Journal of Materials in Civil Engineering

Materials providing an improvement and conformance to increasing technical and ecological requirements plays a crucial role in the sustainable development of resource- and energy-intensive cements and concretes. Over the past decades, an extensive resource base of natural and technogenic materials has been established for alkali-activated materials (AAMs) and is being continuously expanded with the rapid development of the alkali-activation theory and technology and the ongoing studies of many research groups around the world. This paper reviews the recent progress in fiber reinforcing; potential assessment of various aluminosilicates for alkali activation (AA) and modification of alkali-activated cements (AACs); replacement of natural aggregates with wastes and by-products; replacement of expensive alkali activators with more appropriate alternatives; and modification of AACs by chemical admixtures, metals, and nanomaterials. This literature review was carried out from the perspectives of the suitability of materials and their effects on the efficiency improvement of engineering, economic, and ecological performances AAMs.

Concrete, a well-established and well-characterized building material, is also the most used building material in the world. However, many old and new-build structures suffer from premature failures due to extensive deterioration and decreased load-bearing capacity. Consequently, structural monitoring systems are essential to ensure safe usage of concrete structures within and beyond their designed life. Traditional monitoring systems are based on metallic sensors installed in crucial locations throughout the structure. Unfortunately, most of them have relatively low reliability and a very short life span when exposed to often very harsh environments. The ideal solution is therefore to develop a smart concrete having self-sensing capability. A number of studies have shown that conductive cementitious matrixes will undergo changes in their electrical resistivity with variations of stresses and strains or development of microcracking. This behavior can be used as a reliable tool to measure changes. This review provides a comprehensive overview of several nonconductive matrixes, with a special focus on portland cement–based materials, showing self-sensing capabilities by description of detection mechanisms, sensing capabilities, limitations, and potential applications.

An accurate bond-slip model is of fundamental importance to analyze the response of fiber-reinforced cementitious matrix (FRCM) composite-strengthened structures. This study proposes a method to determine the bond-slip model of FRCM-concrete joints based on longitudinal fiber strains. First, discrete strain profiles measured with strain gauges were fitted by a continuous function $\epsilon (y)$, where $y$ is the coordinate along the bonded length. Then the slip $s(y)$ and shear stress $\tau$ ($y$) along the composite bonded length were obtained by integration and derivation of $\epsilon (y)$, respectively. The debonding load and peak load from single-lap direct shear specimens were predicted by the fitted function $\epsilon (y)$ and showed good agreement with test results. From the plot of the $\tau (s)$ relationship obtained from $\epsilon (y)$, an alternative, closed-form, continuous bond-slip relationship was obtained based on the maximum shear stress ${\tau }_m$ and the corresponding slip $s_m$. The fracture energy was compared for both relationships and was in reasonable agreement with values reported in previous studies.

The increasing need to calibrate and validate multiscale numerical models cries out for new experimental devices and methodologies. This paper presents an experimental measurement device of the lateral displacement of concrete specimens having noncylindrical cross section under uniaxial compression testing. This study provides the experimental and data monitoring methodologies needed for the calibration and validation of multiscale models. The system’s intrinsic innovation relates to its ability to measure lateral displacement of noncylindrical concrete specimens. This paper demonstrates its implementation for rectangular cross sections, whereas other shapes require minor modifications. The main challenge of obtaining reliable measurements concerns the attachment of the gauges to specific spots along the specimen during loading. Trying to validate the suggested setup using a digital imaging correlation (DIC) setup failed due to separation of the monitored surface from the rest of the specimen. Therefore, the setup was validated by a test on an aluminum specimen with known mechanical properties. Finally, the methodology has been applied to calibrate and validate mesoscale numerical simulations using the lattice discrete particle model.

Concrete spalling in fire is a common occurrence which has been attributed to two main mechanisms, thermo-mechanical caused by differential thermal gradients and moisture clog due to the buildup of pore water pressure which act either independently or in combination. Quantifying the magnitude of these variables associated with the spalling mechanisms is the scope of this paper. Nine unloaded large-scale reinforced concrete panels tested in a vertical configuration were exposed to a hydrocarbon fire on one side for a duration of 60 min. Two thicknesses (100 and 200 mm) and two compressive strengths (25 and 80 MPa) were investigated. Specimens were instrumented in situ with thermocouples and pore pressure gauges. The degree of spalling was quantified as mass loss from material dislodgment and mass loss due to water evaporation. No consistency in results were observed between identical samples, particularly for 80 MPa 200 mm thick samples that had total spalling mass losses of 26%, 44%, and 54%, respectively. However, explosive spalling only occurred in the thicker 200 mm specimens. Water pooling was observed across all specimens, which resulted in saturation toward the unexposed side due to the drying front derived from the moisture clog mechanism and the migration of water through the cracks developed by flexural forces. This caused strength deterioration of the concrete that ultimately led to spalling. This investigation, in alignment with other works, showed that despite the specimen size or thickness, explosive spalling occurs when all contributing factors coincide at a converging point during the heat exposure. This explains why explosive spalling occurs randomly in a majority of tests reported, and there is no repeatability between identical samples.

Surface soil erosion is one of the most common slope degradation processes. In this study, microbial calcification (MC), a stimulated natural biocementation process, was investigated for its feasibility as a sandy-slope surface erosion control method. An artificial model slope at 30° was treated by MC via the surface spraying method at three cementation solution concentrations (0.2, 1.0, and 2.0 M). Simulated rainfall was sprayed on the slope surface at $5\mathrm{mm}/\min$ for 30 min. Results show that MC treatment with 0.2- and 1.0-M cementation solution improves surface erosion resistance in terms of observed erosion pattern with time, soil loss weight and rate, and outflow properties. However, MC treatment with 2.0-M cementation solution does not improve surface erosion resistance. Instead, substantial soil loss is observed under rainfall impact while soil is washed away in cemented aggregates. At the end of the rainfall erosion test, microstructural features of the surface samples were identified by scanning electron microscope (SEM) observation. It is found that the effectiveness of MC for sandy-slope surface erosion control is determined by (1) overall ${\mathrm{CaCO}}_3$ precipitation content, (2) treatment depth, and (3) competence between ${\mathrm{CaCO}}_3$ crystal growth and nucleation process.

Cement-based materials used as a sealing layer in compressed air energy storage (CAES) underground storage caverns have high requirements for gas permeability and resistance to thermal stress. This experimental study investigated factors reducing the initial gas permeability and the effect of thermal cycles on the gas permeability of mortar samples. The incorporation of silica fume, curing age of mortar samples, and confining pressure applied in the experiment were considered. Results of measurements of the real-time gas permeability of the mortar samples show that the gas permeability of mortar samples can be drastically reduced by replacing part of the cement with silica fume. After the samples were subjected to multiple heating–cooling cycles, gas permeability increased from the initial state. Extending the curing age and increasing the confining pressure improved the thermal stability of the mortar sample and reduced the effect of heating/cooling cycles on gas permeability.

The modulus of the existing asphalt concrete (AC) layer, back-calculated from nondestructive pavement tests, is a crucial input for an accurate overlay design in the pavement mechanistic-empirical (ME) design system. However, nondestructive testing (NDT) data for this purpose are not always available for network-level rehabilitation analyses. To address this issue, this paper proposes a regularized regression method to accurately estimate the moduli with data readily available from pavement management systems, including distress, structural information, and climatic conditions. The data from the Long-Term Pavement Performance (LTPP) database were used for model training. Prediction performance comparisons among three regularization regression methods (ridge, elastic net, and lasso) and the ordinary least-squares regression were conducted. The results showed that the elastic net regression outperformed the other three methods in terms of predictability and interpretability. The mean squared errors of the regularization regression methods were found to be considerably lower than that of the ordinary least-squares regression. The moduli estimated by the regularization methods were very close to the back-calculated ones from the LTPP database, which demonstrated the feasibility of estimating the moduli of existing pavement when in paucity of NDT data. After applying the estimated moduli in the pavement ME design system, the predicted alligator cracking was closer to the measured data than those without these data.

This paper investigates the effect of replacing silica sand (SS) with waste rubber aggregates on the long-term mechanical and transport properties of structurally engineered cementitious composites (ECCs). ECC mixtures prepared with 0 to 30% crumb rubber sand (CRS) or 30% to 40% powder rubber sand (PRS) were tested for up to 360 days of curing. The addition of ground granulated blast-furnace slag (GGBS), metakaolin (MK), and silica fume (SF) in PRS-ECCs with incorporated binary mineral admixture–based fly ash (FA) was also investigated. The compressive and flexural strengths, midspan beam deflection capacity, chloride permeability, water sorptivity, and electrical resistivity of 17 ECC mixtures were studied at different ages. The diverse aggregate vicinities and their interfacial transition zone aspects were analyzed at 28 and 360 days using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results indicate that, from 28 to 360 days of curing, ECC mixtures with CRS and PRS exhibited lower mechanical strengths and enhanced deflection capacities compared to the control mixture. However, ECCs with up to 40% PRS content showed better transport properties than the control ECC mixture, especially when incorporating a binary mineral admixture, including MK and FA. Microstructural investigations confirmed the presence of some gaps at the rubber aggregate interface, which healed partially or completely with long curing times.

The objective of this study is to evaluate the efficiency of a new generation of ultraviolet (UV) light–induced self-healing polymers in enhancing the durability of asphalt mixtures and improving their self-healing capabilities. Mixtures were prepared using two different binders, with and without recycled materials, and self-healing polymers. Results showed that the addition of recycled asphalt materials to mixtures prepared with an unmodified binder (PG 67-22) negatively affected healing recovery at room temperature. The self-healing properties of the mixtures were improved by increasing the healing temperature from 25°C to 50°C, which indicates the temperature dependency of the self-healing properties of asphalt mixtures. The addition of 5% self-healing polymers to the control mixture followed by 48 h of UV light exposure resulted in an increase in the self-healing properties of the mixtures prepared with PG 67-22 binder. Semicircular bending (SCB) test results showed that the incorporation of self-healing polymer and 48 h of UV light exposure improved the cracking resistance of the mixture. Loaded-wheel tracking (LWT) test results showed that the addition of the self-healing polymer caused an increase in the rut depth of the samples prepared with the unmodified binder. However, the final rut depth was less than 6 mm, which is an acceptable rutting performance. Thermal stress restrained specimen test results showed that self-healing polymer improved the low-temperature cracking performance of the mix by increasing the fracture load and decreasing the fracture temperature.

The use of machine learning (ML) techniques to model quantitative composition–property relationships in concrete has received substantial attention in the past few years. This paper presents a novel hybrid ML model (RF-FFA) for prediction of compressive strength of concrete by combining the random forests (RF) model with the firefly algorithm (FFA). The firefly algorithm is utilized to determine optimum values of two hyper-parameters (i.e., number of trees and number of leaves per tree in the forest) of the RF model in relation to the nature and volume of the dataset. The RF-FFA model was trained to develop correlations between input variables and output of two different categories of datasets; such correlations were subsequently leveraged by the model to make predictions in previously untrained data domains. The first category included two separate datasets featuring highly nonlinear and periodic relationship between input variables and output, as given by trigonometric functions. The second category included two real-world datasets, composed of mixture design variables of concretes as inputs and their age-dependent compressive strengths as outputs. The prediction performance of the hybrid RF-FFA model was benchmarked against commonly used standalone ML models—support vector machine (SVM), multilayer perceptron artificial neural network (MLP-ANN), M5Prime model tree algorithm (M5P), and RF. The metrics used for evaluation of prediction accuracy included five different statistical parameters as well as a composite performance index (CPI). Results show that the hybrid RF-FFA model consistently outperforms the standalone ML models in terms of prediction accuracy—regardless of the nature and volume of datasets.

Construction waste slag–clay mixture has been widely used as filling material, which has significant social, economic, and environmental protection benefits. However, the slag–clay mixture undergoes significant particle breakage when compacted in practical engineering, which affects the compaction property of the mixture. To determine the compaction property of slag–clay mixture, a series of compaction tests was conducted to investigate the influences of slag content and initial gradation on its compaction behavior. The factors affecting particle crushing were investigated. The results showed that the optimum water content of the slag–clay mixture decreases, whereas the maximum dry density increases first and then decreases, as the slag content increases. The optimum slag content of slag–clay mixtures is 30% despite different initial gradations. The results also showed that the breakage degree of slag particles increases with slag content. Breakage is greater in slag with uniform gradation and slag with large particles. The compaction and the crushing behavior of slag–clay mixture can be well explained by the structural model of a binary mixture.

The prediction of fatigue cracking is one of the critical items to assess the service life of flexible pavements. Accordingly, researchers have developed several test methods and index parameters to predict pavement performance based on fatigue damage. Recently, researchers at North Carolina State University developed a new index parameter, referred to as apparent damage capacity ($S_{\mathrm{app}}$), which is based on the simplified viscoelastic continuum damage (S-VECD) model. This index parameter is obtained by performing cyclic tension tests and using the simplified viscoelastic continuum damage model with a dissipated pseudoenergy concept (the so-called $D^R$ failure criterion). This paper presents $D^R$ and $S_{\mathrm{app}}$ values for 10 different asphalt mixtures commonly used in Georgia. The relationships among $D^R$, $S_{\mathrm{app}}$, and mix design factors such as nominal maximum aggregate size (NMAS), asphalt binder type, and binder content were investigated to determine ways that these factors affect $D^R$ and $S_{\mathrm{app}}$. The $S_{\mathrm{app}}$ parameter was found to have a strong relationship with the polymer modification and NMAS of the asphalt mixtures. Based on the experimental data and the Georgia Department of Transportation’s practical guidelines for specific mixtures, this study developed $S_{\mathrm{app}}$ threshold values for different traffic levels. Finally, the experimental data were used to run pavement performance analyses using AASHTOWare Pavement ME Design software and FlexPAVE; the latter uses the S-VECD model for cracking evaluation. Top-down and bottom-up cracking performance was determined from a 10.2 cm (4 in.) thick single-layer pavement and a 15.2 cm (6 in.) thick 2-layer pavement. The results are used to discuss the different ways the two programs evaluate cracking.

Pervious concrete (PC) has gained acceptance as a sustainable pavement material because of its ability to capture and infiltrate stormwater through the pavement system, and subsequently augment groundwater recharge. However, a systematic methodology that estimates and assesses the in situ infiltration characteristics of pervious concrete pavement (PCP) systems has yet to be developed. The objective of this study was to establish a rational methodical approach that evaluates the infiltration rates through PC and granular subbase (GSB) layers in a PCP system by utilizing experimental and analytical techniques. Over 20 field test slabs, each measuring $4\times 4\times 0.15\mathrm{m}$, were constructed along a 120-m long stretch using one single PC mix type overlaid on a 0.25-m GSB layer. An experimental field test was designed to estimate the in situ infiltration rate through the PCP system, and was found to vary between 0.11 and $0.32\mathrm{cm}/\mathrm{s}$. Further, an infiltration test was performed on PC slabs to measure the surface infiltration rate (SIR), which ranged from 0.10 to $1.28\mathrm{cm}/\mathrm{s}$. Using the principle of conservation of mass, which assumes that the flow rate through each layer in a PCP system is identical, the infiltration rate of the GSB layer was found to be $0.07–0.11\mathrm{cm}/\mathrm{s}$. A significant contribution of this study was the development of a generic approach toward characterizing the major in situ infiltration parameters of multilayered PCP systems that incorporate a base and subbase layer, which have the potential to serve as effective hydraulic conduits through the system.

During the last 20 years, Superpave pavements were built using mostly coarse-graded mixes as opposed to fine-graded mixes. This is because coarse mix requires less asphalt binder than a fine mix, whereas both mixes fulfill the Superpave criteria. Recently, it was observed nationally that the Superpave mixes have good field rutting performances but poor cracking performances. A common belief now is that fine mixes could have solved this cracking issue of Superpave. The idea is that the fine mixes would have less air voids which would transmit less air and water, and thereby, fine mixes would have less aging/cracking and moisture damage, respectively. To this end, this study evaluates whether a fine-graded mix has better performances than a coarse-graded mix. Both mixes have identical performance grade binder, reclaimed asphalt pavement (RAP) content, and aggregate source and were collected from a road site on New Mexico (NM) 14, where they were applied side-by-side to construct two-lane 2-mile sections in each direction. Both mixes were tested for dynamic modulus, Hamburg wheel tracking device (HWTD) rutting, beam fatigue (BF), thermal stress restrained specimen test (TSRST), and semicircular bending (SCB). The coarse mix shows higher dynamic moduli and better rutting performances than the fine mix, which were expected. The fine mix failed (more than 12.5 mm rutting for 10,000 passes) in HWTD rutting. The coarse mix shows better fatigue performance than the fine mix. Critical fracture energy release rate ($J_C$-integral) from the SCB test demonstrates that both mixes have similar crack resistance properties. TSRST test results demonstrate higher failure strength and lower failure temperature for coarse mix compared with fine mix. Therefore, simply replacing coarse mix with fine mix cannot resolve Superpave’s cracking issue.

The present study investigated the application potential of crushed gravel (CG) aggregates in asphalt mixes. Three different types of aggregates; i.e., gravel (G), crushed gravel (CG), and crushed stone (CS); were used for shape characterization and mix performance evaluations. The CG aggregates were produced by crushing G aggregates using a single-stage jaw crusher. The aggregates of six different sizes; i.e., P19-R12.5 (passing through 19 mm and retaining on 12.5 mm), P12.5-R9.5, P9.5-R4.75, P4.75-R2.36, P2.36-R1.18, and P1.18-R0.600; were considered in this study. The aggregate was subjected to shape characterization using a digital image-based aggregate image measurement system (AIMS). The cumulative shape index (CSI) for each aggregate shape parameter was determined for three control (i.e., 100% G, 100% CG, and 100% CS) and three mix blends (i.e., 25% CG + 75% CS, 50% CG + 50% CS, and 75% CG + 25% CS). The performance of the asphalt mixes under shear, compression, and moisture damage was evaluated using an aggregate slip test (AST), stability (S), and moisture damage potential tests, respectively. Additionally, the correlations between mix performance and CSIs were drawn. The results showed that the crushing of G aggregates significantly improves the angularity, texture, and form2D, but decreases the sphericity. The CG aggregate angularity increases with the decrease in aggregate size. The gradation with 100% G had the least cumulative angularity index (CAI) and cumulative texture index (CTI) followed by the 100% CG and the 100% CS gradations. However, in the cases of cumulative sphericity index (CSpI) and cumulative form2D index (CF2DI), varying trends were observed. The performance tests revealed that all but the 100% G mix combinations satisfied the stability and moisture resistance criteria of asphalt mixes. Also, mixes with 100% CG aggregates offered a relatively higher rutting resistance than the 100% G aggregates. The CAI, CTI, and CSpI exhibited positive correlation with stability and rutting resistance, whereas the CF2DI showed negative correlation. Further, the AST test more effectively captured the effects of aggregate shape than stability. The study concluded that even 100% CG aggregates can be used in asphalt mixes without any detrimental effects on performance.

In this study, quasi-static tensile tests of high-strength steel rebars, after exposure to 20°C–1,300°C, and dynamic tensile tests at a strain rate of up to $0.25{\mathrm{s}}^{-1}$, after exposure to 20°C–900°C, were conducted to understand the effect of elevated temperature and strain rate on the mechanical properties of the high-strength steel rebars. The coupled effect of high temperature exposure and strain rate was discovered; the strength equation and the constitutive model of high-strength steel rebars were proposed with the coupled effect taken into account. Specifically, the color and weight of steel rebars, after exposure to above 700°C, change significantly because of oxidation. High temperature significantly affects the fracture morphology of rebars when statically tested, but it has little effect when dynamically tested. High-strength rebars begin to degrade at 500°C with their residual yield and ultimate strength remaining greater than 60% and 70%, respectively, after exposure to temperatures above 900°C. Their strengths are affected by strain rate more significantly at higher temperatures because of microstructural changes. The hardening strain is related to both temperature and strain rate; the ultimate strain is affected by temperature only.

Temperature of in-service pavements can be regulated by varying the thermophysical properties of the pavements. Although empirical correlation between the thermophysical properties and pavement temperature has been documented, the theoretical basis of this correlation has not been answered completely. This study theoretically models the maxima, minima, and amplitudes of pavement surface temperature, considering the influence of thermal conductivity, heat capacity, density, surface emissivity, and albedo of the pavement on its surface temperature fluctuation. The theoretical model is validated against the simulated pavement surface temperature, which is predicted by a one-dimensional heat transfer model. Results show that the pavement surface temperature fluctuation correlates linearly with the reciprocal of the square root of the thermal conductivity, heat capacity, and density. Increasing one, both, or all of these factors decreases the maximum surface temperature, but raises the minimum surface temperature. In comparison, the maxima and minima of the surface temperature decrease linearly with the emissivity and the surface albedo. Increasing the surface albedo is the most effective way to decrease the pavement surface temperature, whereas the emissivity plays a secondary role in this capacity.

Soil–cement–bentonite (SCB) vertical cutoff walls are commonly used to control the flow of contaminated groundwater at polluted sites. However, conventional backfill consisting of ordinary portland cement (OPC) is associated with a relatively high ${\mathrm{CO}}_2$ footprint. Potential chemical interactions between OPC and bentonite could also undermine the long-term durability of SCB materials. This paper proposes an innovative backfill material for cutoff walls that is composed of MgO-activated ground granulated blast furnace slag (GGBS), bentonite, and soil. The OPC–soil, OPC–bentonite–soil, and OPC–GGBS–bentonite–soil backfill materials are also tested for comparison purposes. The workability of fresh backfills and unconfined compressive strength of aged backfills are investigated. The hydraulic conductivities of aged backfills permeated with tap water, ${\mathrm{Na}}_2{\mathrm{SO}}_4$, and Pb–Zn solutions are assessed. The unconfined compressive strength and hydraulic conductivity of the proposed backfill permeated with tap water are in the range of 230–520 kPa and $1.1\times {10}^{-10}\mathrm{t}\mathrm{o}6.3\times {10}^{-10}\mathrm{m}/\mathrm{s}$ after 90 days of curing, respectively, depending on the mix composition. The hydraulic conductivity of the proposed MgO–GGBS–bentonite–soil backfill permeated with sodium sulfate (${\mathrm{Na}}_2{\mathrm{SO}}_4$) or lead–zinc (Pb–Zn) solution is well below the commonly used limit, while the OPC–bentonite–soil backfill shows a significant loss in impermeability. Environmental and economic analyses indicate that, compared with conventional backfill made from OPC–bentonite–soil mixtures, the proposed backfill reduces ${\mathrm{CO}}_2$ emissions by approximately 84.7%–85.1% and costs by 15.3%–16.9%. The environmental and economic advantages will promote the use of MgO-activated GGBS–bentonite mixtures in cutoff walls and lead to their increased application in land remediation projects.

An experimental study was performed to investigate the fragment distribution, fractal dimension, and energy dissipation of stabilized soil subjected to impact loading. Dynamic uniaxial compression tests on cement–fly ash–stabilized soil with different sand contents ($S=0\%$, 8%, 16%, and 24%) were conducted using a 50-mm-diameter split Hopkinson pressure bar (SHPB) under 0.3, 0.4, and 0.5 MPa gas pressures. Then the experimental results were analyzed on the basis of fractal theory and energy dissipation principles. Experimental results showed that the average size of broken fragments decreases rapidly as the gas pressure increases from 0.3 to 0.5 MPa. In addition, the average size of broken fragments also indicates a decreasing trend with increases in sand content. The distribution of broken fragments obtained from SHPB tests has a fractal characteristic. The fractal dimension of impact fragmentation exhibits an increasing trend with increasing sand content, and it increases linearly when the gas pressure increases from 0.3 to 0.5 MPa. Moreover, the dynamic compressive strength can be enhanced significantly by adding 8% sand to stabilized soil, and the dynamic compressive strength of stabilized soil increases in a quadratic function with increases in fractal dimension. Based on energy dissipation analysis, it is easily observed that the energy dissipation density linearly increases with increases in gas pressure; moreover, it first increases and then decreases as the sand dosage increases from 0% to 24%. The addition of 8% sand is regarded as the optimum content to obtain a preferable energy absorption capability of stabilized soil with sand. In addition, with an increase in the fractal dimension, the energy dissipation density presents a logarithmically increasing tendency. The greater the energy dissipation density, the more efficiently the cracks propagated and became connected, the more severe the impact fragmentation, and the larger the fractal dimension obtained. Finally, an empirical equation is proposed to further describe the variations of energy dissipation density versus fractal dimension and dynamic compressive strength.

To obtain a waterproof binding material for bridge decks with properties of high bonding strength at high temperatures and high flexibility at low temperatures, a waterborne epoxy resin–polyurethane–emulsified asphalt (WEPEA) was prepared which can be constructed in a cold state and cured rapidly at room temperature. The composition of WEPEA was determined based on the tensile strength and elongation at breaking. The road performance of WEPEA was systematically investigated based on its high-temperature bonding properties, low-temperature flexibility, adhesion, waterproofing performance, and aging resistance. In addition, the performance of WEPEA was compared with that of SBS-modified asphalt and rubber asphalt. The viscosity variation and micromorphology of WEPEA were investigated, and the compatibility and stability of each component were verified. The results show that waterborne polyurethane can effectively improve the flexibility of emulsified asphalt with a high content of waterborne epoxy resin. WEPEA exhibited excellent bonding strength, crack resistance and anti-impact properties, adhesion to aggregates, and water stability. These properties of WEPEA were all superior to those of the SBS-modified asphalt and rubber asphalt.

Accelerated bridge construction (ABC) technologies are being adopted by state departments of transportation. ABC requires that bridge precast concrete components be effectively connected to one another in the field. Currently there is a trend of using ultra-high performance concrete (UHPC) to connect precast bridge deck panels or girders in 15-cm (6-in.)-wide closure pours between the precast elements. As an alternative, the Idaho Transportation Department (ITD) is proposing to place high-early strength (HES) concrete with polypropylene fibers in 25-cm (10-in.) closure pours, with standard reinforcing bars at the top and headed bars at the bottom. The advantages of this alternative material are the reduction in costs and construction time. An experimental research project was carried out to determine the effectiveness of the alternative material and connection detail. The experimental work consisted of standard test specimens and specimens with headed bars. Among the six closure pour concrete mixes considered, the mix containing HES concrete, $0.89\mathrm{kg}/{\mathrm{m}}^3$ ($1.5\mathrm{lb}/{\mathrm{yd}}^3$) of fiber, and shrinkage-reducing admixture performed the best. It had the largest compressive strength, the largest tensile strength, the lowest shrinkage, and the largest bond strength. Headed bar tensile strength tests with the optimum mix resulted in bar stress of 67% of the steel specified yield strength. Flexural testing of beams composed of two precast segments with the optimum mix in the 25-cm (10-in.) closure resulted in ultimate moment capacity of about $55\mathrm{kN}·\mathrm{m}/\mathrm{m}$ ($147\mathrm{kip}\text{-}\mathrm{in.}/\mathrm{ft}$).

Permanent deformation of granular base–course materials under repeated vehicle load is an important characteristic that is required to be considered in pavement design. In Alaska, due to the extreme climatic condition, the granular base–course materials in a pavement structure usually undergo significant permanent deformation, which is typically reflected by rutting, cracking, and eventually pothole problems on the pavement surface in spring. Over the years, research efforts on the permanent deformation of base materials, especially for cold regions pavements, have been very limited. To investigate the permanent deformation of granular base–course materials in cold regions, a series of one-dimensional frost heave tests under two extreme water access conditions (i.e., limited and free water access) were conducted on Alaskan granular materials with different fines and initial moisture contents using a one-dimensional frost heave cell. After the freezing process, the repeated-load triaxial test was then performed to investigate the permanent deformation under frozen and subsequent nonfrozen conditions. Test results indicated that frost heave and subsequent permanent deformation of base-course materials were highly dependent on the water access condition during freezing. The fines and water contents, temperature, temperature gradient, stress state, and their coupling effect also played important roles in the permanent deformation of the base-course materials. In addition, regression analyses using a mechanistic-empirical design guideline and Sweere models were performed to predict the permanent deformation of the granular base–course materials with consideration of the influences of fines content, water content, and temperature conditions under thawed and frozen conditions. Compared with the equation from the guideline, the Sweere model provided a better prediction in the material permanent deformation under the unfrozen condition. Using the guideline equation may lead to inaccurate prediction of permanent deformation, especially for granular base–course materials at a relatively higher water content.

To better predict the ductile fracture of welded joints in steel bridges and buildings under seismic load, the fracture behavior of Q345 steel that has been widely used in China was studied under both monotonic and cyclic loadings based on the microscopic mechanism of material fracture. Based on the results of notched round bar tensile tests and finite-element analyses for Q345 steel base metal, weld metal (transverse and longitudinal), and heat-affected zone specimens, the parameters of the void growth model, stress-modified critical strain model, and cyclic void growth model were calibrated. The parameters of characteristic length in the previous models were determined by scanning electron microscope tests. The results indicated that the toughness parameters of the four materials are significantly different, and the cyclic growth capacity of the voids in weld metal and heat-affected zones deteriorates severely under cyclic loading. The toughness parameters of the two oriented weld metals are similar; therefore, the fracture toughness of the weld metal is less affected by the material orientation. The coefficients of variation of the toughness parameters of the four materials were small, and the distributions of the fracture indexes of the specimens with different notch radii were the same, which proved the effectiveness of the microscopic mechanism fracture model in predicting the initiation of ductile cracks of the members with different geometric shapes and stress states. The results of this paper provide the required material data and model parameters to predict the ductile fracture of welded joints made of Q345 steel using existing micromechanical fracture models.

In this experimental study, the effect of silica fume on the grouting performance of superfine cement and the engineering properties of grouted sand was examined. The experiments were first launched with rheological property determination tests. Bleeding, setting time, and viscosity tests were performed on superfine-cement suspensions with or without silica fume in different water/cement (W/C) ratios. Then, groutability tests were performed on fine to medium sand mixtures prepared in various gradations. Finally, unconfined compression strength (UCS) and falling-head permeability tests were performed on the samples that were successful in the grout test at different time intervals. With the addition of silica fume to superfine cement, the initial and final setting times as well as viscosity values increased, whereas bleeding values decreased. With the addition of silica fume to the superfine cement, the groutability slightly decreased, but the grouting pressure values increased. With the addition of silica fume to superfine cement, UCS values increased, although the permeability values decreased. Sand samples grouted with a superfine-cement suspension with silica fume additive gained strength later than sand samples grouted with superfine-cement suspensions with no additive. Experimental studies have shown that the addition of silica fume to superfine cement improves the engineering properties of the grouted sands.

The contribution of fibers to the strength of fiber-reinforced soils is dependent on multiaxial stress space. This study furthers knowledge on the dependency of steady states on anisotropy in unreinforced and reinforced (with 1.5% microsynthetic fibers) well-sorted sands with different shape and size properties. For this purpose, the direction of principal stress orientation varied from 15° to 60°, for an intermediate principal stress ratio of 0.5 and 1.0 and initial effective consolidation stress of 200 kPa. For this study, 24 undrained torsional shear tests were conducted using a hollow cylindrical torsional shear (HCTS) apparatus. When sands were randomly mixed with fibers, a dilative and strain-hardening behavior governed, and undrained strength generally improved. The samples’ anisotropy decreased, and a distortion of the deviatoric strength envelope was produced by the addition of fibers to the host sand. The results indicated that fiber reinforcement contribution is augmented with the growth of the major principal stress direction. This phenomenon is attributed to the sample loading combination changes from compression to torsion. The fiber strengthening contribution across all principal stress directions was higher in the sand with a larger median grain size (${\mathrm{D}}_{50}$) and angularity. Further, an increase in particle shape scale (${\mathrm{r}}_{\mathrm{s}}$ and ${\mathrm{r}}_{\mathrm{r}}$) ratios caused the stress-strain curves to approach another and reduced occurrence in specimen anisotropy. Further explanations on the effect of fiber addition are presented.

Asphalt purchase specifications have used 20-h pressure aging vessel (PAV) protocols to simulate later age binder properties for decades. Industrywide changes have introduced complexities when simulating field aging of asphalt binders, and the severity of conditioning protocols is a common discussion topic. This paper evaluates five field aging configurations in which compacted asphalt mixtures were aged in the same location (Columbus, Mississippi) between 2011 and 2016. Experiments like this, in which 10 different asphalt mixtures are evaluated for aging in one geographic location over five calendar years, are uncommon in the literature. Overall, the five aging configurations were best simulated by 3–11 h of PAV conditioning per year with 20 PAV hours simulating less than 5 years of aging in all but one of the five configurations. Ultimately, changing purchase specification binder conditioning methods would shift binder properties across the market, but changing specified PAV conditioning times cannot decrease the aging variability as seen in this one experimental location over a 5-year period.

Contrary to the extensive literature available on the axial pull-out behavior of individual steel fibers embedded in a cement-based matrix, including different fiber orientations, limited research has been performed which characterizes the transverse pull-out response. The Ohno-beam shear test method, which to the authors’ knowledge has not yet been used to characterize the steel fiber transverse pull-out response, is adapted here for this purpose. Five fiber orientations and two fiber embedment lengths are investigated. Similar characteristic behavior is observed compared with work done by other authors using alternative experimental methods. However, differences are pointed out and ascribed to the different boundary conditions in the different test methods. The knowledge could be used to select the most representative test. The single-fiber shear responses at different orientations bring new insights in the mechanisms governing shear response. Optimized fiber orientations could be selected to improve structural performance of steel-fiber reinforced concrete.

This paper investigates the flexural fatigue behavior of cement mortar mixed with edge-oxidized graphene oxide (EOGO), a carbon nanomaterial reinforcing cement hydration products. EOGO is produced by a mechanochemical process that enables dramatically reduced costs, making it suitable for large-volume infrastructure construction. The compressive and flexural strengths of the EOGO cement mortar mixtures are also compared with the results of fatigue tests. Test results indicate that the cement mortar containing 0.05% of EOGO by weight of cement exhibits the best flexural fatigue performance as well as compressive and flexural strengths. It is also found that the EOGO mixed specimens show a faster increase in flexural fatigue strains than the control specimens under sinusoidal loading. This implies that EOGO helps to prevent or delay the propagation of internal damage (e.g., microcracks) in the cement composites in an early fatigue phase, resulting in enhanced flexural ductility. Thus, it is concluded that the EOGO can be used as an additive, with cost competitiveness, for improving the structural fatigue performance of cementitious composites.

Graphene oxide (GO) and carbon nanotubes (CNTs) hold the potential to improve antiaging properties of construction material such as asphalt binders and mixtures. To prolong the service life of asphalt pavement, the aging resistance of 70# base asphalt binder, GO-modified asphalt binder, and CNT-modified asphalt binder was evaluated. Aged asphalt binders were obtained by the rolling thin-film oven test (RTFOT) and ultraviolet (UV) aging test. The high-speed shear mixing method combined with ultrasonic dispersion technology was adopted to solve the problem of dispersion of nanomaterials in asphalt binder and the asphalt samples were prepared by the melt-blending method. The surface morphology of GO and CNTs was analyzed with a focused ion beam scanning electron microscope (FIB-SEM). The residual penetration ratio (PRR), softening point increment (SPI), residual ductility ratio (DRR), and viscosity aging index (VAI) were employed to assess physical performance attenuation amplitude of asphalt binder samples after RTFOT and UV aging. The rheological properties of GO-modified asphalt binder and CNT-modified asphalt binder were investigated with a hybrid rheometer, and complex modulus ($G^{*}$) ratio and phase angle ($\delta$) ratio were selected as antiaging indexes. The $I_{\mathrm{C}═\mathrm{O}}$ increments were tested by Fourier-transform infrared spectroscopy (FTIR) to identify the chemical structure changes during aging process, and the FTIR of the pure GO (or pure CNT) was also conducted. The physical performance testing results illustrated that both GO and CNT could decrease the physical performance attenuation amplitude. Values of $G^{*}$ ratio and $\delta$ ratio from rheological testing revealed that the addition of GO (or CNT) could effectively suppress the growth of $G^{*}$ and the attenuation of $\delta$. The FTIR results indicated that the lower the $I_{\mathrm{C}═\mathrm{O}}$ value, the better was the antiaging performance. All phenomena indicated that both GO and CNT can help improve the aging resistance of 70# base asphalt binder. This research provides good inspiration for exploring the excellent performance of nanoparticles modified asphalt binder, which can help broaden the application of nanomodification in asphalt materials.

Reactive magnesium oxide (r-MgO) as a replacement of portland cement (PC) not only brings potential to reduce the embodied carbon in construction materials, but also brings uncertainties in the volumetric stability of carbonated r-MgO-PC systems during carbonation curing and sulfate exposure. This study investigates the longitudinal length and mass change of mortar bars with r-MgO replacement levels of 0%, 30%, 50%, and 70% when specimens are subjected to atmospheric drying, accelerated carbonation curing, distilled water immersion, and $50\mathrm{g}/\mathrm{L}$ ${\mathrm{Na}}_2{\mathrm{SO}}_4$ solution immersion. Experimental results revealed that carbonated mortar bars with a 30% r-MgO replacement level achieve a greater expansion after 24 months of sulfate solution immersion compared with mortar bars made with 100% PC. Formation of gypsum and ettringite are expected to be the main reasons for the expansion. The 50% and 70% r-MgO mortars exhibited volumetric and gravimetric stabilities during accelerated carbonation curing and sulfate solution immersion.

The durability of ${\mathrm{CO}}_2$-carbonated reactive magnesia (MgO)-admixed clayey soils against drying-wetting cycles has not been well understood now despite the fact that the engineering properties of ${\mathrm{CO}}_2$-carbonated MgO-admixed soils have been extensively investigated in previous studies. This paper presents the details of a study of the effects of drying-wetting (D-W) cycles on the physical, chemical, mechanical, and microstructural properties of ${\mathrm{CO}}_2$-carbonated MgO-admixed clayey soils, and ordinary portland cement (PC)-stabilized soils used as a control sample for comparison. The results indicate that compared with PC-stabilized soils, the soundness ranks and pH of ${\mathrm{CO}}_2$-carbonated MgO-admixed clayey soils have varying degrees of decline after drying-wetting cycles and ${\mathrm{CO}}_2$-carbonated MgO-admixed clay has a higher mass change ratio and water content than carbonated MgO-admixed silty clay. The residual strength ratios of ${\mathrm{CO}}_2$-carbonated MgO-admixed and PC-stabilized clay were 0.35 and 0.65, respectively, whereas the residual strength of ${\mathrm{CO}}_2$-carbonated MgO-admixed silty clay still was higher than that of PC-stabilized silty clay, although their residual strength ratios both were above 0.8. The elasticity modulus of ${\mathrm{CO}}_2$-carbonated MgO-admixed clay decreased from 260 to 100 MPa after one drying-wetting cycle and was less than that of ${\mathrm{CO}}_2$-carbonated MgO-admixed silty clay ($\sim 400\mathrm{MPa}$), showing weaker and better durability against drying-wetting cycles of ${\mathrm{CO}}_2$-carbonated MgO-admixed clay and of silty clay, respectively. Microstructural analyses confirmed the physical, chemical, and mechanical results.

This investigation is focused on the use of alternative segregation test methods on high-performance self-consolidating heavyweight concrete. Many segregation test methods have been developed by researchers up to now; however, the disadvantages of these methods, such as being time-consuming, the requirement of excessive labor, and the lack of precision, cannot ensure their worldwide prevalence. In the study, the segregation limitations stated in various test methods, that is, the column test, density variation method, and 3-compartment sieve test, were evaluated on self-consolidating heavyweight concrete produced with barite aggregate. For this purpose, in total, eight self-consolidating heavyweight concrete mixtures designed in two water/binder ratios were prepared by replacing viscosity modifier, silica fume, and fly ash with ordinary Portland cement in different amounts. The mixtures were constituted in satisfactory segregation grades, allowing researchers to evaluate the relationship between those methods. The segregation coefficient limits of the column test, density variation method, and 3-compartment sieve test are recommended as 7%, 1%, and 6.3% for the self-consolidating heavyweight concrete mixtures tested in the study.

In this research, techniques of cement paste strengthening and interfacial transition zone (ITZ) microstructure modification were simultaneously used to enhance the concrete engineering properties and a new concrete, named reactive-powder and reactive-aggregate concrete (RPRAC), was introduced. For this purpose, 18 wt.% of cement in concrete mix design was replaced with silica fume to strengthen the cement paste according to reactive powder concrete (RPC) technology and an optimal part of the sand in the concrete mix design was replaced with portland cement (PC) clinker as a reactive synthetic aggregate. RPRAC was then compared with RPC and normal concrete (NC) as controls in terms of workability, setting time, different-age compressive and flexural strengths, chloride penetration depth, open-pore volume, and water absorption. Simultaneous pozzolanic reactions of silica fume and surface hydration reactions of PC-clinker resulted in effective microstructural refinements both in hardened cement paste and ITZ. The achieved results showed that compressive strength of RPRAC was increased by 121% and 170% at 28 days compared to RPC and NC, respectively. The chloride penetration depth in RPRAC decreased by about 71% and 87% after 28 days of immersion in a NaCl solution compared to RPC and NC, respectively.

This work provides a systematic analysis of the expansive and load-deformation behaviors in circular steel tube stub columns (CSTCs) of self-compacting concrete (SCC) blended with ground circulating fluidized bed (CFB) bottom ashes (BAs). A series of SCCs with different expansive properties was fabricated by adding CFB-BAs. As the dosage of CFB-BAs increased, the time-dependent circumferential and axial strains increased. The expansive and load-deformation behaviors of cured SCCs filling the CSTCs were evaluated. Time-dependent expansive strain (TDES) measurements revealed that the expansive behavior in both the circumferential and axial directions had the same variation trend. The circumferential TDES values were much larger than the axial values. The axial load-displacement relations indicated that the specimen with 30% CFB-BAs had a 34% higher ultimate load, and it had a 54% higher ultimate load when 1.5% sodium sulfate was added to the specimen. The prestress had a significant impact on the ultimate capacity of concrete-filled steel tubes (CFTs). However, the ultimate capacity still was determined by the compressive strength of the core concrete, and it was not directly proportional to the initial prestress. The specimen with a 4-mm wall thickness and 30% CFB-BAs gained the most ultimate stress, indicating that the wall thicknesses of steel tubes had a distinct influence on the load-deformation behavior.

The consequences of asphalt pavement in a long tunnel under fire are much more serious than in open air conditions. Micropowder additives directly affect the characteristics of the asphalt binder, influencing the flammability and mechanical performance of asphalt mixtures. This research is aimed at studying the flammability performance of phosphorus slag (PS) powder as an additive for asphalt modification. Asphalt binders mixed with 0%, 5%, 6%, 8%, and 10% PS powder were produced, and conventional physical tests, rolling thin film oven (RTFO) aging tests, and flammability tests were performed on final samples. The results suggest that a micropowder additive with 8% PS is optimal and allows the modified asphalt to meet technical requirements; while, at the same time, improves the asphalt limiting oxygen index (LOI) by 6.4%–7.0%, indicating that the PS micropowder makes the asphalt more difficult to burn. A cone calorimeter test also shows that the PS additive can reduce the amount of smoke of an asphalt mixture during mixing and paving procedures. The overall results indicate that the PS powder as an additive can greatly improve the flame-retardant characteristics of an asphalt binder.

In this study, the compressive strength of recycled aggregate concrete (RAC) was investigated by conducting quasi-static and split Hopkinson pressure bar (SHPB) tests. Three types of RAC specimens with recycled coarse aggregate (RCA) replacement percentages (i.e., 30%, 70%, and 100%) and the natural aggregate concrete (NAC) specimen as reference were prepared and tested. Failure modes of the specimens were observed and compared, and dynamic compressive strength was recorded. The effect of different RCA replacement percentages on the compressive strength under quasi-static and dynamic loads was studied. The empirical formulae were proposed for dynamic increase factor (DIF) of the compressive strength for RAC. In this study, the DIF of compressive strength raises with the rising RCA replacement percentage. Besides, the continuous surface cap model (CSCM) is developed by considering strain rate effect for RAC material, and its accuracy is calibrated with the SHPB testing data by using LS-DYNA. The numerical results show that CSCM incorporating strain rate effect can yield more accurate prediction on dynamic compressive strength of RAC.

A Poisson’s ratio of 0.3 has usually been used for all grades of steel to estimate shakedown limits; however, high-strength steel, heat-treated pearlitic steel, work-hardened (strain-hardened) steel, and the newly developed bainitic steel show better response to deformation than standard carbon steel. The characteristics of these steels are to be considered. Elastic and plastic shakedown limits are expressed in terms of tensile and yield strength using the von Mises yield criterion and Hertz contact theory. Hence, shakedown limits can be computed and a diagram created for each steel. Different steels may thus be compared to facilitate selection of the appropriate steel grade. In this study, elastic and plastic shakedown limits were computed for three grades of American Railway Engineering and Maintenance-of-Way Association (AREMA) steel. The shakedown process was analyzed quantitatively for AREMA steels. Shakedown limits were related by the coefficient of friction, for which a desirable range was determined. The desirable minimum contact area from the wheel load and the tensile strength of the rail was formulated so the wheel-rail profile could be optimized. Finally, AREMA high-strength steel and DOBAIN steel were compared.

This paper presents the study of alkali-activated slags where sodium carbonate acts as a primary activator. The slow activation mechanism of sodium carbonate is accelerated by sodium hydroxide and with traces of calcium hydroxide. Strength development and the progress of hydration of the mixes were studied with the phase transformation and development of microstructural features through quantitative techniques such as thermogravimetric analysis and phase-identification techniques such as Fourier transform infrared spectroscopy and X-ray diffraction. Sodium carbonate replacement with sodium hydroxide and the presence of calcium hydroxide in the binder as a replacement for the slag enhances the rate of dissolution of slag, leading to faster strength development. Calcium hydroxide significantly increases the compressive strength, even at an early age. On the other hand, sodium hydroxide substitution is effective at later ages of the reaction when used at high dosages (e.g., 40%). Formation of strength-giving phases such as hydrotalcite and calcium aluminum silicate hydrate are confirmed with microstructure analysis and explain the strength development.

Using reclaimed asphalt pavement (RAP) in asphalt mixtures has become a common practice to reduce construction costs of asphalt pavements, maintain dwindling natural resources, and improve sustainability. However, utilization of high RAP contents poses technical challenges in terms of asphalt mixture production, compaction, and long-term cracking performance. To meet these challenges, mixture component and/or proportioning adjustments are recommended, such as using a softer virgin binder and/or adding a recycling agent (also called rejuvenator) at a specified dose. In this study, the effect of these adjustments on asphalt mixture stiffness, intermediate- and low-temperature cracking resistance, and rutting resistance at high temperatures was evaluated. The effect of these adjustments on the rheological properties of binder blends was also evaluated. Test results showed that only the mixtures/binder blends with an appropriate dose of recycling agent consistently yielded the best performance after short- and long-term aging conditions.

This work evaluated the use of Pinus sp. wastes treated with a chromium, copper and boron compound (CCB), a wood preservative, to fabricate particleboards based on castor oil–polyurethane resin. The effects of wood particle content, resin mass fraction, pressing time, and their interactions on the physical (thickness swelling, moisture content, water absorption, and density) and mechanical properties (internal bond, and edge and face screw-holding capacity) were evaluated via full factorial design and ANOVA. Two experimental conditions resulted in mechanical properties which meet or surpass the standard requirements and were therefore selected for porosimetric and microscopic analyses. Retention of CCB active ingredients was determined (for particles and particleboards) in order to evaluate possible volatilization during manufacture. The results showed that after a 7.7% increase in wood particle content, the thickness swelling after 2 h decreased by 16.5% and water absorption after 2 h (24 h) decreased by 17.4% (25.3%). In contrast, the moisture content increased by 5.9%. On the other hand, the 25% increase in resin mass fraction resulted in 22.1% and 19% reductions in thickness swelling after 2 and 24 h, respectively. Water absorption after 24 h also decreased by 20.7%. In contrast, internal bond increased by 13.8% with a 25% increase in resin mass fraction. The interaction of factors was not significant for the studied properties. In particular, the factors considered did not significantly affect the screw-holding capacity response. The decrease in active ingredients of the preservative was linked to mass balance by taking into consideration the amount of resin in the composition of the panels.

In the present study, alkali-activated slag (AAS) pastes were prepared using slag and water glass with different modulus, and the effect of a modulus of water glass on the volume change of the AAS pastes was investigated using helium pycnometry (HP) combined with isothermal calorimetry. The initial 24 h of the hydration process are divided into four stages based on the volume changes and heat flow. The AAS has a high shrinkage rate during the acceleration and deceleration periods, and the modulus had a significant influence on the shrinkage rate. This study reveals that HP is a fully automated and continuity method for determining the volume changes of AAS in early hydration.

Currently, soil stabilization is used in road construction in Sri Lanka, especially for soft road shoulders. The socioeconomic demand for sustainable development has raised the necessity of new environmentally friendly soil binders for construction engineering practices, including road construction. Industrial residues such as fly and bottom ashes are commonly used to reduce the amount of cement in concrete mixtures or soil stabilization practices, and new biological materials and methods have been introduced by a number of studies to improve the strength of soils without the use of chemical binders such as cement. Among others, microbial-induced biopolymers have been experimented with as a new binder material for soil treatment due to their high strengthening efficiency and low environmental impact. This study verified the feasibility of biopolymer application on local soil stabilization, specifically for road shoulder construction in Sri Lanka, by comparing the unconfined compressive strength (UCS) of local soil samples treated with cement-ash–based binders and xanthan gum biopolymer. The xanthan gum biopolymer–treated condition had significant UCS strengthening and high ductility compared with other treated conditions. Thus, xanthan gum biopolymer shows promising potential as an alternative material for road construction (particularly for shoulders and subbases) in Sri Lanka and in other nations with similar climates and socioeconomic conditions.

This paper studied the effect of municipal solid waste incineration fly ash (MSWI FA) on properties of magnesium potassium phosphate cement (MKPC) paste. MKPC pastes containing different contents of MSWI FA were prepared. Initial setting time and hydration temperature of fresh MKPC paste were tested. Compressive strength and shrinkage deformation of hardened MKPC paste were determined. Phase composition [via X-ray diffraction (XRD), energy dispersive spectrometry (EDS)], pore structure [via mercury intrusion porosimetry (MIP)], and morphology [via scanning electron microscopy (SEM)] of hardened MKPC paste were analyzed. Leaching concentrations of Pb and Cd from hardened MKPC pastes were detected. Compared with MKPC paste containing no MSWI FA, MKPC paste containing 10% MSWI FA had 20% higher 60-day compressive strength and 20% less 60-day shrinkage deformation. This was due to the higher early hydration degree and denser structure of MKPC paste containing MSWI FA. When the curing time was no less than 7 d, the leaching concentrations of Pb and Cd from MKPC pastes containing 5%–20% MSWI FA met the leaching requirement in the relevant Chinese national standard.

In general, polymers that enhance the mechanical strength of gypsum plaster simultaneously decrease its water absorption capability. In this research, starting from polyvinyl acetate (PVAc) and polyvinyl alcohol (PVA), respectively, two groups of PVA-derived polymers were, partially hydrolyzed polyvinyl acetates (PHPVAs) and polyvinyl alcohol sulfates (PVAS). The modulation of mechanical strength and water absorption of gypsum plaster with PHPVA and PVAS was studied. Their structure–property relationship was investigated. Except for morphology, the influence of product structure on the mechanical properties of the hardened gypsum plaster was studied, including mechanical strengths, dynamic water absorption, hydration degree, and hydration temperature. The mechanical strength initially increased with increasing hydrolysis or sulfonation degree but eventually decreased. The water absorption capability was proportional to the hydrolysis degree but was not significantly related to sulfonation degree. PVAS are the optimum candidate for modeling material, whereas PHPVA is optimal for construction materials. By molecular modification of PVA, highly enhanced mechanical strength can be realized with modulatable water absorption of the hardened gypsum plaster.