Journal of Materials in Civil Engineering

The main objective of this paper is to provide engineers with data on thickness loss of structural steel members resulting from corrosion. To this end, the writers have collected atmospheric exposure data from many research reports and journal papers. The data are presented in graphs of thickness loss versus exposure that demonstrate the effects of types of environment and steel. The environments include rural, industrial, and marine, becoming increasingly severe in that order. The steels under consideration are A242, A588, copper, and carbon steels, with their corrosion resistance decreasing in that order. Comparisons of the data with the medium corrosivity bands for weathering and carbon steels help to determine the severity of environments and the corrosion resistance of steel compositions. For bare exposed structures, a corrosion allowance should be added to all member thicknesses arrived at by stress calculations can be estimated by extrapolating an applicable thickness loss curve to the end of the service life of the structure. The corrosion allowance thickness loss data obtained from simple test specimens, mostly of the $150\times 100\mathrm{mm}$ size of an index card, must be applied carefully to complex structures such as a bridge, which has a variety of details with different exposure conditions. When portions of a bare, exposed structure remain damp or wet for long periods of time, thickness losses can be much higher than those reported for test specimens exposed at $30°$ facing south. Good structural detailing that prevents moisture accumulation is of utmost importance.

Falling weight deflectometer (FWD) testing has been done extensively in the past to assess structural condition and determine the moduli of pavement layers. The set of modulus values for pavement layers obtained from the backcalculation process may not be accurate even though the computed and measured deflection basin may match within tolerable limits. Extensive interpretation is involved in obtaining the layer moduli of these pavements. Guidelines and tools are provided for calculating layer moduli for flexible pavements. FWD interpretation has become increasingly challenging because more and more of our roads have experienced multiple milling operations and overlays. The characteristics of the structure such as damaged layers, thickness variation, and temperature changes can overwhelm the deflection data, having a far more significant effect than those induced by structural layer stiffness. This study emphasizes that proper interpretation of FWD data involves a complete evaluation of all available data, including core data, roadway data, and section-specific distress information. Evaluating multiple FWD measurements along the sections allows for the evaluation of consistency and assures reasonableness of interpretation.

An experimental study was conducted to characterize the dynamic mechanical properties of elastomer-modified asphalt binders at intermediate and high temperatures. Two types of elastomeric modifiers, styrene-butadiene-styrene (SBS) and styrene-ethylene/butylene-styrene (SEBS), were used at three different concentrations. Short-term aging and long-term aging were simulated by the rolling thin film oven test and the pressure aging vessel test, respectively. A dynamic shear rheometer was used to conduct frequency sweeps at temperatures ranging from 5°C to 75°C in increments of 10°C. Two fitting models were introduced to describe the variation of the selected parameters with temperature. An investigation of the resulting isochronal plots indicated that polymer modification is effective in increasing rutting resistance at high temperatures and fatigue resistance at intermediate temperatures. It was also found that SBES improves the binder rutting resistance more than SBS. However, SBS was found more effective in improving the binder fatigue resistance at intermediate temperatures.

Accelerated corrosion by means of the impressed current technique is widely used in concrete durability tests. In this study, the influence of varying the impressed current density level between 100 and 500 μA/${\mathrm{cm}}^2$ on the actual degree of steel reinforcing bar corrosion as well as on the concrete strain behavior due to expansive corrosion products was experimentally investigated. Twelve reinforced-concrete prisms (150×250×300 mm) were used. The prisms were reinforced by two No. 10 reinforcing bars. Corrosion was induced by means of impressed current using electric power supplies. To depassify the steel reinforcement, 5% NaCl by weight of cement was added to the concrete mix. The strain response due to the expansion of corrosion products was measured at each face of the prisms. At the end of the corrosion phase, all the corroded reinforcing bars were removed, cleaned according to the ASTM G1-90 standard, and weighed to get the actual degree of mass loss. The results showed that, up to 7.27% mass loss, accelerated corrosion using the impressed current technique was effective in inducing corrosion of the steel reinforcement in concrete. With respect to Faraday's law, the use of different current densities has no effect on the percentage of mass loss. However, increasing the level of current density above 200 μA/${\mathrm{cm}}^2$ results in a significant increase in the strain response and crack width due to corrosion of the steel reinforcement.

This research studies the potential of using bottom ash from the Mae Moh power plant in Thailand as a pozzolanic material. Bottom ash, which was rarely used in concrete due to its inactive pozzolanic reaction, improved its quality by grinding until the particle size retained on Sieve 325 was less than 5% by weight. Bottom ashes before and after being ground were investigated and compared for their physical and chemical properties. The bottom ashes were used to replace portland cement type I in mortar and concrete mixtures. The results indicated that the particle of bottom ash was large, porous, and irregular shapes. The grinding process reduced the particle size as well as porosity of the bottom ash. Compressive strengths of mortar containing 20–30% of bottom ash as cement replacement were much less than that of cement mortar at all ages, but the use of ground bottom ash produced higher compressive strength than the cement mortar after 60 days. When ground bottom ash was used at a 20% replacement of cement to make concrete, the concrete with higher cement content produced higher percentage compressive strength as well as a higher development rate than those of the low cement content concretes. With the cement content in ground bottom ash concrete of 440 and 260 kg/m³, the concrete needed 14 and 60 days, respectively, to develop higher compressive strength than that of the concrete without bottom ash. As a result of the compressive strengths, it was concluded that ground bottom ash could be used as a good pozzolanic material.

Nowadays, deep cold recycling techniques are increasingly considered an effective method for the preventive and corrective maintenance of existing pavements. Not only are these techniques quickly performed and cost effective, but they also allow one to recycle in-place materials, thus limiting the cost of transportation. Various binders can be used for the cold recycling process, including asphalt emulsion, asphalt foam, hydraulic binders, or mixed binders. Of the latter, asphalt emulsion is most often used with the addition of a small quantity of cement (less than 2% with respect to the total mass of aggregates) to accelerate the breaking of the emulsion. This paper aims at understanding the hydration process, the microstructure, and the mechanical properties of mortars prepared with a new mixed binder made of a cement slurry and a small quantity of asphalt emulsion (SS-1 and CSS-1). Conduction calorimetry data reveal that the cement hydration process is nominally influenced by the presence of a small quantity of emulsion. Scanning electron microscope observations show the good dispersion of the asphalt droplets inside the hydrated cement paste. A cationic emulsion tends to entrain less air than anionic emulsion. Test results also indicate that the introduction of asphalt droplets inside a cement mortar matrix leads to a significant reduction in compressive strength and elastic modulus as well as a slight decrease in flexural strength. Mortars made with the cationic emulsion (CSS-1) show higher strengths and elastic modulus than mortars made with anionic emulsion (SS-1).

Due to increasing traffic levels and vehicle wheel loads, it has become necessary to improve the effectiveness and efficiency of the design of hot mix asphalt (HMA). The Superior Performing Asphalt Pavement (Superpave) mix design and analysis system was introduced for this purpose. The Superpave Gyratory Compactor (SGC) is a vital part of this new mixture design and analysis system. The SGC makes use of a 150-mm- (6-in.) diameter cylindrical mold to produce specimens for design and evaluation under the Superpave system. The objective of this study was to explore the potential for using a 100-mm-(4-in.) diameter mold to produce test specimens in the laboratory. Loose HMA was collected from over 40 paving projects throughout the state of Tennessee. The mixes were tested in the laboratory, and the relative density $(\%G_{\mathrm{mm}})$ of the 150-mm-diameter specimens was statistically compared with that of the 100-mm-diameter specimens. The results of paired t-tests conducted on the data indicate that the difference in $\%G_{\mathrm{mm}}$ is statistically significant. However, further analysis of the data demonstrates that the observed difference in $\%G_{\mathrm{mm}}$ is smaller than the documented precision of the currently available laboratory test methods used. Thus, it is concluded that the observed difference has no “engineering” significance. Based on these findings, it has been recommended to the Tennessee Department of Transportation (TDOT) that it is feasible to use 100-mm-diameter specimens in lieu of the 150-mm-diameter specimens for quality assessment/quality control (QA/QC) acceptance and verification testing of HMA. It should be noted that this recommendation is limited to mixes with a maximum aggregate size of 25.4 mm (1 in.) or less.

The purpose of the present study was to use two solid wastes—fly ash and mixed color waste glass—as constituents in concrete materials. The fly ash with water glass as activation chemical was used as a binder in the concrete, and the waste glass particles were used as aggregate to replace nature aggregate. The present study focused on the potential of alkali-silica reaction (ASR) of glass aggregates used in portland cement mortar and in water-glass activated fly ash (WAFA) mortar. The ASR potential was examined using the accelerated testing method, ASTM C-1260. The results showed that with 10% substitution of natural aggregate by glass particles, the ASR expansion of portland cement mortar depends on the size of glass aggregate. The ASR expansion of WAFA mortar does not depend on the sizes of glass aggregate but on the content of glass aggregate. The ASR expansion of WAFA mortar was below the critical ASR expansion up to 100% of replacement by glass aggregate. The color of glass does not affect the ASR potential of WAFA mortar.

This paper investigates the effect of the processes on fatigue fracture and fracture healing during controlled-strain, dynamic mechanical analysis (DMA) testing. Sand asphalt samples were fabricated with two SHRP-classified binders: AAD-1 and AAM-1. DMA testing was performed at 25°C and at 10 Hz. The mechanical response during DMA testing was monitored using three different damage indicators: (1) change in dynamic modulus; (2) change in pseudo stiffness; and (3) change in dissipated strain energy. When either of these parameters are plotted versus the number of load cycles, two inflection points are apparent that define a significant change in sample behavior due to damage. The second inflection point is a reasonable definition of failure, as it is strongly correlated with the peak of the plot of phase angle versus load repetitions. Furthermore, the phase angle drops precipitously at the second inflection point. By performing controlled-strain torsional fatigue tests at three different strain levels, each great enough to induce damage, a reproducible fatigue relationship (number of load cycles as a function of stress level) is developed. The introduction of several rest periods during testing lengthened fatigue life. Successful development of this testing method is suggested as a potential specification-type test method because of its efficiency, reproducibility, and reliability.

This paper is aimed at investigating permeation-related properties of high performance concrete utilizing fly ash and microsilica as cement replacing materials. Oxygen permeability, porosity, and sorptivity of concrete incorporating fly ash and microsilica prepared with various water-binder ratios were determined. In order to investigate the influence of curing conditions, moist curing, air curing, and curing at 5°C were employed. A mixing procedure of blended systems has been proposed. Based on the experimentally obtained results, prediction models were developed. These enabled the establishment of isoresponse contours showing the interaction between the various parameters investigated. It was found that there is an interaction of fly ash and microsilica with the level of replacement. The incorporation of 8–12% microsilica as cement replacement yielded the optimum permeability, porosity, and sorptivity values.

The effect of waveform and loading sequence on the low-cycle fatigue life of spruce was investigated using parallel-to-grain compressive tests. Triangular, sinusoidal, and square waveforms were used, with a peak stress level of 90% of static compressive strength and a load frequency of 0.5 Hz. Duty ratios ranging from 0.10 to 0.90 were adopted for square waveforms. Two types of stepped-cyclic-loading sequences with a duty ratio of 0.50 were also used. It was found that fatigue life is a function of the work done by the load and the shape of the waveform over a cycle. Damage accumulated most rapidly under square waveforms with a high duty ratio. A triangular waveform is the least damaging of those considered. For waveforms having the same work, the maximum loading rate is the strongest influence on the damage accumulation in wood. High-to-low stepped-cyclic-loading sequences are more damaging than low-to-high sequences, suggesting that wood has “memory.” This study has practical significance to the behavior of compression members and connections within structural systems subjected to cyclic loads.