Journal of Materials in Civil Engineering

Although extensive research has been conducted on the strength and stiffness of stabilised soils, fewer attempts have been made on the compression behavior of artificially structured and remolded soils. In this study, results from oedometer tests are discussed to investigate the compressibility of cement/lime-treated marine soils. The findings show that the difference in compression between structured and remolded soils is caused by soil structure and water content. For certain soil, a minimum binder amount exists beyond which the soil structure can only be observed, and the shape of compression curve changes from single line to two straight lines in a $\log (1+e)-\log {\sigma }_v^{\prime }$ plot. The relationship between compression index and index properties of remolded soils is initially discussed in conjunction with some available data in literature. When the effective stress exceeds the yield stress, the compression curves of both structured and remolded soils can be well normalized to a unique line by using the void index. However, the normalization approach proposed by researchers is proved unsuited to the compression curves of structured soils with yield stress higher than 100 kPa.

This paper deals with the utilization of waste plastic and waste tire rubber with bitumen for construction of low-budget roads instead of conventional polymer modified bitumen (PMB) due to its high price value. Economic growth and changing consumption and production patterns are resulting in rapid increases in the generation of various wastes, such as plastic waste, waste tires of truck and buses, etc., which pollute the urbanized civilization. Among such polymeric wastes only those containing high-molecular—high-density polyethylene (HM-HDPE), polypropylene (PP), low-density polyethylene (LDPE), and tire rubber ash (TRA) are used in this investigation to modify the properties of conventional bitumen. The results of experiment indicate that addition of 1% by weight of mixed plastic (MP) to the hot $60/70$ pen grade bitumen provides the enhancement in the temperature susceptibility resistant characteristics, viscous properties, and elastic recovery properties with good compatibility and cohesiveness at the micro level by satisfying the essential criterion of PMB 40.

The alkali-silica reaction (ASR) is an important problem that has yet to be completely understood. Owing to the complexity of this phenomenon, a number of studies have been conducted to characterize its kinetics, its impact on the material, and its structural consequences. This paper focuses on the deteriorating impact of ASR on concrete material, not only in terms of concrete swelling but also in consideration of the induced mechanical degradation. The relationships between concrete expansion and various engineering properties, which are key parameters in structural assessments, are investigated. First, new mechanical test results are presented. Second, available literature data on the evolution of engineering properties of ASR-affected concrete under free-expansion conditions are collected and statistically analyzed. The elastic modulus was found to be the best indicator for identifying the progression of ASR in concrete. Conversely, the evolution of compressive strength was observed to potentially mask damage resulting from the ASR. The tensile behavior of the affected concrete was better represented by the splitting tensile test.

A new volumetric mix-design procedure utilizing the Superpave gyratory compactor (SGC) was developed for cold in-place recycling (CIR) asphalt mixtures with assistance from the Federal Highway Administration (FHWA). It was developed for partial-depth CIR using asphalt emulsions as the recycling additive. This procedure was calibrated using materials from five geographically varied locations in North America: Connecticut, Kansas, Ontario, Arizona, and New Mexico. It required that specimens be prepared at densities similar to those found in the field. The performance of CIR mixtures prepared in accordance with the new mix-design procedure was evaluated in the laboratory with mechanistic-empirical pavement design guide (MEPDG) models as well as in the field. Creep compliance and strength of the mixtures were determined at 0, $-10$, and $-20°\mathrm{C}$ using the Superpave indirect tensile tester (IDT) with satisfactory results. A field test section also had been established with CIR mixtures in Arizona using this procedure and has been performing well with no significant visible cracking or distresses.

Segregation of grout applied for the protection of posttensioning steel may cause corrosion of steel wires, leading to serious hazards to the safety of posttensioned structures. Several cases of failure of external tendons of bridges have been documented arising from heavily corrosion attacks initiated and propagated in the presence of an unhardened (soft) whitish paste generated by segregation. The reasons for this aggressive corrosion attack are not clear, and improving the knowledge on the properties of the segregated grout would help in clarifying this phenomenon. Chemical, physical, and microstructural properties of grouts collected from the ducts of a bridge where segregation occurred are investigated. Results describe the different stages of segregation of the grout and show that the aggressiveness of the whitish grout could be associated with the high content of soluble compounds produced by early hydration of cement, especially alkalis, which lead to pH values exceeding 14.

Asphalt binder properties play a significant role in the performance of asphalt pavement, but it is impossible to test the properties of asphalt binders under every condition. However, a suitable model that can be established using only a few tests can predict the behavior of asphalt binders under different conditions. Such models have received much attention over the last few decades. Many types of models are available, but most of them focus on only one kind of viscoelastic characteristic, whereas a good model should describe not only the dynamic viscoelastic characteristics of asphalt binders under cyclic loading but also their static viscoelastic characteristics. Based on this idea, the aim of this study is to compare the commonly used models and determine which one(s) can best describe both the dynamic and static viscoelastic characteristics of asphalt binders at intermediate temperatures and are suitable for establishing a fatigue damage model of asphalt binders. The dynamic viscoelastic characteristics as well as the static creep and relaxation characteristics of two kinds of neat asphalt binders were tested. The Maxwell model, three-parameter liquid model, Burger’s model, the generalized Maxwell model, and the 1S2P1D model were compared for describing different characteristics of the asphalt binders. The results indicate that the generalized Maxwell model and 1S2P1D model are better than other models at describing the viscoelastic characteristics of asphalt binders. Both of them have advantages and disadvantages. Together with the ability to describe the behaviors of asphalt binders and the computational difficulty, the generalized Maxwell model is recommended.

Three full-size instrumented test slabs were constructed and tested by a heavy vehicle simulator (HVS) to evaluate the structural behaviors of internally cured concrete (ICC) for pavement use in Florida conditions. Three mix designs from a prior laboratory testing program were selected. The selected mixtures were a standard mixture with 0.40 water-cement (w/c) ratio, an ICC mixture with 0.40 w/c ratio, and an ICC mixture with 0.32 w/c ratio. Concrete samples were made and tested for their strength, elastic modulus, coefficient of thermal expansion (CTE), and shrinkage properties in the laboratory. A three-dimensional (3D) finite element (FE) model developed was calibrated by using a falling weight deflectometer (FWD) deflection basin as well as strain data under the HVS loading. From this study, it was found that ICC slabs appear to have better potential performance on the basis of the results of the critical stress analysis and the visual inspection of the test slabs.

Quenched and self-tempered (QST) steel reinforcement bars (rebars) are manufactured by Thermex or Tempcore processes. Characterization studies of QST rebars are mostly limited to reveal the hardened outer layer and some improved mechanical properties compared to hot-rolled (HR) and cold-worked (CW) rebars. However, investigations on residual stresses and imperfections originating from the manufacturing process as well as stress concentrations arising from the ribbed profile are rarely found in the literature. Surface residual stress may be beneficial or detrimental to the fatigue performance of rebars although they have been studied only on the subsurface of QST rebars. Surface imperfections are zones of stress concentration from where fatigue cracks may initiate. Imperfections are usually identified in the fractured cross section resultant from fatigue tests of rebars. Stress concentrations can also arise from the rib geometry. Although the rib geometric parameters affect the stress concentration factor $K_t$ on rebars, stress concentration analysis are restricted to two-dimensional (2D) finite-element models (FEMs). The study presented herein is part of a further detailed investigation on the fatigue behavior of HR-CW and QST rebars in the very high cycle domain. In the present work, characterization analyses of QST rebars include (1) experimental investigation of surface and subsurface residual stresses on QST rebars by cut compliance and X-ray diffraction techniques (residual stresses from both techniques are discussed); (2) identification of surface imperfections by scanning electron microscopy (SEM) analysis; and (3) three-dimensional (3D) finite-element analysis of stress concentrations on the ribbed profile. The influence of the rib geometry such as radius, width, height, and inclination as well as the rebar diameter on $K_t$ values are analyzed. The critical zones are determined along the ribs.

This study evaluates how elevated temperatures can affect the properties of concrete prepared with steel slag as a coarse aggregate. Four slag-based concrete mixtures were studied, using different types of cement pastes prepared with portland cement, fly ash as a 20% replacement of portland cement, and polypropylene fibers at 0.1% by volume, respectively; an additional dolomite-based reference mixture with portland cement served as a reference mixture. The test samples, which were prepared and aged for 56 days, were subjected to temperatures from 100 to 800°C. The residual mechanical properties of the cooled samples (i.e., their compressive strength and static modulus of elasticity), as well as their weight loss and residual ultrasonic pulse velocity, were determined and compared with those of the reference concrete. Additionally, scanning electron microscope analysis of the concretes and dilatometrical analysis of the cement pastes and aggregates were performed. The obtained results showed that the residual properties of concretes made with steel slag aggregate were comparable to those of the reference dolomite concrete up to a temperature of 600°C, whereas at higher temperatures, the slag exhibited expansion, which negatively affected the residual properties of the slag-based concrete mixtures.

The dry shrinkage characteristics of 23 rapid-set prepackaged cementitious materials collected from the current market have been investigated in this study. The materials showed various trends and rates of free dry shrinkage strain development. Overall, most materials had the free dry shrinkage of less than 0.05% at 28 days; however, only materials with the 28-day free dry shrinkage of less than 0.025% were observed to exhibit a low risk of restrained shrinkage cracking. The restrained shrinkage cracking typically occurred within a week after casting primarily because of the rapid growth of dry shrinkage during this period. A higher free dry shrinkage strain or a higher rate of free dry shrinkage strain development at the early age normally resulted in an earlier formation of cracking and a larger crack size during the restrained shrinkage test. Coarse aggregate extension reduced the free dry shrinkage and the risk or the size of restrained shrinkage cracking or delayed the time of restrained shrinkage cracking.

During this study, the protective effects of heat treatment and micronized copper quat (MCQ) impregnation on wooden surfaces in outdoor conditions were observed. Within the scope of the study, the 15-month weathering test effects on the Uzungöl and Hıdırnebi plateaus on oriental beech (Fagus orientalis L.) and Scots pine (Pinus sylvestris L.) wooden materials were studied. Changes of color, roughness, and visual-macroscopic values were compared on wooden surfaces that were subjected to weathering tests. Changes in the chemical properties of exposed surfaces were investigated with Fourier transform infrared (FTIR) spectroscopy. The presented data have clearly shown that the MCQ and heat treatment methods increased the stabilization of color and have slowed down the physical and chemical degradation on the wood surface under outdoor conditions. Moreover, the best protection methods against weathering were found to be heat treatment of Scots pine and MCQ impregnation of oriental beech.

Portland cement (PC) has been used extensively in ground improvement. However, environmental effects caused by PC production and durability of PC-stabilized soils when exposed to sulfate attack are of global concern. Previous studies show that reactive magnesia-activated ground granulated blast-furnace slag (GGBS) is a viable sustainable alternative binder to PC. However, limited research has been conducted on the durability of GGBS-magnesia (MgO) stabilized soft soils subjected to sulfate attack. This study presents a multiscale investigation on the performance of the reactive MgO-activated GGBS stabilized kaolin clay when soaked in a concentrated sulfate sodium solution. PC is adopted as a control binder for the purpose of comparison. The macroscale variations in mass change (MC), water content ($w$), dry density (${\rho }_d$), soil pH, and unconfined compressive strength ($q_u$) of GGBS-MgO and PC-stabilized kaolin clay under a sulfate sodium solution soaking condition are investigated. The results demonstrate that sodium sulfate attack has much less significant affect on the surface integrity, mass loss, ${\rho }_d$, and $q_u$ of the GGBS-MgO stabilized soil as compared with the PC-stabilized kaolin clay. These results are assessed on the basis of the microscale analyses of major hydration products, microstructure, and pore size distributions of the stabilized soils, which are obtained from X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) tests, respectively.

In this paper, self-healed cracks of engineered cementitious composites (ECC) are observed by optical microscope and scanning electron microscopy, and self-healing products of ECC are analyzed by X-ray diffraction technology. Meanwhile, the reasons for property differences between origin ECC and self-healed ECC with different crack structures exposed to freeze–thaw in water and deicing salt, respectively, are discussed. ECC specimens with a water–binder ratio of 0.25 with 50% fly ash are studied. The experimental results show that the white self-healing products and other chemical composites similar to the color of ECC matrix are present on the surface of self-healed cracks. The self-healing materials of ECC include kinds of hydration/carbonation products and some chemical compounds penetrating into ECC matrix from self-healing environments. Additionally, the differences in self-healing products and hydration products of binder, self-healing extent, damaged polyvinyl alcohol fiber, weak interface bonding, and microcracks could obviously influence the value variation of first cracking stress, ultrasonic pulse viscosity, and absorption coefficient of self-healed specimens.

Using renewed materials in the construction industry is very important for sustainable development. Recycled aggregate concrete (RAC) is one of the renewed materials. RAC uses demolished concrete as aggregate to make concrete. Previous studies showed that the strength of RAC can be improved and made comparable to regular concrete. This study examines the rate effect on fracture properties of RAC using an available improvement method. The RAC was made of 100% recycled coarse aggregate pretreated by a surface coating method. The fracture properties of RAC were tested based on the size effect method. Three different sizes of notched RAC beams were tested under three different strain rates, from ${10}^{-5}/\mathrm{s}$ to ${10}^{-2}/\mathrm{s}$, controlled by crack-mouth-opening-displacement (CMOD). For the beams under high loading rates, the fracture properties were found to be rate-dependent. The critical stress intensity factor, $K_{Ic}$, and the fracture energy release rate, $G_f$, increase with increasing loading rate. Two empirical equations were proposed for $K_{Ic}$ and $G_f$ as functions of the loading rate. Under high loading rates, the RAC beams were found to be less brittle than under the static load. This was also indicated by the test data of effective fracture process zone length, $c_f$, which increased with an increasing loading rate.

Nanoindentation techniques were implemented to calculate and interpret linear viscoelastic properties of asphalt binder and mastic through low-load spheroconical (blunt) nanoindentation. Experiments on three rolling thin-film oven (RTFO)–aged binders (two neat and one polymer modified) and 24 RTFO-aged mastics were implemented for reproducible creep indentations at ultra low loads. Creep compliance model parameters were extracted and used to determine dynamic modulus values for each material. Dynamic modulus values from nanoindentation were validated by using macroscopic dynamic shear rheometer (DSR) testing for two binders and two mastics (RTFO-aged). Atomic force microscopy (AFM) images of binder and mastic microstructure were obtained to shed insight on how microstructural phenomena relate to mechanical properties. The new results were combined with previously determined work of cohesion values for three binders and 30 mastics (RTFO-aged) made with the same materials to link microstructural phenomena with viscoelastic and cohesive properties of asphalt binder and mastic. The AFM results show microstructural changes occurring with the addition of mineral fillers that may relate to observed trends in nanoindentation viscoelasticity and cohesion data. Testing of binder and mastic properties through nanoindentation is an important step toward in situ testing of mastic in asphalt concrete, which is impossible using conventional macroscopic experimental methods.

In this study, a series of laboratory tests were performed to investigate the effects of nanosilica and polyvinyl alcohol (PVA) fiber on the mechanical properties and durability of cemented sand. The cement contents were 2, 4, and 6% by weight of the dry sand, and specimens were cured for 7, 28, and 90 days. The fiber contents were 0.0, 0.3, 0.6, and 1% by weight of dry sand cement mixture, and the nanosilica contents were 0, 4, 8, and 12% by weight of cement. Unconfined compression strength (UCS) and resist chloride ion penetration (CIP) were assessed in this study. The results showed an optimum percentage for the nanosilica in which the behavior of fiber-reinforced cemented sand improves significantly.

Lime stabilization of clay soils is becoming, if not already, one of the most used construction techniques for road embankments and for subbase stabilization. In warm countries, lime stabilization is used without any problems; but in cold countries, some concerns are still present in relation to behavior of lime-stabilized soils at low temperatures, particularly in conditions of freezing and thawing. The research in this paper presents the results of an experimental campaign made on a typical Italian clay soil stabilized with lime. The research studies the evolution of mechanical performances of lime-stabilized soil under the effect of freeze and thaw cycles and after a series of several freezes and thaws. The results of the research clearly show that lime-stabilized soils can have proper mechanical performances after freeze and thaw cycles. In particular, the test campaign shows that lime-stabilized soils have decreased resistance after freeze and thaw cycles and that they almost fully recover their resistance if the temperature comes back constantly to 20°C.

Significant levels of creep deformations in structural steel members exposed to high temperatures has been widely observed in experiments; however, inclusion of creep effects in numerical simulations has been limited due to lack of reliable experimental data and corresponding constitutive creep models for structural steel. This paper presents an experimental investigation into temperature-induced creep in low-alloy Q345 steel, which is commonly used in structural members. A set of creep tests is carried out at various stress levels in 300–900°C temperature range. Data from these creep tests indicate that temperature has significant influence on the level of creep deformations in Q345 steel, especially when the temperature in steel exceeds 400°C. The creep strain at a given temperature increases with stress level and the creep strain at a given stress level increases with temperature.

Cement stabilized soil block (CSSB) is a modern earthen building material that is used in the construction of masonry structures. Most studies involving CSSB have focused on how its composition affects strength characteristics and material properties such as erosion. In contrast, very little is currently known about CSSB structural behavior. This study set forth to address the absence of data in this research area, focusing on flexural panel testing, including separate horizontal and vertical bending tests. It was found that CSSB follows traditional masonry reactions; also, through experimental observation, two separate failure modes were identified. A linear elastic analysis confirmed these failure modes and predicted the cracking moment in the specimens analyzed.

In this study, reinforcing effect of nanomodified coir fibers with ferric hydroxide, $\mathrm{Fe}{(\mathrm{OH})}_3$, and aluminum hydroxide, $\mathrm{Al}{(\mathrm{OH})}_3$, on shear strength of limed marine clay soil was investigated. Accordingly, triaxial compression strength (TCS) testing was carried out to determine the shear strength parameters of the reinforced soil. Also, wetting/drying cycle testing was conducted to assess the durability of samples. The results from the experimental investigation show that the lime and nanomodified fibers improved the shear strength and durability through the intended modification on natural coir fiber. Moreover, an increase in the effective stress internal friction angle and the cohesion intercept were observed. To confirm the morphology alteration in fibers, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) tests were performed. Nanomodification of fibers increased their tensile strength and caused a better interaction with the limed matrix by an enhanced interfacial adhesion. The tensile strength and friction at the interface was the dominant mechanism controlling the reinforcement benefit.

This study aims at understanding various parameters that influence the performance of the sodium silicate (SS) additive along with cement in treating the soft Kuttanad soil. The change in soil structure in the presence of SS additive during cement treatment has been correlated with the engineering properties of cement-treated Kuttanad soil. The unconfined compressive strength (UCS) of samples was measured to study the additive dosage effect and to evaluate the impact of the clay water to cement (W/C) ratio on the additive performance. Microstructural and mineralogical investigations were carried out using X-ray diffraction (XRD) studies, scanning electron microscopy (SEM), pH, and zeta potential measurements. The results show that the presence of SS additive notably impacts the strength behavior of Kuttanad soil treated with cement by more than one mechanism. SS additive accelerates and augments the formation of calcium silicate hydrate (CSH). Further, it is found to induce changes in fabric and pore water chemistry that favor enhanced cementation imparting substantial strength to the cemented soil matrix.

An experimental study that investigates the nonlinear stress relaxation behavior of concrete under sustained strains is presented. Reinforced concrete structures experience both creep and relaxation during their service life. While the creep behavior of concrete has been widely investigated, very little is known regarding its relaxation behavior. This investigation includes testing of concrete cylinders under sustained uniaxial compressive strains. The tests are conducted at two different ages of the concrete to highlight the influence of shrinkage and aging on the behavior. A rigid displacement-control hydraulic system that allows testing of concrete cylinders under sustained strains with monitoring of the stress relaxation with time is used. The sustained strain levels correspond to initial stress levels of 35 and 50% of the compressive strength for one set of testing, and to stress levels of 30 and 60% in the other set. For better understanding of the behavior, the relaxation tests are also accompanied with creep tests under similar levels of sustained loading.