Journal of Materials in Civil Engineering

The objective of this research is to evaluate the permanent deformation of high-modulus asphalt concrete (HMAC) pavement in terms of the viscoelastic theory. Based on the Bailey-Norton creep law, parameters of HMAC were obtained from the creep test. Combined with theses parameters, a finite-element model of a pavement with HMAC in the middle course was constructed and its deformation was simulated. In addition, the impact of HMAC modulus, temperature, and axle load as well as asphaltic thickness on the deformation was analyzed. Results indicate that the deformation of the HMAC pavement was less than that in the asphalt concrete (AC) pavement, and the deformation of the former decreased with the rise of HMAC modulus. Moreover, the optimum modulus ranging from 2,000 to 2,400 MPa is recommended for application. In addition, the pavement deformation increased linearly with depths of the AC courses whereas it decreased with the increase of the HMAC thickness in a cubic polynomial way. Finally, a model to predict rutting in the HMAC pavement is proposed.

The use of modified binders plays a very important role in the construction of more durable pavements. However, the addition of modifiers to the binders could considerably increase their cost, making these materials less competitive. Thus, in recent years, various research studies have been carried out to obtain new modified binders that could lead to an improvement in the mechanical performance of asphalt pavements without a notable increase in their construction costs. To this end, the reuse of wastes and by-products from other industries has been posited as an interesting and sustainable alternative. This study investigates the reuse of scraps from reclaimed geomembranes composed of low-density polyethylene and polyester fibers as modifiers for asphalt binders. For this purpose, different blends of this waste and neat bitumen were manufactured and tested [penetration, softening point, storage stability, frequency sweep, multiple stress creep-recovery (MSCR), and time sweep tests). In addition, the results obtained were compared with those obtained by using neat bitumen and traditional polymer modified bitumen. This study indicates that reclaimed geomembranes could be an interesting modifier for asphalt binders because they can increase their resistance to permanent deformation, stiffness and elasticity, reduce their temperature susceptibility, and extend their fatigue life.

As an environmentally friendly construction technique, modern rammed earth generally stabilized with portland cement has attracted growing interest recently. In this study, cement-based composites (CSCN) consisting of cement, sodium silicate, and composite promoter were used for substituting portland cement, and the effect of fly ash was investigated by unconfined compressive strength (UCS) test, thermogravimetric analysis (TG), X-ray diffraction (XRD), and scanning electron microscope (SEM). Based on the theory of pozzolanic and dispersing (P&D) effects, the contribution of fly ash was regarded as an addition of CSCN, and the quantitative analysis of P&D effects defined as P&D factors was evaluated by the clay-water/CSCN ratio hypothesis. It was found that the P&D factors for both compressive strength and secant modulus varied with CSCN content and curing age. The models of different curing ages for predicting the strength and modulus of specimens stabilized with CSCN and fly ash were developed from the combination of P&D factors and clay-water/CSCN ratio. The precisions of P&D factors and prediction models were verified by comparing predicted results and experimental results, and the deviation was mostly within 10%. The mineralogical and microstructural analyses confirmed that the combination of pozzolanic and dispersing effect hypothesis could be appropriate to study the fly ash effects.

Warm mix asphalt (WMA) describes various technologies that allow asphalt mixtures to be produced at lower temperatures as compared with hot mix asphalt (HMA). WMA technologies also offer improvements in workability, cost, and environmental sustainability, such as reduced fuel usage, greenhouse gas emissions, and wear and tear at plants, while enhancing worker health and safety conditions. The objective of this study was to quantify the laboratory performance of field-produced mixtures that utilize WMA technologies and to evaluate the influence of lowering the production temperature on the mixture properties in the field. To achieve this objective, three field projects across Louisiana were selected to provide eight mixtures for the evaluation of WMA technologies. Plant-produced mixtures were sampled and the laboratory performance of WMA mixtures and conventional HMA was evaluated. Further, the characteristics of WMA mixtures were compared with conventional HMA mixtures during production and construction. Based on the results of the experimental program, it was concluded that there was no difference in the rutting performance of WMA compared with HMA. In addition, the use of WMA technologies improved asphalt mixture fracture resistance. With respect to moisture susceptibility, the tensile strength ratio (TSR) of the WMA mixtures was comparable to the conventional HMA in two projects; however, it was lower than the TSR criterion of 80% in the third project. During production, while the moisture content in WMA was slightly higher than the conventional mixtures, both mixture types met Louisiana’s specifications (with moisture content less than 0.3%). Further, asphalt absorption was not statistically different between HMA and WMA. During paving, the temperature of the mat was distinctly lower for WMA than for HMA. With respect to the compaction effort, there seemed to be no discernible difference in the compaction effort required for HMA and WMA. In addition, the WMA mixtures were able to meet the minimum specification requirement of 92% density in most of the cases.

Various rutting susceptibility parameters for unmodified and modified bitumen were studied at three different temperatures of 40, 50, and 60°C. Wheel rut testing was also conducted on three different bituminous mixes at 60°C. The different test parameters used to evaluate the rutting performance bitumen were correlated with the mix results, and the best suited method was identified. It was found that the ranking of binders with respect to rutting susceptibility remained unaltered irrespective of any test method. Statistically, multiple stress creep and recovery (MSCR) was found to correlate more accurately with the wheel rutting test results as compared to the other test methods. It was concluded that MSCR test is a more rudimentary way of predicting the rutting sensitivity of binder in a bituminous mixture.

This paper presents a comprehensive experimental study on mechanical characteristics of rigid polyurethane foam (RPF) and its application as the structural core of an innovative noise barrier consisting of polyblock, RPF, and polyurea. The mechanical behavior of RPF was characterized by performing tensile, compression, modulus of elasticity, Poisson’s ratio, flexural, shear, pullout, cyclic, and long-term creep tests. Five full-scale walls were also fabricated and their behavior was established under lateral static and cyclic loading. Applicability of the proposed wall system (polywall) in accelerated construction was practically examined. Experimental results were discussed and a preliminary design of polywall was also conducted. Results revealed that mechanical performance of RPF as well as the entire wall system is satisfactory for the investigated application and polywall can be employed in accelerated construction of noise barriers.

In the context of urban heat islands (UHI), sustainable solutions are being devised to craft greener built environments such as cooler roofs and pavements mainly to counter a variation of thermal flux within the urban climates. Modification of the pavement thermal properties is a potential strategy to render pavements cooler with different cooling mechanisms. The thermal behavior of pavements is largely dependent on the different but interactive thermal properties of pavement materials such as thermal conductivity, specific heat capacity, density, albedo, thermal emissivity, and not on one single property alone. The objective of this research study was to investigate the thermophysical properties of different pavement systems through the development of a comprehensive methodology that can quantify contribution of thermal properties on urban climates from laboratory-based measurements. Six different paving mixtures including conventional dense-graded, asphalt-rubber, and cement concrete mixes were prepared encompassing 96 sample data points for the experimental program. With an increase in specific heat capacity, thermal conductivity, thermal diffusivity, and albedo, there was a decrease in the maximum pavement surface temperature of the various mixes. Although the investigation of thermal behavior of pavement materials is complex in nature, this laboratory study has attempted to investigate all major thermophysical properties of different pavement systems in a comprehensive manner. It is envisioned that this research study will help advance the state of the art and knowledge related to pavements’ selection and contribution to urban climates, and in recommending a suitable UHI mitigation strategy from the pavements’ perspective.

The use of recycled materials and sustainability are two factors taken into consideration during the design of environmentally conscious buildings, but structural performance is still the foundation of sound design. Modern day building designs many times incorporate performance-based methodologies to combat the effects of extreme loadings. The key of such designs is to absorb high amounts of energy and sustain loadings under excessive deflections. Fiber-reinforced concrete and concrete containing rubber particles have increased levels of toughness in comparison with conventional concrete. This paper presents the results of an experimental investigation focused on the material properties of fiber-reinforced rubber concrete. Rubber particles were used at various concentrations to partially replace coarse and fine aggregates coupled with the addition of fiber reinforcement. The investigation includes an evaluation of standard fresh and hardened concrete properties. Results show fiber reinforcement counteracts the negative effects of using rubber particles to replace traditional aggregates, confirming the feasibility of combing the two constituents.

This paper deals with the tearing analysis on laminated fabrics used in pneumatic structures (specifically crack propagation and tearing strength). Uniaxial tearing tests were carefully conducted on specimens, and the influences of crack parameters on the tearing behaviors and strength of a laminated fabric were discussed. Afterward, the biaxial tearing tests were performed on the cruciform specimens to study their central tearing properties. The tearing strength and failure performance were significantly related to the stress ratios. With the same equivalent crack length, the samples under biaxial loads could show a higher tearing resistance than those under the uniaxial loads. Finally, the results of three different theories used to predict the uniaxial tearing strength were compared with the experimental results, and it was found that the Thiele theory provided the best prediction for the tearing strength of laminated fabrics.

Steel screw anchors (SSAs) have been widely used in geotechnical engineering practice because they are simple in structure and easy to design and construct. The main disadvantage of SSAs is that they rust quickly and are not found to be suitable for permanent structures, unless adequate corrosion protection measures are provided. Anchors made of glass fiber–reinforced plastic (GFRP) are corrosion-resistant material that are light in weight with a higher tensile resistance in comparison with SSAs. For this reason, GFRP anchors have been found to be a good substitute for SSAs during the last two decades. In this paper, details of a newly developed GFRP screw anchor (GFRP-SA) with respect to the physicomechanical, tensile, and creep properties along with its performance both in the laboratory and in field conditions are provided. A specially developed machine that facilitates quick installation of the GFRP-SA is also briefly introduced. In addition, two full-scale field tests that were undertaken to study in situ long-term performance of the GFRP-SAs for anchoring soil slopes (1) in an expansive soil, and (2) in a compacted subgrade soil are presented and discussed. Furthermore, the average pullout resistances of the GFRP-SAs were also determined from field tests. The results of the field studies suggest that GFRP-SAs can be installed with relative ease and they provide adequate resistance against shallow landslide slope failures. The study presented in this paper is encouraging for the use of GFRP-SAs in conventional geotechnical engineering practice for stabilizing slopes in different types of soils.

Incinerator bottom ash (IBA) has great potential to be utilized for civil engineering applications. This paper is to investigate the characteristic of gas generation from IBA and to study the potential of IBA as an aerating agent. Results show the aeration capacity of IBA used in this study is approximately 1% that of pure aluminum powder by mass. Finer particles, higher alkali molarity, and higher reaction temperature encourage the reaction and more gas is generated per gram of IBA. Type of alkaline solution does not seem to be an important factor for gas generation from IBA. Several exemplary lightweight mortars were produced by incorporating IBA as an aerating agent. It is highly plausible IBA can be used as an aerating agent to replace pure aluminum powder in the production of aerated concrete.

The tensile strength of soil is an important mechanical parameter that controls the development of tension cracks. In this study, randomly distributed polypropylene fibers were employed to improve soil tensile behavior. Direct tensile tests were conducted on fiber-reinforced soil specimens with different fiber contents and compacted at different water contents and dry densities. Desiccation tests were also performed to evaluate the effectiveness of fiber reinforcement in improving soil tensile cracking resistance. The tensile test results showed that fiber inclusion significantly increased the soil peak strength, reduced the postpeak strength, and changed the brittle tensile failure behavior to a more ductile one. Soil tensile strength increased with the increase in fiber content. The tensile strength of both reinforced and unreinforced specimens decreased with increasing water content and increased with increasing dry density. Moreover, a higher soil dry density showed a more positive effect in mobilizing the reinforcement benefit of fibers. Based on the fiber/soil interfacial interaction mechanisms, the fiber reinforcement benefits on soil tensile behavior were analyzed. A linear relationship was obtained between the fiber reinforcement benefit and the fiber/soil interfacial shear strength. The desiccation test results showed that fiber inclusion significantly decreased soil cracking. The surface crack reduction ratio increased while the average crack width and length decreased with increasing fiber content, suggesting that fiber reinforcement was efficient in impeding soil tensile failure.

Ballast and subballast are two layers of noncohesive, granular materials with different grain sizes filled in the track substructure to bear traffic loadings from train passages. The performance and sustainability of a track substructure depend on both of these two granular layers. This paper presents the experimental results of cyclic triaxial testing and postcyclic triaxial testing on individual ballast and subballast materials. Also, to investigate mechanical behavior at the ballast/subballast interface, cyclic tests were performed on composite specimens consisting of the upper half ballast layer and underlying half subballast layer. These cyclic tests indicated that the existence of the ballast/subballast interface depresses the development of permanent axial or volumetric deformation at the interface zone, and this effect vanishes as the initial compaction and confining pressure increase. Postcyclic failure tests show that the ballast/subballast interface zone’s strength is close to that of the ballast material but lower than that of the subballast material.

The use of recycled construction and demolition (C&D) materials in unbound and cement stabilized pavement base/subbase applications has generated growing interest in recent years. C&D materials consisting of crushed brick (CB), recycled crushed aggregate (RCA), and reclaimed asphalt pavement (RAP) have been investigated in unbound and cement stabilized pavement base/subbase applications. However, the high carbon footprint of using cement for pavement base/subbase stabilization has led to this research to seek alternative low-carbon binders. This study evaluates the behavior of C&D materials when stabilized with geopolymers. Fly ash (FA) and ground granulated blast furnace slag (S) were used as pozzolanic binders and a different alkaline activator solution to pozzolanic binder ratio was tested. A maximum of 4% of dry weight of soil was used for geopolymer stabilization of the C&D materials. The binders used were either 4% FA, 2% FA+ 2% S, or 4% S. The geotechnical engineering and strength properties of these geopolymer-stabilized C&D materials were evaluated to ascertain their performance for pavement base/subbase applications. Elastic modulus, compressive strength, and resilient modulus of the blends were tested and analyzed in this research. Both the resilient modulus of the C&D materials and compressive strength were found to increase as a result of geopolymer stabilization. Geopolymer stabilization was found to be most effective for RCA. Higher compressive strength will be achieved by slag-based geopolymer stabilization when compared with fly ash–based geopolymer stabilization. The effect of alkaline activator to pozzolanic binder ratio on the enhancement of geotechnical properties of C&D materials was also analyzed. The performance of the geopolymer-stabilized C&D materials was furthermore compared with that of traditional cement-stabilized C&D materials. Geopolymer-stabilized RCA and RAP were found to be a viable and sustainable option for the stabilization of future pavement bases/subbases.

Compressed earth blocks, a form of earthen construction, is a growing field of natural building. It is a low-cost, locally available material that provides high thermal capacity with low environmental impact. Earthen blocks have been primarily used in warmer climates; however, there is increasing interest in using the blocks in cold climates. Limited research has been done on long-term durability in cold climates. In this study, combinations of cement and lime stabilizers were tested with metakaolin and Plasticure, a water repellant, to determine freeze-thaw durability. Blocks were exposed to up to twelve 48-hour freeze-thaw cycles. Prisms were tested in compression to failure in both the wet and dry condition as a measure of deterioration. Freeze-thaw damage occurred when water was readily available via capillary action. Blocks with 7.5% cement content provided optimum strength retention; however, 10% cement provided higher strengths. The addition of lime, metakaolin, and Plasticure to a 5% cement-stabilized block increased dry strength retention by 75 to 146%, but there was no significant difference when wet. Plasticure reduced variability in strength reduction from as high as 91 to 24%, and increased strength retention by up to 75%. Reductions in both strength and water strength coefficients were observed in different combinations.

A new natural hydraulic lime (NHL) has been fabricated from lime mud and 5–15% by weight fly ash by calcination and it has been applied to the preparation of fly ash bricks. Lime and dicalcium silicate have been identified as the main crystalline phases of the new NHL by X-ray diffraction (XRD) analysis. Tricalcium aluminate and gehlenite were formed when fly ash content was increased. After calcining at 1,000°C, available lime (31–55% by weight) and sulfate (0.53–0.71% by weight) contents of the new NHL have conformed the performance requirements of NHL. Compressive strength of standard mortars showed that the new NHL met performance requirements. Results also showed that for the new NHL, 900–1,000°C was chosen as the optimum calcination temperature and 10% by weight was the optimum fly ash content. Comparison of the compressive strength of fly ash bricks with the new NHL and ordinary lime has indicated that the new NHL shows better behavior than ordinary lime. Moreover, fly ash bricks with the new NHL have high compressive strength in water curing (5.8–19.7 MPa), natural curing (8.5–20.5 MPa), and autoclaved curing (17.4–22.5 MPa) conditions.

On-site addition of accelerator to rapid repair concrete mixtures can result in accidental overdose. Since these mixtures are designed to contain large accelerator dosages, an overdose will produce concrete with extremely high accelerator amounts, well above those recommended by the manufacturer. This study investigated the effect of calcium chloride–based accelerator dosage on the stresses and cracking behavior of realistic concrete mixtures that contain multiple chemical admixtures. The findings indicate the effect of accelerator dosage on increasing the temperature gradient in concrete leading to higher tensile stress generation with upward or downward curling. The effect is exacerbated when there is a simultaneous coincidental occurrence in the maximum of cement paste heat flow and ambient temperatures. The apparent activation energy determined through the heat of hydration or strength measurements shows a drop when chemical retarders are added, whereas for accelerators the effect appears to be dosage dependent. The results of compressive, tensile strength and elastic modulus testing indicate a decrease in the mechanical properties of concrete at high accelerator dosages. Accelerator overdose affects hydration kinetics by limiting the degree of hydration at high temperatures while accelerating the reaction at earlier times or lower temperatures. Modeling indicated that the negative effects of accelerator overdose can be reduced by lowering the concrete placement temperature and placing concrete during evening hours.

Carbonation and chloride ingress are the two main causes of corrosion in reinforced concrete structures. An investigation to monitor the ingress of chlorides and the effect of carbonation on chloride ingression during an accelerated 12 month cyclic wetting and drying exposure regime that simulates conditions in which multiple mode transport mechanisms are active was conducted on ground granulated blast furnace slag (GGBS) concrete. The penetration of chloride and carbon dioxide was evaluated using water and acid soluble chloride profiles and phenolphthalein indicator, respectively. The results indicated that when chloride and carbon dioxide ingress concomitantly the effects can be adverse. Carbonation has a detrimental effect on the binding capacity of the concrete, increasing the concentration of free (water soluble) chlorides. This contributed to greater concentration and greater penetration of chlorides and thus an increased corrosion risk.

Complex modulus of an asphalt mixture constitutes two components: $E^{\prime }$ representing the ability of the mixture to store energy (elastic behavior), and $E^{\prime \prime }$ reflecting the capacity of the material to dissipate energy (viscous behavior). The main objective of this study was to develop predictive equations for the two components, $E^{\prime }$ and $E^{\prime \prime }$, to better quantify and assess the performance of conventional and modified mixtures alternate to standard laboratory testing. The dataset used in this effort encompassed 163 conventional dense graded asphalt concrete (DGAC), 13 asphalt-rubber asphalt concrete (ARAC) gap-graded, and 9 asphalt-rubber friction course (ARFC) open-graded mixes covering 5,550 data points. Aggregate gradation, binder, and volumetric property parameters were used as predictor variables. Squared-error optimization mathematical techniques were employed in developing predictive models. The statistical goodness of fit measures of $E^{\prime }$ and $E^{\prime \prime }$ predictive models were very good to excellent. Validation results of the predictive models reflected effectiveness in reproducing observed values with goodness-of-fit measures in the domain of fair to excellent. Sensitivity performance analyses were also carried out to demonstrate the performance of asphalt mixtures with respect to different material properties.

Paving interlayers have been used in asphalt concrete (AC) overlays for a variety of benefits. An earlier study showed that different paving interlayers improved mixture performance, while the multiaxial interlayer provided the best overall laboratory performance. This paper presents further investigation of the reinforcing effect of the multiaxial interlayer on the entire pavement. Pavement structural analysis using finite-element method (FEM) analysis and several specialized commercially available software were conducted, and field test sections were established and surveyed to further validate findings from the previous study. The pavement structural analyses were in agreement that using interlayer could improve fatigue crack resistance and extend service life. The three-yarn biaxial interlayer showed the best reinforcement potential of fatigue crack resistance, followed by the multiaxial interlayer and the two-yarn biaxial interlayer. The FEM analysis indicated that the multiaxial interlayer could improve stress distribution more effectively than the two-yarn biaxial interlayer. Preliminary results from field evaluations of test sections showed that pavement performance was improved if reinforced by interlayers, in terms of reduced amount and severity of cracking. Further monitoring of field test sections are recommended to give clearer projection of the utility of the paving interlayers in cold regions.

Although bitumen, the binder most commonly used in asphaltic concrete pavements, constitutes only 3 to 5% of the total mixture, it has a significant impact on the total cost of the pavement. Because of this cost factor, this paper investigates the optimal use of the very abundant sulfur as a replacement for the more expensive bitumen. In this study, bitumen-sulfur blends were prepared, using an increasing amount of sulfur as replacement, up to 50% by weight. A group of samples were then short-term and long-term aged by using the rolling thin film oven test and a pressure aging vessel. Aged and virgin samples were then further tested with Superpave binder test methods. The promising results demonstrate that the addition of sulfur not only lowers total costs, but also increases the performance of the binder.

Earthen building materials bear interesting environmental advantages and are the most appropriate to conserve historical earth constructions. To improve mechanical properties, these materials are often stabilized with cement or lime, but the impact of the stabilizers on the water transport properties, which are also critical, has been very rarely evaluated. The researchers have tested four earth-based repair mortars applied on three distinct and representative rammed earth surfaces. Three mortars are based on earth collected from rammed earth buildings in south of Portugal and the fourth mortar is based on a commercial clayish earth. The main objective of the work was over the commercial earth mortar, applied stabilized and not stabilized on the three rammed earth surfaces to repair, to assess the influence of the stabilizers. The other three earth mortars (not stabilized) were applied on each type of rammed earth, representing the repair only made with local materials. The four unstabilized earth materials depicted nonlinear dependence on $t^{1/2}$ during capillary suction. This behavior was probably caused by clay swelling. Stabilization with any of the four tested binders enabled the linear dependence of $t^{1/2}$ expected from Washburn’s equation, probably because the swelling did not take place in this case. However, the stabilizers also significantly increased the capillary suction and the capillary porosity of the materials. This means that, in addition to increasing the carbon footprint, stabilizers, like cement and lime, have functional disadvantages that discourage their use in repair mortars for raw earth construction.

This paper presents the stabilization of expansive soil (C) with steel slag (SS), rice husk ash (RHA), and quick lime (L). The geotechnical properties, shearing strength characteristics, and dynamic properties of stabilized soil have been studied. The optimum mix is found to be in the proportion of $65\mathrm{C}+20\mathrm{SS}+5\mathrm{L}+10\mathrm{RHA}$. The unconfined compressive test shows that strength of treated soil increases about 45 and 90% for uncured and cured samples at 30 days. The soaked California bearing ratio (CBR) test shows that the strength increases with increasing curing periods from 7 to 30 days. Laboratory strain-controlled cyclic triaxial tests have been carried out under undrained conditions to study the dynamic properties of stabilized soil for different strain amplitudes and frequencies. The stiffness of stabilized soil increases to 58–78% as compared to clay soil. This study discussed the suitability of stabilized material for subgrade pavement.