Journal of Materials in Civil Engineering

In this study, the feasibility of coarse (RC) and fine (RF) reclaimed asphalt pavement (RAP) inclusive concrete for sulfuric acid and hydrochloric acid environments is assessed. Moreover, the efficacy of mineral admixtures such as silica fume (SF), fly ash (FA) and bagasse ash (BG) in 100% RC mix was investigated. Three sets of conditions were selected so as to simulate the worst field situation such as the resistance of concrete in completely saturated and dried state and the effect of both acids on residual compressive strength and hydration process. The resistance of RC mixes was found to be superior to RF mixes in both the acidic environments and in both the simulated states. RF mixes were observed to be more detrimental in chloride solution than sulfuric. Inclusions of SF enhanced the performance of 100% RC mix considerably, followed by BG and FA. However, higher doses of FA resulted in significant loss in mass and strength in a sulfuric environment. Based on the findings, it is recommended to utilize only RC in cement concrete pavements prone to sulfate and chloride attack, whereas 10% of cement can also be replaced by the considered admixtures.

In order to prolong the service life of reinforced concrete structures in a severe marine environment, a novel alloy steel (00Cr10MoV) was developed. The passivation behavior of 00Cr10MoV steel in a simulated concrete pore solution (SCPS) was studied by electrochemical impedance spectroscopy (EIS). Furthermore, the influence of chloride concentrations and passive film on the pitting corrosion resistance of 00Cr10MoV steel was investigated using cyclic potentiodynamic polarization (CPP) and scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS). For comparison, conventional low-carbon steel (20MnSiV) and 2304 duplex stainless steel were also investigated. The results indicate that the pitting corrosion resistance of passivated 00Cr10MoV steel is significantly higher than that of passivated 20MnSiV steel. The formation of a protective passive film and the generation of dense Cr-bearing corrosion products of 00Cr10MoV steel are responsible for its high pitting corrosion resistance.

In the present study, the adverse effect of dust on the properties of concrete containing 75% fine reclaimed asphalt pavement (RAP) (75F) (obtained using an uncontrolled milling technique) is minimized by using higher doses of superplasticizers (SP) in combination with silica fume (SF), flyash (FA), and bagasse ash (BG). It was found that the 75F mix requires at least double the amount of SP to achieve the recommended slump value. Moreover, improvement in the fresh state was found to enhance the hardened properties of the 75F mix significantly. Inclusion of the considered mineral admixtures was found to further enhance the compressive strength, splitting tensile strength, and abrasion resistance; however, inclusion of BG and FA resulted in comparable flexural strength. The determination of water absorption and permeable voids was found to be affected by the asphalt film, suggesting this testing should be conducted at a temperature lower than 50°C. Based on the results of the economic analysis, the addition of extra doses of SP should be considered as the best and most economical way of minimizing the effect of dust present in fine RAP aggregates, whereas inclusions of BG and FA could further make the concrete cheaper and more durable.

In this paper, the feasibility of applying the existing empirical models on reactive powder concrete (RPC) reinforced with different types of steel fiber under compression was assessed. The behavior of RPC reinforced with different types of steel fibers of different geometry and volume content was highlighted. The outcomes show that the existing models overestimate the strain at peak stress, modulus of elasticity, and the ascending and descending branches of the stress-strain curve. Also, the influence of different types of steel fibers of different geometry and volume content has not been properly presented in the existing models. As such, an empirical model to predict the complete stress-strain curve of RPC reinforced with different types of steel fibers of different geometry and volume content of strengths ranging from 95 to 130 MPa is proposed. The results obtained from the proposed model were verified with the experimental results of RPC obtained in the literature. The proposed empirical model has been found to be in very good agreement with the stress-strain curves that were obtained experimentally.

Shear friction (SF) theory governs the relationship between the stresses and displacements that occur due to sliding along a concrete-to-concrete interface subjected to varying degrees of lateral confinement. This theory is commonly applied to predict the transverse shear strength of reinforced concrete beams and slabs, the longitudinal shear capacity and behavior of precast connections, the size effect and confinement in compression members, and flexural failure in the compression region flexural members. The SF material properties required for this theory are commonly determined from tests where the confining force across the sliding plane is passively induced through transverse reinforcement and therefore difficult to quantify and isolate from the reinforcement dowel action. In this paper, a new test apparatus is presented to determine the SF properties of ultra-high-performance fiber-reinforced concrete (UHPFRC). The proposed setup has the following benefits: it removes the need for passive reinforcement by applying a normal stress hydraulically, thereby allowing confinement to be directly measured and controlled; it removes the effect of dowel action; and it allows the use of specimens manufactured from $200\times 100\text{-}\mathrm{mm}$ cylinders, which is beneficial because they can be cored from larger specimens to investigate the influence of fiber orientation. To verify this new apparatus, a series of 16 tests were conducted on UHPFRC with a range of short straight and long hooked steel fibers as well as a range of normal confining stresses.

With the advancements made in the spatial analyses, characterizarion methodologies, and management of large data sets, the visualization of geomaterial properties at different stages of civil infrastructure works has become easier to implement. Visualization of material characteristics in the ground has given engineers a realistic three-dimensional image that creates a comprehensive digital ground environment where large complex projects can be effectively conceptualized, designed, and constructed. This research paper presents these material characterization–related advancements made in the better understanding of construction and performance of infrastructure using geospatial and visualization tools. Infrastructure case studies ranging from material characterizations from laboratory and in situ tests to data captured from photogrammetry-based measurements from unmanned aerial vehicle (UAV) platforms are described. The two-dimensional visualization models developed for a pipeline and dam infrastructure provided localized critical zones, which can trigger failure in the event of hazardous conditions. The three-dimensional models, developed using UAV-based photogrammetry studies, provided the health conditions of the structure with a focus on material performance. Future applications encompassing material properties to field measurements are covered in detail.

Production of hot-mix asphalt (HMA) involves high mixing and compaction temperatures, which leads to the emission of greenhouse gases and high fuel consumption. Recently, various warm-mix asphalts (WMAs) have been used for production of asphalt mixes to promote a cleaner environment and better working conditions. Although selected WMA additives may be beneficial in reducing the mixing and compaction temperatures of a binder, they may also adversely affect rheological properties of asphalt binders and thus may discourage users from fully utilizing their potential. The current study evaluates effects of different types of WMA additives on mixing and compaction temperatures, rut resistance, and fatigue performance of an AC-30 binder. A control AC-30 was modified with three WMA [Fischer Tropsch (FT) wax based, water based (WB), and chemical surfactant based (CS)] additives in varying dosages. First, the effect of WMA additives on the viscosity of the AC-30 binder was measured, followed by the effect on mixing and compaction temperatures. Thereafter, rutting and fatigue performance of the AC-30 with and without different WMA additives was evaluated using multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS), respectively. Further, effects of WMA additives on Superpave high-temperature performance grade (PG) of AC-30 was also determined. The paper also discusses changes in chemical composition of AC-30 binder after addition of WMA additives, which was evaluated using the Fourier transform infrared spectroscopy (FTIR) technique. All three WMA additives (FT, WB, and CS) decreased mixing and compaction temperatures of AC-30, except the addition of 8% WB. Superpave high PG of AC-30 did not alter with the addition of WB and CS. Fatigue and rutting performances of AC-30 degraded after addition of WB and CS. The effect of FT was found to be promising not only in enhancing rutting and fatigue performances but also to bump the Superpave high PG of AC-30. Considering reductions in mixing and compaction temperatures and other rheological performances, the effective dosages of FT, WB, and CS for AC-30 binder were found to be 1, 4, and 1%, respectively.

One of the proposed techniques of reducing moisture damage in asphalt mixture is to utilize coating on the aggregate surface. In this study, two types of additives as an aggregate surface modification, two types of aggregates, limestone and granite, along with an asphalt binder of 60–70 are the materials used to make asphalt mixtures. The thermodynamic concepts with cyclic loading have been used to evaluate the effect of using these materials. The results obtained in the study indicate that the hydrophobic coating on the surface of the aggregate has caused the acidic and basic components of surface free energy to reduce and increase, respectively. The changes have caused an increase in the adhesion of the asphalt binder aggregate and the better wettability of asphalt binder over the aggregate. The results of calculations based on the thermodynamic concepts indicate that aggregate surface coating has caused the reduction of debonding energy of the system and the desire for stripping. The results of dynamic modulus ratio in wet to dry conditions indicate that the use of aggregate coating decreases moisture damage of modified mixtures. The combination of thermodynamic concepts and cyclic loading results also shows that the coating on the surface of aggregates has led to reduction in the rates of stripping of the asphalt binder aggregate.

In this paper, experiments carried out on ordinary concrete under multiaxial compression of both full section and local section are presented and the failure modes compared under different loading conditions. According to the stress–strain curves obtained in true triaxial compression experiments, the mechanical properties of ordinary concrete were also extracted under different loading conditions, including full section loading and local loading. Because of the confining pressure, as for full section loading, the peak stresses under multiaxial compression were 1.27–2.27 times higher than those under uniaxial compression, whereas for local loading, the multiple was 1.24–2.05 times. It is obvious that the increasing coefficients under full section compression are more susceptible to confining pressures than those under local compression. The unique point of the experimental method is that ordinary concrete was subjected to full section or local uniaxial compression after full section or local triaxial compression. In this way, the failure modes of ordinary concrete were clearly revealed owing to the initial damage caused by triaxial compression. Meanwhile, the residual mechanical properties of ordinary concrete that had been subjected to full section or local triaxial compression were obtained, contributing to a comprehensive understanding of the mechanical properties of ordinary concrete under triaxial compression. Then a failure criterion of ordinary concrete under local loading was proposed based on the data of true triaxial compression experiments. The failure criterion was verified using data of both relevant scholars’ experiments and independent experiments of local triaxial loading. The results showed that the proposed failure criterion was simple but effective enough to compute the failure strength of ordinary concrete.

This paper presents results from experimental studies on residual mechanical properties of Grade 10.9 bolts exposed to elevated temperatures. The effects of various target temperatures on the residual mechanical properties, including ultimate and yield strengths, stress-strain response, and the failure modes of bolts, were investigated. Furthermore, the influence of temperature level, chemical composition of feedstock steels, and heat treatment parameters in the fabrication process of Grade 10.9 bolts on residual mechanical properties was studied. Data from the experiments indicate quick reduction in residual strength of the bolts when heated up to temperatures greater than 400°C, reaching to 50% of its ultimate strength when exposure temperature reaches 800°C. Tempering the temperature in the bolt manufacturing process and carbon content in steel are two other important factors besides exposure temperature that have a great influence on residual properties of Grade 10.9 bolts. Based on the experimental results, a set of predictive equations is also proposed for assessing the temperature-dependent residual mechanical properties in Grade 10.9 bolts.

In this study, the multicyclic biaxial bias extension test using cruciform specimens with 45°-oriented fibers was carried on an advanced biaxial tensile tester, and three different shear loading histories (SLHs) were utilized to estimate shear properties of polyvinylidene fluoride (PVDF)–coated fabrics. The distribution of shear strain in the area of interest was homogeneous according to the results of digital image correlation. The experimental results showed that shear stiffness of coated fabrics decreased from 11.4 to $3.9\mathrm{kN}/\mathrm{m}$ with the improvement of maximum shear stress. The normal stress in the warp and filling directions enhanced the shear stiffness according to the comparison among three shear loading histories. The reduction of residual shear strain indicated that the zero-shear-stress condition contributed to shear deformation recovery. Finally, the deformation mechanism of biaxial bias extension was considered on the basis of experimental observation. In general, this study proposed a specific test method to understand shear properties of coated fabrics used in membrane structures.

Lightweight self-consolidating concrete (LSCC) is an attractive construction material combining the benefits of self-consolidating and lightweight concrete. The material is especially beneficial for structures in which reduced load and ease of construction among dense reinforcement are needed. While a great potential for lightweight self-consolidating concrete exists, the material’s shrinkage and cracking susceptibility has not been characterized in detail up to date. As such, in this work, laboratory evaluation of LSCC using restrained ring test was conducted. The results showed that the combination of natural and lightweight aggregates resulted in the mixture least susceptible to restrained shrinkage cracking (cracking noted at 6.6 days), compared with all-natural (cracking at 3.0 days) or lightweight aggregates (cracking at 4.6 days). Additionally, the Monte Carlo method was used to develop a model capable of predicting likelihood of cracking in LSCC. The results of the simulations showed good agreement with the restrained ring test results.

Effect of water on asphalt concrete containing air voids in the range 3–5% (the typical composition used for the construction of pavements) has been widely studied. However, it is also necessary to evaluate the effect of water on mixtures with a low amount of air voids and high asphalt saturation ($V_a<3\%$ and $VFA>88\%$; the typical mixture used in impervious barriers), as it is well known that contact with water causes slow oxidation of asphalt (binder), which makes it hard and brittle. In this research, asphalt concrete cylindrical specimens with a low air void content were prepared and saturated, and kept in contact with water for up to 12 months. Then, a process of asphalt recovery was performed on the specimens. Infrared spectroscopy, rheological analyses, and saturates, aromatics, resins, and asphaltenes (SARA) fractionation were performed to characterize the asphalt binder. It was revealed for the time periods considered in this study that the asphalt oxidation level was low, which can be attributed to low air void volumes and high asphalt saturation in the as-used mixture.

Blast furnace slags (BFS) have interesting physical properties and chemical compositions for the production of mastics in asphalt mixtures. However, most of the studies conducted on this material and their applications in asphalt mixtures have been as substitutes for the coarse fraction of natural aggregates (NGA). In the present study, an experimental program was devised to evaluate the effect on the resistance of a hot mix asphalt (HMA), due to the replacement of fine fraction of a NGA by a BFS. The mechanical properties investigated were indirect tensile strengths, resilient modulus, permanent deformation, resistance to fatigue, and moisture damage. Analysis of variance (ANOVA) tests were performed to verify or reject the null hypothesis that the results are statically equal to those of the reference mixture. X-ray diffractometry (XRD) and X-ray fluorescence (XRF) tests were carried out on particles of BFS and NGA. Additionally, the samples were subjected to imaging processing in a scanning electron microscope (SEM). Characterization tests (viscosity, softening point, penetration, and indirect tension) were performed on mixtures made of fine particles (NGA and BFS) and asphalt. The BFS used as fine aggregate tends to generate, in conjunction with asphalt, a material with improved properties of resistance under monotonic and dynamic load.

China Railway Track System (CRTS) II slab ballastless track is a sandwich multilayer structure, and cement emulsified asphalt mortar (CAM), as the middle bonding layer between the track slab and concrete bottom slab, is a key engineering material for slab ballastless track. To improve the interfacial bonding behavior of CAM and reduce the debonding of CAM, the influence of the stabilizer on the properties of CAM was studied. The segregation, interfacial bonding strength, and microstructure morphology of CAM were tested. Moreover, a trial application was performed to determine the field performance of the stabilizer. Results showed that the incorporation of the stabilizer not only improved the homogeneity performance of CAM but also increased the interfacial bonding strength. The debonding rate and gap width of CAM with the stabilizer had sharply decreased on site. This work has demonstrated a new available strategy for reducing the debonding of CAM in CRTS II slab ballastless track.

Analysis and load rating of historic, riveted steel structures typically requires an assumption of rivet shear strength. The AASHTO Manual for Bridge Evaluation (MBE) provides rivet shear strengths based on the year of construction; however, the values provided are more conservative than legacy test data. Following the 2007 collapse of the I-35W bridge in Minneapolis, MN, riveted gusset plate connections, primarily on older structures, became a national concern. Many owners found using the MBE prescribed shear strength values resulted in some connections not satisfying load rating requirements. In such cases, some have elected to remove a number of rivets and perform destructive laboratory testing to obtain actual material properties. This alternative can be an expensive and time-consuming process. As an alternative, some have performed hardness testing on in-situ rivets to estimate the strength of the rivet using known hardness-to-ultimate strength correlations. The following study was performed to evaluate the variability of hardness throughout a rivet to establish if in-situ hardness measurement and correlation with the hardness of the shank is a reasonable method to estimate the strength of a rivet. Hardness testing is an economical and efficient process easily conducted in the field using handheld devices. However, questions have arisen regarding whether measurements made on the surface of the driven rivet are representative of the hardness of the shank, which was not mechanically worked as compared to the button head or head that was created during the driving process. For the current study, rivets were removed from seven structures of varying age and the hardness was measured. In addition, modern driven and undriven rivets were tested to compare historic results to modern materials. Hardness was measured on both the shop and driven rivet heads as well as at several locations throughout the shank of the rivet and compared to historical specification requirements. Variation in hardness throughout the rivet was analyzed to determine if the hardness measurement on the head could be correlated with the rivet shear strength. Measured rivet head hardness was found to have good correlation with hardness measurements throughout the rivet shank.

With the goal of increasing the swelling pressure and lowering the permeability of ordinary sodium bentonite with high concentration cation solutions, the optimum conditions for producing polymerized bentonite (PB) were examined through a series of laboratory tests. Based on the test results, the proposed optimum conditions for using the free radical polymerization are using sodium acrylate as the monomer and potassium persulfate (KPS) as the initiator, pH of 7, the initiator ($I$) to monomer ($M$) ratio, $\mathit{I}\mathit{/}\mathit{M}$, of 0.2 and the monomer content of 10%. Then, the PB produced using the proposed conditions was further investigated on the microstructure and the hydraulic properties. The results of X-ray diffraction (XRD) patterns indicate that the sodium polyacrylate did not modify the interlayer spacing of the bentonite particles, but the scanning electron microscopy (SEM) image shows that the PB particles have rounder edge compared with that of the untreated bentonite (UB) particles because the bentonite particles were coated by the polymer. For the hydraulic properties, the results of a swelling pressure test show that with comparable initial dry density, PB had higher swelling pressure than that of the UB. Under the identical void ratio, the PB had much lower permeability ($k$) than that of the UB with aggressive 0.6 M NaCl and $0.6{\mathrm{M}\mathrm{CaCl}}_2$ solutions. Based on the test results, the PB produced using the proposed conditions can be used as a barrier material against high concentration cation solutions. The proposed optimum condition can be a useful guideline for further investigations on the other properties of the PB.

Premature deterioration has been observed at some joints in concrete pavements. This joint damage has been attributed, in part, to a deleterious chemical reaction between chloride-based deicing salts (e.g., calcium chloride) and calcium hydroxide from the cementitious matrix resulting in the formation of a compound referred to as calcium oxychloride. Calcium oxychloride formation can be mitigated in cementitious pastes through the replacement of cement with supplementary cementitious materials (SCMs) (e.g., fly ash or slag). Although various SCMs are beneficial in mitigating the formation of calcium oxychloride, little has been written to describe similarities or differences between the different types of SCMs relating to their ability to mitigate calcium oxychloride formation. This paper compares various SCM types. Cementitious pastes were prepared with between 0 and 60% of the cement being replaced (by volume) with SCMs for water-to-cementitious materials ratios ($\mathrm{w}/\mathrm{cm}$) of 0.36 and 0.50, which are the lower and upper bounds of the w/cm typically used for pavements and sidewalks. Pastes were cured to develop a high degree of hydration, and subsequently ground to a fine powder for use in thermogravimetric analysis and low temperature differential scanning calorimetry testing to quantify the calcium hydroxide and calcium oxychloride amounts, respectively. The composition of the specific fly ash and slag used influences the calcium hydroxide and calcium oxychloride amounts. As the w/cm increases, calcium hydroxide and calcium oxychloride amounts increase; however, this amount was only between 4 and 30% for the calcium hydroxide and various SCMs. As the volume of supplementary cementitious materials replacing the cement increases, calcium hydroxide and calcium oxychloride amounts decrease. The supplementary cementitious materials reduce the calcium hydroxide and calcium oxychloride formed in the order calcined clay $>$ silica fume $\gg$ fly ash $>$ slag $\gg$ limestone. The contributions of the SCMs to reducing calcium hydroxide (CH) and calcium oxychloride (CAOXY) due to dilution and reaction are separated. The potential benefits of different SCMs in reducing calcium hydroxide amounts in paste can be predicted based on their pozzolanicity (determined from their response in pozzolanic tests based on isothermal calorimetry and thermogravimetric analysis).

This work evaluated the effect of polymer and polyphosphoric acid (PPA) on the aging resistance of different asphalt binders with pressure-aging-vessel (PAV) aging. Two base asphalt binders, three polymers, one recycled crumb rubber, and one PPA were used to produce the modified binders. The tested aging resistance included failure temperature, fatigue factor ($G^{*}·\sin \delta$), phase angle by dynamic-shear-rheometer (DSR) testing, stiffness ($S$), and creep rate ($m$-value) by beam-bending-rheometer (BBR) testing. The $G^{*}·\sin \delta$ values of the modified binders produced by 2% oxidized polyethylene or propylene–maleic anhydride and 0.5% PPA are lower than that of the modified binders produced by 3% oxidized polyethylene or propylene–maleic anhydride. Similarly, the modified binders produced by 2% styrene butadiene styrene (SBS) and rubber and 0.5% PPA show a lower fatigue factor value than those produced by 3% SBS and rubber. The asphalt binders blended with 0.5% PPA show lower phase-angle values than those produced by 3% oxidized polyethylene, propylene–maleic anhydride, or SBS. Moreover, the phase-angle value of the modified binder containing 2% SBS and 0.5% PPA is the lowest. The low-temperature stiffness and failure of modified asphalt with PPA is reduced to 23, 18, and 20°C. Compared with the polymer-modified asphalt, the difference between the stiffness of modified-asphalt binder with PPA at the test temperature of $-18°\mathrm{C}$ decreased by 16.67, 25, 4.17, and 4.17%, respectively. The results showed that using 0.5% PPA as 1.0% polymer replacement has a positive influence on the aging properties of binders. Moreover, the polymers, PPA, and binder sources can obviously influence the fatigue resistance of the binders.

The main objective of this paper is to investigate the effect of nanoclay on the hydraulic conductivity of compacted clayey sands as an earth dam core material. Furthermore, other mechanical characteristics, such as shear strength and dynamic parameters of the treated clayey sand soil, were investigated. The soil samples were prepared by mixing two types of soil including Kaolin clay (KC) and Firouzkooh sand (FS) in proportions of $1:9$ (1-9CS) (sand with 10% clay) and $1:4$ (sand with 25% clay) (1-4CS) by weight, respectively. In the experimental program, initially the compaction parameters (optimum moisture content) of each sample were obtained for preparation. Then, a series of hydraulic conductivity tests were conducted on prepared specimens for different weight percentages of nanoclay (1–4%). The results showed that adding nanoclay up to 3%, as its optimum limit, causes considerable reduction in the hydraulic conductivity to a desirable value for the core material of earth dams. In addition, it was observed that the strength of specimens in drained condition increased, while for undrained condition it decreased. The results also indicated that the treated soil dynamic parameters, such as shear modulus and damping ratio, were decreased and increased, respectively. A complementary series of swelling and self-healing tests were also performed and the results revealed that nanotreatment improved soil performance considering hydraulic conductivity.

Passive (site) stabilization is a novel technique for the mitigation of seismic liquefaction which uses low-pressure injection of colloidal silica in the pores of a granular soil. The applicability of colloidal silica as a grout relies on the control of its time-increasing viscosity. Current knowledge depicts silica type, percentage of silica by weight, pH, and salt (ion) normality as the controlling parameters of colloidal silica viscosity, whereas current practice requires case-specific viscosity measurements before in situ injection. This paper presents a set of viscosity measurements of widely different colloidal silica solutions which confirm literature findings and depict temperature as an additional controlling parameter. The wealth of these measurements enables a reliable statistical analysis, which leads to the proposal of a set of charts and equations for the approximate estimation of the time-increasing viscosity of colloidal silica solutions. This information is paramount for the design of the in situ injection process and its importance is demonstrated via indicative one-dimensional injection tests of colloidal silica in sand columns.

Alkali-activated materials (AAMs) have recently been used as a suitable replacement for conventional ordinary portland cement (OPC) mixtures. This study evaluates rheological, injectability, and mechanical properties of alkali-activated slag (AAS) mixes to assess the possibility of using AAS pastes as coating mortars for the rehabilitation of concrete structures. Mixtures are produced with the incorporation of silica fume (SF) up to 15% of total binder weight in AAS pastes. A combination of sodium hydroxide (NaOH) and sodium silicate (water glass) is used to activate aluminosilicate sources. Water glass:NaOH ratios of 0.4 and 0.5 and activator solution:pozzolan ratios of 0.55 and 0.65 are selected after initial attempts to evaluate the effect of activator solution characteristics on the rheology properties of AAS mixtures. Samples are prepared in two moisture conditions (dry and damp) in order to assess the effect of moisture presence on the performance of AAS injection pastes. Setting time, fluidity, injectability, tensile strength, capillary absorption, and slant shear tests are conducted on AAS pastes. Microstructure analysis is performed on the selected mixtures. According to results obtained from limited experimental work conducted in this study, 5% SF addition results in higher setting time and injectability of AAS pastes. In addition, it is found that an increase in water glass content in AAS pastes results in lower setting time and fluidity, which in turn results in a low level of injectability. The results of tests conducted on damp and dry samples show a high level of compatibility of AAS paste with moisture presence.

In this investigation, highly sensing smart cement grouts were developed using 0.8 water-to-cement (w/c) ratio and adding up to 3% sodium silicate. The sensing grout was also used to repair damaged piezoresistive smart cement cured under room conditions. During the hardening process, the change in the resistivity with curing time was continuously monitored to better understand the process. The sensing grouts showed change in resistivity with applied stress (piezoresistive) behavior, and the changes in the behavior very much depended not only on the curing time up to 28 days of investigation but also the amount of sodium silicate in the mixture. Vipulanandan p-q models were used to predict the curing and also the piezoresisitive behavior of the sensing grouts, and the models predicted the behavior very well. The grout strengths and secant piezoresistivity modulus varied with time, and the Vipulanandan correlation model predicted the changes very well. Also, one-day-old smart cement samples with piezoresistivity in the range of 268–300% were failed and then repaired using the newly developed smart cement grouts.

A facade coating that still has wide applicability is mortar render, whether it is made with lime or cement, whether it is a predosed composition or traditionally made in situ, and whether it is applied in new constructions or for rehabilitation purposes. In fact, this type of coating is very versatile, easy to execute, and inexpensive. Whether the characteristics of a mortar are declared by the manufacturer or established by the user, they are normally determined in the laboratory in accordance with the relevant standards using specimens with recommended dimensions. But when applied to real substrates, will these mortars maintain their characteristics, or will the characteristics of the substrate have a significant influence on them? What will this influence be? Will a porous substrate have more or less influence than a nonporous one? The research carried out at the University of Coimbra in collaboration with the University of Porto and the National Laboratory for Civil Engineering (LNEC) set out to answer these questions. To carry out this experimental campaign, three types of substrates and three types of mortars were selected. The different mortars were applied to the different substrates. All the substrates and mortars were characterized before and after application on the substrates. A comparative analysis of the obtained results was made and it was possible to confirm that the substrates influence mortar characteristics and that this influence varies depending on the type of mortar.

This paper proposes a framework for describing the modulus degradation behavior of cement-treated soft clay. The results show that effect of the mix ratio on the modulus degradation behavior can be captured through the unconfined compressive strength only, rather than through two parameters (e.g., void ratio and cement content) as used in existing models. The parameters for describing the modulus degradation behavior can be evaluated directly by appropriate plots of the data without any iteration. Fitted expressions are also given which relate these parameters to the unconfined compressive strength. The effect of the mean effective stress becomes significant when it is higher than the primary yield stress. Similarly, the effect of overconsolidation increases with increasing overconsolidation ratio. Both parameters can be incorporated into the expressions for the reference strain, $\alpha$, and normalized degraded modulus. These expressions allow the effect of mix ratio, mean effective stress, and overconsolidation to be comprehensively described. Together, the proposed models provide a complete framework for describing the effect of mix ratio, mean effective stress, and overconsolidation on the modulus degradation behavior of cement-treated soil.

In this study, ultra-high-performance concrete (UHPC) was reinforced by hybrid fibers and corundum aggregates. The dynamic behavior of UHPC against multiple bullet impacts was researched. The penetration damage to concrete targets was measured, and the fracture patterns of targets and bullets were observed after each impact. The effects of hybrid fibers and corundum aggregates on bullet penetration depth and damage to UHPC subjected to multiple bullet impacts were researched. An empirical model was proposed to predict bullet penetration depths in UHPC based on the formula developed by Gomez. The fracturing of UHPC was simulated by the finite-element method. Results show that UHPC resistance to multiple penetrations was improved by the hybrid fibers and corundum aggregates (Moh’s hardness of 9.0). The calculated penetration depths were very close to the experimental data using the proposed model and the finite-element method. Simulation showed that depth decreased as erosion strain increased, so an optimal strain for each concrete was determined and used in modeling the hybrid fiber-reinforced cementitious specimens. Concrete target peak pressure varied with depth, and maximum pressure appeared near the penetration end and then gradually dropped until the bottom of the target was reached.

The mechanical behavior and transport properties of cement pastes reinforced with various types and amounts of pristine and functionalized carbon nanotubes (CNTs) are characterized for different water to cement (w/c) ratios. The flexural strength, compressive strength, and dynamic modulus of elasticity of CNT-reinforced cement pastes were up to 38%, 58%, and 22% higher than those of unreinforced pastes, respectively. CNTs were also effective in decreasing the drying shrinkage of cement pastes to 87% lower than that of reference pastes at early ages. Water absorption by immersion and capillary absorption could be also reduced as much as 16% and 38%, respectively. Microstructure and thermogravimetric analysis evidenced effective dispersion, microcrack bridging, and nucleation effects of CNT-reinforced cement matrices. Results show that depending on the type and dispersion procedure, CNTs effectively contribute for the reinforcement of cementitious materials, regardless of w/c ratio.

Construction of new structures, including concrete thin-walled shell structures, using high technology and economic efficiency has been become inevitable due to the advancement and development of concrete industry. Thin-walled shell structures are appropriate elements to construct large installation infrastructures such as oil and water reservoirs and silos. When cylindrical shells are under internal pressure, hoop or tangential stress and strain are generated in the walls, and evaluation of these elements is the purpose of the present research. In this study, hoop stress-strain of fiber-reinforced cementitious composite thin-walled cylindrical shells under uniform internal hydrostatic loading has been evaluated. For this purpose, 36 small models of thin-walled cylindrical shells containing 0, 5, and 10% silica fume (SF) and 0, 0.5, 1, 1.5, 2, and 2.5% glass fiber were made and tested after 28 days of wet-curing conditions. The compressive and flexural strengths of composite samples were tested to relate concrete strengths with the results of cylindrical shells. The results showed that the use of silica fume increased compressive and flexural strengths up to 27 and 32%, respectively. Also, the presence of fibers had no significant effect on the compressive strength, but increased the flexural strength up to 21%. In cylindrical shells, the addition of silica fume increased the hoop tensile strength up to 10% and decreased the hoop tensile strain to 28%. Furthermore, the addition of 2.5 and 0.5% glass fibers raised hoop ultimate strain 7.4 times and hoop tensile strength up to 37%, respectively.

Multiwalled carbon nanotubes (MWCNT) are expected to enhance the load transfer and increase the flexural strength of a MWCNT-cement composite by working as bridges for load across cracks. For this, an adequate dispersion degree of nanotubes throughout the matrix must be obtained, surfactants being one of the most used chemical-dispersing aids to attain this goal. A commercial MWCNT/surfactant aqueous dispersion was used to produce cement pastes with MWCNT additions up to 0.25% by mass of cement. Rheological behavior and mechanical performance were used to characterize the influence of nanotubes on the cement paste. It was found that the MWCNT/surfactant dispersion studied decreased the workability and mechanical properties of the cement paste, regardless of micrographs showing that MWCNT acted as bridges across submicrometric cracks. This was due to a delay of the hydration reaction of cement and an increase of the amount of entrapped air caused by the presence of surfactant. It was concluded that the reinforcing effect of nanotubes was masked by the negative effects of the surfactant on the mechanical performance of the matrix.

The stabilization of problematic soils with chemical additives has become a popular practice globally. However, the mechanical and microstructural characterization of subgrade materials stabilized by alkalinization of raw silty sand, a common soil in British Columbia, Canada, has not yet been studied. This study introduces the novel concept of using an alkaline activator, along with magnesium chloride (${\mathrm{MgCl}}_2$), to activate the silica and alumina components of silty sand. Compaction and unconfined compressive strength (UCS) tests were used to assess the mechanical properties of the stabilized soil. The mechanisms that have contributed to the stabilization process are discussed based on the results of microstructural analysis using field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR) analysis. It was found that the chemical additive improved the compressive strength of the soil significantly. The UCS results revealed that a sample mixture containing an alkaline activator (sodium silicate/sodium hydroxide) ratio of 0.5, an alkaline activator to ${\mathrm{MgCl}}_2$ ($L/S$) ratio of 0.7, and 3% ${\mathrm{MgCl}}_2$ by dry weight of the soil was the optimum mix to improve the strength of the silty sand when cured for 28 days. The FTIR result confirmed the formation of the magnesium hydration products. Additionally, the SEM images and EDS data revealed that the stabilization process produced a cementitious gel, consisting of magnesium silicate hydrate (M-S-H) and magnesium aluminate hydrate (M-A-H) compounds, that bonded soil particles together.

This study investigates the use of thermogravimetry (TG) and X-ray diffraction (XRD) to characterize and quantify the hydration products, particularly calcium silicate hydrate (CSH) and calcium hydroxide [$\mathrm{Ca}{(\mathrm{OH})}_2$], in stabilized soils and to establish correlations between these products and strength gain over time. A pure kaolinite is the soil for this study and portland cement is the selected stabilizer. Untreated and cement-stabilized samples are compacted at their optimum conditions and cured for different periods of up to 90 days. The unconfined compression test, which is a relatively simple and commonly used test, is performed to measure the unconfined compressive strength (UCS) for all the samples and record the macroscopic behavior. A portion of soil from each set of samples is recovered and subsequently subjected to the TG test coupled with mass spectrometry (MS) and XRD. Using TG, the amounts of CSH (mass loss between 105 and 440°C) and calcium hydroxide (mass loss between 440 and 580°C) are measured and monitored with time to establish their correlation with strength gain. Quantitative XRD using whole-pattern fitting (Rietveld analysis) and the reference intensity ratio (RIR) indicated that the amount of kaolinite decreases logarithmically with curing time and a strong linear correlation is observed between the amount of kaolinite and the unconfined compression strength.

Aggregates selected for Wisconsin transportation infrastructure must withstand harsh service conditions. In this paper, results of comprehensive statistical analyses on three sets of aggregate test data (two from Wisconsin and one nationally) are discussed. This included a database containing 2,052 sets of quality control aggregate tests from various construction projects in Wisconsin, an earlier Wisconsin aggregate research study (69 data sets), and a set of test results of aggregates from different parts of the United States and Canada (111 data sets). In addition, tests on 12 types of marginal or poor Wisconsin aggregates (as characterized by the state) were performed. The study objectives were to evaluate relevant statistical parameters for various aggregate test results and identify correlations among them. The possibility of predicting the outcomes of two tests [micro-Deval (MD) and unconfined freeze-thaw (UFT)] from other more common test results was studied. Multiparameter logistic regression analyses indicated that the micro-Deval test’s pass/fail outcomes could be predicted when results of other commonly performed tests were known. However, the outcome of the UFT test could not be forecast using results of other tests.

The compressive strength and elastic modulus of cement asphalt emulsion mortar (CAM) are two fundamental parameters of material design, and their values are highly dependent on asphalt:cement mass ratio (A/C) and temperature. However, there are few quantitative studies about the effect of A/C and temperature on the mechanical properties of CAM. This paper studies the compressive strength and elastic modulus of CAM with varied A/C at different temperatures. A physical and mathematic model is proposed to relate the compressive strength and elastic modulus of CAM to asphalt:cement volume ratio (${\mathrm{V}}_{\mathrm{A}}/{\mathrm{V}}_{\mathrm{C}}$) and temperature. The proposed model calculates the compressive strength (or elastic modulus) of CAM by the compressive strength (or elastic modulus) of cement mortar, ${\mathrm{V}}_{\mathrm{A}}/{\mathrm{V}}_{\mathrm{C}}$, and a parameter $b$. The parameter $b$ is related to the rigidity and adhesive ability of asphalt binder, and it has a linear relationship with temperature. The proposed model can accurately predict the mechanical properties of CAM with different ${\mathrm{V}}_{\mathrm{A}}/{\mathrm{V}}_{\mathrm{C}}$ and temperatures, and thus it provides a good method to study the mechanical properties of CAM. The limitations of the proposed model are discussed.

The sensitivity of fracture-based healing indexes of asphalt mixtures was evaluated using a semicircular bending test following a multiple fracture-rehealing method. Five healing agents (HAs) were applied on the cracks to promote healing. Test results indicated that pre- and postpeak material fracture response properties recovered different values on healing. Prepeak fracture-based indexes such as peak healing index (PI), stiffness healing index (SI), and toughness healing index (TI) were insensitive to postpeak fracture properties, and they showed higher healing values as compared with the fracture energy healing index (EI). Nonetheless, EI, which represented the restored fracture energy on healing, was the most sensitive index to both pre- and postpeak fracture material properties. It could be considered a better index for evaluating the healing performance of asphalt mixtures.

Air-entrained concrete has been extensively used in bridges and water conservancy projects in cold regions. The objective of this study was to investigate the effect of air entrainment on the mechanical properties, chloride migration, and microstructure of ordinary concrete and fly ash concrete. Twelve concrete mixtures were prepared with two water-to-binder ratios (0.53 and 0.35), three levels of air content (no air entrainment; moderate air entrainment, with 4–5% air content; and high air entrainment, with 7–10% air content), and two levels of fly ash (no fly ash and 30% replacement of cement). The results indicated that, compared with ordinary concrete, the addition of an air-entraining agent (AEA) to fly ash concrete resulted in a greater decrease in compressive strength. Care must be taken when introducing artificial air bubbles into fly ash concrete because the bubbles will affect the mechanical properties. With proper air entrainment (air content of 4–5%), stable, closed, and well-distributed air bubbles are introduced into concrete so that the connectivity of the pore system is interrupted and chloride migration is consequently minimized. However, if the concrete contains a large amount of entrained air, a substantial amount of large and detrimental pores is introduced, causing air bubbles to overlap and merge, as well as causing additional chloride migration. This effect is more prominent in fly ash concrete.

In this work, the effect of pyrogenic silica and nanosilica on the properties of portland cement matrices is compared. Two chemically and mineralogically similar mineral additions (amorphous silica) with different particle size and specific surface area were used to prepare pastes and mortars with different solids substitutions of cement by silica. These samples were used to measure water and superplasticizer demand, setting time, hydration kinetics, water absorption by capillary suction, and compressive strength. It was found that specific surface area, rather than particle size, played a crucial role in the amount of water and superplasticizer necessary to obtain a desired workability in pastes and mortars. Such water and superplasticizer demands had a delaying effect on the setting time and hydration kinetics of pastes. Nevertheless, compressive strength results at different curing ages of mortars were found to have a direct correlation with the porous structure of the matrix, rather than with the specific surface area of the silica particles. It was concluded that regardless of its higher specific surface area and greater effect on the fresh state properties of pastes, pyrogenic silica was less efficient than nanosilica to increase the compressive strength of mortars, being considered a less efficient pozzolanic material.

Microbially induced carbonate precipitation (MICP)–based biomediated soil improvement methods have been extensively studied recently due to their versatility, potential environmental sustainability, and potential low cost. However, an efficient MICP-based treatment method specifically designed for surficial soil stabilization against water-induced erosion is still urgently needed. This paper presents a preliminary experimental study on the application of a new polymer-modified MICP treatment for surficial soil stabilization to mitigate water-induced erosion. In the proposed method, the cementation solution for MICP is prepared in a water solution of polyvinyl alcohol (PVA) instead of water alone. Comparative tests are conducted to verify that the PVA-modified cementation solution provides a suitable environment for MICP, as well as to optimize the concentrations of cementation media used in the new method. The proposed method is then applied for bench-scale surficial stabilization of Ottawa sand. The performance of the surficial treatment is demonstrated by flume erosion tests, and the erodibility of the treated sand is evaluated more precisely using an erosion function apparatus (EFA). The experimental results show that the viscous polymer solution anchors the bacteria and cementation media in surficial regions and promotes the precipitation of calcium carbonate. Such a treatment results in a uniform soil crust in the surficial region and reduces the erodibility of sands. The critical shear stress of the treated sand is over 500 times higher than that of untreated sand as demonstrated by the EFA tests.

In order to characterize the ability of tension and compression deformation of asphalt mixture more truly and to improve the test efficiency and scientificity of the tension and compression moduli, the synchronous test method based on the indirect tension test was proposed. The analytical algorithms of the tension and compression resilient moduli of the indirect tension test were derived by integrating the functions of the horizontal and vertical radial strain at the center of a specimen, which was based on Hooke’s law in the two-dimensional stress state and the principle of calculus. The direct tension, unconfined compression, and indirect tension moduli tests were conducted in both dynamic and static loading states, and the test results were compared in different loading states. The research results indicated that the synchronous testing method based on the indirect tension test is effective, and there is a significant difference between the tension and compression moduli of asphalt mixture, and the dynamic resilient modulus from the indirect tension test increases by a power function with the increase of loading frequencies.

Recently, improvement of cemented soils’ properties using nanoparticles has been taken into consideration by engineers. However, no attention has been paid to the effect of using nanosilica and cement on the static cyclic triaxial behavior of sandy soil. In this study, the role of nanosilica on the static and cyclic shear behavior of cemented sand is investigated. For this purpose, shear strength tests are performed, as well as unconfined compressive tests and static and cyclic triaxial tests. In static and cyclic triaxial tests, cement content used is 5% and 14% (dry weight) of the sand. The nanosilica contents were 0%, 5%, 10%, and 20% (dry weight) of the cement. The results of the performed tests show that the strength of specimens increases and then decreases with increasing weight ratio of nanosilica up to 10%. Addition of nanosilica improves the brittle behavior. Moreover, by increasing the weight ratio of nanosilica up to 10%, the dynamic deformation modulus and damping ratio of cemented sand increases at first and then decreases.

Experimental tests were conducted to study the thaumasite formation of sulfate attack (TSA) erosion resistance of cement concrete made with crushed tuff sand. Different specimens made with either crushed tuff sand or river sand were soaked in a mixed solution of sodium sulfate and magnesium sulfate at the temperature of $10\pm 1°\mathrm{C}$ to simulate its working environment, and electrical pulses were used to accelerate corrosive medium migration. Afterward, the compressive strength and erosion products of before- and after-corrosion sample specimens were comparatively analyzed. The results showed that the strength of concrete made with crushed tuff sand was higher than that made with river sand before corrosion. However, the difference in their strengths diminished when the specimens were exposed to sulfate and a pulsed electric field for 2 months. This means that the specimens made with crushed tuff sand suffered a greater loss of strength compared with those made with river sand. The amount of thaumasite was higher than that of ettringite in the specimens made with crushed tuff sand; for specimens made with river sand, the situation was just the opposite. The reason that the crushed tuff sand reduced the sulfate erosion resistance ability of concrete at low temperatures is discussed on the basis of the mineral composition of tuff rock powder, the porous structure of concrete, and the interfacial transition zone (ITZ) microstructure of concrete. It was found that incorporating a certain amount of barium hydroxide can improve the anti-sulfate erosion ability, and the best dosage is around 4%.