Journal of Materials in Civil Engineering

A reliable method of predicting the thickness loss of weathering steel due to corrosion is currently unavailable. Corrosion loss depends significantly on the service life of the structure, the corrosive nature of the environment, and the alloy content of the steel. Therefore, a prediction method accounting for these factors should be possible. Models showing the effects of five alloying elements (copper, nickel, chromium, silicon, and phosphorus) on thickness loss in three environments (rural, industrial, and marine) are provided in this paper based on a comprehensive database. The models result in correlation coefficients higher than 0.95. The effects of the alloying elements indicated by the models show that failure to properly account for the alloying elements can yield as much as 20% error in thickness loss. The model can be integrated with existing service life models to forecast a thickness loss estimate for a required design life.

Polymer cement mortar (PCM) retrofitting is one of the largely used strengthening methods for repairing fatigue deteriorated highway bridge slabs in Japan. In this method, reinforcing bars are arranged underneath the lower surface of the slab and polymer cement mortar is sprayed onto them. Debonding of the PCM overlay is one of the major causes leading to failure of the repaired slabs. This paper mainly discusses this failure mechanism, its initiation, and suggests a method for quantitative analysis of the failure behavior. The stress transfer mechanism was measured using the strain distribution in the strengthening bars and a relationship for the bonding strength was obtained. Hence the relationship for the peeling load was obtained.

The bulk specific gravity $\left({\mathrm{G}}_{\mathrm{mb}}\right)$ of compacted hot-mix asphalt (HMA) specimens is the basis for volumetric property calculations during mix design and quality control and assurance. For many years, ${\mathrm{G}}_{\mathrm{mb}}$ measurement has been accomplished by water-displacement procedures. Water displacement yields accurate ${\mathrm{G}}_{\mathrm{mb}}$ for most conventional dense-graded mixes, but ${\mathrm{G}}_{\mathrm{mb}}$ measurement errors using water displacement have been observed for coarser-graded mixes. Recently, vacuum-sealing technology, using the Corelok vacuum-sealing device has been shown to yield more accurate ${\mathrm{G}}_{\mathrm{mb}}$ values. This study’s objectives were to illustrate ${\mathrm{G}}_{\mathrm{mb}}$ differences between water-displacement and Corelok procedures and resulting changes in volumetric properties and design asphalt contents. Results indicate significant ${\mathrm{G}}_{\mathrm{mb}}$ differences between Corelok and water-displacement procedures, with the Corelok procedure yielding slightly higher ${\mathrm{G}}_{\mathrm{mb}}$ values, resulting in an average increase in design asphalt content and voids in the mineral aggregate of 0.29 and 0.64%, respectively, relative to water-displacement procedures.

The characteristics of engineered cementitious composites (ECCs) subjected to dynamic tensile loading and high-velocity projectile impact have been investigated and are reported in this paper. Hybrid-fiber ECC containing a combination of high-modulus steel fibers and relatively low modulus polyethylene fibers was adopted to achieve a desired balance between the ultimate strength and the strain capacity of the material required for impact- and blast-resistant structures. Dynamic uniaxial tensile tests at varying strain rates of $2\times {10}^{-6}\text{to}0.2{\mathrm{s}}^{-1}$ were carried out, and ECC was found to be able to provide much higher enhancement in tensile strength than plain concrete and still be able to maintain pronounced tensile strain-hardening behavior. At higher rates of strain, ECC showed multiple-cracking behavior, similar to that observed from quasi-static tests, with tight crack width of about $0.1\mathrm{mm}$ . The results from high-velocity $(300–750\mathrm{m}∕\mathrm{s})$ impact tests demonstrated the potential of ECC in providing improved functionality (compared with concrete) as a protective material in aspects such as increased shatter resistance with reduction in damage arising from scabbing, spalling, and energy absorption associated with distributed microcracking.

Measuring the thickness of concrete elements in the field can be challenging. In many cases, such measurements must be made from one side due to a lack of access to the opposite face. One technique commonly implemented in these situations is the impact echo method, which requires advance knowledge of the compression, or P wave, velocity through the concrete at the point of interest. Common practice is to measure the near surface P-wave velocity at that point and then use this velocity to represent the through thickness P-wave velocity in the calculation of thickness. However, the relationship between near surface P-wave velocities and through thickness P-wave velocities can vary significantly under different exposure conditions. Using near surface P-wave velocity to represent through thickness P-wave velocity is not necessarily a valid assumption and should only be done when further information is available to substantiate the relationship. It is possible to detect damage due to sulfate attack in concrete specimens using P-wave velocity measurements, though actual identification of the nature of that damage is not feasible.

A reinforced concrete bridge deck located in Albion, Mich. was subjected to quantitative microcrack analysis for assessment of its health condition. Statistical sampling and quantitative microscopic techniques were used in the investigation. A dedicated software system was developed for image analysis of concrete planar sections and stereological analysis of data to quantify the (three-dimensional) microscopic system in concrete. The bridge deck under investigation was divided into three subregions with different (visual) damage conditions. Cores were extracted from different subregions using statistical criteria to ensure the adequacy of the number of cores. Some cores were used to determine mechanical properties of concrete; others were used for microstructural investigation. Two perpendicular sections were cut from the cores, and were prepared for environmental scanning electron microscopy. Statistical analysis of the quantified (spatial) features of the microcrack system revealed significant difference in concrete microcrack conditions between different subregions. The results emphasized the value of quantitative microscopy in assessment of the health condition of concrete based-infrastructure systems and the relation between microcracks characteristics and transport properties.

Results are presented from experimental work that was conducted in order to study the mechanical behavior of damaged structural elements in bending. Both repaired and unrepaired concrete elements (beams) were considered in this program. These elements were damaged using an accelerated local corrosion process that consisted of chloride penetration. Both locally corroded tensile reinforcement (Series I) and locally corroded compressive reinforcement (Series II) are considered independently. The structural behavior and the efficiency of repair systems in the ultimate and service limit states were evaluated. The work focuses on the pattern of structural cracks, displacements, load-bearing capacity, and ductility variations to examine the influence of the adopted repair systems on both limit states. The experimental results made it possible to assess the effect of the detailing, the degree of corrosion, and the presence of the repair patch in the structural behavior of the beams. As a result, general recommendations are proposed for patch-repaired elements.

Bentonite slurry without cement is used for seepage barriers such as slurry trenches or grouting, but the sodium-bentonite content in the slurry cannot be increased to more than $100\mathrm{kg}∕{\mathrm{m}}^3$ . Slurry with such low bentonite content is not enough to achieve impermeability of the slurry walls or grouting. Using hydrophilic solvents such as ethanol can depress the bentonite swelling, and the liquid limit can be decreased to less than 100%. Therefore ethanol is used for the mixing liquid when preparing the slurry, and the bentonite concentration can be increased to more than $100\mathrm{kg}∕{\mathrm{m}}^3$ in the slurry state. Ethanol/bentonite slurry can be grouted to small spaces with sufficient cutoff performance. This paper reports the high potential of ethanol/bentonite slurry for seepage barriers based on the following characteristics: low permeability, smooth groutability, and sealing ability with the substitution of ethanol with water. The high potential of ethanol/bentonite slurry for grouting was confirmed through the filling tank test.

An extensive experimental study of the monotonic, recovery, and cyclic behavior of two bitumens commonly used for pavement construction in the U.K. was performed over a wide range of strain rates, stresses, and temperatures. The steady-state monotonic and cyclic behavior of the materials followed the modified Cross model with the bitumen exhibiting linear and nonlinear viscous behavior at low and high stresses, respectively. Continuous and pulse-loading cyclic tests revealed that the behavior of the bitumen is mean-stress governed in the continuous cyclic tests while strain recovery is important in the pulse-loading tests. A phenomenological model calibrated by a minimum of four tensile experiments is proposed and shown to capture the bitumen response accurately over all the loading histories (monotonic, continuous cyclic, and pulse loading) and temperatures investigated.

Results of experimental investigation of the properties of rapid-hardening concrete are presented. Three types of cements that can achieve $14\mathrm{MPa}$ compressive strength and $2.4\mathrm{MPa}$ modulus of rupture after $3\mathrm{h}$ at $22°\mathrm{C}$ and remain workable for $10\text{to}15\min$ were selected based on an extensive literature review. The variables in this study were (1) cement type, (2) cement content, (3) water-cement ratio, (4) use of admixtures, and (5) temperature. The measured parameters were (1) strength gain with time, (2) slump loss with time, (3) workability, (4) plastic and drying shrinkage, and (5) relationship between compressive strength and modulus of rupture. Test results showed that for those selected cements it is possible to achieve a workable concrete having $14\mathrm{MPa}$ compressive strength and $2.4\mathrm{MPa}$ modulus of rupture after $3\mathrm{h}$ . The strength gain in flexure was more rapid than the strength gain in compression. The concrete had good flowable characteristics with vibration, and the use of retarding admixtures increased workability time up to $25\min$ . Plastic and drying shrinkage test results showed that rapid-hardening cement is more susceptible to plastic shrinkage than ASTM Type I cement, and care should be taken that exposed surfaces are protected by curing to avoid water loss.

Hydrated lime is evaluated as a filler in bitumen and is compared to similarly sized filler comprised of calcium carbonate, limestone. Extensive laboratory testing is considered, including rheological testing of mastics (with a dynamic shear rheometer, a dynamic mechanical analyzer, and a bending beam rheometer); low temperature elongation and fracture tests on mastics; torsional fatigue testing of mastics; fatigue testing of mixtures; and permanent deformation testing of mixtures. These tests confirm that hydrated lime as a filler significantly impacts the rate and level of microcrack-induced damage, microdamage healing, and plastic and viscoelastic flow in both mastics and mixtures across a wide range of temperatures (from low to high temperatures, representative of the pavement environment). Hypotheses are presented based on rheological models of filled liquids and bitumen microstructure to explain the test results and the fact that the response of hydrated lime as a filler in bitumen requires an understanding of the physical and chemical interactions on both the micro- and nanoscale. Furthermore, the impact of hydrated lime as a filler is dependent on its interaction with a specific bitumen.

A new unified five-parameter failure surface has been proposed for use with normal strength (NC), high strength (HSC), and steel fiber-reinforced (SFRC) concrete under biaxial, triaxial, or axisymmetric loads. The study covers concrete with strengths ranging from $20\text{to}130\mathrm{MPa}$ . The failure surface developed for plain concrete has been modified to account for the presence of steel fibers. The proposed failure surface was verified against experimental data of unconfined NC, HSC, and SFRC under multiaxial loads, as well as concrete confined by steel tubes. To facilitate the implementation of the failure surface into a finite-element package, a closed-form solution for predicting the state of stress in concrete has been developed. This failure criterion was successfully incorporated into constitutive models for plain concrete and SFRC. Experiments of plain concrete cubes and SFRC plates under multiaxial loads, as well as SFRC beams under two-point load, were modeled to illustrate the application of the failure surface to a wide range of concrete under varying load conditions. Good agreement between analytical and experimental results is observed.

This paper focuses on some issues pertaining to brick-mortar bond and masonry compressive strength. Failure theories for masonry under compression make the assumption that the bond between brick and mortar remains intact at the time of failure of the brick or mortar. The influence of bond strength on masonry compressive strength is not fully accounted for in these failure theories. In this investigation, the influence of bond strength on masonry compressive strength has been examined through an experimental program using local bricks and mortars. Masonry prism compressive strength has been determined when the brick-mortar bond strength is varied over a wide range without altering the strength and deformation characteristics of the brick and mortar. Brick-mortar bond strength has been determined through flexure bond strength and shear bond strength tests. A relationship between the masonry prism compressive strength and bond strength has been obtained. The results clearly indicate that an increase in bond strength, while keeping the mortar strength constant, leads to an increase in the compressive strength of masonry.