Journal of Materials in Civil Engineering

Roller-compacted concrete (RCC) and soil-cement are similar materials, in that they both are of zero-slump consistency and are placed and compacted with earth-moving or paving equipment. The construction methods used to produce RCC and soil-cement are also quite similar. Yet, in spite of these similarities, there are some fundamental differences between RCC and soil-cement. The following aspects of these two materials are discussed and compared: historical applications with an emphasis on water resources, mixture ingredients, testing procedures, design procedures, properties, construction methods, and costs. This paper identifies the limitations of each material based on properties and performance so that each material is properly applied to a project. Some recommendations and suggestions are introduced to better understand the practical differences and to improve the quality and cost-effectiveness of using these two similar materials.

 The degree of dispersion of short microfibers in cement, as assessed by electrical resistivity measurement for the case of electrically conductive fibers at a volume fraction below the percolation threshold, is improved by the use of admixtures (namely, silica fume, acrylic particle dispersion, methylcellulose solution, and silane) and fiber surface treatment (such as ozone treatment). Acrylic particle dispersion is more effective than latex particle dispersion.

 A viscoelastoplastic continuum damage (VEPCD) model has recently been developed and validated under the auspices of the National Cooperative Highway Research Program 9-19 project, entitled “Advanced Mixture Characterization for Superpave Support and Performance Models Management.” The VEPCD model is able to characterize the viscoelastic and viscoplastic responses of asphalt concrete (AC) in addition to microcracking. The primary objective of this paper is to validate the model under thermal loading conditions that are distinctively different from the mechanical loading conditions used in model development and calibration. Viscoplastic (VP) behavior is a typical response in AC at high temperatures; however, based on the $t\text{-}T$ superposition principle, it is the slow strain rate observed in thermal cracking that triggers the VP response. Measured responses and fracture parameters from thermal strain restrained specimen tensile (TSRST) strength tests were compared with those predicted using the VEPCD model, the viscoelastic continuum damage model, and the linear viscoelastic model. The comparison confirmed: (1) the ability of the VEPCD model to accurately characterize the tensile behavior of asphalt concrete under thermally induced loading; and (2) a decrease in accuracy as the complexity of the model decreases.

Doubts about the strength of wrought iron used in historic structures can be resolved with appropriate methods of evaluation. Since wrought iron is a composite material of metal and slag fibers, its performance in structures cannot be adequately evaluated by the techniques routinely used for testing structural steel. Both historic and modern test data show that wrought irons from different sources vary little in strength but greatly in ductility. Since adequate sampling for mechanical ductility tests is often difficult, alternatives based on metallurgical analysis can assist evaluation of the metal in historic structures. Test data show that more than 0.3% phosphorus in solid solution embrittles wrought iron. This level of phosphorus can be detected by optical microscope techniques. Excessive or poorly distributed slag fiber is the other principal source of inadequate ductility, and can be evaluated by metallographic examination either in place or on samples much smaller than those required for mechanical testing.

This study evaluates reclaimed building materials (RBM), including waste concrete, brick, and tile, used as aggregate for hot mix asphalt (HMA). The analysis method of gray relational analysis (GRA) is presented to determine the best performance of the varying proportions of RBM with igneous crush stone (ICS) on HMA mixtures. Four types of aggregates are used for the mixtures: (a) 100% ICS; (b) 100% RBM; (c) 50% coarse and fine RBM plus 50% coarse and fine ICS (50% RBM plus 50% ICS); and (d) coarse RBM plus fine ICS (C-RBM plus F-ICS). Two types of asphalt cement, AC-10 and AC-20, are used as a binder for the mixtures. Laboratory tests of permanent deformation, resilient modulus, and stripping were evaluated by analysis of variance (ANOVA) and GRA. On the basis of this study, the ANOVA of the permanent deformation test shows that the type of aggregate has a significant effect, no matter what test temperatures and binders are used. The ANOVA of the resilient modulus test shows that the types of binder and aggregate do not significantly affect at test temperatures of 25°C, but significantly affect the types of binder at 40°C. The GRA result indicates that the best performance is the C-RBM plus F-ICS mixtures. For the stripping test, all 4 mixture types satisfied the Agency’s requirements.

A two-step approach is proposed to predict the modulus of asphalt concrete from existing micromechanical models. The asphalt concrete microstructure is represented by a two-phase model, which consists of a large spherical aggregate particle surrounded by a spherical shell of fine aggregate-filler-binder mixture as the matrix. The fine aggregate-filler-binder mixture is further represented by a two-phase model, which treats fine aggregate as a spherical inclusion and the mixture of filler and binder as the matrix. The modulus of asphalt concrete is predicted from the volumetric fractions, Poisson’s ratios, and moduli of the aggregate and filler-binder mixture by applying the appropriate two-phase models in two steps. An asphalt concrete and two mixtures that replicate the fine aggregate-filler-binder submixture and the filler-binder submixture in the asphalt concrete have been tested for modulus. The tests results show that the predicted results from the appropriate models reasonably approximate the measured results.

Open-graded friction course (OGFC) or porous mixtures consist of an open gradation, mostly of coarse size aggregate with little fines. The benefits of an OGFC mixture are typically increased surface permeability, noise reduction, and enhanced surface friction, especially in wet weather. This paper presents the results of a study investigating four different OGFC mixes containing no additives, cellulose fibers, styrene butadiene rubber (SBR) polymer, and a combination of both fibers and SBR polymer. Mix designs were performed according to the design procedure proposed by the National Center of Asphalt Technology for a range of 4.5–6.5% asphalt content. The mixture containing fibers and SBR polymer was selected as an acceptable mix design with an optimum asphalt content of 6.5%. The moisture susceptibility of the selected mix at optimum asphalt content was evaluated. Results were compared with that for a dense mix.

 Steel strain measurements along reinforcing bars allow an indirect determination of bond shear stresses acting between concrete and reinforcement. Traditional measuring techniques such as the application of electrical resistance strain gauges are not entirely satisfactory because they affect the bond properties. This paper describes experiments using wavelength multiplexed optical fiber Bragg grating sensors for strain measurements along 10-mm-diameter reinforcing bars embedded in reinforced concrete beams subjected to bending. The sensors were found to be capable of measuring large strains and strain gradients with high precision, without significantly affecting the bond properties. The experimental results are discussed and compared with calculations according to three bond shear stress-slip models. Recommendations for the application of optical fiber Bragg grating sensors on reinforcing bars are made and a simple method for the deflection calculation of partially cracked beams is presented, providing lower und upper bounds corresponding to maximum and minimum theoretical crack spacings, respectively.

In situ stabilization using cementitious binders has become a common activity for rehabilitating degraded road pavements in Australia. Industrial waste products mixed with traditional binders like general-purpose portland (GP) cement or limes are used as cementitious binders. This paper presents the stabilization of crushed basaltic rocks and clay mixtures using three cementitious binders, namely, general-purpose cement, blended cement (GB), and a binder involving alkali-activated slag (AAS). The good-quality crushed rock was mixed with reactive fine-grained soil (clay) to represent possible field scenarios in reconstructing degraded pavements. The unconfined compressive strengths of the stabilized material at 1-day, 7-day, and 28-day curing stages were measured for varying binder content. The experimental results clearly indicated that mixing clay with good-quality crushed rock can significantly reduce the stabilization potential of the pavement material. It was also observed that the binders with industrial waste products performed well in comparison with the traditional GP cement binder.

The aim of this work is to establish the original quarries used to construct the Roman bridge in Salamanca (Spain). Nineteen granite-type samples from the bridge were obtained. For comparison, 12 samples were taken from eight different quarries, where the original stones were probably exploited. The study is based on element chemical analysis for major elements. The results have been statistically analyzed using an inertia method based on an HJ-biplot. This method permits the characterization of three different clusters of samples and relates them to the original quarries, from the chemical composition of the samples. We conclude that the following three types of granite were used in the Roman bridge of Salamanca: (1) granodioritic granites from the Los Santos quarry, in Salamanca; (2) leucogranites from quarries in Villaseco de los Gamitos, Ledesma, Trabanca, and Zorita (Los Arribes, Salamanca); and (3) vaugneritic granites, probably from the quarry in Ledesma (Salamanca). The chemical changes produced by weathering of the different types of granites through the different decay processes in different areas of the Roman bridge in Salamanca have also been observed.

 In this study, steel-concrete interface defects were analyzed in order to define their potential to induce corrosion. Various types of steel-concrete interface defects were classified into two main groups: macrodefects and microdefects. Gaps formed beneath horizontal reinforcement as a result of bleeding and settlement of fresh concrete were analyzed for macrodefects. Microdefects presented no signs that could be identified by visual inspection and resulted not only from controlled pull-out of the steel bar but also from bleeding and settlement (but without the production of macrodefects as found with gap formation). Apart from interface defects, cover concrete porosity was defined as an intrinsic defect. The effect of these defects on reinforcement corrosion was investigated. Macrodefects have a direct effect on corrosion, whereas microdefects have no significant effect on corrosion. Where the level of intrinsic defects was high, these had a greater effect on corrosion than interface macrodefects. The behaviors of conventional and self-compacting concrete (SCC) were compared. SCC was found to have better interface quality.

The testing described in this paper was performed to establish the physical and mechanical properties of new and recycled crushed clay brick aggregates for use in portland cement concrete (PCC). Various physical and mechanical properties of eight different types of aggregates were determined and compared with the limits set out in the British Standards for aggregate from natural sources used in concrete. The results were also compared with granite aggregate that has been proved to be a good natural aggregate for producing PCC. The results showed that most of the crushed clay-brick aggregates tested can be used in producing PCC for low-level civil engineering applications and that some kinds of brick aggregate possess good physical and mechanical properties that qualify them for producing high-quality concrete.

A transient, two-dimensional finite-difference model is developed to assess temperature fluctuations in asphalt pavements due to thermal environmental conditions. Fluctuations in temperatures significantly affect pavement stability and the selection of asphalt grading used in pavements. The ability to accurately predict asphalt pavement temperature at different depths and horizontal locations based on thermal environmental conditions will greatly help pavement engineers in performing back-calculations of pavement modulus values and in selecting the asphalt grade to be used in various pavement lifts through detailed examination of predicted pavement temperature distributions on various pavement mixes. A more sophisticated selection of asphalt through specification of less expensive asphalt binders in lower lifts is thus possible for the provision of more economical solutions to rising pavement construction costs. As part of the model validation, sensitivity analyses are performed to study the impact of a number of thermal environmental and pavement geometric parameters on predicted temperature responses.