Journal of Materials in Civil Engineering

The purpose of this paper is to present a new mechanistic-empirical (M-E) rutting model developed for hot-mix asphalt (HMA) overlay thickness design and analysis. After reviewing existing rutting models in the literature, it was found that the well-known VESYS layer rutting model still is a rational choice and was adopted with minor modification to model HMA overlay rutting development. The main feature of the proposed M-E HMA overlay rutting model is to characterize layer specific permanent deformation properties rather than global rutting parameters used in the Mechanistic-Empirical Pavement Design Guide. For each specific layer, the proposed model requires rutting parameters $\alpha$ and $\mu$ ; and these rutting parameters, which are two of the fundamental input parameters required in the proposed M-E rutting model, can be directly determined from the repeated load test following the test protocol discussed in the paper. Additionally, the proposed M-E HMA overlay rutting model was calibrated using 8 test sections of the National Center for Asphalt Technology (NCAT) Test Track 2006, and the calibrated model was further validated using two sets of independent rutting data: three test sections of the NCAT Test Track 2000 and four test sections of Special Pavement Study 5 on US175, Texas. Thus far, satisfactory results have been obtained. However, more field performance data are needed for further model improvement.

This paper describes the initial efforts to explore a new application of metakaolin-based geopolymers to structural health monitoring. A distributed geopolymer-fiber optic sensing (G-FOS) system is proposed, where geopolymers are used as smart adhesives to affix optical fibers to existing in-service structures to form an integrated G-FOS sensor. Results of feasibility testing in the laboratory indicated that the tensile cracking strain of geopolymers can be controlled by finely tuning the Si/Al ratios or adding appropriate aggregate fillers such as sand, thus rendering the “smart” nature of geopolymers for deformation-based sensing. Geopolymers with ${\text{SiO}}_2/{\text{Al}}_2{\text{O}}_3$ ratios $⩾3.8$ are viable adhesives that can develop strong bond to concrete, steel, and glass fiber. Laboratory prototype testing on steel specimens under uniaxial tension and on concrete beams under four-point bending validated the concept and feasibility of the proposed G-FOS system for structural health monitoring. It further demonstrated that the G-FOS system cannot only detect overstraining events in steel but also measure the crack size in concrete.

In many states, coarse aggregate specifications for pavement mixtures are outdated and do not reflect the current level of knowledge concerning desirable aggregate properties for pavement applications. Because the performance of pavements is highly dependent on the quality of aggregate used within them, the quality of the aggregate must be evaluated based on the consistency of desirable aggregate properties. The primary objective of this research was to evaluate the compliance and consistency of coarse aggregate properties with respect to current specification requirements. To evaluate compliance and consistency, testing data from local sources in the state of Minnesota were compared to regional and national records on aggregate quality and specification requirements. Percent within limit calculations were conducted to evaluate the compliance of aggregate properties with respect to the current quality requirements of abrasion resistance, soundness, and percent spalling material. The results of the study demonstrated that aggregates complied very well with current specifications. However, when evaluating the variability of test results, inconsistency between different sources was noticeable even though quality requirements were easily met by tolerance criteria. This study emphasizes the inconsistency of aggregate properties among sources subjected to the same (or similar) specification requirements.

An experimental study was carried out to investigate the shear behavior of corrugated metal ties anchoring brick veneer walls to light wood frame backing. Connection subassemblies were tested under monotonic and cyclic shear, simulating in-plane loading of veneer wall systems, and statistical analyses were conducted to identify and quantify the parameters influencing their behavior. Force-displacement curves obtained under monotonic loading can be considered an upper bound for the hysteresis loop envelopes. Fastener slippage during cyclic loading enabled by the localized damage of the surrounding wood fibers diminished the energy dissipation capacity of the connection and caused pronounced pinching in the hystereses. When corrugated ties with minimum thickness permitted by the Masonry Standards Joint Committee (MSJC) Code were considered under in-plane loading, tie design and bend eccentricity were found to be the most important factors, while tie location in the bed joint, fastener type, and fastener quantity were influential to a lesser degree.

Four kinds of polymer modifier widely used in China are selected to modify the performance of asphalt mixture: styrene butadiene styrene (China), PR PLAST.S (France), Domix (Germany), and Rad Spunrie (China). The main objective of this paper is to evaluate the influence of these polymer modifiers on the performance of asphalt mixture with the dynamic modulus $\left|E^{\ast }\right|$ indicator through simple performance test. Dynamic modulus is adopted as the primary material property of hot mix asphalt mixtures in the M-E Pavement Design Guide 2002. In this study, the influences of temperature, frequency, and confining pressure on the dynamic characteristic of asphalt mixture are analyzed, and the master curves of dynamic modulus are developed and interpreted. The Witczak $\left|E^{\ast }\right|$ predictive model, which is used in the M-E Pavement Design Guide, is also applied to predict the dynamic modulus, and the predicted values are compared with the examined results. Results show that all these polymer modifiers, especially Domix, can strengthen the mixture stiffness, and that high frequency, low temperature, and high confining pressure increase the dynamic modulus of asphalt mixtures. Additionally, the Witczak $\left|E^{\ast }\right|$ model can soundly predict the dynamic modulus of polymer-modified asphalt mixtures.

Abrasion of concrete occurs due to scraping, rubbing, skidding, or sliding of objects on its surface. The abrasion resistance of concrete is influenced by a number of factors, such as compressive strength, surfacing finish, aggregate properties, types of hardeners, and curing. The main objective of this study is to determine the effects of the pozzolanic compositions and matrix structure (or voids) on the abrasion resistance of cement mortars. In this study, the mortars produced with cement samples with seven different compositions and varied with an air-entraining agent were subjected to the abrasive effects. Several examples of mortars were evaluated using samples cured for six different periods throughout 1 year. This study is supported by thin section investigations, in addition to being subjected to the basic tests, such as compression, flexure, and abrasion. The Bohme apparatus was used during abrasion tests. To summarize the most important findings from this study, a compact cement matrix is more effective against abrasive effects than mineral additives.

An attempt was made to improve the physical and strength properties of a reddish-brown lateritic soil. 15–60% of sand by dry weight of laterite was used as a modifier in the stabilization of the laterite with 3–12% by dry weight of cement. Classification, compaction, California bearing ratio (CBR), and unconfined compressive strength tests were carried out on the specimens. The plasticity index decreased from 17% for untreated laterite to 2.5% when treated with a combination of $60\mathrm{\%}\text{sand}+6\mathrm{\%}\text{cement}$ . For the two energy levels of compaction, optimum moisture content (OMC) was found to increase with an increase in cement content but decreased as the sand content increased. The OMC at the West African standard (WAS) energy level was consistently lower than the values obtained at the standard proctor (SP) energy level, while the corresponding values of maximum dry density were higher at the WAS energy level than the values at the SP energy level. The CBR requirements for base course material were met when laterite was admixed with $45\mathrm{\%}\text{sand}+6\mathrm{\%}\text{cement}$ and $30\mathrm{\%}\text{sand}+6\mathrm{\%}\text{cement}$ , and $15\mathrm{\%}\text{sand}+6\mathrm{\%}\text{cement}$ , $30\mathrm{\%}\text{sand}+6\mathrm{\%}\text{cement}$ , and $45\mathrm{\%}\text{sand}+3\mathrm{\%}\text{cement}$ at the SP and WAS energy levels, respectively. It can be concluded that sand enhanced the effective stabilization of Ikpayongo laterite with cement within the maximum cement content specified by the Nigerian code.

This paper presents an experimental study of the influence of steel basic oxygen slag (BOS) and ordinary portland cement (OPC) on the compressive strength and the hydration mechanisms of blended grounded granulated blast furnace slag (GGBS) pastes. The compressive strength, the mineralogical changes due to hydration, the setting times, the alkalinity of the raw materials, and the pore solution, and the volume stability were measured on binary and ternary mixes. It is concluded that the steel slag can be used as an activator of GGBS and the optimum composition of those materials was determined with a proposed parameter called “slag index.” The properties measured in blended OPC-GGBS-BOS mixes showed encouraging results to be used industrially. The mechanisms of hydration of the blended slag mixes are discussed and a hydration model of the blended system GGBS-BOS is proposed.

Asphalt-treated bases (ATBs) are the most commonly used type of stabilized layer in Alaska because of locally available asphalt resources and its relatively lower cost. As an essential material input parameter for pavement design, resilient modulus $\left(M_R\right)$ of ATBs has been studied in laboratory evaluations, field investigations, and empirical and mechanistic modeling. However, most ATBs’ $M_R$ values available in the database of the Alaska flexible pavement design software were obtained from in-service roadways through nondestructive testing and back calculation. Therefore, there was a need to characterize these stabilized materials by taking into account the main factors that influence their engineering behavior. In this study, the $M_R$ characterization of two types of ATBs was achieved through laboratory testing: hot asphalt-treated base (HATB) and foamed asphalt-treated base (FATB). The effects of loading amplitude, confining pressure, temperature, binder content, and aggregate source and properties on the resilient behaviors of HATB and FATB were investigated. Testing results were discussed and used to develop stress-dependent $M_R$ equations for both HATB and FATB that can be incorporated in current pavement design procedures. The effects of temperature and material variables were correlated to regression constants of the equations.

The permeability of asphalt concrete has been the subject of much study by pavement engineers over the last decade. The work undertaken has tended to focus on high air voids as the primary indicator of permeable asphalt concrete. This paper presents a simple approach for understanding the parameters that affect permeability. Principles explained by Taylor in 1956 in channel theory work for soils are used to derive a new parameter—representative pore size. Representative pore size is related to the air voids in the compacted mix and the $D_{75}$ of the asphalt mix grading curve. Collected Superpave permeability data from published literature and data collected by the writers at the Queensland Department of Transport and Main Roads is shown to be better correlated with representative pore size than air voids, reducing the scatter considerably. Using the database of collected field and laboratory permeability values an equation is proposed that pavement engineers can use to estimate the permeability of in-place pavements.

Several studies using vegetable fibers as the exclusive reinforcement in fiber-cement composites have shown acceptable mechanical performance at the first ages. However, after the exposure to accelerated aging tests, these composites have shown significant reduction in the toughness or increase in embrittlement. This was mainly attributed to the improved fiber-matrix adhesion and fiber mineralization after aging process. The objective of the present research was to evaluate composites produced by the slurry dewatering technique followed by pressing and air curing, reinforced with combinations of polypropylene fibers and sisal kraft pulp at different pulp freeness. The physical properties, mechanical performance, and microstructural characteristics of the composites were evaluated before and after accelerated and natural aging. Results showed the great contribution of pulp refinement on the improvement of the mechanical strength in the composites. Higher intensities of refinement resulted in higher modulus of rupture for the composites with hybrid reinforcement after accelerated and natural aging. The more compact microstructure was due to the improved packing of the mineral particles with refined sisal pulp. The toughness of the composites after aging was maintained in relation to the composites at 28 days of cure.

As part of Florida DOT (FDOT)’s Partnering Program, a temporary roadway was designed and constructed using three different pavement sections. The program consisted of pavement construction monitoring and field/laboratory testing during construction, prior to opening to traffic and demolition. The study documents the findings of the ongoing efforts by FDOT to assess the applicability of untreated recycled asphalt pavement (UNRAP) as base course for pavement sections. Three different temporary pavement sections were constructed. Two sections were constructed with UNRAP, one with a stabilized subgrade and the other with a compacted subgrade. The third section was constructed with a limerock base and stabilized subgrade, and was used for comparison purposes. The UNRAP material used in the temporary pavement sections was milled off of the existing roadway. Laboratory and field testing, including Dynaflect and falling weight deflectometer (FWD), were performed and evaluated. The study suggested the UNRAP base performed as well or better than the limerock base. The results of this study, together with a previous study, indicate that UNRAP can be used successfully as base material for both traffic lanes and shoulders. Use of UNRAP for base courses on certain projects is a cost-effective alternate over conventional base materials. The results of the Dynaflect and FWD and the rut depths observed throughout the limited duration of this project were comparable to those of the limerock base. The results also indicate a substantial improvement of UNRAP properties with time. This paper presents the results of the field and laboratory testing, as well as engineering analyses and evaluations. Recommendations for future construction and research will be discussed. The data gathered so far suggest that UNRAP is a viable alternate material for base courses, but are we ready for it?

The strength of fly ash mixture often needs to be enhanced for its better utilization in geotechnical and environmental applications. Many fly ashes often improve their strength with lime but may not meet the requirements. Gypsum, which reduces the lime leachability, further improves the strength. An attempt is made in this paper to study the effect of gypsum on the strength development of two Class F fly ashes with different lime contents after curing them for different periods. The sustainability of improved strength has been examined after soaking the cured specimens in water and with different leachates containing heavy-metal ions. The strength of both the fly ashes investigated improved markedly up to a particular amount of the lime content, which can be taken as optimum lime content, and thereafter the improvement is gradual. The improvement in strength at higher lime contents continues for a longer period (even up to 180 days). Gypsum accelerates the gain in strength for lime-stabilized fly ashes, particularly in the initial curing periods at about optimum lime content. At high lime contents gypsum attributes very high strength after curing for long periods mainly due to the alteration of fly ash lime reaction compounds. Gypsum not only improves the reduction in the loss of strength due to soaking even at low curing periods but also improves the durability of stabilized fly ashes due to repeated cycles of wetting and drying.

Ultrasonic guided waves have been used for monitoring progression of rebar corrosion in concrete in chloride and oxide environments. The effect of rates of corrosion in the two environments on the ultrasonic signals is reported. Surface- and core-seeking guided wave modes were used to monitor beams undergoing accelerated impressed current corrosion in the presence (chloride corrosion) and absence of chlorides (oxide corrosion). Effective combination of guided wave modes could relate to the differences in corrosion mechanisms and rates in the two environments. Ultrasonic test results correlated well with that of the destructive tests.

A closer look at a number of researches carried out on the stripping potential of asphalt mixtures shows that there is no global agreement on a comprehensive procedure for evaluation of the moisture sensitivity of these mixtures. Therefore, an attempt was made to assess moisture sensitivity and its interaction with permanent deformation through performing a dynamic creep test on coarse graded and dense graded asphalt mixtures in different environmental and loading conditions, using a UTM25 loading machine. In the next step, test results were interpreted by using a newly developed three-stage creep model. According to the results, the coarse graded mixtures have lower moisture sensitivity and could better resist permanent deformations than the dense graded mixtures. Based on the creep models, low stress levels cannot appropriately show the behavior of asphalt specimens. It was also concluded that, at higher temperatures, asphalt mixtures might become more sensitive to temperature than moisture.