Journal of Materials in Civil Engineering

A constitutive model was developed for high density polyethylene (HDPE) pipe material using published data considering the strain rate effect. A hyperbolic model was used and a conventional approach was employed to estimate the constants of this model from published test data. The observed form of HDPE material behavior as the strain rate changes suggested that a more systematic approach might yield a more robust predictive model. This paper presents a newly developed constitutive model for HDPE material using both the conventional approach and a more systematic “focus point” method.

This paper examines the question of an appropriate failure criterion for asphalt fatigue characterization. The results presented are based on cyclic fatigue tests and obtained from three mixtures containing different penetration grade bitumens from one and the same source. The mixtures are tested at 0, 10, and $20°C$ using uniaxial testing (tension/compression) on cylindrical samples. It is found that failure can be demonstrated by studying the evolution of the strain field using three parallel extensometers (separated by $120°$ around the specimen). The failure arises from coalescence of microcracks (damage 1ocalization). The decrease in stiffness at failure is related to mixture stiffness, where stiff materials (low temperature and/or mixtures containing low pen grade binder) show comparatively small decrease. A statistical approach based on fatigue tests carried out at different temperatures is suggested, an approach which uses stiffness degradation as a measure of critical fatigue stiffness. The advantage of such a failure criterion compared to the classical failure criterion (decrease in stiffness by 50%) for different temperatures is discussed. Using the proposed criterion, higher consistency in results is achieved compared to results obtained using the classical failure criterion.

Select engineering characteristics of crushed glass produced using two processing techniques (crushing versus screening) to an American Society of State Highway and Transportation Officials No. 10 gradation were experimentally evaluated. The crushed glass samples were classified as well graded sands with gravel (SW) and exhibited excellent strength and workability characteristics. The low specific gravity (2.49) contributed to crushed glass having compacted maximum dry densities on the order of 16.6–16.8 and $17.5-18.3\mathrm{kN}/m^3$ by the standard and modified Proctor compaction tests, respectively. Direct shear friction angles were measured between 47 and 62° at normal stresses ranging from $0\mathrm{to}200\mathrm{kPa}$. Friction angles obtained by drained triaxial shear were on the order of 48° for similar stress ranges. Measured hydraulic conductivities were on the order of $1-6\times {10}^{-4}\mathrm{cm}/s$. The results indicate that crushed glass is a readily available, freely draining, environmentally clean, relatively low cost material whose engineering performance properties generally equal or exceed those of most natural aggregates. Despite these favorable characteristics, there are many real and perceived barriers to increasing the beneficial use of crushed glass, and key examples are provided in an effort to illustrate these unnecessary barriers.

The use of carbon fiber reinforced polymer (CFRP) composites has been investigated in the past few years as a means to rehabilitate aging concrete structures. The detection of disbonds and delaminations between CFRP laminate and the concrete substrate is a critical issue in this area, as the presence of such defects adversely affects the effectiveness of the reinforcement. Thus, the development of a nondestructive testing (NDT) technique to detect these types of defects is of great interest in this field. Furthermore, any such method should also be capable of verifying the quality of the repair of such defects. Near-field microwave NDT techniques, utilizing open-ended rectangular waveguides, have shown great potential in the past for detecting delaminations and disbonds in complex composite structures. Microwave NDT techniques have the added advantages of providing real-time, noncontact, one-sided, rapid, and robust measurements. This paper presents the experimental results of detecting disbonds in a specially prepared CFRP reinforced mortar sample using near-field microwave NDT techniques, as well as the preliminary results showing the capability of this technique for verifying repair quality.

The resistance of natural fiber-filled high-density polyethylene composite specimens to ultraviolet- (UV) and moisture-induced degradation was evaluated by measuring changes to flexural properties. High-density polyethylene (HDPE) served as the polymer matrix for four formulations: two formulations without fiber filler and two formulations one containing wood flour and the other containing kenaf fiber, each added at 50% by weight. Specimens were exposed for 4,000 h to UV radiation and moisture cycling in a laboratory weathering device to simulate the effects of exposure to sunlight and rain. Modulus of elasticity and modulus of rupture were measured prior to and after specific exposure periods. The flexural modulus and strength decreased significantly with increasing exposure for both natural fiber-filled HDPEs, but these composites still outperformed composites without filler. To explore a practical means to predict the changes in flexural properties to observed physical changes, a two-layer elementary mechanics model consisting of a degraded surface layer and an unaffected core layer was considered. The model was only partially successful—it provided reasonable predictions of flexural strength but did not accurately predict modulus of elasticity.

This paper presents the results of an experimental investigation into the effects of high temperatures on the properties of concrete made with crushed clay bricks as the coarse aggregate. Two types of brick of different strength were crushed to coarse aggregate that was used to produce concretes of different strength. Natural granite aggregate was also used to produce concretes in order to compare results. The paper presents the results for brick unit uniaxial compressive strength, aggregate impact value, aggregate relative density, brick and aggregate water absorption, aggregate porosity, concrete density, and concrete strength before and after exposure to high temperatures. The results showed that concrete could be produced using crushed clay bricks as the coarse aggregate and at high temperatures clay brick concrete preformed similar or even better than granite concrete.

In this paper, the behavior of concrete under static and fatigue compressive load is studied. Cylindrical specimens were subjected to static cyclic and constant amplitude fatigue loading. The static cyclic tests were performed by unloading and reloading the specimen at three different points in the postpeak period of the static loading response. Low cycle, high amplitude fatigue tests were performed to failure using three load amplitudes. It is found that under the term of structural compliance the static compressive response of concrete can be used as an envelope for the fatigue failure compressive response. The change rate of stiffness or compliance under fatigue loading follows a two-stage process: a deceleration stage followed by an acceleration stage up to failure. The failure mechanisms for both static and fatigue loading are explained by the band damage zone model and found to be consistent in the term of an inelastic displacement. The results agree well with the previous research work.

Volcanic pumice (VP) from Papua New Guinea was investigated and assessed for its industrial utilization. The compressive strength of several concrete mixtures using pumice as lightweight coarse and fine aggregates in different percentages was found acceptable and satisfied the American Society for Testing and Materials (ASTM) requirement for lightweight structural concrete. Pozzolanic activity of pumice powder as a cement additive was tested according to the Italian standards and found to be acceptable. The strength activity index with Portland cement and the effectiveness of pumice admixture as cement additive in controlling alkali–silica reactions and autoclave expansion, satisfied the ASTM requirements. The utilization of VP as a heat-insulating material was tested and the results were also found to satisfy the ASTM requirements. This fact suggests that VP can be utilized in the manufacture of building blocks. The manufacturing of heat-insulating concrete or building blocks using pumice is of prime importance as an energy saver.

A method is developed to assess hot mix asphalt (HMA) stability during compaction in the mix design process, and prior to conducting further expensive and time consuming testing. The method consists of a mathematical derivation, and an experimental procedure to determine a new stability index, referred to as the contact energy index (CEI). The CEI reflects the ability of the aggregate structure to develop contacts among the particles when subjected to shear stresses. The stability of HMA increases with an increase in CEI. The sensitivity of the CEI to changes in mix components is evaluated by analyzing asphalt mixes that differ in their nominal maximum aggregate size, aggregate gradation, source of aggregate, percent of natural sand, and asphalt content. In addition, the CEI is compared with mechanical properties of a number of asphalt mixes. The results show that the CEI captures the influence of changes in mix constituents on mix stability, and has very good correlation with the mechanical properties.

In this paper a particle assembly model was proposed for high fluidity concrete in the fresh state. This particle assembly is composed of cohesionless particles (aggregates grains) and cohesive particles (cement grains) surrounded by mixing water membranes. By using a microscopic approach and expanding Eyring’s rate process viscosity theory, the flow mechanism of high fluidity concrete having interfriction was clarified, and its flow curve was examined. Furthermore, the effects of normal stress and environmental temperature on the flow behavior of high fluidity concrete were investigated quantitatively. Finally, a shear test apparatus was developed and a series of shear tests were performed to verify the obtained theoretical results.

The microstructure of recycled aggregate prepared from the crushing of old concrete was studied. It was found that the recycled aggregate is covered with loose particles that may prevent good bonding between the new cement matrix and the recycled aggregate. The old cement paste that remained on the natural aggregate was porous and cracked, leading to weak mechanical properties of the recycled aggregate. Treatment of the recycled aggregate by impregnation of silica fume solution and by ultrasonic cleaning was studied with the objective of overcoming the above-mentioned limitations. An increase of $\sim 30$ and $\sim 15\%$ in the compressive strength at ages 7 and $28\mathrm{days}$ was observed after the silica fume treatment. Ultrasonic treatment led to an improvement of $\sim 7\%$.

Dwindling sources of traditional aggregates, ever increasing haulage distance, and diminishing landfills are the primary factors that favor the reuse of construction-quality waste materials in highway pavements. Although numerous studies have been conducted on the performance of municipal solid waste incineration bottom ash (MSWI-BA) in cement concrete, little is known about its characteristics in bituminous concrete pavements, especially in Superpave design hot mix asphalt (HMA). By comparing the air voids and voids filled with asphalt of 20% MSWI-BA HMA samples aged for 2 and $4h$ for a trial mix, all the blends prepared for this research were aged for $4h$ prior to compaction. Varying the slope/curvature, and the proportions of stone sand and stone dust in trial mixes showed that slope/curvature is more significant than aggregate type in increasing voids in mineral aggregates (VMA). The design binder contents in mixes were found to increase from 6.2% for 0% BA content to 7.4% for 20% BA, a difference of 1.2% (a 19% increase). Also, as bottom ash content is increased to 20%, the effective asphalt decreases from 5.1 to 4.4%, while the absorbed asphalt increases from 1.3 to 3.2%. These findings are consistent with the high absorptivities (i.e., 9.2% water) found for the bottom ash and its high internal porosity resulting in total surface area increase of aggregate structures containing MSWI-BA. Although the 13.0% minimum VMA specified by Superpave was met for all MSWI-BA contents of the design mix used for this study, a marked decrease from 15.3% VMA for 0% BA to 13.4% VMA for 20% BA was measured. Results of the $\%G_{\mathrm{mm}}$ at $N_{\mathrm{initial}}$ for 0–20% MSWI-BA HMA are essentially the same, falling between 85 and 86% compaction. Based solely on the results of the Superpave densification values ($\%G_{\mathrm{mm}}$ at $N_{\mathrm{initital}}$ and $N_{\max }$) for this study, substitution of up to 20% MSWI-BA for virgin aggregates yield mixes having aggregates structures that are well developed to resist compaction, rutting, and tenderness in agreement with the findings of Wang et al. in 2000. Obviously, rutting potential, fatigue characteristics, resilient modulus, and field studies should be evaluated to thoroughly investigate the performance of MSWI-BA amended HMA.

This paper summarizes the results of tests on the impact of aggregate angularity on the resilient modulus and shear strength of the base/subbase layers in a pavement structure. Tests conducted with large-scale samples ($300\mathrm{mm}$ in diameter) found that, at low bulk stress levels, the resilient modulus of 0% crushed (natural) material was higher than for 100% crushed mixture. This trend was reversed when the bulk stress was greater than $300\mathrm{kPa}$. The void ratio also had an impact on the resilient modulus when the crushed content was 50% or less. It was also found that with standard $150-\mathrm{mm}$-diameter samples, the resilient modulus was higher for the natural material than for 100% crushed material at all stress levels; it was also about $35-50\%$ higher than from the large-scale tests. From the standard samples, the angle of internal friction ranged between 41 and $46°$ for void ratios around 0.22. For the large-scale samples for a void ratio around 0.16, the angle of internal friction was about $50°$. The particle index is a good indicator of the crushed (angular) content of a given base course. For all practical purposes, the particle index is not a good indicator of the resilient properties of the base course aggregate.

This paper presents use of improved palm oil fuel ash (POFA) as a pozzolanic material in producing high-strength concrete. The POFA was ground by ball mill until the median particle size was reduced to about $10\mu m$. It was used to replace portland cement, ASTM Type I, by 10, 20, and 30% by weight of cementitious materials to make high-strength concrete. It was found that high-strength concrete can be achieved by using ground POFA to replace portland cement Type I up to 30%. At the age of $28\mathrm{days}$, concretes containing 10, 20, and 30% of ground POFA gave compressive strengths of 81.3, 85.9, and $79.8\mathrm{MPa}$, respectively. Concrete with 20% replacement of ground POFA had the highest strength. It is slightly higher than that of concrete containing 5% condensed silica fume and about 92–94% that of 10% condensed silica fume concrete. The ground POFA content up to 30% had slightly effect on lowering the modulus of elasticity of concrete. In addition, the use of ground POFA reduced the peak temperature rise of concrete under semiadiabatic conditions.

Three styrene–butadiene–styrene coblock polymer modified asphalt concrete mixtures (70/100M5, 160/220M5, and 160/220M10) are characterized using complex modulus and fatigue testing. The compositions of the materials investigated are identical (aggregate size distribution, binder, and void contents) and differ solely regarding binder characteristics. The modified binders are manufactured using two base bitumens (70/100 and 160/220) modified by a styrene–butadiene–styrene coblock polymer. The fatigue tests are carried out at three different temperatures (0, 10, and $20°C$) using both stress- and strain-controlled modes. A continuum damage model is used to investigate its ability to characterize fatigue of polymer modified mixtures. The results indicate that the continuum damage model is suitable for characterizing the materials at the test conditions used (mode of loading, excitation amplitude, and testing temperature) in that visually similar material functions are obtained. Using statistical analysis, it was indicated that strain amplitude does not significantly influence the model parameters of the characteristic material functions. However, even though different loading conditions lead to apparently similar material functions, the model parameter values were actually significantly affected by the testing temperature used. Predictions of fatigue path, including number of cycles to failure, based on the material functions indicate reasonable accuracy.

This paper describes the work carried out in laboratory to produce concrete with good properties using oxidizing electric arc furnace (EAF) slag as fine and coarse aggregate. To do this, the slag obtained in the steelmaking process must be crushed and stabilized. First, a suitable mortar must be made and tested. Next, several mixes of concrete are designed in order to analyze their strength and properties. From the results obtained, it can be deduced that this concrete can be produced for use in a wide range of applications in civil engineering and construction. Studies and tests were performed on the durability of these concretes showing an acceptable behavior against aggressive environments. Finally, some leaching tests were carried out in order to verify their environmental compatibility.

The influence of construction materials on the atmospheric radon concentration in an underground facility at the Nevada Test Site was examined. Radon (${}^{222}\mathrm{Rn}$ only) concentrations within the supporting fiber-reinforced concrete (fibercrete) and the native soil were quantified and compared. The average activity concentrations of ${}^{222}\mathrm{Rn}$ were $39\pm 1$ and $12\pm 1\mathrm{Bq}{\mathrm{kg}}^{-1}$ for the native soil and fibercrete, respectively. The average emanation coefficients of ${}^{222}\mathrm{Rn}$, measured via Lucas cell scintillation, were significantly higher for the cured fibercrete at $0.078\pm 0.029$, than for the dried native soil at $0.0053\pm 0.0006$. The emanation coefficient for the in situ native soil is estimated to be $0.020\pm 0.004$. In situ exhalation rates were also determined using passive-diffusion charcoal canisters. The average exhalation rate for the native material surface was $5.8\pm 0.6\mathrm{mBq}{m}^{-2}{s}^{-1}$. This was significantly higher $(p=9\times {10}^{-5})$ than for the fibercrete surface, which exhibited an average exhalation rate of $2.7\pm 0.7\mathrm{mBq}{m}^{-2}{s}^{-1}$. Based on these results, it can be concluded that the addition of fibercrete to wall surfaces reduces the radon concentration in this underground environment.