Journal of Materials in Civil Engineering

A new fiber cocktail reinforced cement–based materials (NFCRCM) with steel, polyvinyl alcohol (PVA) fiber, and calcium carbonate whisker (CCW) was developed to obtain powerful fire resistance in this paper. The flexural properties, synergistic effects, and microscopic mechanism of NFCRCM at elevated temperature were particularly studied. With the introduction of CCW, the degradation of flexural strength and toughness of steel-PVA fiber cocktail reinforced cement–based materials below 800°C was decreased. Below 800°C, the NFCRCM with 1.5% steel fiber $+0.5\%$ PVA fiber $+3\%$ CCW showed a significant positive hybrid effect in flexural strength and toughness resulting from microscopic crack inhibition and nucleation effect of CCW. When the temperature reached 800°C or above, a negative hybrid effect was generally observed due to thermal decomposition of CCW.

Utilizing Internal Curing (IC) technology in the production of high performance concrete (HPC) for structural purposes is the main focus of this investigation. Pre-wetted lightweight aggregates of perlite and pumice in addition to recycled aggregates were utilized to produce internally cured HPC mixtures. Results show that 10% replacement of crushed sand with pre-wetted perlite yields acceptable compressive strength of the concrete. Also, flexural strength was improved with up to 15% replacement of coarse aggregates with pre-wetted recycled aggregates. Shrinkage testing revealed the superiority of internal over conventional curing through decreased shrinkage and minimized surface cracking, as a result of the enhanced hydration process. However, the results of air permeability and chloride ingress testing showed worsened behavior of internally cured concrete as indicated by the amount of internal cracking and air pockets present after the end of curing process. The empty pores in the lightweight aggregates created an interconnected network of voids that eased penetrability of chlorides to reinforcing bars.

The main objective of this study was to evaluate the use of glass fibers and cement as stabilizing agents for highly expansive soil. Fibers with two aspect ratios (12 and 30 mm in length) were added as percentages of the soil’s dry weight (0.5%, 0.75%, 1%, and 1.5%), the cement was added in two percentages by dry weight soil (2% and 6%). Sixteen groups of treated soil specimens were prepared and subjected to laboratory tests—unconfined compressive strength (UCS) after curing (0, 7, 14, and 28 days), swelling percentage, and California bearing ratio (CBR). Interactions at the interface between the fiber surface and the soil matrix were analyzed by scanning electron microscopy (SEM). Also evaluated was effect of fibers on the design and performance of cement-stabilized subgrade layers according to the Mechanistic-Empirical Pavement Design Guide (MEPDG) to compare the performance of flexible pavement sections modeled using default values and laboratory-established soil properties for inputs. Results indicated increases in UCS and soaked CBR and decreases in swelling tendency. The $6\%\mathrm{cement}/1.5\%$ short fiber mixture resulted in a significant improvement in expansive soil properties over other mixtures.

Poor visibility plays an important role in causing road accidents at night. To minimize accidents, road lighting is needed, but this leads to an increase in electricity consumption. The generation of electricity from fossil fuels causes scarcity in fossil fuels and pollutes the environment. Because of this, researchers have shown interest in the generation of electricity from renewable energy resources. In the meantime, the energy released during vehicle movement, and walking, remained unutilized. This paper aims to show how energy is generated from piezoelectric material by using pressure created by pedestrians and the movement of vehicles. Laboratory studies conducted include wheel tracking tests at various pressures to generate power under certain load repetition. Test samples are prepared based on the Marshall Mix design. The results show that the asphalt pavement prepared with stone aggregate and overburned brick aggregate (OBBA), generates a voltage corresponding to 700 repetitions at 0.56 MPa pressure are 9.21 and 8.89 V respectively. A comprehensive cost analysis is also performed for the economic evaluation of the approach. There is a reduction of cost to the amount of 7.21% in the case of OBBA roads for street lighting compared to the expenditure on the existing stone aggregate roads without lighting. This approach shows a new prospect of low-cost street lighting in rural roads made by OBBA instead of stone aggregate.

This work investigated the effects of the aging process on the performance of asphalt binder under multiple environmental conditions based on multitechnique experimental results. The aging process of matrix asphalt binder with the increase of temperature for 96 h, 192 h, and 288 h was simulated by an aging oven. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to quantify the microcosmic characteristics of asphalt after aging. The results showed that the aging process of asphalt is an oxidation process, and the oxygen-containing functional groups (C═O and S═O) increased with aging. At the macroscopic level, the changes of adhesion properties and bond strength of asphalt were studied by testing the changes in three major indexes. The penetration and ductility of asphalt decreased, and the softening point increased with aging. The changes of rheological performance were tested by dynamic shear rheometer (DSR) and Brookfield viscometer. Mutual transformation of aromatic phenol, colloid, and asphaltene led to an increase in asphalt viscosity and decrease in workability. Antifatigue performance gradually decreased under the action of load with the extension of time. The elastic properties were finally damaged by fatigue.

Provision of affordable construction materials will drastically reduce the housing deficit being experienced in developing countries. This study aimed at investigating the properties of adobe bricks stabilized with rice husk waste and lime. Experiments were conducted on adobe bricks of size ${140\times 100\times 100\mathrm{mm}}^3$ prepared with soil, 0.25%–1% rice husk waste, and 10% lime to carry out a comprehensive assessment of the composite material. The study recorded 62% and 95% improvement, respectively, for compressive and tensile strengths at 28 days of rice husk waste and lime stabilized abode bricks over the unstabilized adobe bricks at 0.75% rice husk content. The absorption coefficient of the rice husk and lime stabilized adobe bricks was found to be between 13% and 60% better than the unstabilized adobe bricks. The rice husk adobe bricks with the addition of lime significantly improved the performance of the bricks against the action of erosion. It was also revealed that there was about 71% cost reduction in the production of the adobe bricks compared with the sandcrete bricks. This study will enhance the effective utilization of rice husk waste in building materials, reduce the cost of building materials, and eventually help to reduce the housing deficit in developing countries by using locally available materials.

Understanding of the healing behavior of asphalt binder is critical for fatigue modeling of asphalt paving materials. Binder-healing characterization based on the traditional time sweep test is time-consuming. The purpose of this study was to compare the damage-healing behavior of various neat and modified asphalt binders with the newly developed linear amplitude sweep healing (LASH) procedure, followed by verification on a simplified LASH (S-LASH) procedure to alternatively estimate binder-healing characteristics with reasonable testing efficiency. Thirteen neat and modified asphalt binders (17 sample conditions) were selected and respectively analyzed with standard LASH and S-LASH. Standard LASH showed that the healing performance of neat binders with the same penetration grade generally aligns with increasing damage. For the neat binders with different penetration grades, softer binders have better healing capacity. The negative aging effect on binder healing was demonstrated. Meanwhile, the healing master curve (HMC) was effective in comparing binder-healing characteristics under prefailure conditions. The healing rate ($H^R$) for the tested binders basically varied from 0.1 to 0.2. Finally, mean absolute error (MAE) analysis of HMC and $H^R$ between standard LASH and S-LASH indicated 50% $S_f$ (damage intensity at failure) with a 900-s rest period to be a critical LASH testing condition to derive reliable healing HMC and $H^R$ values. S-LASH is also recommended to estimate binder healing characteristic with significantly reduced testing time.

Installing flue gas desulphurization systems before particulate collectors in thermoelectric plants generates spray dryer ash (SDA), a mixture of fly ash and sulfur products. SDA carries a large environmental liability, and research to exploit this waste is still incipient. An alternative use for SDA is as raw material for civil construction. Therefore, the objective of this article is to verify the feasibility of replacing hydrated lime with SDA in rendering mortars for façades, and using SDA as a mineral addition to concrete. For this, mortar mixes with 0%, 33%, 67%, and 100% SDA replacement contents were prepared, and tests in fresh and hard states performed. For concrete, mixes with 0%, 5%, 10%, and 20% of SDA added to the cement mass were prepared, and mechanical and durability tests performed. Results show that mortar consistency tends to increase with SDA content, decreasing its workability. Mechanical and durability properties are equal to or higher than those of the reference mix, both in concrete and mortar. Also, mortar with 67% of SDA performs the best.

Toward a sustainable approach, concrete consumption is confronted with new challenges to developing and implementing cleaner technology. Concrete production is associated with excessive use of natural resources along with environmental pollution, which can be partially addressed through cement replacement with industrial waste. Red mud (RM), a toxic by-product of alumina refineries, is a potential supplementary cementitious material that has attracted researchers’ attention in the last years. In this study, 10 mixes were prepared and tested to investigate the simultaneous application of RM (10%, 15%, and 20%) and silica fume (SF) (5% and 7.5%) as cement replacement on concrete properties. The properties of fresh and hardened concrete and its durability were investigated. Overall, the mechanical performance of mixes decreased by increasing RM incorporation, whereas the simultaneous application of 20% RM and 5% SF as cement replacement yielded the same compressive strength as the reference. Furthermore, an evaluation of global warming potential and used water as environmental impacts in addition to a simplified cost analysis was performed on all mixes. Overall, the mix made with 10% RM and 7.5% SF achieved the highest consolidated performance score.

Hot-mix asphalt (HMA), which can be employed as a wearing course on concrete bridge decks, provides a smooth surface for riding. However, some bridge deck asphalt surfaces experienced layer slippage, which is a result of failure of interlayer between HMA overlay and concrete deck due to the lack of layer bonding. In this study, the shear properties of the interlayer between concrete decks and HMA overlay were evaluated through inclination shear tests. Three types of interlayer materials were investigated, including asphalt emulsion, asphalt cement, and epoxy asphalt. The inclination shear test procedure was developed to determine the envelope of shear strength and energy consumption during the shear test. This test was used to evaluate the contribution of internal friction angle and cohesion to shear resistance. Results indicated that as the temperature increased, the contribution of cohesion to shear resistance decreased. The contribution of internal friction angle was associated with the applied normal stresses. The energy consumption of cohesion was sensitive to temperature. Epoxy asphalt interlayer exhibited better shear resistance performance than the other two types of material.

A new perspective on the hydration process of graphene oxide (GO)/cement composites is provided in this paper. The quantitative evaluation of GO on the hydration of four minerals and the dissolution sequence of the four minerals were determined through thermodynamic calculation and quantitative results of solid phases. GO promoted the driving force for dissolution of ${\mathrm{C}}_3\mathrm{S}$, ${\mathrm{C}}_2\mathrm{S}$, ${\mathrm{C}}_3\mathrm{A}$, and ${\text{C}}_4\mathrm{AF}$, evidenced from thermodynamic calculations. Quantitative X-ray diffraction analysis proved that GO tended to preferentially affect the hydration of ${\mathrm{C}}_3\mathrm{A}$ and ${\mathrm{C}}_4\mathrm{AF}$ rather than ${\mathrm{C}}_3\mathrm{S}$ and ${\mathrm{C}}_2\mathrm{S}$ before 2 h of hydration. The amounts of the phase consumption and formation of hydration products increased with the addition of GO. The nitrogen adsorption/desorption test confirmed that the gel pore volume was increased in the presence of GO. The improvement of hydration degree was confirmed by ${}^{29}\mathrm{Si}$ magic-angle spinning nuclear magnetic resonance (MAS NMR). A slight increase of ${\mathrm{Q}}^2/{\mathrm{Q}}^1$ ratio and the main chain length in calcium silicate hydrate (C-S-H) gel can be found in GO-containing systems, which is different from that in pure ${\mathrm{C}}_3\mathrm{S}$ systems, and needs further study.

Magnesium oxychloride cement (MOC) is a promising binder with many advantageous properties over traditional binders. Its main downfall, restricting large-scale use, is its inherent susceptibility to moisture. However, in recent years, niche applications have developed where MOC has been deployed successfully. These include lightweight wall panels, floor tiles, and decorative panels. This paper investigates the effect of molar ratios ($\mathrm{MgO}/{\mathrm{MgCl}}_2$ and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{MgCl}}_2$) and curing conditions on MOC. Findings illustrate that the use of appropriate molar ratios and the implementation of a suitable curing regime can significantly improve the moisture resistance of MOC. After 28 days of immersion in water, the MOC samples lost between 40% and 90% of their strength depending on the molar ratio, demonstrating the importance of correct proportioning. It was also found that curing MOC at temperatures between 20°C and 50°C provides the most stable MOC in humid conditions. These findings add to the current knowledge available on MOC. They will help end users to improve the performance of MOC in its current applications and work toward broadening the range of applications where MOC can be used successfully.

In recent years, corrugated high-density polyethylene (HDPE) pipes manufactured from recycled resins have been on the rise for infrastructure sectors as a result of their numerous advantages. Compared to HDPE pipes made with virgin resins, these recycled pipes help solve the problem of plastic-waste management and the environmental impacts of waste. In addition, using recycled materials makes HDPE pipe more sustainable and cost effective. One question stands out: Will HDPE pipes made with recycled resins have the same performance and durability as virgin pipes under the impact of thermal stress during the burial process, environmental variations, and traffic load? This issue needs to be clarified because the demand for recycled pipes is increasing. The aim of this paper is to improve the knowledge to compare the short-term performance of these two types of pipes. The specimens came from four different North American manufacturers with their own production processes. This study provides more detailed data on physicochemical, mechanical, and thermal properties of HDPE pipes. These properties were tested on laboratory equipment according to ASTM standards. The test results can be used to estimate some aspects of the long-term characteristics of HDPE pipes.

Sustainable engineering discourages the use of conventional soil stabilizers such as lime and cement owing to their higher carbon emission rates. To address these challenges, many researchers considered biopolymer stabilization, a promising green technique in geotechnical engineering practice for treating expansive soils. This study evaluated the performance of two biopolymers, xanthan gum (XG) and guar gum (GG), in improving the unconfined compressive strength (UCS) and consolidation characteristics of an expansive soil subjected to different testing conditions. The dosage of the biopolymers (XG and GG) was maintained at 0.5%, 1%, 2%, and 4% by weight of dry mass of soil mass. Biopolymer treated samples were subjected to desiccator and natural curing conditions (i.e., specimens were exposed to different temperature and relative humidity conditions) for 7, 14, 28, 45, and 60 days. Results showed that the UCS of biopolymer-treated soil increased with increased dosage up to 2% and 1% for XG and GG, respectively; strength significantly improved during the first 28 days of curing under controlled conditions. Improvement of strength was due to increased adhesive strength between gum strands and soil particles. One-dimensional fixed-ring oedometer consolidation test results indicated that the compressibility and swelling characteristics of biopolymer-treated soil increased due to the hydrophilic nature of gum and an increase in the repulsive forces between negatively charged clay particles and the respective functional groups of XG and GG. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were performed on both untreated and biopolymer-treated soil to evaluate the interaction mechanism between soil and biopolymer strands. The microlevel studies confirmed the crosslinking of soil particles by gum strands, which aids in the strength improvement.

Calcium sulfoaluminate (CSA) cement showed a good binding capacity on the external ${\mathrm{Cl}}^{-}$ transported into concretes from its surrounding environment. However, it is unclear whether the same binding mechanism can still apply if the ${\mathrm{Cl}}^{-}$ ions were introduced during a concrete mixing stage when marine resources, without being properly processed, are used as fine aggregates. Experimental work on CSA mixes, with different water/powder, gypsum content, and existences of premixed ${\mathrm{Cl}}^{-}$, has been conducted and showed that the highest binding capacity on premixed ${\mathrm{Cl}}^{-}$ was obtained in the mixes with a higher water/powder and without gypsum. Mineralogy and ${\mathrm{Cl}}^{-}$ binding results of the tested CSA mixes proved that except for the calcium monosulfoaluminate hydrate (Ms), which has been well established with a good ${\mathrm{Cl}}^{-}$ binding capacity, the ${\mathrm{CAH}}_{10}$ produced should also contribute to the binding on premixed ${\mathrm{Cl}}^{-}$. The premixed ${\mathrm{Cl}}^{-}$ in the CSA cement led to a conversion of Ms and ${\mathrm{CAH}}_{10}$ to Friedel’s salt and, meanwhile, shortened the setting time, altered the heat release process, prohibited the generation of microcracks, and resulted in a more densified microstructure.

This paper presents an assessment of recycling of thermally treated fluvial sediments as a supplementary cementitious material (SCM). Different calcination treatments were conducted with temperatures ranging between 450°C and 950°C. For each calcined sediment, a detailed characterization was carried out. Subsequently, blended cements containing 25% calcined sediments (CS) were prepared and tested, including portlandite consumption, hydration kinetics, and compressive strength development (41 and 52 MPa at 7 and 90 days, respectively). The results showed that blended cement based on CS at 750°C provided the most favorable hydration kinetics and the highest compressive strength. An optimization design of experiment was followed to maximize the substitution rate of CS. The resulting multivariable function suggests a replacement rate up to 20% to produce a blended cement equivalent to CEM II 52.5 N, and up to 30% to produce a cement equivalent to CEM II 42.5 N. The reported technoenvironmental findings corroborate the use of CS as SCMs and motivate future research on their effect on concrete properties.

Plastic clays in subgrade may cause major engineering defects such as excessive heave or settlement during the wet season that contribute to the formation of uneven geometry at the pavement surface. Soil stabilization is often a requisite to ameliorate the engineering properties of soft soils or reactive clays. This study investigates the application of nano-silica and nano-alumina to improve the California bearing ratio (CBR) of a local clay. The clay was treated with cement (2%–8%), with nano-additive (0.1%–1.5%) and with cement and nano-additive (3% cement + 0.1%–1.5% nano-additive). The compacted sample was cured for 7 days and subjected to soaked and unsoaked CBR tests. The soaked CBR of the nontreated clay increased by 49% and 27% for 1% nano-silica and 1% nano-alumina treated clay, respectively. Although 3% cement addition improved the CBR of the soaked clay by 28%, the combination of 3% cement with 1% nano-silica and nano-alumina resulted in 196% and 164% increase in the soaked CBR of the nontreated clay, respectively. The combination of nano-additives and cement yielded the same soaked CBR as if 6%–7% cement would have been used. Clay treated with 1% nano-silica and 3% cement achieved the highest CBR value within the tested samples and the sample treated with 1% nano-alumina and 3% cement achieved the lowest free swell potential. The scanning electron microscopy (SEM) micrographs of the treated clay showed the formation of uniform fabric with fewer pore spaces and calcium silicate hydrate (CSH)/calcium aluminate hydrate (CAH) products within the fabric of nano-additive treated clay.

Heavier and faster trains have motivated researchers to seek better ways to absorb the increasing amount of energy imparted to rail foundations and mitigate track deterioration. In recent years, resilient rubber products have attracted more attention due to the high level of damping and the associated energy absorbing capacity of rubber. However, because rubber granules have lower shear strength and higher compressibility compared with natural rock aggregates, a better understanding of how rubber inclusions can influence the track system is imperative, especially before putting these recycled resilient materials into practice. In this paper, the performance of rail track incorporating an alternative subballast layer, i.e., a synthetic energy absorbing layer (SEAL) consisting of a mixture of granulated rubber and mining waste is evaluated through large-scale prismoidal triaxial tests and a computational dynamic model. It is revealed that the amount of granulated rubber in SEAL composites has a significant influence on the dynamic behavior of the track. Fundamentally, increasing the amount of rubber within SEAL leads to a higher vertical deformation, increased energy absorbing capacity, and a higher damping ratio and vibration level, while reducing the ballast degradation, track stiffness, and lateral movement (dilation) of the track. It has been found that 10% of rubber by mass is the optimal amount of rubber to be included in SEAL. This amount of rubber will ensure that a ballasted track can efficiently reduce the dynamic contact pressure at the interface between different track layers (i.e., sleeper, ballast, subballast, and subgrade), and reduce the lateral spread (dilation) and breakage of ballast without generating excess vibration and settlement comparing with traditional track materials.

The feasibility of using sugarcane bagasse ash waste (BA) as an alternative raw material for clinker production was investigated. The effect of the BA on the mineral and mechanical properties of clinker at various sintering temperatures, as well as its environmental impact, was examined. The addition of BA increased the formation of ${\mathrm{C}}_2\mathrm{S}$ at 1,250°C but adversely affected the formation of ${\mathrm{C}}_3\mathrm{S}$ at 1,450°C, which caused compressive strength loss. However, the addition of BA up to 1.0 percent by weight at 1,450°C meets the ASTM standard that requires a minimum compressive strength of at least 19.0 MPa for seven days of curing time. In The EPA toxicity characteristic leaching procedure (TCLP) revealed that concentrations of As, Cr, Pb, Fe, and Mn in the raw BA exceeded applicable limits These elements were not detected or were negligible after the sintering process. Results indicate that sugarcane BA waste can be used as an alternative raw material in clinker production as a means of recycling this waste product, thus contributing to sustainable waste management.

The mechanical properties of wood tend to decrease with increasing temperature under normal atmospheric conditions. A pyrolysis zone develops inside wood when it catches fire, and the surface is charred; it is important to understand the mechanical properties of the wood under the charred surface. In this study, the mechanical properties of Douglas fir wood, such as its compressive, tensile, and bending strengths, were measured under nitrogen atmosphere at nine temperatures between 20°C and 280°C for exposure times ranging from 60 to $120\min$. The results indicated that the wood’s mechanical properties under the nitrogen atmosphere (i.e., oxygen-depleted conditions) decreased with increasing temperature, and the exposure time had little effect on the investigated properties. The mechanical properties of the wood under the charred surface exhibited a nonlinear decrease with increasing temperature due to the hydrolysis reactions. The mechanical properties were accurately described by temperature-dependent equations combining a linear model with three polynomial functions. Scanning electron microscopy revealed that high temperatures in the oxygen-free environment induced severe microstructural damage to the wood.

Recently, magnesium phosphate cement (MPC) has received extensive research attention due to its fast construction, excellent bonding performance, and eco-friendly environment. Thus, some scholars believe that MPC is a promising candidate for the partial replacement of ordinary portland cement in construction engineering. However, most of the existing studies and applications of MPC mainly focused on the properties of cement materials and small construction applications, such as rapid repair and strengthening engineering, while the properties of MPC-based concrete were seldom reported. Moreover, there are still some problems that need to be solved, such as high raw material cost, short setting time, and concrete casting. In general, this greatly limits the mass construction application of MPC. This study discussed a new type of MPC-based self-compacting concrete with high early strength using mineral admixtures and composite retarders. Twenty-one mix proportions of MPC-based concrete were mixed with investigating the effect of aggregate cement ratios ($A/c$), mass ratios of fine aggregate to coarse aggregate ($m_s:m_g$), MgO purity and fineness, the water-cement ratio ($w/c$), and glacial acetic acid (GAC) content and mineral admixtures content on the fluidity, setting time, reaction temperature, and cubic compressive strength (CCS) at different curing ages (1, 3, 7, and 28 days), including a total of 252 concrete specimens, and the optimum mix proportion was also given. Finally, the CCS and setting time of the specimens were compared with those of the open literature, and a 4-m long full-scale beam was cast to verify the feasibility of MPC-based concrete in the actual mass pouring. The results indicated that the mix proportion with an MgO purity of 98 and average particle size of $125\mathrm{\mu m}$ had the highest late strength, higher early strength, longer setting time, and better self-compacting and workability under $A/c=1.3$, $m_s:m_g=1:5$, and $w/c=0.12$, and a mineral admixtures content of 10% FA and 10% MK can be applied to mass construction in practical engineering.

The current method for estimating parallel-to-grain dowel bearing strength of cross-laminated timber (CLT) fasteners applied perpendicular to the face in the US adjusts the length of the fastener to account for the effect of cross-layers rather than modifying the dowel bearing strength. This method is counter to more-commonly used methods in Canada and Europe which adjust the dowel bearing strength of the CLT material and using the original length of the dowel. Currently, there are no experimental data supporting the use of an adjusted fastener length. This paper presented an alternative method for CLT dowel bearing strength assessment according to the US design code. The proposed method produced similar or slightly conservative dowel bearing strength values compared with the current US design method. Experimental results of dowel bearing strength were compared against the current design code, the proposed method, and European and Canadian codes. Standard test procedures were used to evaluate, stiffness, yield strength, 5% offset yield strength and ultimate strength. Greater mechanical properties were found for CLTs containing more parallel-to-grain layers, whereas lower mechanical properties were found for CLTs containing more perpendicular-to-grain layers. The current US dowel bearing strength method, the proposed method, and the European design code produced similar results, which were slightly conservative compared with the experimental values. The proposed dowel bearing strength equation is felt to be an improvement given the ease of use and similarity in form to other design formats.

Steam curing is a commonly used method to obtain cement products with high early strength. It is popularly employed to produce prefabricated units in factory. However, the long-term performance of steam-cured products is not as satisfactory as in situ casting samples cured at room temperature. In order to obtain comparable durability of steam-cured products, a low-alite portland cement (LAPC) is used to manufacture steam-cured materials. The results indicate that the later development of compressive strength is significantly promoted by steam curing to LAPC mortars, consistent to the decrease of specific water absorption, which is associated with the optimization of pore structure and notable improvement of hydration degree at late stage compared with ordinary portland cement (OPC). This work can provide a novel strategy to enhance long-term properties of steam-cured products.

This paper presents a series of single fiber pull-out tests on steel and glass fiber embedded in a cementitious matrix. First, the phase of fiber sliding in the concrete matrix was defined using a shear lag model; then, governing equations for the sliding mechanism were derived using the analytical model. FEM analysis was then used to calibrate the frictional coefficient. Further analysis related to the pressure exerted on the fiber by the surrounding concrete revealed that a smaller fiber diameter would improve bond strength. In terms of the relationship between pressure from the surrounding concrete and the diameter of the fiber, the results showed that a smaller fiber diameter would increase the matrix pressure; improved frictional bond strength and behavior would be expected compared to larger fiber diameters. The results also showed that decreasing fiber diameter by 75% would improve the frictional bond strength by as much as 300% for smooth and straight steel fiber, whereas reducing the fiber diameter by 66% would improve the frictional bond strength by 190% for single glass fibers. In addition, the results showed that a smaller diameter of the fiber improves interfacial properties between the fiber and concrete in fiber-reinforced concrete (FRC) composites.

In coastal areas, concrete of subway infrastructure can be jeopardized by coupled degradation conditions of stray current and sulfate solution. This paper focuses on the effect of stray current on the durability of cement-based materials exposed to sulfate-rich environments. In addition to chemical analysis, mechanical, transport, and microstructural properties of specimens exposed to five conditions were analyzed: (1) control environment with no degradation conditions, (2) stray current, (3) internal mixing sulfate, (4) stray current and internal mixing sulfate, and (5) stray current and external sulfate solution. Experimental results of this study reveal that (1) stray current can exacerbate leaching of cement-based materials, and 40-V stray current results in greater leaching compared to specimens subjected to 20-V stray current; (2) compared to specimens subjected to internal mixing sulfate alone, the combined effect of stray current on the production of gypsum and ettringite is slight due to the increase in particle collision induced by stray current; and (3) stray current has a migration effect on the rate of ${\mathrm{SO}}_4^{2-}$ ions ingress, which significantly aggravates the external sulfate attack on cement-based materials. The primary degradation products were ettringite and gypsum, which results in the cracking and the maximum decrease in strength of 47.1% after exposure to coupled conditions of 40-V stray current and external sulfate solution for 150 days.

The application of geopolymer concrete (GPC) in construction could reduce a large amount of carbon dioxide (${\mathrm{CO}}_2$) emission, which is greatly beneficial to environmental sustainability. Structures made of GPC might be subjected to extreme loading such as impact and blast loads. Therefore, a good understanding of the dynamic properties of GPC is essential to provide reliable predictions of performance of GPC structures subjected to dynamic loading. This study presents an experimental investigation on the dynamic compressive and splitting tensile properties of ambient-cured GPC using split Hopkinson pressure bar (SHPB), with the strain rate up to $161.0{\mathrm{s}}^{-1}$ for dynamic compression and $10.3{\mathrm{s}}^{-1}$ for dynamic splitting tension. The failure mode and damage progress of GPC specimens, energy absorption, and dynamic increase factor (DIF) were studied. Test results showed that ambient-cured GPC exhibited strain rate sensitivity. The compressive and splitting tensile DIFs increased with the strain rate and the ambient-cured GPC with lower quasi-static compressive strength exhibited higher DIFs under both dynamic compression and splitting tension. Empirical formulas were proposed to predict the DIF of ambient-cured GPC. Furthermore, the specific energy absorption of ambient-cured GPC under dynamic compression increased approximately linearly with the strain rate.

In this study, the role of mineral fillers on the microsurfacing mix characteristics and performance was assessed for 10 different combinations of mineral filler type (cement and fly ash) and dosages (0%–3%). The mixes were initially characterized in terms of compatibility, cohesion, and adhesion using Schulze-Breuer and Ruck test, cohesion test, and boiling water test, respectively. Subsequently, the performance of microsurfacing mixes, that is, raveling and rutting resistance, was determined using wet track abrasion test and loaded wheel test, respectively. Results indicated that the filler–emulsion system’s compatibility improved significantly with the addition of cement at the proper dosage. In contrast, mixes with only fly ash as mineral filler had inferior filler–emulsion compatibility. Also, the rate of strength development and adhesion was higher with cement than fly ash. The performance, that is, raveling and rutting resistance, positively correlates with the 60-min cohesion, adhesion, and compatibility (abrasion loss). Interestingly, the combination with 2% cement and 1% fly ash as mineral filler had the best mix characteristic and performance, indicating that the careful selection of the type and the dosage of mineral filler could maximize the durability of the microsurfacing mix.

The present study deals with the severity of delay before carrying out the curing of concrete in hot weather. The effect of delay before curing on the strength and durability of ordinary portland cement concrete (OPCC) and portland pozzolana cement concrete (PPCC) was studied and compared. The strength and durability of the PPCC were observed to be higher when resaturated by water after a delay, especially in case of up to 3 days of delay before curing. The partial resumption of the hydration process was observed in both type of concrete when resaturated after some delay but were observed to be higher in PPCC than OPCC, leading to higher regain in long-term strength and durability. The resaturation promoted the moisture movement and leaching of the calcium hydroxide due to greater space provided by the fly ash particles inside the concrete, which in turn induces the hydration process at a higher rate in PPCC. Therefore, better performance of the PPCC may be expected in a hot and dry environment and where proper curing may be interrupted due to some unavoidable reasons.

In recent years, industries have been demanded for better disposal methods of byproducts. In addition, civil construction in Brazil has been steadily growing, necessitating the development of new resources and the use of new materials. Thus, to reduce the environmental impact and costs, the use of byproducts in civil construction plays an important role. This study presents experimental results on the development of cementitious material-based plates for the construction system of panel slabs using powder technology to reduce the amount of concrete in the slab. In this study, sand was partially (58.1% by weight, C3) and totally (C1) replaced by basalt powder, a byproduct of the basaltic rock beneficiation process. Cementitious plates were obtained by uniaxial pressing at different compaction pressures. The moulded plates (M) using sand and cement were obtained as references. The bending strength at 28 days of curing was $2.50\pm 0.10\mathrm{MPa}$, which is higher than that of the moulded plates ($1.94\pm 0.11\mathrm{MPa}$). It was concluded that pressing and sand substitution by basalt reduced the linear expansion from $0.059\%\pm 0.003\%$ (M) to $0.042\%\pm 0.007\%$ (C3), reducing the risk of cracking. The evaluation of the environmental impact showed the potential of replacing sand with basalt, thus reducing the cost of the material. Therefore, pressed plates with the total substitution of sand by basalt achieved better results related to the moulded plates and demonstrated considerable potential for application in the civil construction industry.

This paper summarizes the results of a study that was conducted to evaluate the influence of different factors on the bond strength between a microsurfacing layer and an existing pavement structure. The considered factors included the tack coat residual application rate and the dilution rate, as well as the residual binder content of microsurfacing mix. To this end, five tack coat residual application rates, two dilution rates, and three different residual binder contents of the microsurfacing mix were evaluated. A new method for preparing and testing samples was developed to measure the microsurfacing mix bond strength using pull-off and torque tests. The results of this study indicated that the microsurfacing samples with tack coat had significantly higher interlayer bond strength values than those without tack coat. The use of a high dilution rate resulted in an excess amount of water, which significantly reduced the interlayer bond strength. The results also indicated that the amount of residual binder content in the microsurfacing mix significantly affected their bond strength with the existing pavement. Thus, the results of this paper indicate that the bonding between the microsurfacing layer and the existing pavement layer is a function of the properties of the microsurfacing mix and the applied tack coat material.

This paper aims to develop an optimal design mixture for concrete containing lightweight expanded clay aggregates (LECA) and silica fume with a holistic view in which the mechanical properties, strength retention at elevated temperatures, costs, and environmental impacts are all considered. Following the response-surface methodology, 30 concrete mixtures were developed, which contained different water-to-cement ratios (0.25–0.5), total cementitious materials contents ($300–700\mathrm{kg}/{\mathrm{m}}^3$ of concrete), and different amounts of LECA (0%–100% of the total aggregate volume) and silica fume (5%–15% of weight of total cementitious material). The mixtures were used to fabricate a total of 240 concrete cylinders, half of which remained at the ambient temperature, whereas the other half were exposed to an elevated temperature of 750°C for 2 h. The results of mechanical tests on specimens were combined with the economic and environmental performance indices to find the optimal mix design. The result showed that using a mixture containing 0.33 water-to-cement ratio, $300\mathrm{kg}/{\mathrm{m}}^3$ cement content, 14.97% silica fume and 84% total aggregate replacement by LECA may lead to the concrete that performs the best in terms of mechanical characteristics, strength retention during fire, and economic and environmental impacts.

The purpose of this paper was to investigate the effect of carbon nanotubes (CNTs) and crumb rubber (CR) on the conventional properties, thermal behaviors, and rheological properties of binders. There are four asphalt types employed in this study. Physical property tests were conducted to determine the conventional properties of the asphalts. In addition, thermogravimetry (TG) and differential scanning calorimetry (DSC) were applied to analyze the thermal behaviors of the asphalts. To appraise the high-temperature rheological properties of the asphalts, temperature scanning (TS), frequency scanning (FS), and multiple stress creep and recovery (MSCR) tests were employed. Furthermore, based on the creep characteristics of asphalt, bending beam rheometer (BBR) tests were utilized to evaluate the low-temperature properties of the binders. The results showed that the combination of CNTs and CR modified the physical properties of the binder, which manifested as reduced penetration and increased softening points, viscosity, and elastic recovery rates. CNTs and CR improved the temperature stability of the binder and reduced the amount of asphalt components participating in a phase change at low temperatures. Moreover, the results of the TS, FS, and MSCR tests indicated that CNTs and CR significantly improved the high-temperature rheological properties of the asphalt. Lastly, the results of the BBR test implied that the composite-modified asphalt exhibited better flexibility and stress relaxation ability at low temperatures than asphalt modified with either CR or CNTs alone.

In order to explore the deterioration characteristics of prestressed concrete under the coupling of freeze–thaw and corrosion, a series of aging tests and three-point bending tests was conducted. Furthermore, the deterioration process was analyzed at the meso-level with the help of computed tomography (CT) technology. The following conclusions can be drawn: (1) within a certain range, under the coupling effect, freeze–thaw and corrosion promote each other, and the degradation effect of the coupling test of freeze–thaw and corrosion is greater than the simple superposition of the two; (2) after the aging test, when the number of freeze–thaw cycles or the corrosion rate are higher, the cracking load and the ultimate load of the prestressed concrete are reduced, but the loss rate of the ultimate load is small; (3) the effective prestress of the aging specimen can be obtained according to the cracking moment, and the calculation formula is simplified according to the mechanical characteristics; and (4) under the coupling of freeze–thaw and corrosion, the size of the cracks and the number of the pores inside the specimen increase, whereas the number of pores in the volume range of $0.1–0.5{\mathrm{mm}}^3$ does not change significantly due to the filling effect of corrosion products.

The study reported herein investigates the effectiveness of nano aluminum trioxide (${\mathrm{Al}}_2{\mathrm{O}}_3$) as a bituminous binder modifier. The study assesses the high- and intermediate-temperature performance of bituminous binders modified with three different percentages (0.5%, 1%, and 2%) of nano ${\mathrm{Al}}_2{\mathrm{O}}_3$. A field emission scanning electron microscope was utilized to study the dispersion of nano ${\mathrm{Al}}_2{\mathrm{O}}_3$ in bituminous binder. Fourier transform infrared spectroscopy analysis was used to understand the nature of the interaction between nano ${\mathrm{Al}}_2{\mathrm{O}}_3$ particles and bituminous binder. Different rheological approaches, like the Superpave rutting parameter, multiple stress creep and recovery test, and time-temperature sweep, were used to study the high-temperature performance of nano ${\mathrm{Al}}_2{\mathrm{O}}_3$–modified bituminous binders. All the methods undertaken in the current study to evaluate rutting susceptibility showed that nano ${\mathrm{Al}}_2{\mathrm{O}}_3$ showed modified binders had a very low propensity to accumulate permanent deformation. Fatigue performance evaluated using the Linear Amplitude Sweep test showed that the incorporation of nano ${\mathrm{Al}}_2{\mathrm{O}}_3$ enhanced fatigue performance. Nano ${\mathrm{Al}}_2{\mathrm{O}}_3$–modified bituminous binders were found to be storage stable as revealed by the storage stability test. The high-temperature thermal stability of the bituminous binders measured using thermogravimetric analysis showed an improvement after nano ${\mathrm{Al}}_2{\mathrm{O}}_3$ incorporation.

Iron phosphate cement (IPC) was prepared through the reaction between magnetite and phosphoric acid. The influences of magnetite-to-phosphoric acid ($\mathrm{M}/\mathrm{PA}$) mass ratio on the hydration temperature, setting behavior, compressive strength, hydration product, and microstructure of IPC pastes were investigated. Results showed that an increase in the $\mathrm{M}/\mathrm{PA}$ ratio can slow down the setting reaction and lower the peak hydration temperature. The compressive strengths of IPC pastes at different ages first increased and then decreased with the $\mathrm{M}/\mathrm{PA}$ increasing from 2.3 to 5.5. The $\mathrm{M}/\mathrm{PA}$ of 2.6 generates the highest compressive strengths for IPC pastes specimens at different ages, which were 21, 27, 30, and 33 MPa at 1, 3, 7, and 28 days, respectively. Furthermore, multiple characterizations including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) revealed that the amorphous iron phosphate phase was mainly formed as the binder phase and the transformation of Fe (II) into Fe (III) occurred during the formation of IPC hydration products.

Water vapor diffusing inside asphalt mixtures is one of the most important ways for water molecules accessing asphalt mixtures to trigger moisture damage. Several diffusion models have been constructed to describe the water vapor diffusion in asphalt mixtures based on Fick’s second law, with the assumption that all water molecules are free. However, when water vapor diffuses in asphalt mixtures, there exists free and bound water molecules simultaneously. Most of the current diffusion models ignore the bound phase of water molecules during the diffusion process. This study developed a three-dimensional (3D) two-phase diffusion model in cylindrical coordinates. Fick’s second law was used to describe the free phase of water molecules, and the relationship between free and bound water molecules was formulated to establish the model. The accumulative water vapor diffusion test was conducted on two types of asphalt mixtures at three relative humidity (RH) levels (17.17%, 51.51%, and 90.14%) at 20°C using the gravimetric sorption analyzer (GSA). The initial RH of the test specimens was set to 0% by evacuating the specimens, and then a steady level of water vapor pressure was applied to achieve the specific RH. The mass of diffused water vapor in the specimens was weighed every 5 s by the magnetic suspension balance of GSA. The raw data, consisting of diffused mass of water vapor versus diffusing time, were obtained. The developed 3D two-phase diffusion model with the first 36 terms was used to fit the diffusion data. Four model parameters—diffusivity of water vapor in asphalt mixtures ($D$), maximum mass of diffused water vapor [$M(\infty )$], probability of free water molecules becoming bound ($y$), and probability of bound water molecules becoming free ($\beta$)—were determined after model fitting. Furthermore, the maximum mass of bound water molecules [$M_1(\infty )$] and the maximum mass of free water molecules [$M_2(\infty )$] could be calculated after determination of these model parameters.

To investigate the effects of sustained loading on crack propagation of concrete, three-point bending tests were conducted on prenotched concrete beam specimens under 90% and 95% of the ultimate load until failure. The load versus crack mouth opening displacement ($P–\mathrm{CMOD}$) curves and the failure age of the beam specimens were obtained from experiments. A numerical model was also proposed to investigate the crack propagation of concrete under sustained loading. The combination of the model with the Norton and cohesive stress relaxation models can reflect the viscoelastic property of uncracked concrete and its fracture process zone. Moreover, an initial fracture toughness-based criterion was proposed to determine the crack propagation under sustained loading. By calibrating the creep parameters of the Norton model and using necessary fracture parameters of concrete, the time-dependent crack propagation and failure time of concrete structures could be predicted. The numerical results indicated that for failure of the concrete specimens under high sustained loading, both the CMOD and crack growth rate first decreased and then increased during the sustained loading duration. There existed an inflection point on both the CMOD and crack growth rate versus time curves, which can be used to characterize the stability of concrete structures under sustained loading. Also, the crack propagation length corresponding to the inflection point was found to be approximately equal to that under static loading.

The unconfined compressive strength (UCS) of soils is essential for both researchers and practitioner geotechnical engineers. UCS is well-understood and standardized for laboratory and field tests. Nevertheless, the large number of environmental and physical governing factors makes the reasonable prediction of UCS complicated. In this paper, a deep learning approach using the multilayer perceptron regressor (MLP) method along with the genetic expression programming (GEP) are used to assess nine variables that contribute to form a reflective multivariate formulation of the UCS. These variables include clay mineral percent (CF), specific gravity ($Gs$), dry unit weight (${\gamma }_d$), saturated unit weight (${\gamma }_{\mathrm{sat}}$), natural unit weight (${\gamma }_t$), moisture content (MC), void ratio ($e$), degree of saturation ($S$), and porosity ($n$). MLP and GEP are implemented to classify, correlate, rank, and reduce the number of variables that govern the UCS through the application of classification algorithms, importance analysis, interrelations and interdependency analysis of the variables, and functional indicators that shape the UCS. The changes of UCS in line with the variations of void ratio are analytically formulated according to both the critical state soil mechanics and the inverse proportionality between the voided area and soil strength. Moreover, the validity of the UCS principle is examined as opposed to the variation of the clay percent in the soil. Findings show that there shall be a breakpoint (clay percentage) after which the concept of UCS is radically changed due to the presence of a significant amount of frictional and drainable materials in the soil. The breakpoint appears to be centralized between 40% and 55%. The study is concluded by identifying the fundamental soil parameters, providing practical models to evaluate UCS, developing fundamental relationships between UCS and void ratio, and defining the breakpoint of clay content.

This paper represents a series of laboratory tests to illustrate the effects of natural zeolite and sulfate environment on the mechanical behavior, hydraulic properties, and microstructure of plastic concrete. Plastic concrete (Pl-C) is comprised of cement, water, aggregate, and bentonite. Because cement production is responsible for a significant amount of carbon dioxide emissions into the atmosphere, cement was replaced in five different percentages of 0%, 10%, 15%, 20%, and 25% by natural zeolite (Z). Moreover, all the specimens were cured in chambers simulating sulfate attack. The mechanical behavior of plastic concrete containing natural zeolite (Pl-CZ) was studied using a series of confined and unconfined compression tests. Hydraulic properties were evaluated using three different confining pressures of 200, 350, and 500 kPa. Scanning electron microscopy (SEM) images were utilized to explore the microstructure of Pl-CZ specimens. The test results show that, although increasing the zeolite content decreased the unconfined strength, peak strength, and the elastic modulus in the early ages, at the later ages, it increased the unconfined strength as well as the peak strength and the elastic modulus, while it decreased the permeability. As illustrated in SEM images, specimens cured in the sulfate environment indicated lower porosity which led to having higher unconfined strength, elastic modulus, and peak strength, along with lower permeability.

Recent works have demonstrated that construction and demolition waste (CDW) aggregates for subbase road pavement applications can be stabilized via the alkali activation of their fine fraction ($d<0.125\mathrm{mm}$). Despite the promising results with this method, the durability of alkali-activated (AA) CDW fines (which act to stabilize CDW aggregate mixtures) need to be investigated. To this end, the effects on pavement materials of the typical degrading actions of water, deicing salts, and the freeze-thaw process were investigated. Samples of AA fines were subjected to water, deicing salt, and freeze-thaw treatments and assessed based on the variation in 28-day flexural and compressive strength values with respect to not-degraded materials. In addition to the fines normally present in CDW aggregate mixtures (i.e., the undivided fraction), samples with fines of the main CDW constituents (concrete, asphalt, bricks and tiles, aggregates and soil) were also prepared for comparison purposes. One set of specimens was cured at 20°C to replicate field conditions, and another was treated at 80°C to replicate optimal conditions for AA materials. Although 80°C heat-treated specimens achieved higher strength values, those values fell sharply following the degrading action of water and deicing salts. In contrast, the specimens cured at 20°C retained their mechanical property values even after exposure to water and deicing salt degradations.

The main objective of this study is to quantitatively determine the magnetic field capability of a Helmholtz coil in orienting steel fibers and show the correlation between the fiber orientation and tensile strength of steel fiber-reinforced concrete (SFRC) materials. Using X-ray computed tomography (CT), the exact distribution of fiber orientations was computed for both the magnetized and nonmagnetized samples containing 3, 5, 7, and 9 mm long fibers. The probability of a fiber being aligned parallel to the length of the specimen increased by 28.33%, 44.05%, 49.33%, and 27.12% for fibers with lengths of 3, 5, 7, and 9 mm, respectively. Finally, the uniaxial tensile strength of each sample was determined using direct tension tests. The average tensile strengths of the samples increased 0.51, 0.46, 0.64, and 0.76 MPa for the 3, 5, 7, and 9 mm fiber lengths, respectively. On average, the tensile strength of the samples increased by 27% after being exposed to an external magnetic field.

This research investigated the effect of superabsorbent polymers (SAPs) (0%, 0.17%, 0.35%, and 0.49% of cement content by weight) on the correlation between autogenous shrinkage (AS) and internal relative humidity (IRH) of high strength concrete under sealing conditions. An integrated device was designed to measure the IRH and AS of concrete simultaneously. Experimental results and analysis indicated that (1) the IRH of the SAP-modified concrete at 28 days and the critical time of the IRH increased as dosages of SAPs increased; (2) the expansion of the SAP-modified concrete at an early age was obvious within the first day, and the expansion peak increased as the dosages of SAPs increased; (3) the AS at 28 days and the AS rate of the SAP-modified concrete decreased as the dosages of SAPs increased; and (4) a prediction model for the AS of SAP-modified concrete was proposed considering concrete relative humidity and the quantity of internal curing water.

This paper presents the results of the experimental and analytical studies of the mechanical and thermal properties of laterite composites mixed with reprocessed low-density polyethylene waste (LDPE), calcium phosphate (CaP) and phosphogypsum wastes, and biochar to form brick composites. Bricks with mixtures of 20% by volume LDPE, 15% by volume CaP, and 15% by volume gypsum were shown to have excellent compressive strength, flexural strength, and fracture toughness. The composites with 1% by volume LDPE and 15% by volume biochar had the best blend of mechanical properties, such as flexural strength and fracture toughness, after sintering for $\sim 24\mathrm{h}$. There was a linear association between the strength and the weight loss of the bricks. Scanning electron microscopy and optical microscopy images revealed evidence of crack bridging by LDPE particles. The laterite–LDPE composite mixed with 5%, 10%, and 15% by volume biochar had sintering temperatures of $\sim 850°\mathrm{C}$, $\sim 720°\mathrm{C}$, and $\sim 710°\mathrm{C}$, respectively, after undergoing softening, cold crystallization, and cooling.

Sandy gravel dams with clay core walls are a widely used dam type, and the rolling density of sandy gravel material is evaluated by the relative density $D_r$. Consequently, designing the optimal $D_r$ value is related both to the safety and health of the dam body and the time and cost of construction, but finding the optimal $D_r$ value has not yet been satisfactorily resolved. Here, eight evaluation indices—strength-related, deformation-related, and compatible deformation-related indices—are proposed, and relationships between the indices and the $D_r$ value of shell material are studied through three-dimensional (3D) finite-element calculations. Three efficacy functions that correspond to the above three types of evaluation indices are defined, and multiobjective programming (MOP) is used to analyze the optimal $D_r$. The suggested constraint condition in MOP is $D_r\in [0.75,1]$ rather than $D_r\in [0,1]$. Four MOP schemes based on different weight allocations for the three efficacy functions are suggested. The compatible deformation control scheme was the optimal design for the project, and the optimal designed relative density of sandy gravel is 0.862. The proposed design method meets strength, deformation, and compatible deformation requirements for the dam body.