Journal of Materials in Civil Engineering

This paper presents an investigation correlating tensile properties of glass fiber–reinforced polymer (GFRP) bars with the results obtained from flexural testing. Composite bars, in contrast to conventional steel, when used in structures exposed to aggressive environments can significantly increase the durability and lifetime. However, the use of GFRP bars in concrete structures is still limited due to the variability of mechanical properties and bar quality among different manufacturers. Rational and fast testing methods for these reinforcing bars are needed. A flexure test is relatively easy and potentially could be used to determine the tensile strength of bars, which is a primary mechanical property that must be determined. This research investigates a possible correlation between the tensile strength and the modulus of rupture of GFRP bars. A Weibull weakest link model is employed. The effect of bimodularity of GFRP material in tension and compression also is investigated.

Due to the construction of more civil engineering structures on problematic soils, numerous ground improvement techniques such as soil stabilization have been developed. A wide variety of characteristics and engineering properties are shown by marl soil as a problematic soil; however, its stabilization has not been sufficiently investigated in the available literature. Thereby, this paper presents an experimental study of using natural pozzolans for stabilization of marl soil. Three types of natural pozzolans (volcanic ash) including Qizkorpi, Mamaloo, and Chichest near the city of Urmia, Iran, were used in this investigation. For this purpose, in addition to marl soil identification using X-ray fluorescence (XRF) analysis and its classification, the influence of three types of volcanic ash stabilizer contents of 5, 10, and 15% was evaluated through the maximum dry density (Standard Proctor Compaction Test) and optimum moisture content, Atterberg limits, unconfined compressive strength (UCS), and modulus of elasticity. Based on the results, satisfactory strength and durability characteristics were obtained by the mixtures of marl soils stabilized with three types of locally available volcanic ashes as stabilizers. The obtained results indicated that the increase in volcanic ash content and duration increases the efficiency of stabilized marl soil. In addition, the increase in the contents of volcanic ash decreases the expansion and ductility of marl soil. As a result, stabilized marl soil with volcanic ash can prepare the construction materials of houses and road infrastructures with low costs.

Significant amounts of blast furnace slag (BFS) are generated daily as by-product from iron and steel industries. This waste material usually has interesting physical properties and mineralogical and chemical composition, which can be useful as granular aggregate in the production of hot mix asphalt (HMA). In this study, an experimental program was designed to evaluate the effect on the resistance of a HMA due to the replacement (in mass and volume) of the coarse fraction of a natural aggregate (type limestone; LS) by a BFS. Total aggregate replacement was also evaluated. The mechanical properties were evaluated by carrying out the following tests: Marshall stability, indirect tensile strength (ITS), Cantabro abrasion, resilient modulus, permanent deformation, and fatigue resistance. Water sensitivity or moisture damage was evaluated by determining the ratio of indirect tensile strength (TSR) in wet and dry conditions. X-ray diffractometry (XRD), X-ray fluorescence (XRF) tests, and imaging processing in a scanning electron microscope (SEM) were carried out on particles of LS and BFS. The results revealed a remarkable enhancement in the properties of the HMA mixture when the coarse fraction of the LS was replaced in volume by BFS. When such a replacement was made in mass, the adhesive properties of the asphalt-aggregate system worsened. Total replacement of the LS led to unsatisfactory mechanical behavior.

The effect of warm-mix additive (WMA) on styrene-butadiene-styrene (SBS)-based high-viscosity asphalt (HVA) was conducted in this study. First, the physical properties for control HVA and HVA with WMA (RH, EC-120, and Sasobit with 2%, 3%, and 4%, respectively) were evaluated to select the optimum WMA. Physical tests showed that all WMAs reduced viscosity (135°C) significantly, while absolute viscosity (60°C) was improved by EC-120 and Sasobit. In addition, EC-120 improved toughness and tenacity. The rheology and morphology of HVA with and without optimum WMA (3% EC-120) were tested using dynamic shear rheometer (DSR), bending beam rheometer (BBR), and scanning electron microscope (SEM). The results indicated that the high-temperature rheological performance was improved by adding EC-120 under unaged and short- and long-term aging conditions. In addition, EC-120 improved the low-temperature creep behavior of the asphalt binder after long-term aging. This finding was further demonstrated by morphological observation, in which a multinetwork was formed after long-term aging.

Healing capabilities of shape-memory alloys (SMAs) and steel-reinforced mortar with self-healing microcapsules were investigated. Small cracks ranging from 13 to 152 μm were induced by three-point bending, and specimens were subjected to a 14-day healing period under water-submerged conditions at $55°\mathrm{C}\pm 5°\mathrm{C}$ to induce shape-memory effect activation. Light microscopy investigation was performed at 3, 7, and 14 days of the healing period. Moreover, healing products were investigated using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Healing efficiency improvements with the increase in microcapsule content were reported at 3 and 7 days for steel-reinforced specimens. Furthermore, for all mortar mixes evaluated, SMA-reinforced specimens exhibited a superior healing performance than steel-reinforced specimens at 3 days of healing due the crack-closing action of SMA. The overwhelming majority of healing products were identified as likely calcite crystals, and the limited gellike products also present were presumably calcium silicate hydrate (C─ S─ H).

Vertical drains are extensively used for ground improvement in order to accelerate the consolidation settlement of soft clay deposits. In the case of very soft clay, if sand/aggregate alone is provided, the diameter of the well can be reduced due to necking action and clogging. In order to reduce these effects and increase strength and properties of drainage media, a hybrid mix is developed through experimental model studies. A major limitation of displacement vertical drains is generation of a smeared zone, leading to lower capabilities. This disadvantage could be reduced by penetration of intrusion material in the smeared zone during a second driving at the same point. Efficiency of sand piles with a single or double driving, optimum hybrid mix with a single or double driving, and prefabricated vertical drains is studied by assessing the behavior in the laboratory using large-scale model bed tanks. From the results, it is found that double-driven piles with the hybrid mix show better performance compared with other vertical drains and can be effectively used for ground improvement in very soft clays.

In this research, the multiple impact resistance of hybrid fiber ultrahigh toughness cementitious composites (UHTCC) was studied. By varying the impact velocity, different degrees of initial damage were first induced in the specimens. Then the multiple impact behavior of these specimens, including stress-strain relationship, energy absorption capability, degree of damage, and microstructure of damaged material were investigated and discussed. The results revealed that hybrid fiber UHTCC specimens could maintain their integrity even though the dynamic peak stress was below 10.0 MPa, which significantly reduced the surface spalling of fragments. The specimens with a low-degree initial damage showed improved multiple impact resistance over those without initial damage, because the microstructure of specimens was densified under the low-velocity initial impact load. Through the comparison among four groups of specimens with 2.0% of polyvinyl alcohol (PVA) fiber and different volume fractions (0.0%, 0.5%, 1.0%, and 1.5%) of steel fiber, the specimens with 1.0% steel fiber showed the highest energy absorption capability and sustained the largest number of impacts.

Joint deterioration in concrete pavements is predominantly related to penetrability of concrete and environmental conditions. Saw-cutting as the last procedure in the construction sequence of concrete pavements may compromise the durability of joints due to insufficient curing and uncontrolled evaporation at an early age. Capillary absorption is considered fundamental to understanding the durability performance of porous building materials. Thus, the aim of this study is to develop an analytical model based on Katz-Thompson relationship to determine the absorption capacity of joints in concrete pavements according to an absorption test customized to the joint geometry of pavements. The experimental program involved absorption and mercury-intrusion porosimetry tests conducted on cores extracted from saw-cut concrete slabs with different curing scenarios. The absorption trends were modeled based on the unsaturated flow theory with three dimensional (3D) finite-element software. The results indicated that the unsaturated flow model reliably simulated fluid transport at joint locations in concrete with accurate predictions relative to experimental results.

An experimental and simulation study on mechanical properties and cracking behavior of zinc film on 2Cr13 steel is carried out. The three-point bend with the acoustic emission technique and uniaxial tension tests were innovatively conducted to study the film fracture toughness and the critical thickness of zinc film at different strains. Meanwhile, simulations were made to analyze the influence of different factors on the dimensionless energy release rate of a surface crack and the stress field around the crack tip with the extended finite-element method. Results indicate that the film will not crack until the film thickness reaches the critical thickness, which decreases with the increase of tensile strain. The elastic modulus ratio, the thickness ratio, and the crack spacing have great impacts on the crack energy release rate and substrate stresses around the crack tip. Also, if the substrate stiffness is greater than the film stiffness for a given film thickness, the substrate thickness and the crack spacing are greater when the crack propagation is in a steady state.

Sodium hydroxide (NaOH) and sodium silicate–activated fly ash and slag-based geopolymer composite (NSFSGC) and NaOH and sodium carbonate (${\mathrm{Na}}_2{\mathrm{CO}}_3$)-activated fly ash–based and slag-based GC (NNFSGC) were prepared and their dynamic energy properties were studied comparatively. The results indicate that the specific energy absorption (SEA) of GC increases with strain rate, and the damage degree is greater with the increase of SEA. When loaded with the same strain rate, the SEA of NNFSGC is always greater than that of NSFSGC. The general change law of the SEA of NSFSGC and NNFSGC with strain rate separately fits a linear and a quadratic polynomial relationship; further, the increase rate of the SEA of NNFSGC goes up with the increase of the strain rate and is higher than that of NSFSGC. Thus, NN activators are better at activating the dynamic energy property of GC. Therefore, GC prepared with NaOH and ${\mathrm{Na}}_2{\mathrm{CO}}_3$ shows promise for application in antiexplosion engineering.

When a road is constructed, soils within the embankment are often compacted at the optimum water content to achieve the best performance. The postconstruction water content tends to increase with time due to capillary action, precipitation infiltration, and water condensation. Because soils are sensitive to water content variations, a slight water content increase will cause a significant reduction in soil moduli and a dramatic increase in permanent deformation under cyclic loading. Materials with large pores, such as granular materials and nonwoven geotextiles, are commonly used for the drainage of gravitational water under a saturated condition, but not for the drainage of capillary water under an unsaturated condition. Therefore, the excessive water in the soil accelerates the deterioration of the road with time. Recently, a new geotextile with wicking fibers, which can drain both gravitational and capillary water under saturated and unsaturated conditions, has been developed. Several field applications have proven its effectiveness in dehydrating the road embankment. This paper aims to quantify the benefits of the new geotextile in terms of water removal. First, comprehensive laboratory tests were performed to characterize the properties of the soil, the new geotextile, and the soil-geotextile interactions. Second, the working mechanism and functional range of the new geotextile were determined and the drainage ability of the soil-geotextile system was quantified via numerical simulations. The wicking fabric functions as an effective drainage material to hold and transport capillary water in the in-plane direction. The soil-geotextile system is able to reduce the water content of the base course by 2.2% from the optimum value, and the corresponding resilient modulus can be increased by 2–3 times.

Problems associated with horizontal loading in foundation structures often occur when the surface soil has particular characteristics like the unsaturated, porous, and collapsible soils that are very common in Brazil. In the state of São Paulo, more precisely in the region of Campinas, the occurrence of such soils is detected in several places. For this reason, this work was conceived for the purpose of assessing the performance of four types of deep foundations subjected to horizontal loading via analysis of the load versus horizontal displacement curve and determination of the horizontal reaction coefficient of the soil ($n_h$). To accomplish this, load tests were carried out with bored piles, continuous flight auger piles (CFA), steel piles, and belled caissons at the Experimental Site of Foundations at the State University of Campinas—Unicamp, Campinas, São Paulo, Brazil. The tests were performed under soil conditions of natural moisture and after 48 h of flooding. The results showed a large drop in parameters of soil resistance due to flooding—an approximately 50% drop on average for the ultimate load and 70% for the horizontal reaction coefficient of the soil.

Numerous regulations have been imposed worldwide by governments and environmental organizations in order to reduce the negative environmental impact resulting from large numbers of solid waste landfills. Recycling of industrial by-products is a step toward sustainable waste management. By utilizing ceramic waste powder (CWP) as a partial cement replacement, the construction industry can play a significant role in energy conservation and limit future generations of ${\mathrm{CO}}_2$. This paper examines the feasibility of producing self-compacting concrete (SCC) mixtures yielding acceptable fresh and hardened concrete characteristics with the inclusion of high-volume CWP as partial replacement of cement. The fresh properties of the new SCC are evaluated through various tests (i.e., slump flow, J-ring, column segregation, V-funnel, and L-box). The investigations show a slight reduction in the slump flow but with an enhancement of the other fresh properties. In addition, the use of CWP slightly reduces compressive strength. It is shown that it is possible to produce SCC with acceptable properties incorporating high-volume CWP.

There is little knowledge on the effect of stress on corrosion of mild steel and how the combination of stress and corrosion affects the mechanical properties of mild steel. This paper presents a comprehensive experiment to provide evidence of the effect of stress on corrosion progress and mechanical properties of corroded steel. Test specimens, both stressed and nonstressed, were immersed in hydrochloride solutions with various acidities. Cause and effect relations among stress, corrosion, and mechanical properties of corroded steel are investigated and analyzed quantitatively at both macrostructural and microstructural levels. It is found that stress can accelerate the corrosion process and contribute to intergranular corrosion and intergranular stress corrosion cracking of steel. Consequently, stress can expedite the reduction of mechanical properties of corroded steel, especially the ultimate strength and failure strain. The significance of this paper is that it not only proves the effect of stress on corrosion and mechanical properties of corroded steel but also provides a more accurate understanding of cause–effect relationships among stress, corrosion, and mechanical properties of corroded steel.

The purpose of this study is to analyze the influence of recycled coarse aggregates (RCA) used to manufacture self-compacting concrete with recycled aggregates (SCRC) by evaluating the characteristics of this concrete, particularly its self-compactibility. Another aim is to determine the simple compressive strength at 28 days and the durability (water penetration and carbonation). The concrete was prepared with different RCA percentages (0%, 20%, 40%, 60%, 80%, and 100%) and water:cement (w/c) ratios of 0.45, 0.50, and 0.55. A constant percentage of superplasticizer was added, and two saturation methods were analyzed with a $\mathrm{w}/\mathrm{c}=0.45$ ratio, one before and one during mixing. The results indicate that using up to 20% RCA has little influence on the characteristics of the SCRC, meaning that SCRC can be prepared with up to 40% substitutes, depending on the water:cement ratio.

The optimum weight percentage of tire-derived aggregates (TDAs) mixed with ballast, as a new approach to rehabilitate the performance of ballast layer in desert areas, has been suggested as 5% in the presence of sand fouling. The current paper is devoted to the effect of moisture content (MC) on the mechanical behavior of sand-fouled ballast with and without TDAs. A number of ballast box cyclic tests were conducted on mixtures of fully fouled ballast, TDA, and water. The samples contained 0% and 5% of TDAs by ballast weight as well as 0%, 5%, 10%, 15%, and 20% of MC by sand weight. The gradation of ballast and TDAs was in accordance with current standards, and the particle size distribution of sand ranged from 0.075 to 0.84 mm. The parameters measured are the settlement, stiffness, and damping of samples, which did not follow a constant trend by varying the MC. According to the laboratory results, an MC of 5% decreased the settlement and increased the stiffness and damping of fouled non-TDA samples, whereas increasing the MC up to 10%, these samples experienced their minimum stiffness as well as maximum settlement and damping. Inclusion of TDAs had no effects on the variation trend of settlement and stiffness versus the MC. Consequently, from a practical standpoint, the MC of 10%, which eliminated the influence of TDAs on the sample damping, was regarded as the critical moisture content.

For several decades, researchers have attempted to develop statistical models through individual and combined use of ultrasonic pulse velocity (UPV) and rebound hammer data to enhance the prediction of concrete compressive strength and durability. This study proposes statistical univariate and multivariable regression models to predict compressive strength, abrasion, and salt scaling of concrete using UPV and rebound hammer measurements. Stepwise regression analysis was undertaken to develop the proposed models that were then validated using independent data. A scaling quality classification table using rebound hammer, and based on a $k$-means clustering algorithm, is also proposed. The measurements support the combined use of UPV and rebound hammer to predict compressive strength. On the other hand, rebound hammer values are the only statistically significant variables to predict abrasion and salt-scaling resistance of concrete. Concrete properties had a significant impact on the mean and dispersion values of UPV and rebound number (RN). The procedures used in this paper for model development can serve as a general guideline for developing statistically valid univariate and multivariable regression models for other applications when predicting concrete properties.

The thermal conductivity of soil is an important parameter in many engineering problems involving heat transfer, such as in ground source heat pump systems and freeze-thaw prevention projects. In these projects, not only must the undisturbed soils be accounted for, but the disturbed soils, such as the backfill, should be as well. In the present work, the thermal conductivities of remolded loess and undisturbed loess were tested. A model was then selected to predict the thermal conductivity of remolded loess. Finally, the thermal conductivities of remolded loess specimens were compared with those of their corresponding undisturbed loess specimens. The results showed that the thermal conductivities of the remolded loess and undisturbed loess were both increased as water content increased. The thermal conductivity of remolded loess increased as the dry density increased, but the thermal conductivity of undisturbed loess with a lower dry density was not always lower than that of undisturbed loess with higher dry density at a similar degree of saturation. The thermal conductivity of undisturbed loess was always larger than that of remolded loess when the two types of soils possessed the same degree of saturation and dry density.

Experimental studies have showed that the static preload increases the dynamic tensile strength of concrete under certain conditions. But its mechanism still remains open. In this study the authors focus on the dynamical damage failure mechanism of concrete with the static preload, and propose a mesoscopic damage dynamical model to evaluate the elastic modulus and strength enhancement parameters of concrete that is considered as a three-phase heterogeneous composite material. A mesoscopic dynamical model is developed to implement the numerical simulations of dynamic flexural-tensile damage and failure processes of concrete under shockwave and cyclic triangular wave loads. The numerical results agree well with the experimental ones reported in previous studies. This study illuminates that the static preload has an enhancement effect on the dynamic tensile strength. Such an effect essentially results from the double-sided features of the strain rate enhancement and damage deterioration of concrete.

This study investigated, on a laboratory scale, the effect of the durability of the incorporation of ornamental stone waste in the production of red ceramic parts in order to improve material properties and durability. To reach this objective, ornamental stone waste material, of up to 10% by mass, was introduced to the red ceramic mass. Several other techniques were employed, including X-ray fluorescence chemical analysis, differential thermal analysis, and X-ray diffraction analysis. The samples, pressed to dimensions of $11.0\times 2.5\times 1.0\mathrm{cm}$ with 8% humidity, were oven dried and sintered at 750°C, 850°C, and 950°C and analyzed for water absorption, linear shrinkage, and flexural strength. To predict the strength behavior of the red ceramic parts over time (or over the long term), a low-cost experimental procedure was used to relate the accelerated degradation time in the laboratory for 200 days of saturation and oven-drying cycles at 110°C to the time exposure of the samples to weathering, in this case, for 5 years. The wetting–drying cycles were used to represent the most unfavorable environmental condition for deterioration processes, and the choice of flexural strength over the other properties was due the higher effect of degradation on this property. The useful life of red ceramic parts was defined as when the minimum value of 1.5 MPa was reached, obtaining 14 years for samples sintered at 950°C with stone waste content of 5% by mass and 4.8 years for samples sintered at 950°C with stone waste content of 0% by mass. The durability of red ceramic parts made with stone waste increased 2.91-fold due to the alkali and earth alkali of the stone waste that form molten flux during sintering and the vitreous phase during cooling, closing pores, and thus improving product quality. Furthermore, the stone waste material was inert, leading to proper disposal in the environment.

The current practice of using the binder blending chart to select a performance grade of the virgin binder may not be applicable for mixtures containing more than 25% reclaimed asphalt pavement (RAP), since the binder blending chart assumes full blending between virgin and RAP binders. For such high RAP percentage cases, a blending chart based directly on the performance of mixtures would be a better choice. This study develops a mixture blending chart based on the dynamic modulus values of RAP mixtures to better control their performance. Three rules of mixtures were considered to develop the mixture blending chart, including Voigt rule, Reuss rule, and a joint Voigt and Reuss (V&R) rule. The dynamic modulus values of three sets of RAP mixtures were measured in this study. The results indicated that the dynamic modulus values calculated by the joint V&R rule matched the measured values of the corresponding RAP mixtures better than those calculated by the Reuss rule and Voigt rule. Digital images of two-dimensional slices of the laboratory specimens were taken and used to construct the ideal binary-blended RAP mixtures, and the finite-element analyses were conducted to determine the modulus values of these digital RAP mixtures to verify the developed mixture blending chart. The modulus results of digital RAP mixtures matched the modulus values determined based on the joint V&R rule. We conclude that the joint V&R rule could be used as the mixture blending chart to select an appropriate virgin binder when designing high RAP content mixtures.

Full-depth reclamation of asphalt pavement and underlying materials is one of the most effective methods of rehabilitation for severely deteriorated roads. This paper examines the feasibility of using clay at different percentages in a recycled mixture with bitumen emulsion and lime at relatively higher dosages than those specified in previous studies. The most important mechanical tests included indirect tensile strength in dry and wet conditions, resilient modulus, and indirect tensile fatigue tests. Also, microstructural analyses were performed using scanning electron microscope and X-ray diffraction methods on cured pastes of various combinations of clay, bitumen emulsion, and lime. Based on mechanical tests, the addition of clay up to 10% would not have any destructive effects on stabilized specimens. In addition, specimens containing 10%–15% clay showed acceptable behavior. Specimens with higher clay contents showed some deficiencies in mechanical and durability tests. Microstructural analyses have shown that additives like lime and emulsion, which usually play the role of binder in such mixes, work independently, and the simultaneous use of lime and emulsion would not lead to a new composite binder. However, the presence of emulsion may delay the development of clay–lime reaction and therefore the curing progression of the stabilized layer.

In this study, triaxial tests are performed on rockfill material (weakly weathered fresh tuff) with different porosities in order to obtain the stress–strain curves of the test specimens. The confining pressure and porosity are found to affect the rockfill material. The suitability of the Duncan–Chang model is assessed, and it is found that this model is not suitable for analyzing the mechanical behavior of rockfill materials with low porosities subjected to low confining pressures. Two models are proposed to overcome the limitations of the Duncan–Chang model: (1) an exponential–parabolic nonlinear elastic model, and (2) a modified Nanshui double yield surface model. Both of these models fit better with the stress–strain data obtained from experiments. Following this, regression models are developed to predict the parameters of the constitutive models as a function of the porosity of rockfill materials with high accuracy, which will enable researchers to obtain fast and reliable estimates of the parameters. The results can be used to lay the theoretical groundwork for finite-element simulations of rockfill dams, taking into account the differences in the constitutive model parameters due to spatial variability in the compaction quality of rockfill materials.

Concrete structures that employed general and multicomponent blended binders were constructed using a low-carbon, ecofriendly microwave heat curing technology with the aim of accelerating the concrete’s curing process. In this study, a field-cast concrete tunnel lining that employed a general binder (portland cement) and a precast box culvert that employed a multicomponent blended binder were constructed using the microwave heat curing technology. In the precast concrete box culvert, portland cement was partially replaced by ground granulated blast furnace (GGBF) slag and fly ash, and rapid-cooled steelmaking slag was used as an alternative to fine aggregates. Through a series of evaluations, it was found that the proposed curing technology was able to fully complete the curing process with the use of electric power alone, reduce the time required to cure the concrete in the field-cast concrete tunnel lining and permit form removal to 4 h, and potentially lower the cost of curing by about 70% compared with conventional steam curing.

Alkali-activated binders have received substantial attention due to their excellent potential in enabling the reuse and recycling of industrial solid wastes and by-products. One-part or just-add-water alkali-activated binders are an approach to reduce the negative aspects of using an alkali solution during the preparation of traditional two-part alkali-activated binders. The work aims to utilize the maximum content of ceramic wastes in alkali-activated blast-furnace slag/ceramic binders. The ground granulated blast-furnace slag was partially replaced [10%, 20%, and 30% in weight (wt.)%] by two types of ceramic wastes (porcelain and raw; i.e., fired and unfired). Moreover, the coarse particle size of porcelain ceramic waste was used as recycled aggregate. The specimens were cured under two different curing regimes: (1) sealing with plastic; and (2) using thermal curing conditions for 3 h in 60°C after demolding and then sealing until the test day. Mechanical testing and microstructural analysis were used to characterize the effects of different curing regimes and different ceramic sources. The results showed that replacing ground granulated blast-furnace slag with all types of ceramic wastes reduced the compressive strength; this reduction was mainly caused by reduction of the calcium content. This strength loss was also governed by the ceramic waste type, curing regime type, and curing duration. The microstructural analysis indicated that some cracks formed between the ceramic waste particles and the matrix. Moreover, the microscopic analysis indicated the use of preheating could eliminate cracking.

Cold recycling is a cost-effective and sustainable rehabilitation technique. Proper mixture design and optimization in terms of emulsion and cement contents can be helpful to ensure satisfactory performance. A balanced mixture design approach for cold recycling is proposed. The indirect tensile asphalt cracking test (IDEAL-CT) performed at 25°C with a 100-mm-diameter gyratory mold compacted at 50 gyrations and 62-mm-high cylindrical specimens and a loading rate of $50\mathrm{mm}/\min$ is used to assess the cracking resistance of cold recycling. The resulting cracking test index (CTI) can differentiate mixtures with varying emulsion and cement contents. A wheel tracking test performed at 60°C on cold recycling slabs is used to evaluate the rutting resistance. The cracking and rutting tests can be highly valuable for selecting optimum emulsion and cement contents. Setting proper CTI and dynamic stability (DS) limits can aid in achieving an optimum design.

Organic montmorillonite (OMMT) was obtained by reacting montmorillonite (MMT) with the surfactant cetyltrimethyl ammonium bromide (CTAB). The crystalline phases of MMT and OMMT were characterized by microscopic performance analysis using an X-ray diffractometer (XRD) and scanning electron microscope (SEM). The effects of rubber, attapulgite, columnar diatomite, and disk diatomite on the technological and rheological properties of OMMT-modified asphalt were studied using a dynamic shear rheometer, and the low-temperature properties were determined from their creep characteristics by a bending beam rheometer. The short-term, long-term, and ultraviolet (UV) aging of modified asphalt were tested, respectively. After adding five types of modifiers to the asphalt, the high-temperature rheological and aging resistance of matrix asphalt and modified asphalt can be improved. In particular, it is shown that modification with OMMT with attapulgite as comodifier had a positive influence on asphalt thermo-oxidative aging and UV aging.

The mechanical reinforcement effect of roots on soil shear strength is widely recognized and can be used in slope stability analyses based on the limit equilibrium or finite-element method. Although some advanced root reinforcement models have been proposed to evaluate root cohesion, these models require complicated algorithms and a large quantity of experimental data. This paper provides a simple method to estimate root cohesion based on an uncertainty characterization of a widely used root reinforcement model, the Wu and Waldron model using root cohesion data for four riparian tree species. The capacity of the newly developed method is validated using the root cohesion data for another three species. It is found that the newly developed method has a much higher estimation accuracy of root cohesion than the Wu and Waldron model and has a potential to be applied to other tree species used for soil stabilization projects. The new method provides an alternative option for practitioners to evaluate root cohesion in stability analyses of hillslopes and riverbanks because it is simple and does not need many experiment data.

There has been significant utilization of standard fly ashes, Class C and Class F fly ashes, in the cement industry and in soil stabilization applications. However, the majority of the fly ashes that do not satisfy the chemical standards [off-specification (off-spec) fly ashes] have been disposed in landfills because of their unfavorable chemical properties such as high carbon content or high ${\mathrm{SO}}_3$ content. In this study, a clay soil was stabilized with different proportions of the standard and off-spec fly ashes. A series of unconfined compression (UC) tests were conducted on the specimens that were prepared to observe the suitability of the off-spec fly ashes for soil stabilization. The test results indicated that the off-spec fly ashes showed superior performance compared with the standard fly ashes due to their high CaO contents regardless of their ${\mathrm{SiO}}_2+{\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{Fe}}_2{\mathrm{O}}_3$ and ${\mathrm{SO}}_3$ contents. It was recommended that chemical- and performance-based standards should be used instead of only chemical-based standards to determine whether a selected fly ash is suitable for soil stabilization.

Proper disposal of industrial waste, the need to conserve nonrenewable resources, and high ${\mathrm{CO}}_2$ emissions are the major environmental issues at the present time. A significant portion of emissions from portland cement production is related to the energy required to maintain the clinker kiln at a temperature of approximately 1,450°C, which is necessary for alite formation. The alternative belite phase, however, requires lower temperatures for its formation (below 1,250°C). Although belite is less reactive than alite, it is equally efficient at higher hydration times. Thus, a belitic cement produced entirely with industrial waste (grits from the pulp and paper industry, steel slag, and quartzite mining tailings) is presented in this research. The raw meal was proportioned based on Bogue calculation and the firing was performed in a muffle furnace at a temperature of 1,250°C. A reference belitic cement was produced with limestone and clay under the same conditions. The results showed that both cements presented high belite contents and expected technological performance. The reference belitic cement revealed a higher reactivity, whereas the waste cement proved to be a technically feasible low-impact alternative.

ASTM C1556-11a [ASTM (2016). Standard Test Method for Determining the Apparent Chloride Diffusion Coefficient of Cementitious Mixtures by Bulk Diffusion] provides a systematic procedure to determine the apparent diffusion coefficient of concrete, which is generally used to assess concrete’s ability to resist chloride ingress and to make service life predictions. Although ASTM C1556-11a and other similar tests are widely used, they are time-consuming and expensive to perform. The formation factor can be used as an alternative to rapidly assess the transport properties of concrete; however, it does not consider chloride binding. In this paper, a theoretical relationship is developed to relate the formation factor, chloride binding parameters, and apparent chloride diffusion coefficient. A simplified equation based on this theoretical approach is proposed as an alternative to estimate the apparent chloride diffusion coefficient. The chloride profiles obtained using the apparent diffusion coefficients and surface chloride concentrations from the theoretical approach and ASTM C1556-11a were compared. Combining the formation factor with chloride binding properties provides an alternative to ASTM C1556-11a for determination of the apparent chloride diffusion coefficient and surface chloride concentration.

In this work, a simulation of thaumasite sulfate attack on portland cement mixtures was performed, using synthesized cement phases. Three model systems containing ${\mathrm{C}}_3\mathrm{S}$, ${\mathrm{C}}_3\mathrm{A}$, and alkali sulfate (${\mathrm{CaSO}}_4$, ${\mathrm{Na}}_2{\mathrm{SO}}_4$, and ${\mathrm{K}}_2{\mathrm{SO}}_4$, respectively) and a fourth one consisting of ettringite and C−S−H, were designed, and several mixtures were prepared. $\mathrm{Ca}(\mathrm{OH}{)}_2$ and ${\mathrm{CaCO}}_3$ were optionally added. Specimens stored at 5°C and 20°C in an atmosphere saturated in water vapor for 75 months were investigated with X-ray diffraction analysis and scanning electron microscopy. Thaumasite formed in all samples without ${\mathrm{C}}_3\mathrm{A}$ at 5°C, and at 20°C when sulfates were derived from ${\mathrm{CaSO}}_4$. Solid solution of thaumasite and ettringite was detected in samples incorporating ${\mathrm{C}}_3\mathrm{A}$ and ${\mathrm{CaSO}}_4$ or ${\mathrm{Na}}_2{\mathrm{SO}}_4$ at 5°C. This was also observed at 20°C when ${\mathrm{CaSO}}_4$ was the source of sulfates, whereas ettringite formed in the case of ${\mathrm{Na}}_2{\mathrm{SO}}_4$. The absence of thaumasite and ettringite in specimens containing ${\mathrm{C}}_3\mathrm{A}$ and ${\mathrm{K}}_2{\mathrm{SO}}_4$ was attributed to the alkali carbonation process. In the fourth system, decomposition of ettringite occurred in the specimens exempt of ${\mathrm{Ca}(\mathrm{OH})}_2$. The work is supposed to contribute to understanding the primary causes of concrete damage when the concrete is subjected to long-term sulfate attack.

This paper investigates the influence of mineral admixtures and fibers on workability and mechanical properties of reactive powder concrete. Preliminary tests of materials and multiple trial mix designs are carried out to establish a proper control mix of ultrahigh-strength concrete satisfying workability and mechanical properties. Cement is replaced with silica fume and ultrafine ground granulated blast furnace slag (GGBS) in the range of 0%–15%, and sand is replaced with quartz powder in range of 0%–15%. These mixes are investigated individually and in combination for workability and mechanical properties such as compressive strength, split tensile strength, and flexure tests for various curing regimes, namely normal curing, preheat curing, and postheat curing. X-ray diffraction (XRD) analysis investigates the composition responsible for the high mechanical and durability characteristics. The study is extended to improve the ductility of reactive powder concrete by addition of various synthetic and natural fibers to investigate its mechanical properties. The best mix is selected considering the workability and mechanical properties of the reactive powder concrete developed.

Environmental sustainability is the need of the hour. The dependency on natural river sand has to be decreased, and an environment friendly disposal of waste rubber tires needs to be promoted. The application-specific properties of concrete such as damping or vibration absorbing capacity can be enhanced, by the use of scrap rubber tires as aggregates in concrete. This paper evaluates the feasibility of using shredded waste rubber as a partial replacement to fine aggregate, with respect to mass, by conducting investigations on its mechanical properties. In addition, the effect of polymeric fibers which is incorporated in rubberized concrete is probed. The reuse of waste rubber and fiber resulted in improved ductility and damping ratio; however, it reduced the strength values. At a maximum of 7.5% replacement in both plain rubberized and fiber reinforced rubberized concrete, the loss in strength percentage is within acceptable limits making it suitable for use as vibration attenuators in applications such as road curbs and barriers, paving blocks, trench filling, and machine foundations.

Asphalt concrete has been used as an appropriate impervious barrier for water retention. The performance of asphalt concrete in dam cores, reservoir coatings, and canals is comparable with other existing alternatives. However, the methodology used to determine the amount of asphalt binder in the mixture is based on some experiences and recommendations; knowledge about the effect of the aggregate gradation on the permeability of asphalt concrete used in these barriers is limited. In this investigation, permeability and cracking susceptibility of asphalt concrete specimens made from different gradations and asphalt binder content are studied to propose a design method of asphalt mixtures for impervious barriers. Permeability tests under different conditions of hydraulic head and indirect tensile strength (ITS) tests were performed. As an outcome, for the materials used in this study, gradation limits were determined for pervious and impervious asphalt concrete. Considering that the mineral aggregate can have asphalt binder absorptions in a very wide range, it is proposed to use effective asphalt film thickness to determine the minimum asphalt binder content. It was found that the best performance of the mixture was achieved with an effective film thickness between 10 and 13 μm.

Cement-based grouting materials can be applied to reinforce unsafe rocks of stone carvings that are attached to or carved out of cliffs. However, studies on the evaluation, that is, the pros and cons of the applied grouting materials, are relatively scarce. In this study, five grouts prepared with different binders [ordinary portland cement (OPC), superfine cement, $\mathrm{OPC}+$ metakaolin] and additives (water glass and organosilicone) were assessed through both laboratory tests and on-site operation. The results revealed that the use of superfine cement instead of ordinary portland cement could result in a more waterproof and durable mortar, at the same time having better injectability and less subsidence as a grouting material. The addition of organosilicone in cement-based grouts could improve waterproofness, greatly increase freeze-thaw resistance, and give better injectability. The incorporation of water glass could greatly increase freeze-thaw resistance. The use of metakaolin in cement grouts could reduce the dissolution of ${\mathrm{OH}}^{-}$ and ${\mathrm{Ca}}^{2+}$ and result in a more even distribution of the mortar components in the hardened grout, yet at the same time inducing higher porosity and lower mechanical strength and significantly promoting ${\mathrm{SO}}_4^{2-}$ precipitation of the mortar.

The procedure of soil treatment with industrial and domestic wastes such as ground glass and coal ash (acting as pozzolans) and carbide lime is a sustainable practice when the assignment involves amendment of the native soil for the production of engineered fills and stabilized bases of pavements. This research assesses the efficiency of sandy soils treated with industrial and domestic residues, demonstrates that the porosity/binder index ($\eta /B_{iv}$) (equivalent to porosity divided by the volumetric content of pozzolan plus carbide lime) performs an essential function in the assessment of the goal blend strength, and proposes a general model that controls the strength-porosity/binder index behavior of sandy soil-pozzolan-lime blends. The controlling parameters evaluated are the amounts of pozzolan and carbide lime, the porosity, and the porosity/binder index. A series of unconfined compression tests was carried out reflecting distinctive amounts of pozzolans, diverse porosities, and discrete carbide lime amounts. The results show that the unconfined compressive strength ($q_u$) increases in a power shape with the reduction of $\eta /B_{iv}$, in which $B_{iv}$ is amended by an exponent (0.28 for the soil-pozzolan-lime blends investigated). For each specific soil, pozzolan, and carbide lime used and each curing period, independent of the amount of binder (herein considered as pozzolan plus carbide lime) and the porosity of the blends, a single correlation is found between $q_u$ and $\eta /{(B_{iv})}^{0.28}$ for the compacted soil–binder mixtures studied herein. The alternative binders studied herein are seen as a sustainable solution for soil stabilization.

The disposal of fly ash is an environmental challenge globally, and the only viable solution for its mass disposal is its use in the construction industry, especially for brick production. Hence, the substantial growth in masonry structures using fly ash bricks in India where coal-based power plants dominate the power sector has been recently seen. However, the safety and strength assessment of structures made of fly ash bricks often require the modeling of the uncertainty of its properties. The present study investigated the variability of compressive strength of fly ash bricks and proposes the most appropriate model for the statistical distribution. Twenty-six probability distributions were considered to conduct the three goodness-of-fit tests, namely, Kolmogorov-Smirnov, Kolmogorov-Smirnov-Lilliefors, and Anderson-Darling tests. The analysis concluded that the Johnson SB distribution is the best suited of the distributions considered for similar cases to model the variability in the compressive strength of fly ash bricks. In addition, the microstructures of these bricks were examined to investigate the cause of such variations.

This paper presents an experimental study in which molded gypsum specimens with different crack geometries (T-shaped and X-shaped cross crack) were tested in biaxial compression. Crack propagation and failure behaviors were investigated and nine crack types were detected, namely, wing crack, antiwing crack, secondary crack, horizontal wing crack, quasi-coplanar wing crack, quasi-coplanar secondary crack, far-field crack, surface spalling, and lateral split crack. Moreover, horizontal wing crack and quasi-coplanar wing crack were first observed in the rocklike specimens, which was caused by the added confining pressure. Besides, the cracks and failure modes under uniaxial and biaxial compression were compared according to proposed nine types of new cracks. With an increase in confining pressure, surface spalling and lateral split crack appeared. Lateral split cracks were observed only in T04 (${\sigma }_2=1.5\mathrm{MPa}$), X03 (${\sigma }_2=1.0\mathrm{MPa}$), and X04 (${\sigma }_2=1.5\mathrm{MPa}$), which indicate that lateral split crack is hardly induced under lower confining pressure. The reason is that confining pressure prevents the lateral deformation, therefore, failure can appear only along the free face such as surface spalling and lateral split crack. In practice, surface spalling is the common failure near excavation faces in deep tunnels, which validates the experimental results here.

There has been growing interest to reduce the use of conventional natural aggregates to promote sustainability in construction industry. In this study, quartz sandstones are substituted for natural igneous coarse aggregates in concrete and tested for chloride and corrosion resistance. The results indicate that the depth of chloride penetration increases with increasing quartz sandstone substitution, with similar depth of penetration to that of the control mixture observed up to approximately 20% replacement by volume. Results from corrosion potential measurements indicate no significant corrosion occurring in specimens made with either natural or coarse aggregates after 180 days of ponding.