Journal of Materials in Civil Engineering

The research investigation presented herein is intended to study the abrasion resistance early-opening-to-traffic portland cement concrete pavements also known as fast-track concrete. The selected matrices are examined using two categories of opening-to-traffic times (6 and $8\mathrm{h}$ ). Type III portland cement and three different cement factors with and without an accelerating admixture were used. The trial mixtures are examined for plastic properties (slump, air content, bleeding, setting times, and adiabatic temperature), bulk characteristics (demolded unit weight and compressive strength), and resistance to abrasion. Depth of wear and rate of deterioration as functions of matrix proportions, opening-time categories, and testing age (up to $20\min$ or $0.12\mathrm{in.},$ whichever is reached first) are determined. The influence of other parameters such as cement factor, curing age, and accelerating admixture on resistance to wear of the selected matrices are discussed. Other properties, namely rate of abrasion, relative gain of abrasion, coefficient of variation, and abrasion index, are examined. Finally, the relationship between the abrasion resistance (depth of wear) and bulk characteristic (compressive strength) at both opening and maturity ages are investigated. The findings of this investigation shall benefit highway agencies and municipalities by providing abrasion resistance data on a wide range of matrix constituents and proportions that may be used for fast-track concrete construction.

The writers have carried out an investigation to develop apparent pH profiles of concretes for a variety of cement blends viz. normal portland cement containing by mass 30% pulverized fuel ash, 50% ground granulated blast-furnace slag, 10% metakaolin, and 10% microsilica, chosen to replicate common replacement levels, along with 100% normal portland cement (OPC) mix. The samples were exposed in an accelerated carbonation environment (5% $\mathrm{C}{\mathrm{O}}_2$ ) for $6\text{weeks}$ during which pH profiles were obtained every week as the concrete carbonated. Measurement of air permeability, carbonation depth, resistivity, and calcium hydroxide content were performed to assist in interpretation of the results. The nature of the pH profiles obtained depended on both the type of binder and the duration of exposure to the carbonation environment. Utilizing the pH profiles, a rate of carbonation was determined, which was found to depend on the type of binder. Both the rate of carbonation and the depth of carbonation after $6\text{weeks}$ of exposure indicated that OPC concrete performed better than concretes containing supplementary cementitious materials. It was also determined that the gas permeability alone cannot provide an accurate indication of the likely rate of carbonation. The thermogravimetric analysis suggests the existence of a relationship between calcium hydroxide content and the apparent pH of carbonated concretes. On the basis of the results in this paper, it can be concluded that the pH profiles, using the technique described in this paper, can be used for measuring the carbonation resistance of concretes containing supplementary cementitious materials.

An experimental investigation of the behavior of interlocking grouted stabilized sand–fly ash brick masonry under unaxial cyclic compressive loading with different bed joint orientation is presented. Five cases of loading at 0, 22.5, 45, 67.5, and $90°$ with the bed joints were considered. The brick units and masonry system developed by Professor S. N. Sinha are used in the present investigation. Eighteen specimens $500\mathrm{mm}\times 100\mathrm{mm}\times 700\mathrm{mm}$ and 27 specimens $500\mathrm{mm}\times 100\mathrm{mm}\times 500\mathrm{mm}$ were tested. The envelope stress-strain curve, common point curve, and stability point curve were established for all five cases of loading with respect to the bed joints. A general analytical expression is proposed for these curves which fit reasonably well with the experimental data. It was inferred that the peak stress of the stability point curve may be considered as the maximum permissible stress level and is found in the range of 0.745–0.775 times the masonry strength depending upon the load case. It was also inferred that the permissible stress level depends on the plastic (residual) strain present in the material under cyclic loading.

ASTM C 33 limits the amount of aggregate smaller than $75\mathrm{\mu }$ m (No. 200 sieve) to be used in concrete. There is considerable interest in altering ASTM C 33 to allow a higher percentage of these microfine aggregates, particularly in the case of manufactured aggregates. However, before this can be done, the positive and negative effects of microfine aggregates on concrete performance must be fully investigated. Previous research has indicated that there is not a strong correlation between standard aggregate characterization tests and concrete performance when microfines are present. In this study, several methods of characterizing microfine aggregates were investigated. The intent was to identify the characteristics of microfines that govern their effects on concrete performance. A second goal was to identify easy-to-use test methods that could be used to simply and inexpensively identify good and poor performing microfine aggregates. Three easy-to-use tests were identified that correlated well with concrete performance: the methylene blue test, a particle packing assessment by the weight of microfine aggregates adhering to a single drop of water, and the loose packing tests described in ASTM C 1252.

Capacities of wood connections with laterally loaded dowel fasteners by plastic analysis can be predicted using the European yield models (EYM) equation. The underlying concept is that failure occurs due to crushing of wood beneath fasteners and / or formation of plastic hinges in fasteners with a rigid-plastic representation of the materials involved. EYM prediction is now “the” way within design codes to calculate the maximum attainable capacity per fastener. Subsequent adjustments discount those predictions through factors which account for unequal sharing of force between fasteners and premature connection failure by fracturing. In North America the EYM is the basis for lateral load capacities of connections made with bolts, drift-pins, screws, nails, and timber rivets. This paper addresses the capability of the EYM for predicting load carrying capacities of solid wood (sawn softwood lumber) and laminated strand lumber (LSL) connections employing tight-fitting steel tube fasteners with external diameters up to $12.7\mathrm{mm}$ . EYM prediction is compared with experimental test results for arrangements with one or four fasteners loaded in double shear. Accuracy of predictions depends on factors such as connection geometry and the type of wood member involved. Prediction is always accurate if a connection has only one fastener, or if joined members are made from LSL. If members are made from sawn softwood lumber premature brittle splitting type failure modes occur for multiple fastener situations, with impairment of capacity inversely proportional to the fastener outside diameter. Suggestions are made here regarding the nature of codified design rules for steel tube fastener connections, with the intent that such provisions be enacted within North America.

This study investigates the effects of steam and microwave curing on the strength development and freeze-thaw durability of concrete. Two steam-curing treatments, four microwave curing times and four types of concrete mix, were used in this study. The test results indicated that microwave heating could further increase the early strength of concrete. Pozzolanic reaction of silica fume, fly ash, and blast-furnace slag was observed to be further promoted by steam-microwave curing. Concrete samples with 10% silica fume added responded well to microwave curing. The strength gain development of concrete appeared to level off after $40\min$ of microwave curing. Thus, a 40-min microwave heating time appeared to be the optimal curing time. The microwave-cured concrete did not show an increase in deterioration relative to the concrete that was steam cured, but showed an increase in strength. The strength of the top layer of the steam-cured concrete blocks is lower than the strength of the middle or bottom layer.

This paper presents the development of new methods for measuring aggregate resistance to polishing, and degradation. These are important properties that influence pavement skid resistance and resistance to distresses under traffic loading. The aggregate imaging system is used to measure aggregate surface texture after different polishing time intervals in the micro-Deval test. Mathematical functions are then used to describe the initial texture, rate of polishing, and final texture. Aggregate abrasion is quantified by the percent difference in surface angularity before and after the micro-Deval test, while aggregate breakage is described by the weight loss in this test. The efficacy of the new methods is demonstrated through the analysis of aggregates from different sources that exhibit a wide range of properties. In addition, the new methods are verified by comparing the measured aggregate properties to the degradation of these aggregates in hot mix asphalt mixtures due to compaction forces.

Current pavement design procedures recommend the resilient modulus of subgrade materials for pavement design and analysis. The objective of this paper is to develop two statistical models to predict the resilient modulus of subgrade cohesive soils from the dynamic cone penetration (DCP) test parameters and soil properties. The first model correlates resilient modulus to the dynamic cone penetration test parameters, while the second model correlates resilient modulus to both the dynamic cone penetration test parameters and soil properties. Field and laboratory experiments were conducted at 31 sites in Louisiana that contain four common soil types (A-4, A-6, A-7-5, and A-7-6). Field tests included DCP tests and soil sampling, while laboratory tests included determining basic soil properties and resilient modulus. Statistical analyses were conducted on the collected data, and two statistical models were developed for the prediction of resilient modulus of cohesive subgrade soils from the DCP test parameters and soil properties. The models predicted a separate data set that was not used in their development, indicating the success of the application of the dynamic cone penetration test in evaluating the resilient modulus of pavement subgrade soils. The predicted values obtained from the proposed models corresponded well with the measured resilient modulus values from the repeated load triaxial test.

The Mechanistic-Empirical Pavement Design Guide (MEPDG) made available by the National Cooperative Highway Research Program in 2004 uses a power model that incorporates dynamic modulus (DM) as a factor in predicting rutting performance of asphalt concrete. The rutting model is empirical and the rutting profiles obtained from the model are based largely on the adjustment of calibration constants, not the DM. Various DM values would be capable of producing similar rutting profiles based on the current model. This study evaluates using accumulated strain data obtained from the Repeated Load Test (RLT) as an alternative to using DM. In addition, a model to represent the accumulated strain data obtained from the RLT is developed. The accuracy and behavior of the current model and the model developed in this study in representing a mix from Louisiana are compared. Alternatives for incorporating the RLT data into the MEPDG are also presented.

The main objective of this study is to validate a new mix design procedure for cold in-place recycling using foamed asphalt (CIR-foam) developed for the Iowa Department of Transportation. First, reclaimed asphalt pavement (RAP) materials were collected from seven different CIR construction sites located across the state of Iowa. To determine the consistency of a new CIR-foam mix design procedure, the mix design was performed seven times using these RAP materials. The test specimens were prepared using gyratory compactor rather than Marshall hammer because it produced more consistent mixtures for various foamed asphalt contents and curing conditions. The indirect tensile strength test was performed on the vacuum-saturated specimens prepared using each of seven RAP material sources for five different foamed asphalt contents (1.0, 1.5, 2.0, 2.5, and 3.0%), given a fixed moisture content of 4.0%. As the foamed asphalt content increased from 1.0 to 3.0% at 0.5% increments, air voids in the CIR-foam mixtures decreased gradually. The indirect tensile strength of CIR-foam specimens cured for two days at $60°\mathrm{C}$ was significantly higher than that of CIR-foam specimens cured for three days at $40°\mathrm{C}$ . Based on the new mix design procedure, the optimum foamed asphalt contents were consistently found at values between $1.5$ and $2.5\%$ for all seven different RAP materials. The stiffer residual asphalt required more foamed asphalt, whereas the higher residual asphalt content did not require a smaller amount of foamed asphalt. The raveling test result was very sensitive to the curing time and the foamed asphalt content, such that RAP materials with a large amount of stiff residual asphalt would exhibit more potential for raveling.