Journal of Materials in Civil Engineering

This study addresses the characterization of fiber-matrix interfacial properties and the apparent strength of high-strength hydrophilic fibers. Single-fiber pullout bond tests and single-fiber pull-to-rupture strength tests were conducted by employing polyvinyl alcohol (PVA) fibers. The pullout bond tests showed that these fibers have surprisingly high chemical and frictional bond strengths. The chemical bond strength was relatively stable independent of a water-to-cement ratio of matrix and the fiber type tested, contrary to the friction bond strength. The pull-to-rupture strength tests revealed that the apparent strength of the PVA fibers in cementitious composites is considerably lower than that in standard fiber strength tests. The apparent strength was further reduced with inclining angle of fiber alignment. This effect was captured by a simple phenomenological model in this study, which introduces the apparent strength reduction factor. The combined effects of high bond strength and degraded fiber strength will likely contribute to composite performance less than would be expected from a high-performance fiber.

The purpose of this publication is to determine the relationship between cracking in the loaded reinforced concrete and corrosion of embedded steel in a chloride environment. This paper deals with the synthesis carried out over a 12-year period on reinforced concrete elements kept in a loading state, in a confined salt fog. Test specimens were 3-m-long beams, which is a sufficient size to be representative of the actual operating conditions of reinforced concrete structures. The development of corrosion in concrete specimens was assessed by recording the development of secondary cracking. The interpretation of the results obtained on the different type of beams allowed one to conclude that the development of reinforcement corrosion is not influenced by the widths of cracks (for widths less than 0.5 mm) or by the crack itself. The results appear to indicate that the load applied to a reinforced concrete beam plays an important role in the penetration of aggressive agents and then in the corrosion of the reinforcement.

Measurements of the permeation or sorption characteristics of concrete are increasingly being used as indexes of durability or resistance to chemical attack of new concrete. This investigation was intended to find if these relatively simple, inexpensive tests can be used to assess the condition of the concrete in mature structures that may have deteriorated during their service life. Such structures may be nearing the end of their design life, but it may be necessary to extend their service life. In such cases the state of the concrete needs to be assessed. The paper explores the profiles of oxygen permeability and water sorption, with distance from the surface, of concrete taken from in-service structures typically in the 20 to 30 year age range and hence proposes generalized permeability and sorption profiles. However, as the two types of measurement, permeability and sorption, do not, for concrete from in-service structures, correlate one with the other or with carbonation depth or strength, it is unlikely that either parameter is a valid index of the overall state of concrete from a mature structure.

The rheological properties of asphalt binder have a great influence on asphalt pavement performance, particularly in terms of rutting, thermal, and fatigue cracking. The current asphalt specifications, such as those used in Arabian Gulf countries, are based on conventional consistency tests focused on the workability of asphalt during the construction of pavements. These methods do not have the capability to predict pavement behavior and performance. This study is an effort to address the importance of adopting newly developed asphalt specification tests by the Strategic Highway Research Program (SHRP), to characterize and evaluate Arabian Gulf produced asphalts in terms of low-temperature cracking. The major finding of this study has been that all Arabian Gulf asphalts can satisfactorily withstand the low-temperature effects prevailing in the area.

Flowable concrete is used for the basemat of Kawasaki Manmade Island, because only superplasticized concrete can meet the stringent performance requirements of this project. Due to the large volume of concrete required, construction joints are bound to occur. To assist in the development of an ultimate concrete placing cycle for the basemat, a series of tests has been conducted to evaluate the possible effects of construction joints in this mass flowable concrete. The general procedure for these tests is designed to simulate the worst real condition that could be encountered in the field. Simulation of construction joints is achieved by creating an artificial joint in each of the concrete test samples. Compressive strength and concrete flowing capability are used as the main criteria. The key data generated and observations made during the evaluation are presented. Conclusions and recommendations regarding placement of mass flowable concrete are given.

When junk automobiles are shredded to recover the ferrous and nonferrous metals for recycling, a large quantity of nonmetallic residue, commonly called automotive shredder residue (ASR), is generated. Because ASR mostly contains plastic and rubber related materials, and the addition of plastic and scrap rubber from waste tires as a road material has been proven to be effective in solving existing pavement related problems, attempts were made to examine the feasibility of ASR as a road material additive. As a part of this effort, compatibility, rheological, and leaching properties of ASR modified asphalt were studied. The photomicrographs and Tg of ASR modified asphalt demonstrated some compatibility between ASR and asphalt. Dynamic mechanical analysis indicated that rutting and aging properties of asphalt should improve with the addition of ASR. The toxicity characteristics leaching procedure test indicated that leaching levels of various metals from ASR modified asphalt were well below the Environmental Protection Agency regulatory level.

This paper presents experimental results regarding freezing and thawing performance of various concrete paving blocks using a standard accelerated laboratory test, ASTM C 666, procedure A. A total of 124 paving blocks having eight different mixture proportions, prepared at optimum moisture content and fabricated at a commercial plant site, were used. The parameters investigated included bulk characteristics (density, absorption, and compressive and splitting tensile strength) and mass loss under various freezing and thawing cycles. It was found that ASTM C 666 can be utilized successfully to evaluate the relative performance of various paving blocks. Mass loss correlated well with the cement content (aggregate-cement ratio) and the bulk properties of the paving block samples. Minimum cement content, instead of minimum strength or maximum absorption, is the most suitable requirement for ensuring a reasonable freezing and thawing resistance for concrete paving blocks.

Fiber-reinforced polymer composite (FRPC) wrap has been established as an effective method for rehabilitation and strengthening of concrete structures. This paper presents the results of an experimental study on the performance of concrete columns wrapped with carbon and glass FRP composite sheets subjected to wet-dry and freeze-thaw conditions. Concrete columns were wrapped with three different types of FRP tow sheets: two carbon and one glass. Test variables included the type of fiber (C1, C5, and GE) and the environmental exposure conditions. The specimens were conditioned in the following three different environments: (1) room temperature (+20°C); (2) 300 wet-dry cycles using salt water; and (3) 300 freeze-thaw cycles. At the end of each exposure, stress-strain behavior in compression was obtained to evaluate their strength, stiffness, and ductility, which were compared with the performance of unconditioned samples. Results show that the specimens wrapped with carbon fiber–reinforced polymer (CFRP) experienced no reduction in strength or ductility caused by wet-dry exposure, whereas samples with glass fiber–reinforced polymer (GFRP) experienced reduction in both strength and ductility. In the case of freeze-thaw exposure, both CFRP- and GFRP-wrapped specimens experienced significant reductions in strength and ductility. The specimens subjected to freeze-thaw cycling also exhibited more catastrophic brittle failure as compared with the unconditioned and the wet-dry conditioned specimens.

A compilation of experimental results on the mechanical properties of concrete when exposed to rapid heating as in a fire are presented. Emphasis is placed on concretes with high original compressive strengths, that is, high-strength concretes (HSCs). The compiled test data were categorized by the test methods and the types of aggregate used and compared for behavioral differences. The comparison revealed distinct difference in mechanical properties of HSC and normal-strength concrete (NSC) in the range between room temperature and approximately 450°C. The differences narrowed at temperature above 450°C. Also presented is a comparison of these test results with existing code provisions on the effects of elevated temperature on concrete strength. It is shown that the Eurocode provisions and the Comités Euro-International Du Beton (CEB) design curves are more applicable to NSC than to HSC. In fact, these provisions are unsafe when compared with HSC test results. The study showed a lack of experimental data for lightweight HSC and HSC heated under a constant preload to simulate the stress conditions in HSC columns.