Journal of Materials in Civil Engineering

This paper presents the results of a theoretical and experimental study aiming to develop a stress-based roadway energy harvesting system. It describes two prototypes using piezoelectric elements. Prototype I consisted of 4, 8, and 16 8-mm-diameter cylindrical piezoelectric elements sandwiched between two copper plates. Prototype II consisted of a stack of 11 50-mm-diameter piezoelectric elements connected in parallel by alternating their polarities. Basic piezoelectric theory suggests that the relationship between power output and stress is nonlinear. Finite-element (FE) analysis shows a dependency of the power output of a cylindrical piezoelectric unit on loading frequency. The experimental evaluation included testing the prototypes in a universal testing machine under controlled temperature conditions. In addition, Prototype II was subjected to repetitive loads using an asphalt pavement analyzer without observing any loss in power output. Three-dimensional dynamic FE simulations were performed to determine the optimum installation depth of an energy harvesting module in an asphalt concrete pavement structure. Assuming moderate traffic levels and installation in the right-wheel path only, the energy output estimated per Prototypes I and II was 360 and 171 W-h annually. This technology shows promise in powering self-standing data acquisition systems or light-emitting diode (LED) lights in rural areas where there are no electrical power lines roadside.

Choosing an aggregate gradation is an important step in the design of concrete mixtures. This work presents a systematic laboratory study to find practical limits for the workability and finishability of these mixtures for slip-formed concrete applications. It investigates the upper and lower gradation limits for coarse aggregates, gradations that have no material on single and adjacent sieves, idealized aggregate gradations from previous publications, and insights into sieves responsible for cohesion and finishability of concrete mixtures for slip-formed applications. The work shows that a wide range of successful aggregate gradations can be used to produce concrete mixtures with satisfactory performance; however, certain gradation characteristics can lead to poor performance. These guidelines can be used to assist producers in making concrete mixtures with improved economy, durability, and sustainability.

Compaction and portland cement addition are among the promising ground improvement procedures to enhance the mechanical properties of chalk putty. The present investigation intends to compute the effect of portland cement content and dry density on the mechanical properties (stiffness and strength) and performance (durability) of compacted chalk putty–cement mixes. The most significant addition to knowledge is quantifying the accumulated loss of mass (ALM) after wet-dry cycles, initial shear modulus ($G_0$) and unconfined compressive strength (${\mathit{q}}_{\mathit{u}}$) as a function of the porosity-cement index. In addition, the existence of an exclusive relation connecting accumulated loss of mass divided by the number of wetting-drying cycles and porosity-cement index is empirically revealed. Besides, a power relation was found between initial shear modulus at small strains after wet-dry cycles ($G_0$) and average loss of mass after each cycle. This broadens the applicability of such an index by demonstrating that it controls not only strength and stiffness but also endurance performance of compacted chalk putty–portland cement blends.

This paper investigates the effects of curing conditions on a high-strength geopolymer material synthesized by activating different combinations of Class F fly ash (FA), ground-granulated blast-furnace (slag), and ultrafine fly ash (UFFA) with a unified mixture of D-grade sodium silicate (${\mathrm{Na}}_2{\mathrm{SiO}}_3$) and 12-M sodium hydroxide (NaOH) solutions. The effect of ambient air and water curing on the strength properties, cumulative porosity, and microstructure of geopolymer mortar samples was evaluated at room temperature. Subsequently, the effects of two different sand-binder ratios, the amount of FA replacement with UFFA, and slag on the short-term mechanical properties and workability of geopolymer mixtures is also discussed. The results show that the geopolymer specimens cured in water possessed a higher total porosity in relation to the air-cured samples. Air curing resulted in additional polymerization and fewer microcracks were observed within the scanning electron microscope photographs, which led to an increased compressive strength. Moreover, the use of UFFA was observed to significantly improve the strength of FA-slag blended geopolymers, where reduced porosity and denser microstructure in FA geopolymers was observed with the inclusion of slag at higher quantities.

The filling layer of a China rail track system III (CRTS III) type ballastless track structure of a high-speed railway is a complicated structure typically constructed from self-compacting concrete (SCC). Excellent properties of SCC are of great importance to ensure the quality of construction technology and long-term service performance of the filling layer. In this study, preparation methodologies and properties of SCC applied as a filling layer are systematically investigated by series of experiments. The results indicate that high-performance SCC with high stability in a fresh state and low deformation in a hardened state was successfully achieved by optimizing aggregates and binder components. Use of viscosity-enhancing compounds can not only effectively improve the workability of fresh SCC, but also significantly enhance mechanical properties and decrease drying shrinkage and creep of hardened concrete.

Recycled engine oil bottoms (REOB) are commonly used in asphalt cements to enhance their grade span and/or lower cost. REOB has been linked to premature road failures, resulting in bans and limits set on its use. This study aims to examine different methods of quantifying REOB in asphalt cement to determine if samples are within allowed limits, as well as measuring their feasibility and accuracy. A total of 17 REOB samples, over 30 mixed REOB in asphalt samples, and over 100 contract samples were examined. X-ray fluorescence (XRF), nuclear magnetic resonance (NMR), and infrared (IR) spectroscopy were all successfully calibrated to quantify the REOB content of a binder. Error is added to the quantification because the type of base asphalt will affect results obtained for each analytical method. Errors from different types of asphalt can be minimized using strategies such as weighted averages of results from different indicators, but error from the variability of REOB composition remains significant.

This paper focuses on the feasibility of using construction and demolition (C&D) waste materials, particularly blends of recycled concrete aggregate (RCA) with recycled clay masonry (RCM), as unbound granular materials (UGMs) for road construction in Egypt. The proportions of the RCA/RCM blends were $100/0$, $90/10$, $80/20$, $70/30$, $55/45$, $40/60$, $20/80$, and $0/100\%$ of the total aggregate mass. In addition to the index properties of the blends, the samples of RCA and RCM before and after mixing were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The initial matric suction was measured for the selected blends. Static triaxial shear and repeated load triaxial tests (RLTT) were conducted on triplicate specimens prepared according to the modified Proctor optimum moisture content and maximum dry density. Results showed that the initial matric suction increased by decreasing the RCM at a given moisture content. The RLTT results showed that as the RCM increased, the resilient modulus generally decreased. The universal resilient modulus (${\mathrm{M}}_{\mathrm{r}}$) model was modified by incorporating the content of the RCM to predict the resilient modulus for the RCA/RCM blends. The proposed model yielded accurate predictions with the $R^2$ of 0.82. Finally, the pavement performance in terms of rutting and fatigue cracking was estimated using multilayer elastic analysis along with the mechanistic-empirical pavement design guide (MEPDG) performance models and transfer functions. The predicted pavement performance of the sections with recycled materials as the subbase/base layers was better than the sections constructed with the typical virgin aggregate.

Lightweight cellular concrete (LCC) materials have been used in various civil engineering applications for several decades. In this study, the dynamic behavior of LCC materials was evaluated for possible geotechnical applications, such as mechanically stabilized earth (MSE) retaining walls. Lightweight cellular concrete materials having four different unit weights were subjected to various amplitudes of sinusoidal waves at effective normal stresses ranging from 25 to 350 kPa. Results from this study show that the effective normal stress influenced the shear strength and stiffness more than the unit weight of the LCC materials. The backbone curves could be represented with a hyperbolic function, which can be developed for a known effective normal stress using the equations proposed in this paper. The maximum shear moduli of the LCC materials increased with a decrease in the unit weight and an increase in the effective normal stress. Likewise, the rate of reduction in normalized shear modulus ($G/G_{\text{max}}$) with strain also decreased with an increase in effective normal stress applied during seismic loading. Moreover, the damping ratio decreased with an increase in shear strain up to certain shear strain, which ranged from 0.25 to 0.35% for effective normal stresses of 25 and 350 kPa, respectively, and increased with shear strain after that transitional shear strain. The damping ratio of each type of LCC material tested was similar at the highest shear strain, i.e., 0.5% at a given effective normal stress. The results from this study can be used to evaluate the shear strength and deformation of the LCC materials in various geotechnical projects, such as in the backfill of MSE walls.

This study set out to determine the effect of dry powder nanosilica (nS) on the sulfate resistance of mortars when paired with portland cements (PCs) of contrastingly different fineness and tricalcium aluminate (${\mathrm{C}}_3\mathrm{A}$) content. Several mortar mixtures containing incrementally higher cement replacement with nS were prepared with a lower-Blaine 4.1% ${\mathrm{C}}_3\mathrm{A}$ and a higher-Blaine 12.3% ${\mathrm{C}}_3\mathrm{A}$ PC. Similar mixtures for both cements containing microsilica (mS) were also prepared for comparison. Results indicated that microsilica increased sulfate resistance more effectively than nanosilica due to its superior dispersion in comparison to the agglomerated state of the nS. Poor dispersion of the dry powder nanosilica used in this study is suspected to increase mortar permeability and hinder the reported filler, paste, and interfacial transition zone (ITZ) densification effects of nS. Mortars made with a lower-Blaine and low-${\mathrm{C}}_3\mathrm{A}$ cement paired with the agglomerated nanosilica exhibited more sulfate attack expansion in comparison to the control. Microsilica resulted in both pore and grain refinement of the mortar pastes. Increasing cement fineness proved beneficial in combination with either pozzolan regardless of the cement’s ${\mathrm{C}}_3\mathrm{A}$ content.

In this study, wood waste from demolition was used by replacing natural aggregate for developing lightweight mortars. Many domestic buildings in the historical city centers of Spain have wooden floors and roof structures. Their rehabilitation process produces a large amount of waste, including wood waste. In this study, the wood waste, wood shavings, and sawdust were tested in ratios of 2.5, 5, 10, and 20% by weight of sand. Mortars containing wood were characterized in fresh and hardened states by means of their consistency and bulk density (fresh state) and mechanical tests, bulk density, water absorption by capillarity, vapor permeability, and thermal behavior (hardened state). The results showed that increasing the amount of waste hinders the workability of the sample and prolongs setting times. Furthermore, compounds with larger-sized particles, those based on wood shavings, showed a more pronounced decrease in density and produced the best thermal results. Finally, contrary to what one might expect, the wood-shavings compounds also presented better mechanical properties.

To decrease the usage of energy and improve waste recovery, dynamic simulations are conducted to understand the diffusion mechanism and rheological properties of bio-oil regenerated asphalt. A new simplified model of bio-oil modified asphalt (BMA) is built to calculate diffusion coefficients, diffusion driving force, viscosity, solubility parameters, and ductility. The calculated diffusion coefficients of bio-oil, asphaltenes, saturates, and resins are $4.5\times {10}^{-3}{\mathrm{cm}}^2/\mathrm{s}$, $3.6\times {10}^{-4}{\mathrm{cm}}^2/\mathrm{s}$, $4.2\times {10}^{-4}{\mathrm{cm}}^2/\mathrm{s}$, and $5.1\times {10}^{-4}{\mathrm{cm}}^2/\mathrm{s}$ at 298 K, respectively. Results indicate that the bio-oil diffuses faster than asphaltenes, saturates, and resins, and that it can increase the ductility of asphalt and improve asphalt’s elastic property. Moreover, potential energy is the key driving force of diffusion. There is no chemical reaction involved in the diffusion process of BMA and bio-oil can both reduce the viscosity of asphalt and soften it.

The use of recycled concrete aggregates as an alternative aggregate material in concrete has been studied over the past two decades. It is now recognized that the recycled aggregate concrete (RAC), where natural aggregates are replaced with recycled concrete aggregates, is a promising technology for conserving natural resources and reducing the environmental impact of concrete. This paper presents a study on mechanical and durability properties of concretes manufactured with recycled aggregates of different sizes and contents. A total of 14 batches of RACs were manufactured. Tests were undertaken to establish the compressive strength, elastic modulus, flexural strength, splitting tensile strength, workability, drying shrinkage, and water absorption of each batch. Test parameters comprised the recycled aggregate replacement ratio, size of coarse aggregates, and mixing method used in the preparation of concrete. The results indicate that the compressive strength is not the only decisive factor on mechanical and durability-related properties of RACs. It is shown that the properties of different RAC mixes of the same compressive strength are affected by the size and content of the coarse aggregates.

The aim of the study is to evaluate both acid and sulfate resistance of alkali-activated binders (AABs): (1) AAB-1 made up of slag, palm oil fuel ash, and rice husk ash alongside a 2.5 M NaOH solution; and (2) AAB-2 with the same binders except for palm oil fuel ash, which was replaced by fly ash. Acid and sulfate resistance of mortar specimens were evaluated by visual observation, weight change, compressive strength change, and microstructure analysis. AABs mortar specimens showed superior test results in terms of weight loss and compressive strength reduction compared with an ordinary mortar when immersed in 3% ${\mathrm{H}}_2{\mathrm{SO}}_4$ and 3% HCl solutions for 270 days. On the other hand, the AAB-1 mortar specimen showed a better sulfate resistance than those of AAB-2 and an ordinary mortar when immersed in 5% ${\mathrm{Na}}_2{\mathrm{SO}}_4$ and 5% ${\mathrm{MgSO}}_4$ solutions for 270 days. The microstructure analysis revealed a significant residual gel structure in case of AABs mortar specimens compared with an ordinary mortar specimen after 270 days in both acid and sulfate media.

This paper presents an evaluation of dual self-healing mechanisms in concrete, with a focus on the application of microcapsules and shape memory alloy (SMA). To achieve this objective, the study evaluated the self-healing effectiveness of calcium nitrate microcapsules in concrete beams reinforced with steel and SMA. The undamaged stiffness, damaged stiffness, peak strengths, and deformations were measured and compared with postcuring time values. Further, crack monitoring coupled with an energy-dispersive X-ray (EDX) spectroscopy analysis was used to evaluate crack healing over time and to characterize the healing components in the cracked areas. Experimental results suggest that microcapsules caused a direct effect on decreasing the flexural strength of concrete beams, attributing the results to the presence of high air content when the microcapsules are used. Although microcapsules tended to lower the flexural strength of the beams, the stiffness recovery values were higher for those specimens prepared with microcapsules. An image analysis conducted after the water curing period revealed that specimens with microcapsules showed the best crack healing efficiency, regardless of the use of steel or SMA. In the use of heat activation, not only was crack healing efficiency observed with SMA, but also a noticeable difference was found in SMA samples, with or without microcapsules.

Recycled asphalt pavement (RAP) has received considerable interest in recent years for economic, environmental, and social reasons, and it is necessary to discover what effect the inclusion of RAP into asphalt layers has on the fatigue life of a pavement. Multigrade bitumen is less sensitive to temperature compared with conventional bitumen; therefore, it is expected that multigrade bitumen asphalt will perform much better than conventional asphalt. It is important to investigate the performance of RAP-added multigrade bitumen asphalt as an innovative pavement material. Therefore, in this study the effects of multigrade bitumen types and the amount of RAP content (e.g., 0 and 15%) on the fatigue life of this innovative pavement material were investigated in the laboratory using a four-point beam fatigue testing apparatus under controlled temperature. The results suggested that multigrade bitumen asphalt with and without RAP has higher fatigue life compared with the conventional bitumen asphalt. Further, it was revealed that the type of multigrade bitumen has significant effects on the fatigue performance of multigrade bitumen asphalt. It was observed that the effect of the RAP on the fatigue performance of multigrade bitumen varies with the type of multigrade bitumen. The study was further expanded to develop a master curve for a given mixture and the master curve can be used to obtain flexural modulus of the mixture at a given temperature and at a given loading frequency. The results show that multigrade bitumen and RAP inclusion can have beneficial effects on pavement design thickness.

Poor affinity of asphalt toward mortar paste has been testified as the primary reason for reducing the reclaimed asphalt pavement (RAP)–inclusive concrete properties, although the effect of dust present in RAP aggregates due to extraction of RAP using demolition techniques has not been investigated so far. The present paper discusses the effect of different extraction methods on the mechanical properties of fine RAP aggregates. Also, the effect of incorporation of fine RAP aggregates on fresh, mechanical, and durability properties of concrete has been investigated. It was found that as the substitution level of fine natural aggregates (NA) by fine RAP (0, 25, 50, 75, and 100%) increases, the properties of concrete tend to decrease gradually. From the present laboratory investigation, it is learnt that 50% fine RAP (extraction made using demolition technique) can be used for construction of major highways, whereas 100% fine RAP may be suggested for less important roads and in lower layers of pavement.

The objective of this paper was to examine the effect of the nominal maximum aggregate size (NMAS) on the rutting and stripping performance of Georgia asphalt mixtures containing reclaimed asphalt pavement (RAP) mixtures using the Hamburg wheel-tracking device (HWTD). Five NMASs of 25, 19, 12.5, 9.5, and 4.75 mm of Superpave mixtures were investigated at three test temperatures of 50, 64, and 70°C. The test results were analyzed in terms of five indexes of rutting and stripping resistance: (1) number of loading passes at failure ($N_F$), (2) rut depth at 20,000 wheel passes, (3) stripping inflection point (SIP), (4) creep slope (CS), and (5) stripping slope (SS). The results indicated that Superpave mixtures containing RAP with large NMAS performed better than those with small NMAS in both rut and antistripping resistance. The relationships between the NMAS and SIP showed high correlation coefficients of more than than 0.86 at 64°C. The test temperatures of 64 and 70°C are appropriate for distinguishing size effect for the mixtures with regard to the three parameters of the number of wheel pass at selected rut depth, SIP, and CS.

Calcium chloride (${\mathrm{CaCl}}_2$) from deicing salts can react chemically with calcium hydroxide [$\mathrm{Ca}{(\mathrm{OH})}_2$] from hydrated cement paste to form an expansive product, calcium oxychloride, that can damage concrete. This paper uses two experimental techniques, volume change measurement and low temperature differential scanning calorimetry (LT-DSC), to characterize the phase transitions associated with the formation of calcium oxychloride in the $\mathrm{Ca}{(\mathrm{OH})}_2─{\mathrm{CaCl}}_2─{\mathrm{H}}_2\mathrm{O}$ system. The temperature at which calcium oxychloride begins to form increases as the ${\mathrm{CaCl}}_2$ concentration increases, and it is not influenced by the [$\mathrm{Ca}{(\mathrm{OH})}_2/{\mathrm{CaCl}}_2$] molar ratio. Within the testing temperature range, the extent of reaction [the mass percentage of $\mathrm{Ca}{(\mathrm{OH})}_2$ consumed to form calcium oxychloride] increases as the ${\mathrm{CaCl}}_2$ concentration increases; the extent of reaction decreases as the [$\mathrm{Ca}{(\mathrm{OH})}_2/{\mathrm{CaCl}}_2$] molar ratio increases. The temperatures associated with the phase transitions are used to develop phase isopleths for the $\mathrm{Ca}{(\mathrm{OH})}_2─{\mathrm{CaCl}}_2─{\mathrm{H}}_2\mathrm{O}$ system for varying concentrations and molar ratios. These phase isopleths are integrated to form a ternary phase diagram of the $\mathrm{Ca}{(\mathrm{OH})}_2─{\mathrm{CaCl}}_2─{\mathrm{H}}_2\mathrm{O}$ system. The phase diagram provides a powerful tool to determine the phase transitions in the $\mathrm{Ca}{(\mathrm{OH})}_2─{\mathrm{CaCl}}_2─{\mathrm{H}}_2\mathrm{O}$ system as the [$\mathrm{Ca}{(\mathrm{OH})}_2/{\mathrm{CaCl}}_2$] molar ratio varies.

The fresh-state behavior of plain and silica fume (SF)-modified cement pastes was measured using a wide-gap viscometer. The Herschel–Bulkley (H–B) model was used to describe the rheology of fresh cement pastes. The H–B parameters (including yield stress, consistency coefficient, and flow index) under coupling effect of SF and water addition time were provided. According to the experimental results, the shear-thickening behavior was found to be strongly influenced by the SF content as well as the time after water addition. The flow index declined with SF and water addition time in general. Finally, simplified models were constructed by forecasting the value of flow index as well as H–B yield stress of pastes containing different mineral admixtures under coupled SF content and water addition time.

The original intent of the $J_{nrdiff}$ limit applied to multiple stress creep and recovery test results was to ensure that an asphalt binder does not fail if, under real-world application, it experienced higher stresses or temperatures than what was considered in the laboratory. In recent years, challenges meeting the $J_{nrdiff}$ specification for asphalt binders with low $J_{nr3.2}$ (mainly less than $0.5{\mathrm{kPa}}^{-1}$) have been documented, with reported $J_{nrdiff}$ values greater than 400% in some cases. This paper presents an argument that $J_{nrdiff}$ is an inaccurate representation of stress sensitivity, unfairly penalizes asphalt binders with low $J_{nr3.2}$, and lacks correlation with expected changes in field rutting performance. A new parameter that more appropriately describes stress sensitivity, $J_{nrslope}$, is presented. $J_{nrslope}$ shows a better performance-based relationship to expected changes in rutting and more accurately ranks the study asphalt binders than $J_{nrdiff}$. $J_{nrslope}$ also demonstrates the ability to capture changes in $J_{nr3.2}$ with respect to increases in test temperature. Finally, a conceptual, performance-based $J_{nrslope}$ specification limit is presented. Overall, $J_{nrslope}$ provides an alternate parameter to accurately interpret and describe stress and temperature sensitivity and demonstrates potential as a performance-based parameter.

Given the high costs associated with using polymer-modified bitumen in asphalt pavement for roads, this research set out to develop more competitive modifiers that are able to offer environmental advantages through incorporating waste polymers such as bitumen modifiers. For this purpose, the present study assessed the viability of using reclaimed geomembrane modified binder (RGMB) for use in asphalt mixtures. The impact of using RGMB as binder modifier on the behavior of stone mastic asphalt (SMA) is assessed by testing this mixture and comparing its performance with a control mixture containing a conventional binder without RGMB, and with one obtained using a commercial polymer-modified binder, the latter both with and without fibers. The tests included wheel tracking, binder drainage, moisture susceptibility, and stiffness modulus test. The results show that using the binder produced with reclaimed geomembranes has a number of positive effects on the properties of SMA, producing higher resistance to moisture damage, higher resistance to plastic deformations, and lower binder drain-down.

Laminated veneer bamboo (LVB) is a relatively new building product made from layers of glued bamboo and used in applications similar to lumber. Few studies exist on its mechanical performance; in particular, its failure behavior in dowel-type connections. This study uses both experimental and numerical methods to shed light on the complex stress state of an LVB dowel connection when progressively loaded in compression parallel to grain. A 2D elastic, plane strain finite element model is developed for a 15.9-mm (5/8-in.)-diameter bolt with a bolt hole size of 17.5 mm (11/16 in.) following the associated ASTM standard for full-hole specimen protocol. Experimental tests are used to validate and calibrate the model. Results show that predominant failure occurs off-center of the bolt contact region where the shear stress-to-strength ratio governs. Tensile stress perpendicular to grain, often the primary cause of wood failure, is found to be an influential secondary cause of failure. In addition, a frictional contact analysis leads to the finding that the coefficient of friction is a key factor in predicting shear stress.

The objective of this paper is to refine the calculation method for improving the regression accuracy of fatigue failure criterion of asphalt binder using the linear amplitude sweep (LAS) test, especially for the highly modified asphalt binders. The maximum stored pseudo strain energy (Max $W_s^R$)-based failure criterion was studied for interpreting the LAS test data under multiple-loading rates to predict the fatigue life of asphalt binders. However, the regression accuracy of the Max $W^{R}s$-based failure criterion for neat asphalt binders is generally better than that of modified binders. In this paper, a parameter of total released pseudo strain energy (TRPSE), which measures the area under the pseudo strain energy (PSE) curve until fatigue failure occurs, was developed as a material characteristic parameter, which demonstrates that no matter what loading rates are conducted during the LAS tests, the TRPSE value is constant at a specific temperature for a given asphalt binder. The proposed TRPSE value was obtained from the averaged results of the six replicates under three LAS loading rates; then the failure criterion was recalculated, and the regression accuracy significantly improved for the studied neat and modified binders. Applying this improved TRPSE-based failure criterion for the prediction of fatigue life presented more reasonable results, especially for the modified binders studied at multiple temperatures and strain amplitudes.

The contamination of ballast (a.k.a. ballast fouling) because of the intrusion of clay, rock dust, coal dust, or any other agent accelerates track degradation and affects the stability of the ballast in particular and the track in general. The feasibility of nondestructively characterizing the structural integrity of ballast using the dynamic stiffness measured with the impulse response (IR) method is explored in this paper. A number of large-size laboratory specimens were constructed at three different degrees of fouling using both rock dust and clay as fouling agents. Each specimen was tested at three moisture contents. Four different source-sensor configurations were examined. Characterizing the impact of ballast fouling with the IR method is feasible. Based on the practicality of field implementation and the detectability of fouling and moisture effects, the test configuration where the hammer energy is imparted to the tie and the receiver is placed on the ballast is the reliable one. The dry density and fouling percentage influence the IR stiffness more than the moisture content. The preloading force applied to the tie before IR testing also strongly influences the IR stiffness of clay-fouled and rock dust–fouled specimens.

A special device was designed, manufactured, and used to create a three-dimensional (3D) layout of rigid supports to investigate the spatial tensile behavior of the geosynthetic reinforcement material over rigid supports. A polyester (PET) sheet was used to simulate the geosynthetic reinforcement material. The results from the model tests using this device were used to evaluate the spatial distribution of tension and the deformed shape of the simulated geosynthetic reinforcement material. A couple of analytical solutions currently available in the literature were selected for the comparison of the calculated tension and deflections with the measured data. This study found that the maximum tensile force in the simulated geosynthetic reinforcement material occurred at the corners of rigid supports, followed by that at the edges of rigid supports. The tensile forces along the simulated geosynthetic reinforcement material were nearly uniform in the central area and increased toward the rigid supports. The test results showed that the three-dimensional deformation pattern of the simulated geosynthetic reinforcement material should not be ignored. A second-order power law formula predicted the deformed shape of the simulated geosynthetic reinforcement material satisfactorily for practical applications. The strain compatibility methods gave good prediction of the maximum tensile force and vertical deflection of the simulated geosynthetic reinforcement material between two adjacent piles. Further research is needed to improve analytical methods by considering the 3D nature of deformation and the spatial distribution of tension in the reinforcement.

The present study explored the influence of two types of nanosilica hydrosols (with different specific surface areas of 100 and $300{\mathrm{m}}^2/\mathrm{g}$) on short-term mechanical, durability, and microstructural properties of white portland cement mortar containing low-activity blast furnace slag (ASTM C989 Grade 80). Accordingly, various tests, including mechanical (compressive and flexural strengths), durability (electrical resistivity, chloride ion penetrability, and water absorption), and microstructural (X-ray diffraction, thermogravimetry/differential scanning calorimetry, and field emission scanning electron microscopy), were carried out on the combined performance of low-activity blast furnace slag (BFS)–nanosilica in a white cement mortar system. Based on the obtained results, substitution of a high volume of BFS for cement (30 and 50%) brought about a dramatic decrease in mechanical strength and porosity-related durability indices (e.g., water absorption). Nonetheless, electrical-based durability parameters such as resistivity and chloride ion impermeability were enhanced as the content of BFS was increased. Furthermore, the combinations of low-activity BFS and nanosilica hydrosols were synergistic in improving the mechanical and durability properties of white cement mortar. The synergistic effect of the aforementioned blends was more pronounced in electrical resistivity test results and less significant in flexural strength test results.

Polyurethane has been widely used as new chemical grouting material. Expansion characteristics caused by chemical reactions make polymer grout different from other types of grout. To throw light on the diffusion process of polymer grout in a fracture, a density model was derived by fitting the experimental data based on the polymerization mechanism of polyurethane. In addition, a numerical simulation of polymer diffusion in a single fracture was developed to predict the pressure distribution. An experiment was carried out to analyze the diffusion distance and pressure field under different grouting masses. Comparison of results from numerical calculation and experiments indicates that the numerical approach is able to predict polymer diffusion in the fracture. The numerical simulation is suitable for rapid determination of the grouting mass, diffusion shape, flow-front position, and pressure distribution, which could provide guidance on assessing polymer grouting parameters.

In concrete block pavement, individual blocks are laid in a predetermined pattern to create a surface interlocked with joint filler that has some discontinuities rather than continuous paving. The overall structural stability is guaranteed by minimizing the rotation and displacement of the blocks. In this paper, dynamic dropped loading tests were conducted to evaluate the load dispersion capacity of concrete block pavement with various block shapes and different laying patterns. The results showed that the vertical deflection increased logarithmically with increasing load pressure. No significant shape-dependent differences in load dispersion were observed, except for the stack pattern. The herringbone pattern showed the best performance of the three different laying patterns that were studied. In all laying patterns, the ratio of stress transferred from the applied pressure on the surface to the base tended to decrease exponentially as the applied pressure increased, consisting of three phases. Whereas the herringbone pattern had the highest load dispersion capacity in Phase 1 (${\sigma }_0<0.2\mathrm{MPa}$), the difference between the patterns decreased as the applied pressure increased in Phase 2 ($0.2\mathrm{MPa}\le {\sigma }_0\le 0.6\mathrm{MPa}$), and in Phase 3 (${\sigma }_0>0.6\mathrm{MPa}$) the ratio became constant even though the applied pressure increased. The block shape did not exert a significant influence on the load distribution capacity.

Aging, as an integral part of organic materials like asphalt binder, imposes a significant effect on chemical, physical, and performance-related properties of asphalt mixtures. One of the methods that has been proposed for consideration of aging in constitutive models of asphalt binder and asphalt mixtures within a linear viscoelastic range is time-temperature-age superposition of material function master curves. However, use of this method has not yet been verified for different bituminous materials. Thus, in this study, the validity of time-temperature-age superposition for different bituminous materials was tested. Furthermore, a valid framework to apply time-temperature-age superposition to viscoelastic material functions of asphalt binders was proposed. Oscillation tests within linear viscoelastic limits of asphalt binder and asphalt mixtures were applied on laboratory-aged specimens. Phase angle and complex modulus master curves were determined and the applicability of time-temperature-age shifting was evaluated. The results suggest that temperature-independent horizontal shift factors can be considered for asphalt binders. Furthermore, dynamic modulus testing of the asphalt mixtures at different aging levels shows that because of a local maximum existing in the phase angle master curve of asphalt mixture, horizontal and vertical shift factors cannot yield a superposition of the phase angle master curves. It can be concluded that time-temperature-age shifting cannot be used to implement aging in the constitutive models of asphalt mixtures.

This study tests the physical and mechanical properties of fresh bamboo to explore its suitability for reinforcing the embankment of a highway. A series of experiments is performed using a bamboo species (Sinocalamus affinis) and soil specimens with bamboo grids that are similar to geogrids. The testing indexes include the natural density, water content, wall thickness, and the outer perimeter of bamboo culm. The mechanical property tests include a uniaxial compression test on bamboo culm, tensile and flexural tests on bamboo strips, a friction test on the bamboo–soil interface, a pullout test on a single bamboo strip in a soil specimen, and a triaxial compression test on a soil specimen with a bamboo grid. The results show that the density and water content of fresh bamboo become relatively stable after growing for 2 years and the bamboo strips can satisfy the specification requirement for a traditional geogrid because of their excellent mechanical properties. Based on the physical and mechanical test results, appropriate cutting age of fresh bamboo is 2 years and more. In addition, the compressive strength for bamboo grid–reinforced soil is significantly greater than that of prime soil, and could effectively prevent filling embankments from settling. In addition, its increased shear resistance could suppress a slip shear failure in the filling embankment.