penetration resistance is strongly dependent on the carbonation duration and its corresponding carbonation depth. Mortar specimens with a slag content between 35-55% carbonated before chloride exposure showed less influence of carbonation on the chloride penetration resistance.Civil Engineering and GeosciencesStructural EngineeringMaterials and Environmen
Search for systematic errors in a stopping anti-proton experiment in the Saclay 81 cm chamber
No full text
Measurement of B(d)0 - anti-B(d)0 oscillations
No full textBd 0meson oscillations are measured in hadronic Z0decays using the charge of a lepton or the mean charge of an event hemisphere to sign the presence of a b or a b quark when it is produced, and using the charge of a lepton emitted at large ptor of a D∗±to sign the presence of a B or a B meson when it decays. With 3.2 million hadronic Z0decays registered by DELPHI between 1991 and 1994, the mass difference Δmdbetween the two physical Bd 0states is measured in four channels: Δmd= 0.523 ± 0.072 ± 0.043 ps-1(D∗±- Qhem) Δmd= 0.493 ± 0.042 ± 0.027 ps-1(ℓ - Qhem) Δmd= 0.499 ± 0.053 ± 0.015 ps-1((π∗- ℓ) - Qhem) Δmd= 0.480 ± 0.040 ± 0.051 ps-1(ℓ - ℓ). Taking into account the statistical overlap between these measurements and the common systematic uncertainties, the combined result is: Δmd= 0.497 ± 0.035 ps-1.0info:eu-repo/semantics/publishe
Energy consumption of a laboratory jaw crusher during normal and high strength concrete recycling
No full textThis paper presents the measurement and analysis of energy consumption of a laboratory jaw crusher during concrete recycling. A method was developed to estimate the power requirements of a lab-scale jaw crusher. The impact of material properties on the crusher performance is studied. Eight concrete strength classes (C20/25–C80/95) were considered in the approach. Concrete specimens were cured for 28 days; at which time, concrete properties were obtained through tests such as bulk density, compressive strength, tensile strength, rebound number and ultrasonic pulse velocity. The impact of different aperture size (5 mm and 25 mm) on the energy consumption was also studied. From the experimental results, it is demonstrated that there is a strong dependance of energy consumption on the compressive strength of concrete. Energy of crushing for specimens with a 90 MPa compressive strength was four times higher than the energy needed to crush specimens with a 28 MPa compressive strength. Furthermore, the crushing requires three times more energy when the smaller aperture size is used to process concrete specimens. The results of this study can form a basis for a future large-scale field analysis and a detailed determination of the energy and economic efficiency of concrete recycling.Materials and EnvironmentHeritage & Architectur
- …
