Journal of Materials in Civil Engineering

Measuring surface hardness and correlating it to shear strength is a nondestructive test method that can be used when a more accurate estimate of rivet strength is necessary. The objectives of this research were to (1) correlate the surface hardness to shear strength of driven rivets, and (2) determine if a subset of rivets could be tested to estimate the hardness of all rivets on a structure. Modern rivets were driven with a pneumatic rivet hammer and tested with a portable hardness tester. The shear strength was then estimated using the approximate tensile strength and two factors, 0.58 and 0.85, from previous research. When using the 0.85 factor, the difference between estimated and actual shear strengths was as low as 1%–6%, compared with 28%–34% when using the 0.58 factor. A factor of 4.8 MPa/hardness Rockwell B (HRB) ($0.7\mathrm{ksi}/\mathrm{HRB}$) was then proposed as a direct correlation between surface hardness and shear strength. The range of rivet hardness measurements was approximately 30 HRB for each of the three bridges tested. Thus, it would be inappropriate to estimate the hardness of all rivets from a small subset of tested rivets. A proposed method is to test a subset of rivets on a member or connection of interest and use those measurements to estimate the hardness of rivets only on that member or connection.

Polyurethane (PU) is a synthetic material available for researchers to be designed in terms of their demands. This study prepared a novel polyurethane thermoplastic elastomer (PUTE) as an asphalt modifier through the reasonable selection of raw materials and formula. The results of the Fourier transform infrared spectroscopy (FTIR) test confirm the chemical reaction between ─ NCO groups in PUTE prepolymer and ─ OH groups in the most polar asphalt molecules (asphaltenic regions). Effects of the PUTE modifications (1%, 3%, 5%, 7%, 9%, 11%, 13%, and 15% by asphalt binder weight) on the asphalt binder properties were then studied through a series of tests. PUTE is demonstrated to play a positive role in high- and low-temperature properties and the mechanical properties of the asphalt binder. All of the PUTE modified binders have desirable storage stability. Moreover, using 11% PUTE is recommended. Finally, the technical properties of PUTE and SBS modified asphalt mixture were compared. The results indicate that the PUTE modified asphalt mixture performs better in low-temperature property and moisture stability than the SBS modified asphalt mixture, whereas the PUTE modified asphalt mixture has worse high-temperature property than the SBS modified asphalt mixture.

The aggregate segregation during construction has a significant impact on the performance of asphalt pavement; however, the segregation evaluation parameters selected by different researchers varied a lot. Also, standard criteria for the impaction of segregation on the performance are still lacking. Therefore, this research proposed a set of segregation evaluation indexes that divided the gradation types into five levels, from coarse-severe to fine-severe gradation. The impact of various segregation levels on the volumetrics, mechanical performance, and road performance of the pavement were evaluated. The mechanical test results indicated that, given the change in the segregation degree from coarse to fine, the Marshall stability and immersive residual stability of the asphalt mixture obviously increased, and the dynamic stability and low temperature failure strain of the heavy segregation gradation obviously decreased. The result also indicated that the rutting resistance first increased first and then decreased because of the cohesion reduction when the gradation was changing from fine to coarse. The result found that the proposed evaluation index can reasonably characterize the degree of aggregate segregation.

This paper analyzed the deterioration model of concrete in dry–wet cycles and sodium sulfate solution. The calculation method of stress transformation from dry–wet cycle and salt crystallization was established from the aspects of water saturation, salt accumulation concentration, and salt supersaturation. The results showed that the calculation results of concrete strain caused by dry–wet cycles and sodium nitrate crystallization are in good agreement with the experimental results, which proves the reliability of the stress calculation method. The calculation method of concrete strain caused by dry–wet cycles and sodium nitrate crystallization was extended to the deterioration process of concrete caused by dry–wet cycle sodium sulfate crystallization, and the strain caused by dry–wet cycle sodium sulfate crystallization is calculated. The results of strain comparison showed that the strain of mortar produced by each action increases with the increase of cycle times after degradation by dry–wet cycle sodium sulfate solution, but because mortar with a higher water to cement ratio has weaker resistance to sulfate attack, a large number of cracks appear in the later stage of degradation, and the calculation method of strain caused by dry–wet cycle salt crystallization is therefore no longer applicable.

The recycling of waste materials (e.g., coal wash, steel slag, recycled rubber, and fly ash) is becoming increasingly popular in ground engineering projects. While the physical properties of these waste materials can be different from those of traditional aggregates, their strength properties are often comparable to traditional quarried materials. This paper examines the stress-strain properties of four mixtures of coal wash and rubber crumbs (CWRC) under monotonic, consolidated drained conditions considering four confining pressures (i.e., 10, 25, 50, and 75 kPa). A three-dimensional (3D) function is proposed to describe the effect of rubber inclusion on the peak friction angle and the shear strength of the mixture. Also, the role of rubber inclusion on the characteristic state, peak state, and critical state is addressed and quasi-critical state parameters are defined to incorporate the ongoing rubber deformation even after large axial strains (i.e., $>20\%$). Given that one component of the mixture is highly compressible (i.e., rubber), a new equation that accounts for the compression of rubber particles and the associated change in the volume of the solid phase is proposed to estimate the void ratio. Alternatively, a modified void ratio that is independent of the volume of rubber within the mixture is defined and a dilatancy model is proposed accordingly.

Tailings dam disasters are reported almost every year and are triggered by mechanisms, such as overtopping, piping, and others. The failures due to inadequate management cannot be neglected as well. These dams are constructed mostly in a step-by-step construction method that leads to a continuously changing state of vertical loads during construction and may lead to particle breakage and changes in strength. Therefore, a layer of tailings dam today may not be the same tomorrow during the construction phase. To study the effects of different loads on particle breakage and strength, direct shear tests were performed on remolded tailings samples that were separated into different particle sizes. The tests were performed using different normal stresses that ranged from 50 to 500 kPa. The results indicate that finer tailings exhibited slightly more shear resistance than that of coarser tailings irrespective of the deposition method. For normally deposited specimen, the dilatant and contractant behavior in vertical height was observed when the normal effective stress was less than 300 kPa and greater than 300 kPa, respectively. Under the vertical deposition method, the finer tailings showed contractant height behavior when subjected to a normal effective stress of 300 kPa. The friction angle and the cohesion of vertically deposited specimens were slightly higher and slightly lower, respectively, than that of normally deposited ones. The breakage of tailings particles was observed to be proportional to the particle size of the tailings.

This study focuses on the shear-strength properties of polyurethane polymer–treated sand stored at different temperatures. The triaxial test was performed at unconsolidated and undrained conditions on the specimen after 2 days of curing at room temperature and 1 day of curing at various temperatures. The effects of polymer content and dry density on strength properties were also considered. Polymer reinforcement mechanism was analyzed using scanning electron microscope images. Results indicated that the stress-strain relationship exhibited increasing ductility as temperature increased; the shear strength, energy absorption, and cohesion tended to decrease initially and then increase, while the friction angle remained stable at approximately 30°. The strength properties were in proportion to an increment in polymer content, and the trend became more apparent in a warmer environment. The shear strength, energy absorption, and cohesion increased up to about 2.4 MPa, 65 kPa, and 400 kPa, respectively. A higher dry density resulted in significant improvement in strength properties, except for a slight reduction in ductility, no matter the temperature. The presence of a polymer matrix formed a honeycomb and special net structures among sand via coating, bridging, and filling effects; hence, the treated sand turned into a whole system exhibiting favorable strength properties. This reinforcement effectiveness depended on polymer content, dry density, ambient temperature, soil grain, and polymer characteristics.

Cement–bentonite mixtures are commonly used to build cutoff walls, which limit water flow and underground transport of pollutants. These artificial materials are employed due to their very low permeability and adequate shear strength and ductility. In this paper, experimental results about the microstructure and mechanical behavior of three different cement–bentonite mixtures are presented. Specimens of these mixtures were subjected to oedometer and consolidated-undrained triaxial tests. These results were then used as a basis for the definition of a suitable constitutive framework. A quite good reproduction of the experimental results up to the peak strength was obtained using the classical Modified Cam Clay model, which could then be used satisfactorily when conventional analyses aimed at assessing the stability of cutoff walls are required. The reproduction of the strength degradation and the strains occurring in the postpeak stage requires, however, a more advanced constitutive model. To this extent, the Modified Cam Clay framework was enhanced by introducing some features commonly employed to reproduce the mechanical behavior of granular materials. This model may be useful for the real-scale analysis of more critical cases when local failure mechanisms are likely to occur and may influence the functionality of the wall.

The oily fraction allows expansion and dissolution of the polymer particles within the bituminous matrix. This contribution studies the effects of adding a small quantity of a used engine oil (UEO) to bag waste plastic-modified $40/50$ grade bitumen. The objective is to investigate the possibility of using the used oil as a plastic-bitumen compatibilizing agent. Penetration, softening point, Rolling Thin Film Oven Test (RTFOT), and Fourier transform infrared spectroscopy (FTIR) tests were used in this paper to characterize the waste plastic-modified bitumen (WPmB) and the used engine oil plastic-modified bitumen (UEOPmB). The Van Der Poal nomograph is used to complete the characterization of the studied binders. It was observed that adding used engine oil allowed incorporating greater plastic quantities into the pure bitumen. Moreover, both the WPmB and the UEOPmB have shown improved mechanical properties compared with pure bitumen. Obtained results demonstrated that oil addition enhances the aging resistance and reduces the low temperature cracking resistance of the UEOPmB.

Polyurethane grouting can be used for antiseepage and reinforcement in underground construction. Understanding the diffusion characteristics of polyurethane grout is critical for good grouting design. However, the influence of water pressure on the diffusion of polyurethane grout is not clear. The aim of this work is to experimentally investigate the diffusion behavior of polyurethane grout in a water-bearing fracture. A series of laboratory experiments was conducted using a self-designed visual fracture grouting device under different conditions. The influences of grouting quantity and water pressure on grout diffusion distance and flow field are discussed. The results show that grout expansive diffusion and the pressure field change of the grout–water system have a phased characteristic. Also, the change of grout pressure is not synchronized with grout diffusion distance. The grout diffusion radius increases with the increase of grouting quantity, but decreases with the increase of hydrostatic pressure. The study helped gain insight into the performance of polyurethane grouting in fracture under static water condition.

The performance of a structure depends on its material characteristics under various conditions of loadings, strain rate, and temperature, and therefore, it is necessary to understand these characteristics properly for the safe and reliable design of structures. In this paper, the flow stress behavior of AZ81 magnesium alloy is determined under tensile, compressive, and flexural loads at different strain rates and temperatures. An electromechanical universal testing machine of capacity 250 kN is used to perform quasi-static tests (${0.0001–0.1\mathrm{s}}^{-1}$) under tension and compression; and three-point bending (flexure) tests using suitable fixtures at crosshead speeds ($1–100\mathrm{mm}/\min$) for varying span lengths ($80–160\mathrm{mm}$) and orientations (flat and transverse) at room temperature, 25°C. The thermal and fracture behaviors of the alloy at various temperatures (25°C, 100°C, 150°C, and 200°C) are studied under quasi-static tension (${0.001\mathrm{s}}^{-1}$). The heating rate of the tensile specimens is $20°\mathrm{C}/\min$ and the soaking time is $15\min$. Dynamic tensile (${850–\mathrm{1,400}\mathrm{s}}^{-1}$) and compressive (${\mathrm{1,900}–\mathrm{3,300}\mathrm{s}}^{-1}$) experiments are conducted using appropriate arrangements of Hopkinson bar systems. The effects of specimen geometry on the flow stress of the alloy are observed under compression. Ductility and toughness are determined to establish the energy dissipation capacity of the alloy. Fractographs of the fractured tensile specimens are studied by scanning electron microscope (SEM). Also, the applicability of the existing Cowper–Symonds and Johnson–Cook models in the aforementioned loading conditions is discussed.

In this study, the method of changing the surface layer microstructure of cementitious composites by ultrasonic surface treatment at the early stage of hydration is introduced, and the formation mechanism of the gel phase powder layer (GPPL) formed by ultrasound is analyzed. The microstructure of GPPL is observed and analyzed by laser confocal microscopy scanning (LCMS), scanning electron microscopy (SEM) and backscattered electron (BSE) imaging. The phase component is measured by X-ray diffraction (XRD) and thermogravimetry (TG). Four ultrasonic frequencies (28, 40, 80, and $120\mathrm{kHz}$) were used in the experiment. Apparent density and water vapor permeability of the cement paste specimens with GPPL structure were tested. The accelerated carbonation test of concrete and mortar specimens with GPPL structure were carried out. It is proved that GPPL structure can significantly improve the carbonation resistance performance of cementitious composites. Finally, the prospects for engineering applications of this method are presented.

Low-temperature cracking is a very common type of distress in flexible pavements in cold areas that extends in the form of longitudinal and transverse cracks on the surface layer. Modifying the properties of the control asphalt cement to improve its performance at low temperatures is a way to control this type of cracking. The effect of using ultrahigh-molecular-weight polyethylene (UHMWPE) as a polymeric additive was investigated with rheological, mechanical, and thermodynamic tests. Bending beam rheometer (BBR) testing of the asphalt cement at low temperatures and mechanical tests, including pull off (PO) and semicircular bend (SCB), were performed on asphalt mixtures to examine the effect of this additive on the low-temperature cracking potential of hot-mix asphalt. In addition, thermodynamic tests, including asphalt cement and aggregate surface free energy (SFE) using the Wilhelmy plate (WP) and the universal sorption device (USD) methods, were performed to better understand the results. Based on the results of the BBR test, the application of UHMWPE improved the performance of the modified asphalt cement at low temperatures. Also, the results of the SFE test showed that using UHMWPE increased the cohesion and the adhesion free energies. These changes were closely correlated with the results of the PO test in cohesive and adhesive modes, respectively. The results of SCB test for parameters including peak load, fracture energy, and fracture toughness demonstrated that the incorporation of UHMWPE significantly improves the low-temperature properties of the modified asphalt mixture. Moreover, based on the statistical analysis, the SFE parameters had a positive effect on peak load and fracture energy. The results for the fracture energy parameter revealed that, after crack formation, only the cohesion free energy parameter was effective on asphalt concrete resistance until the moment of failure.

Enzyme-induced carbonate precipitation (EICP) has been described as a bioinspired solution for ameliorating the mechanical properties of soil by precipitating calcium carbonate to bond sand particles. This study investigates the use of EICP utilizing a cost-effective jack bean meal as a source of enzyme to cement sand. Three different EICP cementing solutions were used to treat sand specimens in this study. The performance of biocemented sand was investigated under several key environmental conditions. These conditions include the effect of the EICP cementing solution concentration, curing time, temperature, wetting and drying cycles, exposure to sulfate contamination, and exposure to seawater. Increasing the concentration of the EICP solution facilitates dense calcite precipitation, which leads to higher soil strength. Scanning electron microscopy was used to observe the carbonate precipitation pattern. The images showed that increasing the curing temperature up to 40°C has led to more calcite and dense aragonite than vaterite, which means the enzyme has greater efficiency. A substantial increase in the unconfined compressive strength after one cycle of treatment with jack bean meal as the source of the enzyme was achieved, which tolerated the high salinity of the EICP cementing solution. The unconfined compressive strength of treated soils with a high-molarity EICP cementing solution was around 2.9 MPa at 5.6% ${\mathrm{CaCO}}_3$. Finally, the EICP-treated sand specimens showed higher resistance against seawater and wetting/drying cycles of freshwater, whereas less resistance was observed for the case of immersion in a 5% sulfate solution.

The use of waste cooking oil (WCO) and nanoclay (NC) in the modification of asphalt binder can produce sustainable material for paving applications. This study evaluated the change in physical and rheological properties attained by modification of a conventional asphalt binder using varying percentages of WCO and NC; 0%, 2.5%, and 5% WCO was used to modify a VG 30 binder, followed by reinforcement using four different dosages of montmorillonite NC (0%, 2%, 4%, and 6%). A total of 12 combinations of asphalt binders were produced (VG30, 2NC, 4NC, 6NC, 2.5WCO, 5WCO, 2.5WCO2NC, 2.5WCO4NC, 2.5WCO6NC, 5WCO2NC, 5WCO4NC, and 5WCO6NC) and subjected to physical (penetration, softening point, viscosity, and temperature susceptibility) and rheological [high-temperature performance grading (PG), multiple stress creep and recovery (MSCR), and linear amplitude sweep test (LAS)] measurements. The physical and rheological measurements showed that the use of NC in WCO-modified asphalt binder could reverse the softening effect caused by the inclusion of WCO in VG 30. At 50°C and 60°C, 2.5WCO with 4% and 6% NC had higher values of percentage recovery ($R$) compared with VG 30. It was found that the use of NC insignificantly increased the strain susceptibility of the asphalt binders at intermediate temperatures for all WCO levels. Statistical analysis revealed that the effect of modification on unrecoverable creep compliance is less significant than the change in $R$ for a temperature range of 40°C–70°C. The significance of modification at intermediate temperatures was not consistent and clear. A simple cost–benefit analysis was proposed, which indicated that 2.5WCO6NC is the optimum combined blend for obtaining higher benefits relative to the cost of modification.

The requirements on service life of reinforced concrete structures, as prescribed by design codes, may be difficult to be fulfilled in highly aggressive environments such as marine ones, in which premature degradation is most likely to occur. In the aforementioned situations, to avoid expensive repair activities, different protective systems, including, among the others, self-healing concrete, could be adopted. Researchers have found self-healing as a way to face degradation problems in chloride-rich environments. If a significant degree of crack sealing can be achieved, the physical properties of a cracked element can trend back to those of an identical uncracked element, which may also result in a slower penetration rate of aggressive substances. The main problem in exploiting this methodology is related to its reliability. In this context, an experimental program aimed at investigating the effectiveness of crystalline admixtures as healing stimulating agent in chloride-rich environments was carried out. The influence of the exposure conditions on the compressive strength development and on its recovery in predamaged specimens was first analyzed. Afterwards, crack sealing and chloride permeability of sealed cracks were evaluated for specimens continuously immersed or subjected to wet/dry cycles in a 16.5% NaCl aqueous solution. Both an enhanced recovery of compressive strength and an improved crack sealing ability were observed for samples containing the healing agent. A microstructure study of the healing products was conducted by means of scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis as well.

The emphasis of the current study was on the calcination of lime sludge, performed at different temperatures from 650°C to 750°C, which consumes less energy as compared to the industrial process of calcination. Different proportions of calcined lime sludge and raw lime sludge were used with cement to form cementitious binders. M25 grade concrete was prepared with the application of the prepared binders and tested for strength properties at 7 and 28 days of curing. The binder consisted of 10% substitution of cement with as-received lime sludge and 30% substitution with calcined lime sludge and produced a compressive strength of concrete approximately similar to the control concrete. Reactive lime and metakaolinite performed an active role after the calcination of lime sludge at 650°C, which worked as pozzolana. This effect is also confirmed with isothermal calorimetry of the prepared binder. The prepared binder was sustainable with approximately 20% less production cost and 55% less emission of greenhouse gases as compared to ordinary portland cement.

Most previous stress relaxation tests were based on steel wires and steel strands. This test performed $\mathrm{1,000}\mathrm{h}$ of stress relaxation test on stainless steel cables and Galfan-coated steel cables with diameters of $Ø14$, $Ø20$, and $Ø26\mathrm{mm}$. Three different initial tension levels were tested, and three control values of 30%, 50%, and 70% of the ultimate tensile strength of the cable were used as the load control points. The stress relaxation tests were carried out in a factory building, and the temperature was not strictly controlled. The stress relaxation of the cable is the stress relaxation under the combined action of temperature relaxation, stress relaxation, and time relaxation. To make the research more valuable, the thermal expansion coefficient of the cable was used to eliminate the influence of temperature on the stress relaxation test, and the data were adjusted to correspond to 30°C. The test results were analyzed, and formulas for calculating the tension loss of steel cables were established. The results showed that the exponential equation of time logarithm can better express the relation between tension loss and time. The relation between the coefficients and the initial tensile force was established. This test also compared the relaxation properties of stainless steel cables and Galfan-coated steel cables. For steel cables with the same initial tension level and the same diameter, the Galfan-coated steel cables had much larger relaxation rates than the stainless steel cables.

Ultrahigh-performance fiber-reinforced concrete (UHPFRC) is endowed with outstanding durability. The first results of accelerated migration tests with an adapted procedure highlighted a very low chloride permeability profiles for undamaged UHPFRC with organic and metallic fibers. However, some of the samples with steel fibers showed useless results in the accelerated migration tests because they presented signs of corrosion and cracks. This paper proposes to analyze by imaging the UHPFRC with steel fibers after the accelerated migration tests to better understand why some samples do not successfully pass the test. Image analyses were applied to characterize the distribution of the fibers, in terms of volume, homogeneity, and orientation. The results presents some correlation between those parameters and define some limitations on the type of UHPFRC that can be successfully characterized with accelerated migration test.

This article utilized waste glass in the form of glass powder (GP) and researched its effects on the properties of magnesium phosphate cement (MPC), which were investigated via working properties, mechanical properties, microstructures, and hydration products. The results showed that successive additions of GP to MPC led to a cumulative decrease in setting time and fluidity. A suitable dosage of GP (within 15%) as magnesia replacement improved the mechanical properties of hardened MPC mortar, but it decreased upon more additions. The sample blended with 10% GP exhibited a fluidity of 242 mm and a setting time of 20 min, with a 28-day compressive strength of 78.2 MPa, which was the highest among all the groups, and it met the requirements for applying in field construction. The XRD, SEM-EDS, TGA-DTG, and NMR tests showed that GP accelerated the hydration rate and promoted the crystallization process of hydrates. More gels were produced in MPC after incorporating GP, where some calcium-phosphate and sodium-phosphate gels were formed by the alkali components with phosphate. However, activating the silicate glassy phases content in GP was difficult. The microstructure observed via SEM and the pore structure measured by an optical microscope with MIP illustrated that GP compacted the microstructure, reduced the total porosity, and improved the pore size distribution of MPC by the pore-filling effect. The research indicated that GP could be regarded as a mineral admixture in MPC, making MPC more eco-friendly and suitable for use as a rapid repair material.

The purpose of this study is to evaluate and quantify the construction costs, energy costs, and environmental benefits of using cold in-place recycling (CIR) as a pavement rehabilitation technique. For this study, the costs of using CIR mixes prepared using either asphalt emulsion (CIR-E) or foamed asphalt (CIR-F) were compared with conventional 5.1-cm (2-in.) hot-mix asphalt (HMA) mill and overlays. Three different costs were considered for the production of each pavement rehabilitation technique: (1) construction, (2) energy, and (3) environmental costs. To facilitate the cost comparisons, an equivalent pavement structural analysis was conducted between each pavement rehabilitation technique using a standard design method. The results of the study showed that initial construction costs of using CIR are less than the conventional HMA mill and overlay. The energy and environmental costs were also found to be much lower for CIR mixtures compared with the HMA mill and overlay, with energy savings of up to 63%. Overall, when considering all costs, the use of CIR has lower costs compared with traditional HMA overlays. Cost savings of approximately $34,000–$39,000 were observed when using CIR with HMA overlays, with a total cost savings between 41% and 47% over traditional HMA mill and overlays. This study gives an overall procedure for assessing the economic and environmental costs of different pavement rehabilitation techniques and provides further evidence of the cost benefits associated with CIR to practitioners.

Ultra-high performance concrete (UHPC) has more severe autogenous shrinkage than ordinary concrete, which may lead to increased cracking risks. Thus, a suitable and effective agent for internal curing (IC) of UHPC without a negative effect on the strength is needed to solve this problem. A type of strong and porous aggregate made of calcined bauxite was used in this study to achieve low shrinkage and lower-cement UHPC based on the modified Andreasen and Andersen model, and together, a reference mixture made of basalt aggregate was prepared. The autogenous shrinkage of UHPC with basalt aggregate reached $570\mathrm{\mu m}/\mathrm{m}$ at the age of 28 days, while the autogenous shrinkage of the UHPC with calcined bauxite was substantially reduced or a slight expansion occurred. This was found to be due to the internal curing effect provided by the calcined bauxite aggregate. A pronounced 56-day compressive strength of 148 MPa was achieved for this standard-cured UHPC without steel fibers. The low shrinkage UHPC internally cured by calcined bauxite aggregate can be applied to on-site cast UHPC structures or bridge decks that are prone to shrinkage cracking.

Cemented paste backfilling is a novel tailings-management method that is widely used in the mining industry to minimize the environmental and geotechnical risks associated with traditional mine-waste management techniques, ensure safe work conditions in underground mines, and increase mine productivity. To enhance the early age strength of cement paste backfill (CPB), sodium silicate has been proposed and adopted as an admixture in CPB systems due to its activation ability. However, no studies have been done to gain insight into the effect of temperature on the rheological properties (yield stress and viscosity) of CPB with sodium silicate and different types of binders, although a CPB with sufficient flowability is critical for its successful application, and CPB is subjected to various temperatures in the field during its transport. Thus, this study aims to investigate the effect of temperature (2°C, 20°C, and 35°C) and time ($0–4\mathrm{h}$) on the rheological properties (yield stress and viscosity) of CPB samples with different amounts of sodium silicate (0%, 0.1%, 0.3%, and 0.5%) and different binders. The results show that the yield stress and viscosity of CPB with sodium silicate increase with time and temperature. It is also found that the partial replacement of portland cement with blast furnace slag or fly ash enhances the flowability (reduces the rheological properties) of CPB, regardless of the temperature. Also, an increase in the sodium silicate dosage will increase the yield stress and viscosity of CPB at any temperature. The findings of this research will contribute to a more efficient design of CPB transportation systems.

Mixing waste rubber in cementitious materials such as concrete is an effective way to reuse the rubber, which is important due to its environmental significance. This work predicted the strength evolution of rubberized cementitious materials based on their rubber content and porosity. Mortar specimens with rubber content ranging from 0% to 15.3% per mortar volume were prepared based on the method of making pores in cementitious materials with soft materials, i.e., the virtual pore method. Their porosity and compressive strength at 3, 7, and 28 days were measured by tests. With the increasing volume fraction of rubber particles, the porosity of the specimens increased and the strength decreased. By dividing the pores in cementitious materials into matrix pores and virtual pores, the strength of the rubber free cement mortar and the effect of rubber particles were considered separately and a predictive strength model of rubberized cementitious materials was established based on their rubber content and porosity. The proposed model is applicable to materials of different ages and hydration degrees. It was applied to the strength prediction in the available literature, and the predicted values were in good agreement with the test values.

An analytical model was developed to describe the influence of silica fume on the mechanical behavior of ultra-high-performance concrete. The model defines a single parameter, $t_{\mathrm{paste}}$, which estimates the thickness of paste surrounding all inert, unhydrated cement, and unreacted silica fume particles. The model considers adjustments for partially hydrated cement and partially reacted silica fume to model more accurately the total surface area in the system. The adjustments made for partial hydration and reaction enable the model to be applied to both water-starved and water-saturated mixtures. The compressive strengths of 82 UHPC mixtures containing eight different sources of silica fume were compared with model results, and results suggested that increasing paste thickness led to a decrease in the measured compressive strength.

This study aims to evaluate the performance of granulated blast furnace slag (GBFS) and metakaolin (MK)-based geopolymer concrete (GC) under different curing conditions. GC was derived from a portland self-compacting concrete (PC). Three curing modalities were considered: (1) $20°\mathrm{C}-50\%$ relative humidity (RH); (2) $20°\mathrm{C}-90\%$ RH; and (3) 20°C-water immersion. The results showed that both PC and GC cured under water possess similar compressive strength. However, GC presented a lower elastic modulus and higher shrinkage and porosity. It was also found that hardening at 90% RH reduces both water porosity and shrinkage and enhances the mechanical performance of GC, which can be explained by the formation of more compacted geopolymer matrix. The validity of a current European standard to predict the compressive strength evolution and shrinkage development was verified. It was established that the standard relationship proposed for the prediction of strength evolution can be extended to GC, and a modification of the shrinkage development model was proposed. Finally, it was concluded that the use of the GBFS/MK mixture overcomes the mechanical performance degradation commonly known for GC immersed in water.

A mixed pore-forming agent composed of starch and calcium carbonate (${\mathrm{CaCO}}_3$) is proposed to assist the fabrication of high-porosity and high-strength ceramisites from solid wastes of municipal sludge and fly ash. The maximum porosity of the sintered body without adding a pore-forming agent was only 38.5% under a premised strength higher than 8 MPa. In comparison, the porosity and compressive strength of the sintered body reached 68.7% and 13.2 MPa under the optimized conditions of ${\mathrm{CaCO}}_3$ and starch content at 10% and 15% by weight. The performance comparison with those in the literature indicates that the proposed strategy is promising for fabrication of high-performance lightweight ceramisites from solid municipal sludge and fly-ash wastes. A schematic diagram for the sintering and pore-forming mechanism was proposed to attribute the high porosity of the sintered ceramisites to a low-temperature combustion of starch and a high-temperature decomposition of ${\mathrm{CaCO}}_3$. Simultaneously, the volume shrinkage caused by starch and expansion by ${\mathrm{CaCO}}_3$ counteracted each other, thus preventing cracking of the ceramisites after sintering and ensuring the high strength of the sintered compacts.

In this study, thin armor panels were designed and constructed using ultra-high-performance fiber-reinforced concrete (UHPFRC), and their ballistic resistance to armor-piercing small arms fire was assessed. The fiber dosages selected for the panels were 3% and 4% by volume, with average UHPFRC compressive strengths at 28 days of 144 MPa ($\pm 4.5$) and 141 MPa ($\pm 12.1$), respectively. The panels’ front and rear surfaces were $350\times 350\mathrm{mm}$, and the thicknesses were 40, 50, and 60 mm. Ballistic performances of the panels were assessed at two bullet velocities representing different operational distances. The two distances were based on a threat associated with urban operations (approximately 10 m) and field operations (approximately 300 m). A $7.62\mathrm{mm}\times 51$ armor-piercing round was used for testing. The testing demonstrated that at close range the panels could absorb a high level of energy, up to 3,089 J, and at this range, all panels were perforated. The results of the 60-mm panels impacted by a 300-m equivalent range shot, absorbed energy of up to 2,066 J, and slowed down the projectile to a very low velocity or a complete stop. Basic and advanced predictive models were used to estimate the resistant energy of the panels according to material characteristics such as fiber content, thickness, and mechanical properties. A numerical model was also developed. An ANSYS version R18.2 smooth particle hydrodynamics Autodyn model provided good predictions of the crater dimensions. It also demonstrated an impact behavior similar to that of the UHPFRC panel compared to real tests; however, further work is needed to represent the bullet core and jacket more accurately.

In this paper, styrene butadiene rubber (SBR) was utilized to improve the low-temperature performance of Buton-rock asphalt (BRA)-modified asphalt. Firstly, the optimum content of SBR modifier agent was determined by basic mechanical property tests, including penetration, ductility, and soft point tests. The comprehensive road performance, including high- and low-temperature performance, moisture resistance, and antifatigue performance at a low-temperature condition, of SBR-BRA-modified asphalt mixtures was evaluated by comparison with a base asphalt mixture, SBR-modified asphalt mixture, BRA-modified asphalt, and styrene-butadiene-styrene (SBS)-modified asphalt mixture. The fatigue test under the experimental temperature of $-10°\mathrm{C}$ and loading frequencies of 0.01, 0.1, 1, 5, and 10 Hz were designed to evaluate the antifatigue capacity of SBR-BRA-modified asphalt mixture under the low-temperature region. The S-N fatigue equation with the stress ratio related to loading rates was proposed to characterize the fatigue property of asphalt mixtures and reveal the different effects of loading frequency and materials on the fatigue property of asphalt mixtures. The tests results demonstrated that the SBR-BRA-modified asphalt has an equal road performance to SBS-modified asphalt. Analyzed by the S-N fatigue equation with the stress ratio related to loading rates, the fatigue test results under different loading frequencies could be fitted to a fatigue curve, and the fatigue curves of different asphalt mixtures exist at an angle and intersect at point $(1,1)$.

The long-term integrity of fly ash (FA) geopolymer-stabilized high-percentage reclaimed asphalt pavement (RAP) in the pavement base layer was investigated in this research. The FA geopolymer-stabilized RAP and virgin aggregate (VA) mixes were studied as an economical and durable alternative to 100% VA bases, with an emphasis on the influence of curing time. The maturity age of FA is usually set as 28 days, similar to traditional portland cement. However, due to partial pozzolanic reactions, though geopolymerized, the dilution of partial FA particles does not fully play its role at 28 days of curing time. Hence, this is not a realistic reference time for predicting the service life of FA geopolymer-stabilized aggregate blends. Therefore, a detailed experimental investigation was undertaken to evaluate the ultimate strength, durability, and microstructural characteristics of four distinct FA geopolymer-stabilized RAP:VA blends for a long-term ambient curing time up to 270 days. In this study, the long-term cured specimens showed significant improvement in mechanical strength and stiffness, yielding lower permanent deformations. It was noticed that only about 12% and 40% average unconfined compressive strength (UCS) could be achieved in 7- and 28-day cured specimens, respectively, with reference to their ultimate strength at 270 days. Hence, to examine the microstructural characteristics of powdered FA geopolymer blends, X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), and Fourier transform-infrared spectroscopy (FT-IR) studies were performed. The test results revealed that the consumption of reactive metal ions was continued for an extended period under a controlled curing regime, which resulted in improved mechanical strength and durability of the solidified product.

Open-graded friction course (OGFC), also called permeable friction course (PFC), is a thin and permeable asphalt concrete whose skeleton is composed mainly of coarse aggregate, leading to an immediate drainage of water and an adequate frictional resistance, thus reducing traffic accidents and improving driving environments on rainy days. However, high porosity and open aggregate structures may readily contribute to stripping and raveling of OGFC. Application of fog seal on slightly cracked and/or raveled OGFC is one preventive measure to extend its service life. This study quantitively examined the influence of fog-seal application on the OGFC’s behavior, such as water permeability, skid resistance, and raveling susceptibility. Laboratory tests, including the permeability test, texture depth test, and loaded wheel abrasion test, were conducted on samples obtained from the lane and shoulder in a section of OGFC pavement. Results demonstrate that as fog-seal application rate increased, permeability decreased. Fog seal temporarily reduced the texture depth. However, texture depth could be recovered after the loaded wheel test. Obviously, fog seal can play a beneficial role on abrasion resistance, thereby presenting a potential to ameliorate the durability of OGFC pavements.

Masonry blocks are extremely popular for a wide range of masonry structures around the world. However, the ever-increasing cost of materials and overexploitation of natural resources in the production of blocks pose grave environmental concerns. Three waste materials and industrial by-products from the palm oil and steel industries, namely, palm oil clinker powder (POCP), palm oil clinker (POC), and steel slag sand (SSS), have been utilized to replace cement, coarse aggregate, and fine aggregate in the development of hollow masonry blocks (HMBs). Further, the hardened properties on HMBs such as density, water absorption, and compressive and flexural strengths were investigated. The results indicate that the use of 30% POCP, 50% POC, and 75% SSS, respectively, as the replacement materials for cement, coarse aggregate, and fine aggregate in HMBs produced acceptable engineering and radiation shielding performance. A reduction in ${\mathrm{CO}}_2$ and cost could be envisaged based on the environmental and economic indexes.

Ice formed on asphalt pavement in winter reduces the skid resistance of the pavement surface, which would likely cause traffic accidents. To guarantee driving safety, a super-hydrophobic anti-icing coating on asphalt pavement was studied. First, suitable materials were selected, and the sol–gel preparation method was adopted; thus, a super-hydrophobic coating slurry was produced and coated on asphalt mixture slab specimens for evaluation. Second, the corresponding evaluation criteria, such as contact angle, rolling angle, and film formation of the super-hydrophobic coating, were measured and analyzed to determine the optimum composition and preparation technology. Third, the functional groups and micromorphology of the coating were investigated to analyze the formation and hydrophobic mechanisms. Finally, anti-icing indicators such as freezing delay time, freezing amount, and ice–pavement adhesion strength of the coating were adopted to evaluate their anti-icing properties. Meanwhile, the effect of coatings on skid resistance of asphalt pavement and their economy and practicality were also analyzed. Based on the test results and analysis, an optimum formulation ratio of super-hydrophobic coating slurry is recommended: silane coupling agent/high hydrogen silicone oil at 25%, deionized water/high hydrogen silicone oil at 130%, and tin catalyst/high hydrogen silicone oil at 20%. Microscopic experiments showed that the micro-nanostructure on the coating surface is fundamental to achieving super-hydrophobicity. The anti-icing effect test results showed that, with the formation of a super-hydrophobic coating on the pavement, the beginning freezing time of water on the pavement surface was delayed by 100–30 min, and the complete freezing time was delayed by 120–30 min, respectively, at $-2°\mathrm{C}$ to $-10°\mathrm{C}$. Compared with common pavement, the adhesion strength between ice and pavement surface coated with super-hydrophobic coating was reduced by more than 60% at $-2°\mathrm{C}$ to $-6°\mathrm{C}$. Even at $-8°\mathrm{C}\text{to}-10°\mathrm{C}$, 100 kPa reduction can be obtained. In addition, spraying the siloxane coatings has little effect on the skid resistance of the pavement. From these results, it can be concluded that the super-hydrophobic coating developed has excellent anti-icing properties and economic benefits, and it can prevent vehicle sliding and reduce ice removal labor.

Aggregate gradation is crucial for the performance of asphalt mixtures. However, the adequate mix design must include the compromise between performance and workability. This study used two compaction methods: the impact (Marshall Hammer, Humboldt, Elgin, Illinois) and gyratory [Superpave Gyratory Compactor (SGC), Pine Instrument Company, Grove City, Pennsylania], to investigate the influence of aggregate gradation on the compaction of asphalt mixture utilizing the concept of the locking point. For the impact compaction, an accelerometer was placed on the falling mass of the Marshall Hammer to record the asphalt mix response, with which the impact locking point was defined. For the gyratory compaction, the densification curves were utilized to define the locking point. Twelve mixes, three for each mixture type (base, intermediate, and surface) were designed and prepared in the laboratory. The asphalt mixes were tested for their locking points in relation to their type and gradation. Results indicated that the locking point could be determined for the majority of the mixtures compacted by both the impact and gyration methods, except for the mixture composed of the bigger stone and coarser gradation. The locking point of the asphalt mixture was strongly dependent on its gradation. A coarser mix resulted in a higher locking point. Thus, the maximum aggregate size was not the only factor that determined the locking point but the whole gradation.

With the extensive increase in exploitation of shale gas/oil, the mechanical/physical properties of oil well cement paste (OWCP) are paid special attention to. The mechanical and physical properties of OWCP is believed to be closely related to its microstructure and hydration behaviors. Both microstructure and hydration behaviors of OWCP cured at high temperature evolve with curing age. Taking advantage of multiple techniques, this study devotes itself to investigating the impact of curing age on the evolution of microstructure and hydration behaviors of OWCP cured at 80°C. The results show that both the capillary pore space and porosity decreased with curing age, while the gel porosity and specific surface area increased with curing age; Ca/Si ratio of calcium silicate hydrate (C─ S─ H) decreased fast during the first 3-day curing age, and then it is maintained around 1.82 in the following curing age; both evolutions of degree of hydration and chemical shrinkage with curing age obey the Avrami-type exponential equation; and the porosity of OWCP measured through mercury intrusion porosimetry correlates linearly with gel/space ratio as does the relationship between the degree of hydration and total amount of portlaindite determined by thermogravimetry-differential thermal analysis (TG-DTA), and both linear relationships are independent of curing temperature.

Steel corrosion is an important factor in the durability loss of reinforced concrete members. Many studies have examined reinforced concrete eccentric compression members in natural stress-free states and have drawn conclusions about durability from these data. To study the influence of different stress levels on the corrosion and eccentric compression performance of reinforced concrete columns, this study applied an accelerated corrosion test to reinforced concrete specimens with different preloading levels and then conducted eccentric compression axial force capacity tests and analyses. The results showed that for an ordinary reinforcement stirrup member, an increase in the level of preloading reduced the mass loss of the reinforcing bars, and there was a corresponding decrease in the loss of eccentric compression capacity and stiffness. For members with an epoxy-coated reinforcement stirrup, an increase in the preloading level increased the mass loss of the reinforcing bar, and the ultimate axial force capacity of the member under eccentric compression was reduced accordingly.

Interfacial strength between asphalt binder and aggregate plays a vital role in maintaining the mechanical integrity of asphalt mixture. Given the lack of accurate testing instruments for the interaction of asphalt–aggregate interface, the adhesive interaction and failure evolution occurring at this interface has not been fully understood. In this study, molecular dynamics (MD) simulation was utilized to elucidate the mechanical and deformation behavior of the asphalt–aggregate interface under tensile stress from the atomic perspective. The interface system was constructed with a 12-component asphalt molecular model bonding on a silica substrate. This asphalt molecular model, combining the polymer consistent force field (PCFF) adopted to describe the inter-/intra-action of the system, was first validated. A stress-separation law of this interface can be obtained by tracing the atomic force during the tensile process. From this stress-separation law, the interfacial strength and work of adhesion can be derived. The influences of model size, loading rate, asphalt film thickness, and moisture were investigated. It was found that the interfacial failure type transfers from adhesive failure to cohesive failure as the loading rate decreases to a certain level. Moreover, the interfacial strength is highly associated with the failure type. The interfacial strength of the adhesive failure is about five times that of the cohesive failure, which demonstrates the traditional method of improving the adhesion performance of asphalt on aggregate through increasing its viscosity from the aspect of atomic modeling. Furthermore, the water molecules absorbed at the interface are crucial to the durability of the asphalt–aggregate system. This study provides deep insight into the interfacial failure of the asphalt–aggregate system and could serve as an initial step in multiscale modeling using bottom-up approaches for asphalt mixture.

Asphalt oxidation induces asphalt binder embrittlement, which in turn increases the susceptibility of flexible pavement to fatigue and low-temperature cracking. It is critical to determine an index that can appropriately track the oxidation extent of asphalt binder and assess its cracking susceptibility. The objectives of this study are to investigate the connections between the chemical changes by oxidation with rheological parameters, and to identify suitable chemical aging indices and rheological parameters to assess the cracking susceptibility of Alaskan asphalt binders. A total of 13 typical Alaskan asphalt binders were collected from three different suppliers. The Glover-Rowe ($G\text{-}R$) parameter, rheological index ($R$-value), $\mathrm{\Delta }T$, and fatigue parameter ($N_f$) were selected as rheological parameters to quantify the change of cracking susceptibility of asphalt binder with aging. Fourier transform infrared spectroscopy (FTIR) technologies were applied to obtain the chemical aging indices such as the ratio of peak height between $\mathrm{C}═\mathrm{O}$ and ${\mathrm{CH}}_2$ ($\mathrm{C}═\mathrm{O}/{\mathrm{CH}}_2$), Carbonyl Index, and Sulfoxide Index. The results indicated that the $\mathrm{C}═\mathrm{O}/{\mathrm{CH}}_2$ was the most effective chemical aging index to track the oxidation extent of asphalt binder. The $G\text{-}R$ parameter was the most promising rheological index among the evaluated rheological parameters (i.e., $G\text{-}R$ parameter, $R$-value, $\mathrm{\Delta }T$, and $N_f$) to evaluate the durability and cracking susceptibility of asphalt binder because it correlated well with the $\mathrm{C}═\mathrm{O}/{\mathrm{CH}}_2$. The $R$-value was not desirable in some cases due to the difficulty in calculation. The fatigue parameter ($N_f$) showed a weak correlation with the chemical aging indices. A fair correlation could be developed between $\mathrm{\Delta }T$ and the $\mathrm{C}═\mathrm{O}/{\mathrm{CH}}_2$, but the correlation was not as strong as that developed for the $G\text{-}R$ parameter.

Cement kiln dust (CKD) is produced in the kiln as a byproduct during the production of cement clinker. CKD is undesirable material for a clean environment. The main purpose of this study was to evaluate the feasibility of using CKD, a byproduct of cement manufacturing, to improve engineering properties of hot mix asphalt (HMA). The study evaluated the effect of replacing the limestone filler in the asphalt limestone HMA mixes and asphalt basalt HMA mixes by CKD. A comparison study was made to compare the effect of replacing the filler by CKD on the mechanical properties of the asphalt mortar (asphalt cement with mineral filler) and HMA mixes. The test results showed that CKD increased the softening point and viscosity of the asphalt cement; however, no changes were required in the mixing procedure nor time of mixing for the HMA mixes. The inclusion of the CKD resulted in an increase of the optimum binder content of the HMA mixes with improving the asphalt resistance for stripping and an increased fatigue life and indirect tensile strength. In addition, the diametral resilient modulus was improved by 130% and 144% for the basalt and limestone mixes, respectively. Moreover, the research proved that the inclusion of CKD in asphalt mixes has no adverse environmental effects on neither the underneath soils nor the underground water.

By combining the nearest surface distribution function and hydration kinetic equation, analytical equations are proposed to determine the pore phase and solid phase evolution in the interfacial transition zone (ITZ). In addition, the numerical models for concrete with a single flat aggregate are constructed based on the CEMHYD3D hydration model. The results show that the degree of hydration is the main factor affecting the ratio of the average porosity to the matrix porosity in the ITZ. With an increase in the aggregate volume fraction and interface thickness, the volume fraction of the ITZ first increases and then decreases. The degree of overlap increases linearly with the interface thickness and the aggregate volume fraction. As the distance from the aggregate surface increases, high-density C-S-H increases, while low-density C-S-H and calcium hydroxide phases decrease. Finally, the predicted results using the analytical equations and numerical simulation are verified by testing via back-scattered electron microscopy, which indicates that the experimental results are more consistent with the predicted results of the analytical model than with those of the numerical model.

Dispersive clays are characterized by deflocculation in the presence of relatively pure and still water, which can lead to erosion, piping, and other earth instability problems. These can be addressed by stabilization with calcium-based materials (e.g., lime), which are nonetheless environmentally harmful, sometimes inefficient, and cannot guarantee the requested performance. Thus, this technical note intends to examine the performance of a dispersive clay amended with two residues: grounded glass powder (from glass waste recipients), and carbide lime (a by-product of the acetylene gas production). The present study is innovative in that it considers the stabilization of a dispersive soil using these sustainable binders. More specifically, it assesses the effect of the following controllable factors in the strength, stiffness, and more importantly durability of compacted dispersive clay-binder blends: ground glass and lime contents, dry unit weight, curing temperature, and molding moisture content. The statistical analysis of the results has shown that curing temperature was the most influential factor regarding strength and stiffness responses, followed by dry unit weight. Regarding the durability results, the dry unit weight and the amount of carbide lime were the most impacting variables. Likewise, such results could be successfully correlated to the adjusted porosity/lime index, thus yielding a series of equations to predict the blends behavior with great coefficients of determination ($R^2$).