Journal of Astm International 

About: Journal of Astm International is an academic journal. The journal publishes majorly in the area(s): Corrosion & Paris' law. It has an ISSN identifier of 1546-962X. Over the lifetime, 2058 publications have been published receiving 15831 citations.

A New Test Method for Porosity Measurements of Portland Cement Pervious Concrete

Abstract: Pervious concrete is emerging as an alternative material for paving to help curtail nonpoint source pollution problems. The porosity of pervious concrete is an important variable needed for pavement system design and for material comparisons. This paper researches a method for measuring the porosity of pervious concrete from field-obtained cores by applying the Archimedes principle and using standard materials laboratory equipment. The error between different operators at different testing facilities was found to be around 2.2 % porosity.

Fracture Resistance Characterization of Superpave Mixtures Using the Semi-Circular Bending Test

Abstract: The fracture resistance of asphalt mixture is an important property directly related to pavement distresses, such as cracking. This paper reports the investigation of a newly-developed semicircular bending (SCB) test as a candidate test for the fracture resistance characterization of asphalt mixtures. Thirteen Superpave mixtures, designed with four different binder types (AC-30, PAC-40, PG70-22M, and PG76-22M) and four different compaction levels (Ndesign = 75, 97, 109, and 125), were considered in this study. The SCB tests were conducted at 25°C using a three-point bending fixture in a MTS testing system. The fracture resistance was analyzed based on an elasto-plastic fracture mechanics concept of critical strain energy release rate, also called the critical value of J-integral (JC). Preliminary results indicate that the JC values were fairly sensitive to changes in binder type and nominal maximum aggregate size (NMAS) used in Superpave mixtures. This study suggests that the SCB test could be a valuable correlative tool in the evaluation of fracture resistance of asphalt mixtures.

Proposed Method for Determining the Residual Mortar Content of Recycled Concrete Aggregates

Abstract: Recycling concrete from demolition of existing structures and using it as recycled concrete aggregates (RCAs) in structural-grade concrete have significant economic and environmental benefits. Currently, only a small portion of the concrete waste is reused in building construction, while most of it is used as either pavement base course or sent to landfills for disposal. The lack of confidence in the material properties of the concrete produced with RCAs is generally the main reason for its under-utilization in structural concrete. It has been demonstrated in the literature that the amount of residual mortar attached to the original (or “virgin”) aggregate particles is one of the factors affecting the material properties of RCAs. Therefore, before using RCAs in new concrete, it is crucial that the residual mortar content (RMC) is determined accurately; however, currently there is no standard procedure to determine this quantity. In this paper, an experimental method is proposed to determine the RMC of RCAs. The method comprises a combination of mechanical and chemical stresses that disintegrate the residual mortar and destroy the bond between the mortar and the natural aggregates. The mechanical stresses are created through subjecting RCA to freeze-and-thaw action, while the chemical degradation is achieved through exposure of the RCA to a sodium sulphate solution. The results of the proposed test procedure are validated by means of comprehensive image analysis. With the proposed approach, the attached residual mortar can be adequately removed, and the residual mortar content can be determined.

Pervious Concrete Mixture Proportions for Improved Freeze-Thaw Durability

Abstract: Recent stormwater management regulations from the Environmental Protection Agency (EPA) and greater emphasis on sustainable development has increased interest in pervious pavement as a method for reducing stormwater runoff and improving stormwater quality. Pervious concrete is one of several pervious pavement systems that can be used to reduce stormwater runoff and treat stormwater on site. Pervious concrete systems have been used and are being proposed for all parts of the United States, including northern climates where severe freezing and thawing can occur. The purpose of the research is to develop pervious concrete mixtures that have sufficient porosity for stormwater infiltration along with desirable porosity, strength, and freeze-thaw durability. In this research, concrete mixtures were developed with single-sized river gravel aggregate (4.75 mm) and constant binder contents, together with high range water reducer. River sand was used as a replacement for up to 7 % coarse aggregate. Two different types of polypropylene fibers (a shorter fibrillated variable-length and a longer fibrillated single-length) were incorporated at several addition rates from 0 to 0.1 % by volume of concrete. The engineering properties of the aggregate were evaluated along with the porosity, permeability, strength, and freeze-thaw durability of selected concrete mixtures. The results indicate that the use of sand and fibers provided beneficial effects on pervious concrete properties, including increased strength, maintained or improved permeability, and enhanced freeze-thaw resistance.

Review of Deformation Mechanisms, Texture, and Mechanical Anisotropy in Zirconium and Zirconium Base Alloys

Abstract: The deformation systems in hexagonal close-packed (hcp) metals are not as symmetrically distributed as in cubic ones. Furthermore, because the primary slip systems are not as numerous and are limited to deformations in the direction, twinning competes with slip in plastic deformation and can, depending on the deformation conditions, play an essential role. In order to explain the conditions in Zirconium and Zircaloy, the well-established relationships of hcp metals are discussed and so are their dependencies on the metal-specific parameters of the hexagonal structure. The interactions between deformation mechanisms and texture formation on the one side and deformation mechanisms and mechanical anisotropy on the other can be likewise transferred to other hcp metals, if one takes into account the differences in dependence of the metal-specific parameters. The low offer of slip systems, their asymmetrical distribution (prism slip in directions and — under constraint — pyramidal slip in directions) as well as the strict crystallographic orientation relationships of first and second order pyramidal twinning result in the formation of a strong deformation texture. By virtue of twinning, even small deformation rates lead to large lattice rotations, which change the orientation of the crystallites where all basal poles align in the direction of the compressive force. The fact that in Zirconium and Zirconium base alloys the preferred crystallographic orientation, which is spread in the transverse direction, is also retained as the final stable position is explained by pyramidal slip. The decisive factor in texture development is the material flow, the degree of freedom of which is lowest for tube reducing as compared to sheet rolling and wire drawing processes. Therefore tube reducing (characterized by reductions in cross-section RA, wall thickness RW, and diameter RD) permits the most precise predictions of the operative forces and the resulting deformation mechanisms. Systematic investigations on the influence of the reduction parameters on the resulting preferred crystallographic orientation in Zircaloy tubing have shown that the determining factor controlling the texture development is the ratio RW1RD. For RW1RD > 1, the basal poles align preferentially in the radial direction. For RW1RD = 1, the basal poles are randomly distributed in the radial-tangential plane. For RW1RD 1, because in both examples the material flow is characterized by a preponderance of wall thickness reduction. The fiber texture of wire is identical to the texture of tubes for RW/RD = 1. One can visualize the wire deformation as corresponding to that of concentric tubes with different diameters to comply with tube reduction rates RW1RD = 1 under the condition of constant volume. Independent of the fabrication method for the cold-worked semi finished products, a first order prism pole aligns itself parallel to the direction of elongation. (During recrystallization, the basal poles do not change significantly. The basal planes, however, rotate continuously with increasing annealing temperature by ± 30° around their pole, so that in the final stable position, instead of a first order prism pole [cold deformation texture], a second order prism pole becomes parallel to the axial or rolling direction, respectively.) Knowing these dependencies, it is possible to tailor the texture of Zirconium base alloys tubing within the given limits to the requirements in nuclear application. For textured materials, on the other hand, the deformation mechanisms are also responsible for the strong anisotropy of the mechanical properties. This is discussed on the example of specially prepared Zircaloy tubes, which were machined out of a sufficiently thick Zircaloy plate with pronounced sheet texture. By this procedure, one obtains around the circumference of the tubing continuously changing preferred orientations of the basal poles with the extreme orientations possible in Zircaloy tubing. For the different uni- and multiaxial loading conditions applied, the theoretical predictions of the mechanical behavior agrees in any case with the experimental results. In nuclear application, the anisotropic behavior of biaxial loading conditions is represented by yield loci, creep loci, or burst loci according to the respective criteria yield stress, creep rate, or fracture stress. Depending on the texture and the loading conditions, an attempt is made to correlate the shape of the loci to the operative deformation mechanism. In this way, it is possible to find selection criteria for the desirable texture in Zircaloy cladding tubes.