Journal of Materials in Civil Engineering

This paper introduces rice husk ash (RHA) as an acceptable replacement for cement in the chemical stabilization of sand, with economic and environmental benefits. Unconfined compression strength (UCS), bender element (BE), and cyclic triaxial (CT) tests were conducted on various samples containing different contents of cement, RHA, and polypropylene fibers. The test results were then used to develop new relationships for the dynamic characterization of stabilized sand in terms of damping, shear modulus, and degradation index. The accuracy of the proposed predictive models was subsequently validated using two independent CT tests carried out on arbitrary samples containing stabilizers in the applicable range of the study. Also, the effects of the relevant parameters on the degradation index were investigated using a three-dimensional graphical parametric study. Sensitivity analysis was conducted to show which parameters had the greatest and least effects on the dynamic properties of stabilized and reinforced samples. To investigate the mechanisms behind the reactions, microstructural investigations were used. An application of the proposed relationships in the dynamic design of pile-supported foundations is presented.

Grout injection is an efficient method to improve the mechanical characteristics of masonry walls, in the presence of voids or cracks. Masonry made up of two exterior leaves with the space between them filled with poor infill with a large amount of voids is common in many existing structures. In other cases, dry stack masonry is used. Grouting of these types of vulnerable masonry with lime-based grouts was proven mechanically efficient. The success of this technique depends on several parameters, such as injection pressure, the general condition of the masonry (materials and mechanical properties), and the rheological properties of the grout. The effect of ternary grouts and hydraulic lime-based grouts on the compressive and shear strength of three-leaf stone masonry has been widely investigated. However, fewer studies have been done on walls with one or two leaves, as done in this paper. The present research aims to investigate the mechanical performance of schist masonry walls before and after injection. Six masonry walls of typical schist stone constructions from the north of Portugal were constructed in accordance with the original construction materials and tested under compressive load. Two different grouts were chosen to inject the wall specimens (one commercially available and another prescribed). The results obtained showed that these strengthening techniques were successful in increasing the compressive strength of the walls and improving their behavior under compressive loads.

Biogeomaterials are developed based on microbially induced calcite precipitation (MICP) technology, which is a recent innovation in civil engineering. Acid pollution, such as large amounts of distributed sulphate saline soil on site and acid leachate from an industry factory site, has been considered when using new biogeomaterials. The purpose of this study was to evaluate the stability of the anticorrosion and corrosion properties of a biogeomaterial as well as the induced corrosion mechanism in a sulfate acid environment. The mechanical properties and pore characteristics of this biogeomaterial were examined via unconfined compressive strength and microscopic characteristic testing. The fractal characteristics of pore size were also investigated in various corrosion stages. The results show that dynamic equilibrium is maintained between two crystals that exist in different stages of corrosion, resulting in the different acid corrosion properties of the biogeomaterial. As a bonding material and strength supplement, calcium carbonate crystals induced from MICP were constantly dissolved when corrosion began. The porosity of the biomaterial increased gradually while its mechanical properties decreased dramatically. Furthermore, calcium sulfate crystals, a new chemical product having a larger volume and lower mechanical strength than calcium carbonate crystals, was generated from the dissolution of calcium carbonate crystals. It is concluded that the ability of a biogeomaterial to resist sulfuric acid corrosion is not as weak as expected because of the formation of slightly soluble calcium sulfate. This finding provides important insight into the corrosion resistance of biogeomaterials in sulfuric acid environments.

This paper explored the relationship between ambient temperature, calcium oxide (CaO) hydration, and calcium carbonate (${\mathrm{CaCO}}_3$) generation in cold and moderate ambient temperatures (2°C–19°C). A total of 22 samples from 2 commercial soundless chemical demolition agents (SCDAs) were tested in $36\text{-}\mathrm{mm}\text{-}\mathrm{diameter}\times 170\text{-}\mathrm{mm}\text{-}\mathrm{long}$ steel pipes. The raw powder and materials resulting from hydration were subjected to X-ray diffraction analysis, derivative thermogravimetric analysis, and thermogravimetry analysis. Raw and hydrated specimens proved chemically distinctive. Experimental results showed that (1) the unconfined portions of hydrated specimens contained more ${\mathrm{CaCO}}_3$ due to carbonation of $\mathrm{Ca}(\mathrm{OH}{)}_2$, and confined portions had higher $\mathrm{Ca}(\mathrm{OH}{)}_2$ concentrations; (2) all materials tested at 19°C ambient temperature had $\mathrm{Ca}{(\mathrm{OH})}_2$ concentrations nearly 10% greater than those tested at 2°C; and (3) the higher $\mathrm{Ca}{(\mathrm{OH})}_2$ concentrations formed at 19°C generated 350% greater expansive pressure than did those that formed at 2°C.

Geopolymer-blended aerogel materials (GAMs) prepared by adding different proportions of water and ${\mathrm{SiO}}_2$ aerogel (AG) were studied with respect to stability, viscosity, segregation degree, density, thermal conductivity, compressive strength, and interfacial characteristics. These properties were tested by contact angle tester, rheometer, thermal conductivity tester, universal testing machine, and scanning electron microscope, among others. Results indicated that AG can stably exist within GAMs regardless of its high alkaline activator. With increasing AG content, the apparent viscosity of GAM slurry rose obviously and segregation degree increased slightly, then remained at around 2.6%. Due to its high porosity, an increased volume of AG generally contributed to a lowered density and thermal conductivity. The relationship between thermal conductivity and AG content conforms to a modified Maxwell-Euchen model, and the value of parameter $t$ is determined as 1.1–1.2. However, AG generally can lead to reduced compressive strength of GAMs. Considering this disadvantage, the AG surface was further modified with epoxy resin AB adhesive and silence coupling KH550. The compressive strength of GAMs with modified AG reached 46 MPa, a 30% increase, due to enhancement of the intertransition zone between aerogel and geopolymeric matrix as witnessed via scanning electron imaging.

The method of gathering data using remote sensing enables efficient selection of different target regions for the procurement of various scoria rocks (SR), which are under investigation. Thermal Emission and Reflection Radiometer (ASTER) is one of the five-spectroradiometer sensors mounted onto the Japan and the National Aeronautics and Space Administration’s (NASA) TERRA spacecraft. Informative radiance data reflected from different regions, containing SR, collected by ASTER could be converted into reflectance. Pozzolanic activity index (PAI) of ground SR samples was measured in their standard mortar mixtures. PAIs of the procured samples could be well correlated to their reflectance values at two effective ASTER Bands (B4 and B5). It is concluded that SR samples with lower reflectance are characterized with high PAIs that varied from about 91%–100% at 28 and 90 days. The reflectance of different regions in the same area of reported PAIs could be obtained using established mathematical correlation techniques and verified from reported data. Results have shown that there is a reasonable agreement between the estimated and reported ranges of PAI values.

In this research, a silica-based crystallizing protective material was integrated into a fresh concrete mix to evaluate its efficacy in reducing water absorption while preserving the compressive strength level of the mixture. An optimum concrete mix design was determined, by producing several concrete mixes with different water-to-cement ratios (w/c) of 0.32, 0.37, 0.40, and 0.46, and treated with 2% and 4% of the crystallizing admixture. Water absorption and the mechanical properties of the treated and control mixes were measured, using the initial surface absorption test (ISAT) and the compressive strength and the flexural strength tests, respectively. Results showed that it is possible to obtain a water-resistant concrete without compromising its compressive strength if the right w/c ratio was used and the proper dosage of the crystallizing material was added. In addition, results revealed that treatment is beneficial only in the case of producing concrete with low w/c ratios of 0.32 and 0.37 and treated with crystallizing material. The compressive strength can increase up to 42% and with a significant drop in water absorption reaches 65%. Treated concrete was analyzed thoroughly under the scanning electron microscope (SEM) and X-ray diffraction (XRD) instrument to show the development of crystals with time and their interaction with the concrete mix.

In the present study, rice husk ash (RHA) was evaluated as supplementary cementitious material in portland cement pastes subjected to acid attack from vinasse, an acid residue from ethanol production. RHA and quartz (inert) were used in amounts of 10% and 20% in cement pastes. Mass loss variation, surface roughness, degradation-front progression, compressive strength, portlandite content, and mineralogical changes of the pastes were evaluated during 3 months of continuous exposure. In general, physical and mechanical properties were seriously affected for all pastes, except for the mix containing 20% RHA. The use of RHA did not cause a considerable change in the mineralogical composition of the pastes, being quite similar to that in the reference (Ca-bearing phases). As a consequence, chemical resistance of all pastes showed similar behavior in terms of mineralogical assemblage after exposure in vinasse, according to thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) results and a qualitative analysis of X-ray diffraction (XRD) results, since the aggressiveness of the attack by the weak acids present in the vinasse is strongly related to the solubility of their calcium salts.

Recycled concrete aggregate (RCA) is traditionally limited to nonstructural applications. Although the crushing process results in weak mortar particles and surface cracks throughout the RCA, RCA concrete can be employed as rigid pavement materials after its mechanical strength has been improved. This research evaluated the novel use of polyvinyl alcohol (PVA) and fly ash (FA) for the improvement of mechanical strengths of RCA concrete. The influence of PVA to binder ($p/b$) and FA/cement ($\mathrm{FA}/c$) ratios on the mechanical strength of RCA-PVA-FA concrete was assessed by compressive, split tensile, and flexural strength tests. The mechanisms controlling the improvement of mechanical strengths were discussed based on the results of microstructural analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) methods. The results of this research indicate that the addition of PVA resulted in a reduction of the compressive strength of RCA concrete in both the short and the long term. However, with an optimum $p/b$ of 1%, both the flexural and tensile strengths increased significantly. At the optimal $p/b$, the PVA films infiltrated into cementitious matrixes and enhanced the reinforcing ability within the matrixes. However, excess $p/b$ retarded the hydration process and caused reductions in the cementitious tensile bonding. The long-term mechanical strength ($>28\mathrm{days}$) was remarkably improved by FA addition at optimum $\mathrm{FA}/c$ of 20:80, and the presence of cementitious products on the FA grains and in the voids was clearly observed. The highest long-term flexural and tensile strengths were found at $p/b=1\%$ and $\mathrm{FA}/c=20:80$, whereby the 28-day flexural strength was higher than the requirement specified by the US Army and the US Air Force. The 28-day compressive strengths were also higher than the requirements specified by Department of Highways, Thailand. The outcome of this research will result in the promotion of using wastes, namely RCA and FA, in rigid pavement application, which is practical and preferred from engineering, economic, and environmental perspectives.

Asphalt concrete behavior under load is heavily influenced by displacement rate and temperature. It was the objective of this study to quantify the effect of these two parameters on asphalt mix performance under a semicircular bend (SCB) test. The ultimate goal of this study was to find the most suitable combination of displacement rate and temperature for the SCB test to be conducted in the northeast region of the United States. In addition, the effects of air void, binder content, and binder stiffness in the SCB test were investigated. SCB tests were performed at a temperature range from 10°C to 30°C, and displacement rates ranging from 1 to $50\mathrm{mm}/\min$. Material variables included air voids (4% versus 7%), binder contents (design versus design + 0.5%), and binder stiffness (three different grades). Characterization parameters from the test included fracture energy (FE), flexibility index (FI), peak load (PL), stiffness index (SI), and prepeak fracture energy (PPFE). The data were analyzed statistically to evaluate the sensitivity of characterization parameters to material variables under different displacement rates and test temperatures. The results indicated that FE, PL, and SI all increase with the increase of displacement rate and decrease with the increase of test temperature, while FI exhibited an opposite trend. The previously used PPFE demonstrated poor sensitivity to material variables regardless of displacement rate and test temperature. FE, FI, and SI show higher sensitivity to material changes compared with PPFE. Among all response parameters, PL proved the most sensitive to material variables irrespective of test conditions. The effective temperature concept was used to determine a suitable fatigue test temperature for the northeast region. The level of sensitivity was not affected as a result of changing the test temperature from 25°C to the effective temperature. Based on the test results, a displacement rate between 5 and $20\mathrm{mm}/\min$ is recommended for use with the SCB test.

Polyurethane materials have been widely applied in the mending of cementitious materials, and the mending efficiency is highly impacted by the bond strength between the polyurethane materials and the cement base. This paper aims to evaluate both the shear and flexural bond strength between cement mortar and polyurethane with different water and modifier contents. The shear and flexural bond strengths were examined using a slant shear test and three-point bending test on mortar samples prepared with a polyurethane interface. The effect of the polyurethane/water ratio on the bond strength was first examined, and both the highest shear and flexural bond strength were achieved for the samples with a 30% polyurethane/water ratio. To further enhance the bond strength, ethylene-vinyl acetate (EVA) was further added to the polyurethane, and the effect of the replacement ratio on the bond strength was further examined. The macro-size strength tests indicated the highest strength was achieved for the polyurethane samples that had a 10% EVA replacement ratio. The mechanism behind the effect of water and EVA content was further examined with a scanning electron microscope (SEM) and atomic force microscope (AFM). The examined relationship between water and EVA content and bond strength can provide useful information for the field application of polyurethane materials.

Investigating the mechanical properties of stainless-steel cables at elevated temperatures is important for the fire-resistant design and fire simulation analysis of prestressed structures. Stainless steel cables comprise several stainless-steel wires encircling a core wire in different layers. The overall mechanical capacity of a stainless-steel cable is attributed to the individual properties and collaborative mechanism of the stainless-steel wires. In this study considering the number of layers of a stainless-steel wire, 42 stainless steel cables with 19, 37, and 61 wires were tested under steady-state tension at ambient and elevated temperatures ranging from 100°C to 600°C. The test results show that the cables exhibit typical nonlinear characteristics with a lower proportional limit and no obvious yield plateau. There is no obvious effect of twisting characteristics on the elastic modulus of the cables; however, the ultimate tensile strength and 0.2% proof strength decrease gradually with the increase in the number of wire layers. The reduction factors of the mechanical properties of a stainless-steel material at elevated temperatures obtained as per EN1993-1-2 were higher than those obtained in this study, particularly of the 0.2% proof strength. Equations for the elastic modulus, ultimate strength, 0.2% proof strength, and fracture strain of the cables at elevated temperatures are proposed in this paper. Furthermore, a modified two-stage Ramberg–Osgood model for stainless steel cables at ambient and elevated temperatures is proposed.

In China Railway Track System II, the bonding of a cement asphalt mortar (CA mortar) layer to concrete slabs is a decisive factor for its durability and serviceability. In this study, the interfacial bonding strength between two types of CA mortar, $\mathrm{A}/\mathrm{C}=0.2$ and $\mathrm{A}/\mathrm{C}=0.6$ (A/C, asphalt to cement ratio in mass) and the concrete slab was investigated by pull-off tests, and effects of polymer latex, expansive agent, and temperature cycles were considered. Results indicate that the bonding strength of the CA mortar at a high A/C is obviously higher than that at a low A/C. The modification by polymer latex effectively increases the bonding strength and the effect is greater at a higher A/C. Similarly, the presence of expansive agent in the CA mortar increases the bonding strength but the effect is greater at A/C of 0.2 because of a different mechanism. From the microstructural point of view, the bonding strength of the CA mortar at a lower A/C is primarily decided by the mechanical interlocking whereas the bonding strength of the CA mortar at a higher A/C is firmly related to the adhesion of asphalt binder. Temperature cycles decrease the interfacial bonding possibly due to the weakened mechanical interlocking forces at the interface caused by the mismatch deformation between the CA mortar and the concrete slab. The incorporation of polymer latex reduces the temperature sensitivity of the bonding strength at A/C of 0.6. In contrast, the inclusion of expansive agent increases the temperature sensitivity.

One of the most destructive environmental issues around the world is the disposal of construction and demolition (C&D) wastes such as recycled concrete aggregate (RCA), crushed rock (CR), waste glass, and scrap tire. Therefore, using the waste materials in civil projects such as road pavement applications would significantly reduce the consumption of quarry-based virgin materials, alleviate landfill disposal, and minimize greenhouse emissions. Numerous studies have evaluated the effect of crushed glass (CG) for construction applications; however, the effect of CG on the behavior of the crushed recycled materials together with crumb rubber (R) have never been studied for road pavement applications. A series of geotechnical laboratory tests, including modified compaction, unconfined compression strength, California bearing ratio (CBR), and resilient modulus tests, have been done on the blends of different percentages of CG added to the RCA and CR aggregates, together with R for pavement base/subbase applications. The results indicated that the blends of the waste materials, as a low carbon concept, could be a viable and satisfactory alternative solution for future base/subbase applications.

The strength and stiffness characteristics of infill masonry wall significantly influence the behavior of reinforced concrete framed structures. Although such characteristics for conventional masonry infill walls, like clay and fly ash bricks, are well documented in the literature, experiments for the evaluation of similar properties for modern infill walls using autoclaved aerated concrete (AAC) blocks are limited. This paper reports the experimental results of an investigation of the structural properties of AAC block masonry required for mathematical modeling of AAC masonry-infilled framed structures. It also investigates some of the physical properties of AAC blocks that influence their structural properties and overall behavior.

Effects of varying calcination conditions on the chemical and physical properties of magnesium oxide (MgO), an essential component of magnesium-based cement, were investigated using the more sustainable precursor material of magnesium hydroxide [$\mathrm{Mg}{(\mathrm{OH})}_2$]. Extremely pure and thus more reactive MgO was obtained using a 17.6% less-energy-intensive calcination regime compared with industrial-grade MgO obtained from the calcination of dolomitic lime. As a result, the magnesium oxychloride cement (MOC) that was produced from the sustainably sourced MgO obtained a 50% increase in flexural strength and 22% increase in compressive strength. This was mostly due to its homogenous microstructure, consisting predominantly of the phase-5 hydration product, verified visually using a scanning electron microscope (SEM) and crystallographically using X-ray diffraction (XRD). Based on these findings, it has been revealed that the calcination therapies currently used in industry are impractical for both economic and sustainability purposes; MgO can be manufactured in a more sustainable and thus more competitive means, as discovered in this study.

The damage monitoring and evaluation of a fiber-reinforced polymer (FRP)/steel–concrete hybrid box girder subjected to four-point bending is reported in this paper. The target is to integrate the improved mechanical behavior of a FRP/steel-concrete girder with acoustic emission (AE) response. The damage growth and the failure mechanism of the structure are investigated with AE parametric analysis. The amplitude distribution analysis can successfully discriminate the macrodamage signals from the microdamage signals. The time-dependent dynamic analysis of extended features, including RA-AF, b-value, damage parameters, and bending stiffness, show great potential in evaluating damage states, identifying critical points, and providing warnings for catastrophes. The favorable correlation between cumulative AE energy and local strain response provides a viable alternative for meaningful local damage monitoring and prediction. The synthesis analysis of multiple indicators overcomes the disadvantages of single-indicator parameters in to determining complex damage properties, identifying instant damage status, and providing critical warning information for composite structures.

Asphalt binder phase plays a significant role in cracking resistance of asphaltic mixture. Therefore, selection of appropriate asphalt binder combination becomes important, especially when asphaltic pavement is expected to experience heavy traffic under intermediate-temperature conditions. Previous research shows that the use of polyphosphoric acid (PPA) along with reactive elastomeric terpolymer (RET) may improve various performance parameters; however, it may increase the energy requirement during the construction stage. To address this issue, use of warm-mix additives (WMAs) has been recommended. Therefore, the present study aimed at evaluating effects of different WMAs (wax, chemical, and zeolite based) on intermediate-temperature fracture properties of PPA- and RET-modified asphalt binder using a double-edge notched tension (DENT) test. It was found that chemical-based WMA may significantly improve the fracture properties of control binder. On the other hand, wax-based WMA may have a negative impact on the fracture properties of control binder. Likewise, zeolite-based WMA was found to improve the fracture properties of control binder by a marginal amount. Although the use of WMA may reduce the energy requirement, it may increase the moisture damage potential. To protect the asphaltic mixture from moisture damage, use of lime has been conventionally recommended. Therefore, the effect of lime on fracture properties of various asphalt binder combinations was also examined. It was found that irrespective of the asphalt binder combination, addition of lime may produce a negative impact on fracture properties of control binder with or without WMA.

This paper evaluates the cracking mechanism and material characteristics of rocklike specimens under five loading rates (0.02, 0.06, 0.10, 0.14, and $0.18\mathrm{mm}/\mathrm{s}$). The rocklike cylinder specimens were prepared and mixed using river sand (as aggregate sources) and cement, gypsum, and starch (as binders). Uniaxial compression tests associate with binarization imaging processing were carried out using the five loading rates to evaluate the cracking propagations and characteristics of rocklike specimens. The results show that with the increase in the loading rate, the peak tensile and compressive strengths of the rocklike specimen increases. The relationship between the ratio of stress to peak stress, and the five loading rates of the rocklike specimen can be expressed as a natural logarithm model while the relationship between the initial crack length of the rocklike specimen and the five loading rates can be represented by as an exponential function. The average rate of crack propagations increases exponentially as the loading rate increases. Based on all test and analysis results and, the paper concludes that the characteristics of cracking mechanism, propagations, and characteristics of rocklike materials show the similar mechanical behaviors as compared with other rock specimens.

This paper investigates complete recycling of waste concrete to produce new geopolymer concrete (GPC). Specifically, GPC was produced using waste concrete fines (WCF) and class-F fly ash (FA) together with mixed sodium hydroxide (NaOH) and sodium silicate (${\mathrm{Na}}_2{\mathrm{SiO}}_3$) solution as the geopolymer binder and waste concrete aggregates (both coarse and fine) as the aggregate. The effect of NaOH concentration, ${\mathrm{Na}}_2{\mathrm{SiO}}_3$ solution to NaOH solution mass ratio (SS/N), cement (WCF and FA) to aggregate ratio (C/A), water-to-cement ratio (W/C), and curing temperature on the initial setting time and the 7-day unconfined compressive strength (UCS) of the GPC was systematically studied. For comparison, GPC using natural aggregate (NA) was also produced and studied at similar conditions. The results indicated that the GPC produced from recycled aggregate (RA) has higher UCS than the GPC from NA at both room (23°C) and 35°C curing temperatures. This is mainly due to the stronger interfacial transition zones (ITZs) in the RA-based GPC than in the NA-based GPC. Based on this study, it can be concluded that waste concrete can be completely recycled (both WCF and RA are reused and no NA is needed) to produce new structural geopolymer concrete with sufficiently high compressive strength.

This paper investigates the effects of different aging temperatures on the performance of asphalt binders through a comprehensive experimental procedure. Two kinds of asphalt binders with the same 70/100 penetration grade were used in this study. The two types of asphalt binders were short-term aged at three different temperatures: 123°C, 143°C, and 163°C. The short-term aged asphalt binders were long-term aged according to the standard pressure aging vessel (PAV) tests protocol. Dynamic shear rheometer (DSR) and Fourier-transform infrared spectroscopy (FTIR) were adopted to quantify the performance of asphalt binders under different aging conditions. The DSR results showed that different critical aging temperatures can be found for the two kinds of asphalt binders. The Superpave performance grading can reflect the viscoelastic property of asphalt binder, whereas penetration grading cannot do so in grading asphalt binder. The FTIR test results showed that the $I_{\mathrm{c}═\mathrm{o}}$ and $I_{\mathrm{s}═\mathrm{o}}$ bonds were good indicators to evaluate the aging effect of different temperatures. The correlation between $|G^{*}|$ and $I_{\mathrm{C}═\mathrm{O}}+I_{\mathrm{S}═\mathrm{O}}$ occurred for both asphalt binders under different aging conditions.

The postfire mechanical properties of cold-formed steel (CFS) are fundamental parameters for evaluating the residual performance of CFS structures after exposure to fire. In this paper, 230 tests were performed to obtain the postfire mechanical properties of commonly used Q345 and G550 CFS with thicknesses ranging from 0.75 to 1.9 mm. An electric furnace was used to heat the specimens in batches, and a shielding isolation was specially designed to avoid direct thermal radiation from the heating elements, which might cause nonuniform temperature distribution of the specimens. In addition, to accurately identify the critical exposure temperatures at which the postfire yield strength of CFS becomes less than its original value or nominal value, additional specimens were separately heated in a furnace. Subsequently, tensile tests of postfire specimens were conducted at ambient temperature. The critical exposure temperatures of Q345 CFS were found to be much higher than those of G550 CFS. In most cases, the effect of the present steel thickness on the reduction factors of postfire mechanical properties was insignificant and the corresponding difference between reduction factors was generally less than 0.1. Additionally, visual observations of postfire CFS specimens were presented, which can be used to judge the maximum temperatures reached by CFS in fire. The results showed that significant differences exist between the present and previous postfire experiments for CFS and hot-rolled steel. Hence, some conservative formulas for the postfire mechanical properties of Q345 and G550 CFS are proposed.

Rollable prefabricated asphalt pavement technology consists of prefabricating and crimping the asphalt pavement in the factory. It can be laid on the pavement as carpets so that the construction and traffic barring can be completed quickly; it provides a new approach to pavement repair. However, the damage to prefabricated asphalt pavement caused by curling is different from that caused by repeated load on conventional asphalt pavements. Thus, it is necessary to study the self-healing performance of the rollable asphalt mixture. In this paper, a test method for evaluating the self-healing performance of rollable asphalt mixture was designed by using a three-point bending test. The influence of the test temperature, the damage level, the asphalt type, and the asphalt-concrete ratio on self-healing performance of the rollable asphalt mixture was analyzed. Results show that (1) the self-healing performance of asphalt mixture is best when the test temperature is 10°C; (2) the self-healing index of flexural-tensile stress and flexural-tensile strain of the mixture decreases with the increase of the damage degree of the asphalt mixture; (3) the addition of a special modifier can improve the high-temperature performance and bending performance of the mixture but also influences the self-healing ability of the mixture after flexural failure; and (4) increasing the asphalt-concrete ratio is helpful to improve the self-healing performance of asphalt mixture.

Microscale defects (microannuli) at the steel-cement and rock-cement interfaces are a major cause of failure in the integrity of wellbore systems. Microscale defects/microcracks as small as 30 μm are sufficient to create a significant leakage pathway for fluids. In this paper, the authors propose the use of nanomodified methyl methacrylate (NM-MMA) polymer as a seal material for 30-μm microcracks. Four materials were evaluated for their ability to serve as an effective seal material to seal 30-μm microcracks: microfine cement, epoxy, methyl methacrylate (MMA), and NM-MMA incorporating 0.5% by weight aluminum nanoparticles (ANPs). The seal materials’ bond strengths with shale were investigated using push-out tests. In addition, the ability to flow fluid through the microcracks was investigated using sagittal microscopic images. Viscosity, surface tension, and contact angle measurements explain the superior ability of MMA seal materials to flow into very thin microcracks compared with other materials. Post-test analysis shows MMA repair materials are capable of completely filling the microcracks. In addition, incorporating ANPs in MMA resulted in significant improvement in seal material ductility. Dynamic mechanical analysis (DMA) showed that incorporating ANPs in MMA reduced the creep compliance and improved creep recovery of NM-MMA. X-ray diffraction (XRD) analysis shows that incorporating ANPs in MMA resin increases the degree of polymer crystallization, resulting in significant improvement in seal material ductility.

Additives such as Sasobit, polyethylene, and paraffin can enhance the durability of pavement and prevent further environmental pollution by changing the functional behavior of bitumen. Combining Sasobit with two other low-priced waxes and achieving a satisfactory performance can help moderate the price of Sasobit, making its use pervasive. Therefore, this study aimed to investigate the mechanical and rheological properties of bitumen modified with Sasobit, polyethylene, and paraffin additives, separately and simultaneously. Accordingly, penetration, softening point, ductility, rotational viscometer, dynamic shear rheometer, and bending beam rheometer tests were performed on 10 mixtures in both aged and unaged states. The results of rheology tests indicated an improvement in the phase angle and high-temperature performance of bitumen modified with Sasobit and polyethylene waxes. The results of the rotational viscometer test indicated that the viscosity of bitumen modified with the Sasobit, polyethylene, and paraffin waxes and their mixture was reduced at high temperatures. Sasobit, polyethylene, and paraffin and their mixtures worsened the medium- and low-temperature performances; however, these negative impacts were lower in the combination of Sasobit and polyethylene.

In this study, superabsorbent polymers (SAP) were introduced as an admixture in subgrade soils for the potential of improving their moisture susceptibility under moisture variation conditions. A series of experiments was performed on the soil samples to investigate the feasibility and influences of SAP on their fundamental physical properties and mechanical performance. In addition, wetting-drying (W-D) cyclic tests were conducted on the samples to simulate the moisture varying conditions that subgrade soils could experience in service. Compaction tests showed that SAP decreased the maximum dry density, but had no effect on the optimum moisture content. Soil amended by SAP exhibited superior uniformities in moisture distribution and grain size distribution. SAP helped enhance the direct shear behaviors of subgrade soils and increased the cohesive strengths and internal friction angles. The W-D cycles obviously degraded the mechanical properties. During the W-D cycles, SAP could also remarkably improve shear strength and the larger the SAP content, the better the shear performance. Results proved that a proper content of SAP ($\le 0.75\%$) added in the subgrade soils had no apparent impact on the volume stability, however a high content of SAP could significantly increase the volume by as much as 12.35%. Based on the test results, an optimal SAP content of no more than 0.75% is recommended.

This work studies the effect of the organic matter content on the efficiency of the biocementation process due to the precipitation of calcium carbonate (${\mathrm{CaCO}}_3$) induced by the urease enzyme. Eight different mixtures of an organic soil and a clayed soil are analyzed, which correspond to a range of organic matter content from 0% to 11.3%. The impact of the biocementation process is examined in terms of the strength and stiffness obtained from unconfined compressive strength tests and complemented by measuring the amount of ${\mathrm{CaCO}}_3$ precipitated, pH value, X-ray diffraction (XRD), and scanning electron microscopy (SEM) tests with energy dispersive X-ray (EDX). In general, the biocementation induces an increase in the strength of the material and an increase in the brittleness of the stress-strain behavior. The results also show that the strength gain due to biocementation increases with the amount of ${\mathrm{CaCO}}_3$ precipitate, with greater significance when the content of ${\mathrm{CaCO}}_3$ is lower than 0.5%. The XRD and SEM/EDX tests are coherent with the amount of ${\mathrm{CaCO}}_3$, and both confirm the existence of the precipitation of ${\mathrm{CaCO}}_3$.

The strength development of standard and adiabatically cured concretes was determined. The concrete mixtures had 28-day cube strengths of 30 and 50 MPa. For both strength classes, portland cement (PC) was partially replaced with fly ash (FA) and ground granulated blast-furnace slag (GGBS) at 50% and 30%, respectively. The peak adiabatic temperature was effectively reduced with GGBS addition but was only reduced with FA addition for the lower water-to-binder ratio ($w/b$) concrete. Considerable early age strength enhancements resulted from the adiabatic curing regime. The Nurse-Saul and Arrhenius-based maturity functions were used to estimate the increases in early age adiabatic strength. The Nurse-Saul function underestimated the effect of high early age curing temperature for all concretes, but did so to a greater extent for those with GGBS and FA, whereas the Arrhenius-based function, which allows for the consideration of an apparent activation energy, gave more-accurate estimates. Strength estimates for adiabatically cured concretes and isothermally (50°C) cured mortars were also compared, and results indicated that the latter might have been affected by the detrimental effect of high curing temperatures starting from an early age.

Sphericity, form dimensions, and angularity are important morphological properties of aggregates that significantly affect the microstructure of grain-based materials and their macromechanical performance. The objective of this paper was to quantify aggregate morphology, including sphericity index (SI), dimension index (DI), and angularity index (AI) based on three-dimensional (3D) solid modeling. The methodology consisted of three main steps, as follows: (1) the 3D solid model of each aggregate was developed from X-ray computed tomography (CT) imaging; (2) the model surface was discretized into triangle facets, and the vertexes of facets were used to accurately retrieve the minimum bounding sphere (MBS) and the minimum bounding box (MBB) of the aggregate model for SI and DI calculation, respectively; and (3) consequently, the facets were well clustered to represent aggregate angles for their magnitude measurements, which were used to quantify the AI. The 3D SI, DI, and AI of 11 grains were measured virtually with the proposed approach, which indicates the benefits of the 3D method in the accurate quantification of aggregate sphericity, form dimensions, and angularity.

The present study aims to explain the dependency of different mechanical properties [penetration, softening point, viscosity, and dynamic shear rheometer (DSR) parameters] and chemical parameters of reclaimed-asphalt pavement (RAP) binder. Viscosity grade (VG30) and VG40 virgin binders, RAP binder, and different VG30 + RAP blends, were investigated. Complex shear modulus and phase angle were measured at different temperatures, and creep compliance and percent recovery were evaluated at 60°C. Functional groups were evaluated using Fourier-transform infrared spectroscopy. Aging parameters ICO, ISO, and ICC increased with RAP proportion, whereas ICH decreased. No trend could be observed for OH/CH. The ICO, ISO, ICC, and ICH parameters correlated well with the mechanical properties of the blends. This study will be useful for better understanding of the relationship between the mechanical and chemical properties of RAP binders. The demonstration of the applicability of the rule of mixes for different mechanical and chemical parameters will be useful in the design of RAP mixes.

This paper presents the results of a study that was conducted to understand the impacts of aging and rejuvenation on fundamental properties of asphalt binders. A Performance Grade (PG) 64-22 binder was aged to simulate the aging of asphalt mixes during construction and in-service conditions. The binders’ surface tension property, i.e., contact angles between binder and three probe liquids, was measured using a sessile drop device. This property was then used to estimate surface free energy components of the control binder, aged binders, and rejuvenated binders using the Good–van Oss–Chaudhury postulation. Cohesive and adhesive bond energies of asphalt–aggregate systems under dry and wet conditions were also analyzed. The aggregates considered in this study were limestone and granite; these aggregates have different moisture affinities. The data showed that as asphalt ages, the contact angle between a liquid (distilled water) and the asphalt surface increases; however, for the other two probe liquids (formamide and glycerol), no pattern was observed. For the surface free energy components of the control binder, the aged binders, and the binders with rejuvenators, the contribution from Lifshitz–van der Waals components were comparatively much higher than those from acidic and basic components. The rejuvenators seemed to be effective at improving the cohesive energy of asphalt binder, suggesting an improvement in the water damage resistance of the mix. In general, the limestone-based asphalt concrete mixture showed a higher moisture damage resistance than the asphalt concrete mixture with granite.

Almost all of the available test data for pressure–volumetric strain curves [equations of state (EoS)] of concrete are based on static triaxial tests and one-dimensional impact tests, for example, the flyer-plate impact test, because of a lack of equipment for conducting synchronized triaxial impact tests. The EoS based on static triaxial and dynamic uniaxial tests does not necessarily represent the true behavior of concrete under hydrodynamic loadings. Therefore, to derive an accurate dynamic EoS of concrete material, it is essential to develop reliable techniques for conducting true synchronized triaxial impact tests. This paper presents an innovative three-dimensional split-Hopkinson pressure bar (3D-SHPB) test system recently developed by the authors and some preliminary test results. A comparison of true triaxial dynamic test results and true triaxial static test results was carried out. It was found that the bulk modulus of concrete was strain-rate sensitive. Theoretical and numerical analyses with a mesoscale model were carried out to examine and explain the test observations. It was found that the increase in bulk modulus under hydrodynamic loadings could be at least partially attributed to water pressure, because the pore water in the cement paste could be drained during the dynamic loading phase. The resistance of microscopic viscosity to the development of microcracks is another reason for the strain rate sensitivity of the bulk modulus. An empirical relation is proposed in this study for the dynamic increase factor (DIF) of the concrete bulk modulus with respect to the strain rate.

Microwave-deicing technology is a clean and efficient method, but due to the inefficient microwave absorptivity of pavement materials, this technology is difficult to apply in large-scale applications. The microwave absorptivity of pavement materials can be greatly improved by functionalized aggregate, which makes microwave deicing possible. Magnetite, a common microwave-absorbing material, is an outstanding microwave absorber that can be used in pavements for deicing. In this work, magnetite was scattered in functional aggregate as a microwave-deicing functional phase, and the microwave-heating aggregate (MHA) was prepared by means of sintering to realize aggregate functionalization. Microwave-deicing mortars were prepared using MHA. The effect of aggregate content on average heating rate, reflectivity, and the effect of ambient temperature and ice layer thickness on deicing performance were investigated, and the heating uniformity of the mortar specimen is discussed. The results indicate that the average heating rate of MHA ($4.83°\mathrm{C}/\mathrm{s}$) is much higher than that of ordinary aggregate ($0.49°\mathrm{C}/\mathrm{s}$). Thus, the deicing performance of the deicing pavement was greatly improved by adding MHA compared with ordinary pavement; the deicing time of MHA100 at $-20°\mathrm{C}$ and $-5°\mathrm{C}$ decreased by 56.0% and 54.8%, respectively. The deicing performance is greatly influenced by ambient temperature but less influenced by ice-layer thickness. Adding MHA reduced the heating uniformity of mortar specimens, which may degrade the deicing performance.

Internal vibration is adopted worldwide for consolidating fresh concretes in field construction. Improper manual operation of the vibration process can easily induce segregation and bleeding of fresh concrete and subsequent degradation of long-term durability of real structures. In this paper, the settlement of aggregates in fresh concrete upon vibration was theoretically analyzed and equations were proposed to predict the segregation induced by poker vibration. On the other hand, eight mixtures with variable rheological parameters were subjected to different poker vibrators with two typical vibration durations to prepare prism specimens. The segregation state of each concrete prism was assessed by the apparent density variation along the vertical pouring direction. It was found that segregation caused by poker vibration was much more dominated by plastic viscosity than by yield stress of fresh mortar matrix. Prolonged vibration duration led to a more adverse effect on segregation for the mixture with the relatively lower yield stress, and the high vibration amplitude generally aggravated segregation more severely for the mixture with a higher plastic viscosity.

Clay brick waste is one of the largest construction wastes by output. Traditionally, clay brick waste is reutilized in mortar/concrete as aggregate replacement after crushing or as cement replacement after grinding, but these two methods of reutilization have certain adverse effects on the quality of mortar/concrete. In this study, a new method, named the paste replacement method, was developed; in this method, clay brick dust (CBD) is used to replace cementitious paste with the paste composition kept unchanged. To compare the effectiveness of the paste replacement and cement replacement methods, mortar mixes with different replacement ratios of CBD (either as paste replacement or cement replacement) were tested to study their workability, strength, and microstructure. The test results showed that CBD added as paste replacement improved the strength and microstructure and substantially reduced the cement content, whereas adding CBD as cement replacement decreased the strength and loosened the microstructure. Hence, the paste replacement method is more promising for recycling clay brick waste and producing eco-friendly concrete.

The mechanical behavior of rock mass is strongly influenced by internal joints. To investigate the effect of hidden joints on the strength and deformation behavior of rock mass, a series of triaxial compression tests was carried out using specimens made from rock-like material. In the experiments, a self-designed pouring apparatus was used to prepare specimens with hidden smooth joints at a given inclination angle. Based on the experimental results of axial stress–axial strain curves, the effect of joint inclination angle and confining pressure on the mechanical behavior of the jointed specimens was analyzed. Four failure modes, which are related to joint inclination angle, were identified. An anisotropic effect parameter was proposed to reflect the degree of strength anisotropy affected by joint angle and confining pressure. It was found that the strength anisotropy decreases with the increase of confining pressure. Finally, the Mohr–Coulomb and the Hoek–Brown failure criteria were applied to describe the strength of the jointed specimens. It was found that the strength parameters of the two failure criteria are closely related to joint inclination angle. The Hoek–Brown failure criterion described the strength envelope of the jointed specimens better than the Mohr-Coulomb failure criterion.

In grouting practices for tunneling in loose deposits, the traditional grouting materials often suffer from its disadvantages, such as prolonged gel times, poor stability, an uncontrollable range of diffusion, and large grout consumption. In this study, an organic–inorganic hybrid chemical grouting material based on polymerization of hydrogen double bonds, Ca-C connection and excellent synergistic interactions among cement, polyethylene glycol (PEG) 200, sodium silicate, and polycarboxylate superplasticizer (PS) was prepared with a simple process. Based on percentages of water/cement at 1, PEG200 (2%), sodium silicate (10%), and PS (0.2%), the obtained modified cement-sodium silicate grouting material (C-S-P) forms a three-dimensional network structure and results in a high stability, good pumpability, satisfactory initial compressive strength, and relatively lower permeability performance. The C-S-P was primarily composed of amorphous PEG and crystalline polysilicic $\mathrm{Ca}{(\mathrm{OH})}_2/{\mathrm{Ca}}_2{\mathrm{SiO}}_4/{\mathrm{SiO}}_2/{\mathrm{CaCO}}_3$ composite, and its probable formation mechanism was evaluated. The proposed new grouting material was applied for reinforcing a tunnel in loose deposits, and the results illustrate that the C-S-P turns out excellent grouting performance and mechanical performance, thereby fulfilling the requirements for tunnel rapid excavation in loose deposits. This study presents the methodology for preparing a new grouting material for reinforcing loose deposits.

Bamboo scrimber is a new type of composite bamboo lumber. Its mechanical properties, for example, flexural strength parallel to grain, are superior to that of untreated bamboo lumber, and it can be used in many fields of construction. When employed outdoors, construction materials will be exposed to water in the form of rain and air humidity, and their moisture content (MC) will change constantly. It is therefore important to understand the influence of MC on the expansion rate, flexural strength parallel to grain, flexural modulus, and stiffness of bamboo scrimber. The results of this study show that the expansion in width and thickness of bamboo scrimber increases logarithmically with an increase in MC. The flexural strength parallel to grain and modulus of bamboo scrimber decrease significantly with an increase in MC until the fiber saturated point (FSP) is reached; increasing the water content further results in smaller flexural strength parallel to grain and modulus reductions. The FSP of the bamboo scrimber obtained in this study is 19.9%.