Journal of Materials in Civil Engineering

This paper presents results of an experimental investigation on the effectiveness of benzotriazole (BTA) as anticorrosion material for steel reinforcement in concrete structures. BTA is used in three different corrosion-protection systems: BTA inhibition, BTA coating, and BTA as a hybrid system. Reinforced concrete beams were cast, exposed to a 3% sodium chloride solution, and subjected to drying and wetting cycles to accelerate the corrosion attack. Electrochemical measurement techniques were used to evaluate the corrosion behavior of reinforcement. These measurements include macrocell corrosion current, linear polarization resistance (LPR), corrosion potential ($E_{\mathrm{corr}}$), and electrochemical impedance spectroscopy (EIS). Chloride penetration profiles for the concrete cover and visual inspection of the reinforcing steel bars were also obtained. The results show that a BTA-steel complex film was formed on the steel bar. This film improves the corrosion resistance of the reinforcing steel. Second, the application of the BTA as a coating system showed better results than the inhibition system. Finally, the results indicated that mixing both systems to form a BTA hybrid system was the best, and it provided higher corrosion resistance and a lower corrosion rate.

The generalized Maxwell model has been widely adopted for the prediction of relaxation modulus of viscoelastic materials, specifically asphalt materials. For practical reasons, relaxation modulus is rarely measured; instead it is predicted from creep compliance tests. In reality, the generalized Maxwell model is an approximate approach to simplify the process of inverting the Laplace transform of the Prony series function such that the computation process of obtaining relaxation modulus from creep compliance can become less complex. An alternative function can be derived to directly invert the Laplace transform of the Prony series function and predict relaxation moduli of viscoelastic materials. This paper presents a computation procedure on the basis of an alternative function that can be used to predict relaxation moduli of viscoelastic materials. The proposed model is capable of inverting the Laplace transform of the Prony series function and predicting the relaxation moduli of viscoelastic materials with only the component of one Maxwell model and one Kelvin element known as a Burger model. The algorithm presented in the proposed model is simple such that it can reduce the complexity of the computational process of inversing Laplace transform and generating Prony series parameters.

During the hydration of Portland cement concrete, free water reacts with the compounds of unhydrated cement to form the hydrated phases that make up concrete. The chemical reaction results in a reduction in the amount of free water and consequently produces hydration products. Thus, the estimate of free water content and other components in hardening concrete is very helpful in understanding the behavior of early age concrete and the ultimate quality of concrete that can be achieved. Although many properties of concrete are related to the volume fractions of its components, dielectric properties are a beneficial parameter for identifying characteristic components of hardening concrete over time. They can also serve as a useful and continuous nondestructive measurement technique applicable during the hydration process. This paper defines a volumetric relationship of fresh concrete and describes an approach to estimate the volume fraction of the different phases or components that make up hardening concrete. Additionally, the use of the approach was validated by comparing the results with the laboratory test data.

Sustainable development demands contributions across all economic sectors. Thus, the infrastructure field, in this case road infrastructure, also has to contribute its part by generating road materials and road construction with lower environmental impacts. This paper analyzes the environmental potentials hidden in road materials used in Swiss road pavements. For several materials used in road construction, cradle-to-gate life-cycle assessments (LCA) were performed, taking into account all environmental impacts from raw material extraction to the finished product at the production plant. Environmental improvement potentials were analyzed for the production of asphalt mixtures, concrete mixtures, and subbase mixtures, using eight different environmental impact indicators. The results show differences in the environmental impact between best case and current status production setup of up to 54% for asphalt mixtures, 38% for concrete mixtures, and 93% for subbase mixtures.

The characterization of aluminum waste (AW) as a supplementary cementitious material (SCM) and its effect on concrete properties were investigated. This paper proposes a model for the prediction of the compressive strength of AW-cement concrete using Scheffe’s theory. The powder (material) derived from aluminum smelting waste obtained from the aluminum extrusion plant, Inyishi, in Ikeduru local government area in Imo State, Nigeria was used in this research as partial replacement for cement in various mix proportions. The compressive strengths predicted by this model agreed with the corresponding experimentally obtained values. The optimum compressive strength of AW-cement concrete predicted by Scheffe’s simplex model is $28.832\mathrm{N}/{\mathrm{mm}}^2$. The density of the resulting AW-cement concrete was not significantly affected by the partial replacement of cement with aluminum waste. The addition of AW decreased both the initial and final setting times. The initial and final setting times for 0% cement replacement were 62 and 532 minutes while the corresponding values for 5, 10, 15, 20, and 30% replacement ranged from 36 to 58 min for the initial and 435 to 518 min for the final setting times. It was also observed that the AW absorbed water from the mix and therefore reduced workability. The model developed was tested for adequacy using $t$-statistic and $f$-statistic tests and were found to be adequate.

Calcium carbide residue (CCR) and fly ash (FA) are both waste products from acetylene gas factories and power plants, respectively. The mixture of CCR and FA produces a cementitious material because CCR contains a lot of $\mathrm{Ca}(\mathrm{OH}{)}_2$, while FA is a pozzolanic material. This paper investigates the possibility of using this cementitious material (a mixture of CCR and FA) to improve the strength of problematic silty clay in northeast Thailand. The influential factors involved in this study are water content, binder content, $\mathrm{CCR}:\mathrm{FA}$ ratio, and curing time. The mechanism controlling the development of strength is also illustrated. Strength development is investigated using the unconfined compression test. A microstructural study using a scanning electron microscope and thermal gravity analysis is performed to understand the microstructural changes that accompany the influential factors. Both strength and microstructural investigations reveal that the input of CCR reduces specific gravity and soil plasticity; thus, the maximum dry unit weight and water sensitivity. The maximum strength of the stabilized silty clay occurs at approximately the optimum water content for different binder contents, $\mathrm{CCR}:\mathrm{FA}$ ratios, and curing times. The improvement in strength for a particular curing time is classified into three zones: active, inert, and deterioration. In the active zone, the strength increases remarkably with the CCR content for all $\mathrm{CCR}:\mathrm{FA}$ ratios. The input of FA (CCR replacement) does not significantly enhance strength development because all input $\mathrm{Ca}(\mathrm{OH}{)}_2$ is consumed by the natural pozzolanic material in the soil in the pozzolanic reaction. This active zone can be determined from the CCR fixation point, which is simply obtained from the index test. The input of FA (CCR replacement) is effective when the CCR content is in excess of the active zone, where insufficient natural pozzolanic material in the soil is present to react with the $\mathrm{Ca}(\mathrm{OH}{)}_2$. The possible mechanism controlling strength development that is presented in this paper can be applied to the other clayey soils stabilized with different cementitious materials, produced from $\mathrm{Ca}(\mathrm{OH}{)}_2$-rich materials and pozzolanic materials, to explain and analyze strength development. Further study on a development of rational dosage methodology will be fundamental.

The importance of particle shape, when considering the engineering behavior of sand, has been well-documented. Angular sands tend to have greater maximum and minimum void ratios, a larger friction angle, and a greater compressibility potential than their rounded counterparts under similar conditions. These differences in particle shape affect the behavior of the sands during in situ testing and in estimating soil behavior in a number of other capacities. This paper compares the results of roundness ($R$) and sphericity ($S$) estimates of ten individual particles and then later collectively on six sand specimens by several observers. An existing visual comparison method, manual methods, and automated methods are used to classify particle shape. Coefficient of variation (CV) values between 9 and 45% were obtained between the observers for visual estimates of single particles and of collective observations of sand specimens. These results are within CV values obtained when estimating other geotechnical parameters for soils and when considering in situ test variability. The visual estimates were comparable to the automated imaging system (AIMS) method for angularity measurements for the natural fine to medium sands but not for the very angular and crushed sands. Visual sphericity estimates for all sands also appeared to differ from the AIMS 2D form measurements. Research regarding automated quantification methods should continue because there would be a benefit in quickly and accurately measuring the particle shape of sand as in quality control applications for aggregates; however, there currently appears to be some limitations with the automated methods especially for fine to medium sands, sands with quartz or other translucent minerals, or very angular sands. In the meantime, qualitative particle shape estimates by using a simple visual procedure are able to provide usable first-order estimates of roundness (angularity) and sphericity sufficient for many practical geotechnical engineering applications.

Compression tests on cylinders were performed to characterize the compressive stress-strain behavior of steel fiber-reinforced concrete (SFRC) with a high reinforcing index. The reinforcing index, defined as the product of the volume fraction and the aspect ratio of the fibers, of steel fibers examined was as high as 1.7. Hooked-end fibers of various lengths and aspect ratios were considered. The test results indicated that a higher reinforcing index was associated with a higher strain at the peak stress and a higher toughness of SFRC, up to a reinforcing index approximately equal to that corresponding to a 2% fiber volume fraction. Adding steel fibers had little effect on the modulus of elasticity and compressive strength of SFRC. Long steel fibers and fibers with a lower aspect ratio resulted in a larger increase of the toughness of SFRC. On the basis of the test results, analytical models of the stress-strain curve in compression and toughness of SFRC with a reinforcing index up to 1.7 are developed.

On the basis of laboratory investigations, this paper presents the chloride penetration and diffusion over different exposure conditions of three commercial polymer-modified mortars, styrene-butadiene rubber (SBR), polyacrylic ester (PAE), and vinyl acetateethylene (VAE), and unmodified conventional mortar mix and composites. The results indicated that within 15% of polymer addition in cement mortars, there was a substantial decrease in chloride penetration. The diffusion coefficients of chloride ions estimated from the simplified linear error function–based (SLEM), Newton-Raphson, and least-squares fit methods showed increasing value coefficients with the increasing age of specimens or cycles of exposure. The results also revealed that at 15 and 40 cycles of wetting and drying, the cement mortars modified with VAE exhibited a much superior quality in chloride penetration than SBR- or PAE-modified mortars.

Internal curing has emerged over the last decade as an approach to counteract the negative effects associated with self-desiccation in low water-to-cement ratio (w/c) mixtures. Specifically, much of the early research on internal curing focused on the reduction of autogenous shrinkage. Recent work has demonstrated, however, that internal curing can also be beneficial in reducing drying-shrinkage cracking, reducing the propensity for thermal cracking, reducing fluid absorption, and reducing ion diffusion in concrete. However, several aspects of internal curing still require closer examination. One of these aspects is the application of internal curing for mixtures with a wider range of water-to-cement ratios. This paper describes results from experiments that investigated the potential use of internal curing in mortar systems with w/c ratios of 0.30, 0.36, 0.42, and 0.45 that were cured under sealed conditions, in terms of water absorption and electrical conductivity. Test results show that internal curing reduces the water absorption in all the systems. Similarly, results obtained on electrical conductivity at late ages (1 year) also show a benefit. Care needs to be taken to analyze electrical conductivity results at early ages because of the increased amount of fluid resulting from the inclusion of the prewetted lightweight aggregate.

Other than through the creation of fracture surfaces, cementitious materials do not generally contribute significantly to strain energy dissipation or damping during dynamic loading of civil infrastructure. In this paper, the potential to increase damping of cementitious materials through utilization of poromechanical effects is evaluated. Pervious cement paste and mortar specimens were fabricated and their uniaxial damping measured at loading frequencies ranging from 0.01–25 Hz. To evaluate the poromechanical effect, the damping of specimens with water, glycerol, and glycerol/water blends constituting the pore fluid was measured, and the results were compared with the measured damping of dried specimens. It was found that significant poromechanical damping can be generated in cementitious materials, and the frequency at which the damping is maximized can be controlled by changing material properties that dictate the hydrodynamic relaxation time. It was also discovered that poromechanical modeling under predicts the measured damping increase induced by saturating porous concrete, indicating that the degree of saturation influences the inherent viscoelastic damping of cementitious materials.

Past studies evaluated the mechanistic properties, economic benefits, and ecological impacts of sustainable asphalt mixtures. However, questions remain concerning the effects of these technologies on structural pavement design and performance. The objectives of this study were to evaluate the effects of selected sustainable technologies [warm-mix asphalt (WMA), reclaimed asphalt pavement (RAP), crumb rubber modifier (CRM), and sulfur additive] on the performance predicted by the Mechanistic-Empirical Pavement Design Guide (MEPDG) software and to assess the life-cycle costs (LCC) of pavement structures constructed with these sustainable alternatives. This study also determined if the MEPDG software is sensitive to variation in the mechanistic properties of asphalt mixtures containing selected sustainable technologies. Three typical pavement structures were analyzed at three traffic levels (low, medium, and high). On the basis of the results of this analysis, it was determined that the performance predicted by the MEPDG software was improved because of the use of sustainable mixtures. In addition, results indicated that sustainable technologies have the potential to reduce production and LCCs compared with conventional asphalt mixtures.