Journal of Materials in Civil Engineering

Self-consolidating concrete (SCC) is known for its excellent deformability, high resistance to segregation, and use in congested reinforced concrete structures characterized by difficult casting conditions without applying vibration. The use of known mineral admixtures such as fly ash and slag cement has proved very effective in the production of nonexpensive SCC with satisfactory fresh and hardened properties. However, the use of volcanic ash (VA) in SCC is new and can provide low cost SCC. This paper presents fresh, mechanical, and durability characteristics of VA based SCC mixtures (VA-SCCs). VA-SCCs are developed by varying water-to-binder ratio, percentages of VA as cement replacement, and dosages of superplasticizer (SP). Mix design parameters are optimized to achieve minimum use of SP and optimum use of VA. The fresh concrete properties are determined from slump flow, V-funnel flow time, bleeding, air content, and segregation tests. The mechanical properties and durability characteristics such as compressive strength, freezing-thawing resistance, rapid chloride permeability, surface scaling resistance, and drying shrinkage are determined to evaluate the performance of VA-SCCs. The study produces encouraging results and confirms the production of satisfactory VA based SCC mixtures with acceptable properties. VA-SCCs having a minimum strength of 15 MPa (requirement for some structural concrete applications) can be obtained by replacing up to 50% (by mass) of cement by VA. Development of nonexpensive and environmental friendly VA-SCC with acceptable strength and durability characteristics (as illustrated in this study) is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.

The main objectives of this study are: (1) to develop a postprocessing method for analyzing the dynamic modulus test of compacted asphalt mixtures; (2) to identify optimum regression equations for the compressive stress and its corresponding strains in a dynamic modulus test using this method; and (3) to evaluate the accuracy of the proposed method compared with the method in the current equipment specification. Including the procedure used in the current equipment specifications, two procedures for fitting the dynamic stresses and three procedures for fitting the corresponding strains were employed in the postprocessing method. The coefficients of the regression equations in the five procedures were used to determine the dynamic modulus and phase angle. Uniaxial compressive dynamic modulus tests of 10 asphalt mixtures were conducted at five temperatures and six frequencies with Universal Test Machine (UTM). A total of 1,800 test results were processed with the procedures in the proposed method. On basis of the standard errors of the least square fit, the procedures in the postprocessing method were evaluated. It was found that the procedure in the equipment specification was inaccurate to fit the strains, especially at the higher temperatures and low frequencies. Therefore, correction coefficients were recommended for the measured dynamic modulus and phase angle from the currently used UTM. The potential application of the proposed method is significant since it will improve the degree of accuracy of the dynamic modulus values used in the mechanistic-empirical pavement design procedure.

Moisture-induced damage has long been recognized as one of the major concerns for asphalt pavements. To mitigate potential moisture damage, one general method is to add mineral antistripping additives or liquid antistripping agents into hot-mix asphalt (HMA) mixtures. In this study, a comparative laboratory experiment was conducted to investigate the effectiveness of cementitious fillers on moisture susceptibility of HMA mixtures. Five types of cementitious fillers were considered: fly ash, cement kiln dust, and three types of hydrated lime with different finenesses. The laboratory performance of HMA mixtures subjected to moisture conditioning was evaluated through the following tests: dynamic modulus test; superpave indirect tensile tests; and tensile strength ratio test. The test results indicate that the cementitious fillers were generally effective in reducing the moisture susceptibility of HMA mixtures. The finer the hydrated lime particle, the more resistant the asphalt mixtures. In addition, dynamic shear rheometer test was conducted on asphalt mastics to explore the stiffening effect of different cementitious fillers.

There is a renewed interest in using steel fiber reinforcement within the critical hinging regions of reinforced concrete (RC) members as a means for improving their seismic response. Examples include beam-column joints, structural walls, and shear walls coupling beams. The presence of steel fiber reinforcement in these regions confines the concrete, improves the bond strength of the steel bars, and reduces the bond degradation, leading to reduced damage and increased energy absorption and dissipation capacities under cyclic loading. This paper presents a synthesis of the results of a series of experimental and analytical investigations undertaken by the writer on the use of steel fiber reinforcement for improving the bond capacity and bond stress-slip response of steel bars under static and cyclic loading and its implication on the static and seismic response of RC members. The experimental results are discussed, a design expression for evaluating the effect of fiber reinforcement on the bond or development/splice strength of steel bars in tension is described, and a new model of the local bond stress-slip response under generalized (cyclic) excitations is presented.

Ensuring sufficient water availability in hydrating concrete is a key to achieving quality curing that protects the fresh concrete in the short term and develops the potential properties of the mixture for long-term performance of concrete pavement. Excessive early-age evaporation from the concrete pavement surface can potentially result in plastic shrinkage cracking, high porosity, and low strength at the concrete surface leading to a variety of surface distresses. Application of liquid curing compounds on newly placed concrete pavement surfaces has been widely used to minimize evaporation. However, the availability of a test method to assess the efficacy of a curing compound relative to the actual environmental conditions encountered in the field is still lacking. Therefore, advancements are needed to further facilitate the evaluation of curing effectiveness (CE). This paper presents a laboratory-based procedure, which bridges laboratory measured parameters to performance in the field, as part of a process to qualifying the effectiveness of a curing compound membrane. The curing monitor system, a device capable of accurately recording relative humidity and temperature at three critical locations along with wind speed and solar radiation, is used as part of a test procedure to assess the efficacy of a curing compound. A compound curing evaluation index (EI) is defined in terms of the effective curing thickness concept and moisture loss at 24 h after placement. The EI is useful to rank the curing compound relative to laboratory test conditions. From the limited field application studies, it has been observed that the proposed test procedure has good potential to be an effective tool to assess CE and quality under field conditions.

Sustained research and development work on the utilization of waste (fly ash and silica fume) for various productive uses have been carried out. In the construction industry, major attention has been devoted to the use of fly ash and silica fume in concrete as addition to or as cement replacement. The utilization of a solid waste, fly ash and silica fume, in polymer concrete was reported in this paper including the effects on the compressive strength, flexural strength, and split tensile strength. The results show the influence of fly ash and silica fume content on the mechanical properties of polymer concrete with epoxy resin. The fillers improved the mechanical characteristics of polymer concrete compared to that of polymer concrete without filler: the compressive strength of polymer concrete with fly ash content was favorably influenced by the filler compound to polymer concrete with silica fume.

The determination of built-in material properties is a difficult step during the structural assessment of historical structures. Large variations of material characteristics and the difficulty of obtaining an adequate number and type of material samples are among the major problems. In this study, the material characterization of the approximately 135 years old historical Akaretler Row Houses was carried out. Since several structural walls of the row house complex were to be removed according to the restoration design, a large number of different types of specimens could be collected for laboratory tests and a considerable amount of in situ destructive and nondestructive tests was carried out. The laboratory tests included mechanical, physical, and chemical tests on original materials such as bricks, mortar, brick prisms, cores consisting of two layers of bricks and one layer of mortar between bricks, and wallets. The in situ tests included destructive shear tests and nondestructive rebound hammer tests. At the end of the extensive experimental study, the basic material characteristics of the late period Ottoman construction system were obtained. In addition relations between various mechanical characteristics of the construction materials, as well as the relations between the results of the laboratory and in situ tests, and destructive and nondestructive tests are presented.

The moisture damage in polymer modified asphalts has been studied for decades, yet the effects of chemical functional groups on moisture sensitivity are not known. In this study, a nanoscale experiment is conducted to measure these effects in terms of adhesive/cohesive forces using an atomic force microscopy (AFM). A base asphalt binder and two polymers such as styrene-butadiene (SB) and styrene-butadiene-styrene (SBS) modified asphalts are used to prepare an AFM sample on glass substrates. The AFM samples are conditioned under dry and wet conditions. In the AFM, these samples are probed by silicon nitrite $\left({\text{Si}}_3{\text{N}}_4\right)$ , carboxyl $\left(\text{COOH}\right)$ , methyl $\left({\text{CH}}_3\right)$ , and hydroxyl $\left(\text{OH}\right)$ functionalized AFM tips and nanoscale pull-off or adhesion/cohesion forces between asphalt and tip molecules are measured. Based on the ratio of wet to dry adhesion/cohesion forces, it is shown that the polymer modification makes binders less susceptible to moisture damage. Among the four tips, the $\text{COOH}$ tip shows almost no difference in adhesion forces between wet and dry samples. Using $\text{OH}$ tips, it is shown that the cohesion in SBS modified wet asphalt samples is significantly higher than the cohesion in SB modified wet asphalt samples. The ${\text{Si}}_3{\text{N}}_4$ tip shows higher adhesion in SB modified wet samples than that in the SBS polymer modified wet samples. Based on the adhesion/cohesion force, 3% polymer is found to be the optimum for both SB and SBS polymers. In addition, this study determines the methodology for sample preparation and testing parameters for nanoscale AFM testing on asphalt binders.

Field and laboratory testing programs were conducted to develop an efficient methodology for estimating resilient modulus $\left(M_r\right)$ values of subgrade soils for use in the design of pavement structures. The field testing program consisted of obtaining Shelby tube samples of subgrade soils from different pavement projects throughout Louisiana. The laboratory program included conducting repeated load triaxial $M_r$ tests as well as physical property tests on the collected samples. The validity of the correlation equations developed by the long-term pavement performance (LTPP) to predict the $M_r$ was examined. In general, the LTPP model underestimated the values of $M_r$ coefficients obtained in this study. A comprehensive regression analysis was conducted to develop models that predict the $M_r$ coefficients of different subgrade soils in Louisiana using different physical properties. A good agreement was observed between the measured and predicted $M_r$ coefficient values. Furthermore, the developed models had a better prediction of measured $M_r$ coefficient values than the LTTP models. Finally, a catalog of resilient modulus of subgrade soils at different moisture content levels was developed.

The laboratory testing of concrete has shown that elevated temperatures cause air permeability index (API) increase and elastic modulus $E$ decrease. Indeed, the API response typically spans several orders of magnitude making it a sensitive indicator of elastic modulus reduction. However, the API versus $E$ data has been historically assumed to be both event and concrete composition specific, thus limiting its applicability for predictive or modeling purposes. In response, a theoretical model is developed here by (1) establishing that the API is equivalent to the Darcy permeability; (2) developing a microcrack flow model accounting for tortuosity, crack density, and microcrack geometry; and (3) interpreting the Giordano and Colombo elastic modulus damage formulas in terms of the corresponding increase in permeability. The resulting general model depends on stress conditions (plane stress versus plane strain) and a single microcrack flow parameter. For materials with small Poisson’s ratios, however, the model becomes independent of stress condition and both equations converge on the same simple solution. The model is verified with both field and laboratory data of concrete response to typical fire elevated temperatures and shown to be comparable in accuracy to previous empirical approaches requiring many more degrees of freedom. Moreover, the data on fire damaged concrete were found to collapse to a single curve suggesting that the microcrack flow parameter is sensitive to elevated temperature but insensitive to concrete composition. The success of the model implies certain limits to microcrack geometry and airflow turbulence in damaged concrete, both of which are discussed.

The ability of in-place pervious concretes to effectively drain storm water runoff gradually reduces as it becomes clogged due to the ingress of fine particles into its pore structure. This study systematically investigates several pervious concrete mixtures proportioned using different size aggregates and their blends on their propensity to clogging so as to bring out the influence of pore structure features on particle retention and the consequent permeability reduction. A finer and a coarser sand are used as clogging materials and the experimental study on permeability reduction (as a result of particle retention) is carried out using a falling head permeability cell. Significant permeability reductions are observed when finer sand is used as the clogging material. A certain effective pore size to clogging particle size ratio is found in this study, that is most conducive to particle retention. Thus pervious concrete specimens of similar porosity, having very large $\left(\sim 5–6\text{mm}\right)$ or very small $\left(\sim 1–2\text{mm}\right)$ pore sizes are found to be less susceptible to clogging under the conditions of this study. An idealized three-dimensional geometry obtained from two-dimensional planar images of pervious concrete sections is used, along with a probablistic particle capture model to predict particle retention associated with clogging material addition and simulated runoff. The trends in the predicted particle retention and the experimentally determined permeability reduction agree well. A “clogging potential” is defined in this paper, either as a ratio of the porosity reduction because of clogging to the initial porosity, or as a ratio of the permeability reduction to the permability in the unclogged state.

The amount and magnitude of absorption and scattering of stress waves in concrete, mainly due to internal friction and aggregate inclusions, may be different when concrete mix proportions vary. In this study, we investigate the effect of concrete composition on the measurements of self-calibrated surface wave transmission functions (TRFs) and spectral energy transmission ratios (SETRs) which are used for crack depth estimation in concrete slabs. A series of experiments is carried out on a range of concrete specimens having more realistic crack (not a notch). It is found that the self-calibrated TRFs are very sensitive to both the concrete composition and the crack depth. However, the SETR is less sensitive to the concrete composition and more sensitive to the changes of crack depths. In conclusion the spectral energy transmission method can be effectively used for crack depth estimation in concrete regardless of their material compositions.