Journal of Materials in Civil Engineering

This paper addresses the effectiveness of geocell mattress prepared with waste plastic bottles with fly ash as a filling material overlying soft clay bed through laboratory model tests. The test beds were subjected to loading by means of a square rigid steel plate as a footing. The effect of height and width of geocell mattress as well as basal bamboo geogrid underneath geocell mattress on overall performance of the system in terms of footing pressure, settlement, and the adjacent surface deformation (heave/settlement) has been systematically studied through a series of tests. Test results indicate around twofold increases in the bearing pressure by placing a jute geotextile separator beneath the unreinforced fly ash bed, whereas reinforcing the fly ash bed with geocell mattress in presence of a basal bamboo geogrid and jute geotextile separator can produce sevenfold increases in the footing pressure. Inclusion of a basal bamboo geogrid improves overall behavior of the reinforced bed. No surface deformation occurred in the unreinforced beds. Inclusion of a geocell mattress improves the footing pressure, but creates surface deformation (heave/settlement). Increase in height as well as width of geocell mattress not only diminishes the surface heaving but also increases the footing pressure. As the present study carries limitation of boundary and scale effects, the quantitative results must be extrapolated by dimensional analysis before use in practical applications or a field study is required. However, the qualitative results encourage the use of waste plastic bottles for soft ground improvement, which in turn may solve the disposal issue to a certain extent.

This paper presents comparative thermal and mechanical performance of geopolymers derived from metakaolin (MK), fly ash (FA), and their combinations. Bending and compression tests, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectrum, mercury intrusion porosimetry, and dilatometric tests were conducted on three types of geopolymers (MK, MK-FA, and FA based) to evaluate comparative mechanical properties, thermal behavior, and microstructure. Results from these tests show that MK-based geopolymers experience significant thermal shrinkage, high mass loss, and large strength degradation after exposure to high temperatures up to 800°C. FA-based geopolymers exhibit low bending and compressive strength at ambient temperature due to incomplete reaction of fly ash particles and high retention in compressive strength at high temperature, and this is facilitated from the formation of large size pores as channels to release vapor pressure and sinter reaction of fly ash particles. However, blended MK-FA–based geopolymers exhibit higher bending and compressive strength both at ambient temperature and after exposure to high temperatures up to 800°C and this is facilitated through the utilization of specific characteristics of both MK-based and FA-based geopolymers.

In the one-phase construction of cutoff walls, the slurry plays two contradictory roles: it should be fluid while excavating the trench but behave like a solid of low permeability afterward. For hydraulic containment applications, a mixture of water, cement, and bentonite fulfils these requirements, but the range of mix proportions is very limited. In the past, this discouraged systematic research on the subject, and, in consequence, a certain empiricism still prevails in the definition of the slurry composition. This paper presents the results of an extensive experimental program, which is part of a broader investigation regarding the technology of self-hardening slurry walls. Referring to triaxial tests, the stress-strain behavior and permeability of cement-bentonite slurries fabricated and cured in the laboratory is characterized. A conceptual microstructure model is proposed to explain the slurry’s behavior in light of the chemical reactions between its constituents. The final objective is to establish a relationship between the behavior of lab-made slurry and that of in situ slurry, and consequently to be able to predict the long-term behavior of the wall.

Surface treatment, using two slurries containing nanomaterials, was applied to recycled aggregate (RA). Experimental studies were conducted (1) to compare properties of RA before and after the surface treatment; and (2) to examine the modification effects of the surface treatment with nanomaterials on the microstructure and macroproperties of recycled aggregate concrete (RAC). The nanoindentation technique was used to achieve elastic modulus of different interface transition zones (ITZs) and old and new mortars in RAC. Test results show that both nanoslurries enhanced new ITZs between the old and new cement mortars. Although they did not work on old ITZs between the virgin aggregate and the old cement mortar, old mortars were surface strengthened. It is also proved that properties of both RA and RAC on the macroscale were improved by the surface treatment using nanomaterials.

Sugarcane bagasse ash is obtained as a by-product from cogeneration combustion boilers in sugar industries, and is reported to be a useful supplementary cementitious material in concrete. A clear evaluation of pozzolanic activity of sugarcane bagasse ash is imperative to achieve its effective utilization in concrete instead of being disposed as a waste in enormous quantities. Pozzolanic activity of raw sugarcane bagasse ash and a processed sample of the same was assessed by five different standard methods in this study. The methods used were: strength activity index test, lime reactivity test, Frattini test, electrical conductivity test, and lime saturation test. In addition, chemical and mineralogical analyses were also performed on the bagasse ash. Durability performance of concrete with bagasse ash blended cement was evaluated and compared with fly ash-based concrete. The results from the studies indicate that raw bagasse ash has low pozzolanic activity due to presence of fibrous carbon particles. Removal of these fibrous particles from raw bagasse ash, which occurs during the processing methodology followed in this study, significantly improves its pozzolanic activity. The permeability of bagasse ash blended concrete was found to be significantly reduced compared to control and fly ash blended concrete, at an equivalent level of compressive strength.

${}^{29}\mathrm{Si}$ MAS NMR spectroscopy was employed for the evaluation of the alkali-silica reaction (ASR) in laboratory and field concrete specimens. A series of NMR data was collected on the individual constituents of cement as well as on samples subjected to accelerated aging in a carefully controlled laboratory setting. Peaks associated with ASR were assigned and quantified. In spite of the spectral complexity due to the diverse constituents and the heterogeneous nature of concrete, changes due to ASR, including increased polymerization of C-S-H and A-S-H formation, could be identified and quantified. The trends established through ${}^{29}\mathrm{Si}$ NMR spectroscopy of the laboratory specimens were used to identify the presence and extent of the alkali-silica reaction in samples from operational bridges. Both bridge samples exhibited spectral evidence of ASR. Fourier transform infrared spectroscopy was used to verify the ${}^{29}\mathrm{Si}$ NMR spectroscopy observations.

This experimental study examined the mechanical behavior in three types of reinforced concrete steel. An evaluation of the mechanical behavior in dual-phase steels $\mathrm{B}{400}_{\mathrm{C}}$, $\mathrm{B}{450}_{\mathrm{C}}$, and $\mathrm{B}{500}_{\mathrm{B}}$ of high and medium ductility class, with a 16 mm nominal diameter, was conducted before and after exposure in a laboratory salt spray environment. The results of all mechanical tensile tests were compared and combined with the results of scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis and consequently led to the following findings: The reduction in strength properties in the precorroded specimens was almost equivalent to the mass loss, which meets the demands set by Eurocode 2 (EC2) for safe structures. However, the drop in ductility properties, expressed as the deformation at maximum strength, is below the minimum limits. The findings also suggest that the degradation in the mechanical performance of steel cannot be attributed to a specific mechanism, but it appears to be the result of several interrelated factors, such as the development of pits in the outer surface of steel and various side effects within the martensitic layer, which occur from the presence of extensive porosity close to the surface as well as several sulfide compounds like MnS.

Many reinforced concrete (RC) structures use thermomechanically treated (TMT) bars as reinforcement and are designed to withstand fire loads. Though the properties of mild steel at elevated temperatures have been extensively studied, there is little information available about how TMT bars are affected. An attempt is made here to study the effect of elevated temperature exposure on the metallographic characteristics and mechanical properties of TMT bars. Fe500 high-strength deformed TMT bars were exposed to peak temperatures up to 950°C for durations up to 240 min. The samples were then allowed to cool to room temperature in air before a microstructure examination and other tests (tensile behavior and hardness) were carried out. A temperature of approximately 500°C was found to be a “threshold” for the TMT bars, beyond which substantial damage was found to occur. It was found that in addition to temperature, the soaking period could also bring about 6–8% additional loss in strength. Exposure to elevated temperatures also showed irreversible changes in the microstructure, with hard martensite getting converted to softer ferrite–pearlite, and these changes also explain the changes in mechanical properties. Using peak temperature and soaking period as independent variables, the empirical relations for changes in the mechanical properties are also developed.

The core-drilling method (CDM) is a stress-relief technique used to determine in situ stresses in concrete. A small hole is drilled into the concrete of a structure and the resulting displacements are measured and then converted into in situ stresses using elasticity theory. Three major factors that influence stresses determined with the CDM have been identified: (1) swelling of concrete around the core hole caused by exposure to water used during the drilling process; (2) changes in the measured deformations caused by relief of differential shrinkage stresses; and (3) steel reinforcement in close proximity to a core hole. Recent research has addressed each of these factors through analytical and numerical techniques that adjust CDM-calculated stresses. This paper describes experiments performed to verify these approaches and to show that the CDM can determine accurate in situ stresses in concrete structures. Concrete plates loaded in compression were subjected to hole drilling, and the resulting displacements were measured with three-dimensional digital image correlation. Stresses calculated from measured displacements agreed with applied stresses to within 28%. When the calculated stresses were modified to account for the effects of the three influencing factors, the relative error in applied versus measured in situ stresses in the experiments was less than 10%.

Tire-derived aggregate (TDA) has been used in many civil engineering applications. Despite its successful use in the past, the amount of experimental research available on TDA applications is not sufficient to provide data for the evaluation of an appropriate constitutive model. The majority of TDA constitutive models have been developed from laboratory tests performed on tire chips smaller than those used in field applications. In this study, nonlinear elastic material models, with an elastic modulus that varies as a function of vertical stress, have been developed for TDA produced from passenger and light truck tire (PLTT) and off-the-road (OTR) vehicle tires. The material model for TDA is established based on previous large-scale laboratory constrained compression tests conducted on TDA up to 300 mm in size. The model is used in a finite-element (FE) analysis using geotechnical software to predict the settlement of full-scale test embankment during construction. The results indicate that the settlements obtained from the FE analysis agree with the settlements measured in the field during construction of full-scale test embankment. This paper also provides design charts to compute overbuild required on top of TDA layer(s) to compensate immediate compression under an applied load during the placement of cover on top of TDA.

Huge volumes of expanded polystyrene (EPS) waste are landfilled every year, increasing the damage that the environment is suffering. The production of a lightweight construction material made with gypsum and EPS waste is an alternative method to reduce EPS waste landfilling. However, this material has a very low mechanical strength, not meeting the minimum requirement for compressive strength. Therefore, the aim of this research work is to study the reinforcement of this lightweight material by incorporating different additives (latex, binding additive, plasticizers) and fibers (glass fiber and polypropylene fiber). Detailed consideration is given to the particle size of EPS waste; therefore, reinforced composites have been designed for fine EPS waste (1–2 mm) and coarse EPS waste (2–4 mm). The characteristics of these composites were defined and tested by fixing the consistency at a good workability and then studying their density, Shore C surface hardness, flexural and compressive strength, and their thermal conductivity. Results show that it is possible to create a lightweight material made with gypsum and EPS waste with enhanced mechanical properties, low density, and an outstanding thermal behavior. However, the use of coarse EPS waste has a negative effect on the Shore C surface hardness, especially with latex and fibers.

A key step in mix design is the selection of an appropriate aggregate structure since this affects mix performance and the amount of asphalt in the mix. This paper explores the effects that fines adhered to larger particles have on the batch gradation and the resulting optimum binder content and dust proportion. It shows that conventional batching procedures can produce gradations with a substantially larger percent passing the sieve No. 200 relative to the target gradation. A batching procedure that corrects for fines adhered to larger particles and trapped moisture is proposed and shown to replicate the target gradation. Asphalt content was determined using the superpave method for both a gradation batched conventionally and a gradation batched with the corrected procedure. It is shown that the asphalt content and volumetrics obtained in both cases are substantially different. To obtain more-representative batch gradations, the corrected procedure is recommended for routine batching of specimens. Further research is recommended to assess potential changes in mix design criteria and effects on performance tests.

Acoustic emission (AE) has been increasingly used for assessment and prediction of fatigue cracks in steel bridge members. Fatigue cracks develop at the transverse weld toe of stiffeners, attachments, and cover plates in steel bridge members. Effectiveness of AE to assess fatigue crack initiation from weld toe is investigated in this study, and an attempt is made to predict the crack growth behavior using AE signal features. Cruciform specimens consisting of a single tension pull plate with transverse fillet-welded plates attached at midspan are tested in this study. The transverse plates represent stiffeners and/or short attachments typical of welded steel bridge details. The specimen provides realistic initial conditions of fatigue crack initiation and growth from high stress concentration regions. Consequently, AE waveform characteristics representative of those expected on bridge structures are produced. Accurate stress intensity factor values are difficult to obtain because of the small, nonuniform crack growth conditions at the weld toe. Finite-element method analysis for welded geometries capturing stress fields at the weld toe of stiffener details is performed, and numerical results are incorporated into an existing analytical stress intensity factor framework. Procedures for assessing the crack size and predicting remaining fatigue life of the specimen using absolute energy feature of AE signals are demonstrated.

Polyethylene (PE) waste often piles up in the environment for up to 30 to 50 years, without complete degradation. This paper describes how PE waste can be used as a reinforcement in laterite bricks for sustainable building materials. The bricks are produced with different volume percentages (0–30 vol. %) of PE. The flexural/compressive strengths and fracture toughness values of the composite blocks are compared with those of mortar (produced from river sand and cement). The composite containing 20 vol. % of PE is shown to have the best combination of flexural/compressive strength and fracture toughness. The flexural/compressive strengths and fracture toughness values increase with increasing volume percentage of PE up to 20 vol. %, before decreasing to minimum values for composites with 30 vol. % of PE. The trends in the measured strengths and fracture toughness values are explained using composite and crack bridging models.

A method for establishing the relationship between stress and crack face opening for steel fiber–reinforced concrete (SFRC) beams under three-point loading was proposed using inverse analysis. The relationships were set up in two parts: Fracture mechanics theory was used before the hinge formation, followed by a classical mechanics of materials approach after the hinge was formed. This methodology did not incorporate any assumptions and was validated by the construction of experimental load versus crack mouth opening–displacement (CMOD) curves and by predicting the experimental load versus CMOD relationship for independent flexural tests on beams of different sizes. The proposed method can simulate and predict the complete flexural performance of SFRC beams under three-point bending.

Because of environmental and economical benefits, the paving industry has made attempts to incorporate recycled asphalt pavement (RAP) or recycled asphalt shingle (RAS) into warm mix asphalt (WMA). However, the low temperatures at which WMA is produced may affect the virgin-recycled binder blending in RAP/RAS mixtures. In this study, a lab testing procedure was developed to evaluate the effects of WMA technologies on binder blending. The results from the study showed that WMA additives, including sasobit, rediset, cecabase, and evotherm, slightly decreased the viscosity of the asphalt binder at 135°C. However, control binder tested at 165°C showed significantly lower viscosity than WMA binders. This may raise the concern over workability of nonfoaming WMA mix. WMA additives yielded higher blending ratio than control mix produced at 135°C, but hot mix asphalt (HMA) produced at 165°C still showed the highest blending ratio value. This indicates that a concern still exists over asphalt blending even if WMA additives are used. Foaming technology yielded a higher blending ratio, indicating that foamed WMA may yield a higher blending than regular HMA. It was also found that temperature is critical to blending in RAS mixture. Finally, the mix produced with coarse virgin aggregates and medium RAP may not be sensitive enough to test the effect of WMA additives on blending, whereas the mix with medium virgin aggregates and fine RAP was more effective.

Utilization of reclaimed asphalt pavement (RAP) in the construction industry is gaining an advantage over conventional materials in terms of sustainable credits. However, the amount of production of RAP and its utilization has no comparison. The general practice is to replace a small fraction of virgin aggregates with RAP, usually restricted to a maximum of 30%, in base layers to promote RAP usage in the pavement industry. The present study focuses on the utilization of a high proportion of RAP ($>50\%$) substitution in virgin aggregates (VA) as a base material in low volume roads (LVR). Mixes containing $100:0$, $80:20$, and $60:40$ proportions of $\mathrm{RAP}:\mathrm{VA}$ stabilized with different dosages of fly ash were evaluated for maximum dry density (MDD), optimum moisture content (OMC), unconfined compressive strength (UCS), resilient modulus ($M_r$) and California bearing ratio (CBR). It was observed that the $80:20$ $\mathrm{RAP}:\mathrm{VA}$ design mix with 40% fly ash meets the design requirements ($\mathrm{UCS}>1.7\mathrm{MPa}$ and $\mathrm{CBR}>80\%$) specified by the Ministry of Rural Development (MoRD), Government of India, and was considered to be an optimum mix. An example is discussed to design an LVR with an optimum mix according to the Indian Roads Congress (IRC) and AASHTO methods. The results revealed that the fatigue and rutting strains are well within the permissible limits for the new mix. The new mix design proved economical, as there was a 50% reduction in base layer thickness compared with the conventional design mix.

The prediction of ground response against wave propagation is essential for construction materials and the safe design of civil engineering infrastructures, such as, embankments, retaining walls, or foundations subjected to machine vibrations. For ground response analysis studies, the shear modulus and material damping, which are expressed as a function of shear strain, are the important properties of soils. The volumetric threshold strain is also a key property in order to evaluate possible permanent deformations or substantial increase in pore water pressure in saturated soils during dynamic loading. The paper presents dynamic test data derived from resonant column experiments on volcanic granular soils which are characterized by low unit weight and weak grains of intraparticle voids. These materials can be used as potential lightweight backfill in retaining walls or other applications with a demand in reduction of vertical or horizontal stresses to the ground and structural facilities. Additional experiments on quartz sands were conducted for comparison. The volcanic soils had much lower small-strain shear modulus than that of quartz sands and higher linearity in the range of medium strains, by means of normalized stiffness and material damping curves. The elastic and volumetric thresholds were shifted to larger strains for the volcanic soils in comparison to the quartz sands. Different prevailed micromechanisms possibly contributed to these observed trends.

This paper experimentally investigates the steel-to-concrete bond phenomenon in two kinds of deformed bars: black steel and hot-dip galvanized steel. The differences in the steel-to-concrete bond behavior are identified in terms of the load-slip curves and the acoustic emission (AE) patterns measured during pull-out tests. Test results show that the bond capacity and the initial stiffness of the bond stress–slip curve of black steel are approximately 20 and 50% greater, respectively, than those of galvanized steel, and the slip corresponding to the maximum bond stress is approximately 20% times larger in the latter. By measuring the AE activity, it is possible to identify the transitional points between the four stages characterizing interaction between the concrete and the bar subjected to pull-out force. Each transition coincides with a sudden drop in the AE activity.

Properties of a porous material such as concrete are strongly dependent on its pore structure features. This study deals with developing an understanding of the material structure-compressive response relationships in concrete under high strain rates. Concrete specimens with different pore structures were proportioned and subjected to quasi-static and dynamic compression tests. This experimental investigation uses split Hopkinson pressure bar (SHPB) to achieve high strain rates. A mercury-intrusion porosimetry (MIP) investigation was carried out to examine the pore structure of concrete. Experiments indicate that the compressive behavior of concrete varies with strain rate and pore structure. The compressive stress-strain response of concrete under high strain rates, a model to predict the stress-strain response, and its relationship to pore structure features are outlined.

The in situ density of compacted layers obtained from sand-cone test is commonly used to assess the quality of compaction of pavement layers. This test is tedious, time consuming, and sometimes not feasible to perform in accordance with specifications. In this study, a lightweight deflectometer (LWD) is used to measure the modulus of deformation, ${\mathrm{E}}_{\mathrm{LWD}}$, of pavement layers and to perform the quality control (QC) of pavement layers. An extensive LWD field testing program was undertaken on 95 test locations of an expressway along the outer ring road located in Hyderabad, India, and the ${\mathrm{E}}_{\mathrm{LWD}}$ values of the compacted base and surface layers were commonly found to range from 45 to 60 MPa and 105 to 120 MPa, respectively. The coefficient of variation of the ${\mathrm{E}}_{\mathrm{LWD}}$ of base and surface layers was found to range from 4 to 12%. Finite-element analysis was also carried out to study the effect of bottom pavement layers on measured ${\mathrm{E}}_{\mathrm{LWD}}$ values from LWD testing. The results showed that the top stiff layer absorbs a significant portion of the load applied on the surface of the layered pavement system, indicating that the ${\mathrm{E}}_{\mathrm{LWD}}$ obtained from LWD testing is affected predominantly by the top stiff layer. Finally, a case study on a low-volume road is presented to demonstrate the relationship between the LWD modulus of deformation and in situ density obtained from a sand-cone test. The LWD device was found to provide quick test results and simple to operate on any pavement layer, and hence the frequency of QC tests can be increased, leading to an improvement in the overall quality of compacted pavement layers and, thus, pavement performance.

Polymers are commonly used to modify asphalt binder in order to satisfy the performance-grade binder’s rheological properties, such as shear, storage, loss, and bending stiffness. However, it is not known what types and percentages of polymers affect these properties under conditions of aging. To this end, base asphalt binders were modified with styrene-butadiene and styrene-butadiene-styrene polymers at 3, 4, and 5% and then aged in the laboratory using a rolling thin film oven for short-term aging, a pressure aging vessel for long-term aging, and a draft oven for intermediate aging. The stiffness properties of the modified binders were determined using dynamic shear rheometer (DSR), multiple-stress creep recovery (MSCR), Brookfield rotational viscometer (RV), and bending beam rheometer (BBR) tests. Comparison of aging indexes for storage and loss modulus indicated that aging increases the elastic or storage component more than the viscous or loss component of the complex shear modulus. It was shown that increasing the percentage of polymer results in a decrease in aging for both SB- and SBS-modified binders. Those modified with SB are more resistant to aging than are those modified with SBS.

The recycling of asphalt shingles in flexible pavements has received considerable interest in recent years for economic, environmental, and social reasons. The objective of this study was to evaluate the effects of adding ground shingle using the wet process on the binder rutting and fatigue behaviors. The effects of recycled asphalt shingle (RAS) on the binder rutting and fatigue characteristics were investigated using the multiple stress creep recovery (MSCR) and the linear amplitude sweep (LAS), respectively. Further, the influence of adding ground shingle on the binder chemical composition was investigated in the laboratory using the Fourier transform infrared analysis (FTIR) and saturates, aromatics, resins, and asphaltenes (SARA) fraction analysis performed using a thin film chromatography. Based on the results of the experimental program, it was found that the use of RAS in the binder blends was associated with an increase in the percentage recovery and a decrease in the nonrecoverable creep compliance, which indicates an improved resistance to rutting damage. On the other hand, results of the LAS test showed that an increase in RAS content is associated with an improved resistance to fatigue cracking. This is in contradiction to what would be expected, because the asphalt binder in RAS is air-blown, which is extremely stiff and brittle compared to the binder used in roadway applications. Further evaluation of the LAS test with RAS-modified binders is recommended. In addition, analysis of the FTIR spectra showed a slight increase in asphaltenes when RAS was incorporated into the asphalt binder. The increase in asphaltenes was correlated to a slight decrease in maltenes (saturates, aromatics, and resins).

In tropical countries, roads built with asphalt layers must be made with bituminous mixtures containing asphalt that is reasonably stiff to increase resistance against permanent deformations, i.e., rutting. When the available asphalt is not stiff enough, an alternative is to modify it using Gilsonite. This article presents the laboratory results of tests performed on samples of Gilsonite-modified hot mix asphalts modified by wet and dry processes. Gilsonite increases the stiffness and improves the performance grade of a virgin binder at high temperatures of service. Additionally, Gilsonite-modified hot mix asphalts developed a greater strength and stiffness under monotonic and dynamic loading.

The objective of this study is to demonstrate using weak form partial differential equation (PDE) method for a finite-element (FE) modeling of a new constitutive relation without the need of user subroutine programming. The viscoelastic asphalt mixtures were modeled by the weak form PDE-based FE method as the examples in the paper. A solid-like generalized Maxwell model was used to represent the deforming mechanism of a viscoelastic material, the constitutive relations of which were derived and implemented in the weak form PDE module of Comsol Multiphysics, a commercial FE program. The weak form PDE modeling of viscoelasticity was verified by comparing Comsol and Abaqus simulations, which employed the same loading configurations and material property inputs in virtual laboratory test simulations. Both produced identical results in terms of axial and radial strain responses. The weak form PDE modeling of viscoelasticity was further validated by comparing the weak form PDE predictions with real laboratory test results of six types of asphalt mixtures with two air void contents and three aging periods. The viscoelastic material properties such as the coefficients of a Prony series model for the relaxation modulus were obtained by converting from the master curves of dynamic modulus and phase angle. Strain responses of compressive creep tests at three temperatures and cyclic load tests were predicted using the weak form PDE modeling and found to be comparable with the measurements of the real laboratory tests. It was demonstrated that the weak form PDE-based FE modeling can serve as an efficient method to implement new constitutive models and can free engineers from user subroutine programming.

The increasing use of self-compacting concrete (SCC) in the construction industry should be assured by the development of mix designs adequate to improve their fresh/hardened state properties and their economy. This paper presents a methodology for the formulation of SCC that achieves some of these developmental goals without reliance on extensive laboratory testing and batch trials. Applications, results in the fresh and hardened state, and discussion of the SCC obtained are presented. The proposed method can provide lower costs when compared to a current SCC mix design method and the literature used for comparison.

Preparation of uniform and repeatable reconstituted sand specimens of required density is a prerequisite for obtaining reliable results from laboratory tests. An air pluviation technique is widely used to achieve uniform and repeatable sand specimens. Many of the previously developed air pluviation setups were stationary in nature, and these setups have inherent limitations, which do not allow the preparation of large, uniform sand beds. In this study, a mechanized traveling pluviator (MTP) is developed, which has two main features, including a freely movable hopper and rigid tube made up of Plexiglas to observe the sand flow during pluviation. This study aims at understanding the effect of the number of diffuser sieves, deposition intensity (DI), and height fall (HF) on the relative density (RD) and uniformity of sand specimens. The uniformity of a sand bed is verified by conducting cone penetration tests (CPTs) using a miniature cone. Using the developed MTP setup, large uniform sand specimens with a wide range of relative densities (viz, 38%–100%) can be prepared. For the sand used in the present study, the height of the fall and the depositional intensity significantly influence the RD of sand beds, whereas diffuser sieves control the uniformity of sand beds.

The objectives of this study were to assess whether temperature differentials measured using infrared thermography (IRT) occur in an overlay built on top of discontinuities such as joints and cracks and to study the horizontal and vertical thermal profiles in the asphalt overlay using a validated finite element (FE) modeling approach. To achieve this objective, an infrared camera was used to monitor the temperature profiles in the asphalt mat in a number of field projects from the time it was placed to after completion of the compaction process. The temperature profiles were monitored on top and away from severe discontinuities and joints in the existing pavement. Based on IRT measurements, cracks in the existing pavement did not influence the thermal profiles in a hot-mix asphalt overlay. However, thermal measurements on top of a joint were consistently lower than away from it as observed in thermal images, which may indicate that temperature loss may occur at the joints. Based on FE simulations, the model predicted a slightly higher rate of thermal decrease at the bottom of the overlay above the joint than away from it attributable to convection losses at the joint. While this difference may not be large enough to be identified as thermal segregation, it can influence the bulk properties of the overlay at the joints and promote early cracking. Results also show that thermal differences occur in the vertical direction as well as in the horizontal direction in the asphalt mat.

The continuous increasing demand and limited availability of artificial pozzolans has led to a search for alternative supplementary cementitious materials such as natural pozzolans. This study was performed to compare the effects of pumice powder and fly ash–blended cement mortars on fresh properties, strength development, drying shrinkage, sulfate resistance, and chloride ion permeability. The experimental study was carried out on seven different paste and mortar mixtures. Mixtures were prepared by replacing 15, 25, and 35% of portland cement with pumice powder and fly ash by weight. Pumice powder adversely affected the consistency of the paste because of its porous and rough structure. On the other hand, the mortars with pumice powder achieved higher strength development and sulfate resistance, lower drying shrinkage, and chloride ion permeability compared to mortars with fly ash. Therefore, pumice powder can be used in producing sustainable, economical, and environmentally friendly cement by reducing the amount of portland cement consumed.

Determination of shear strength of brick–mortar bed joint is critical to overcome the sliding-shear or joint-shear failure in masonry. In the recent past, researchers have attempted to enhance the shear strength and deformation capacity of brick–mortar bed joints by gluing fiber-reinforced polymer (FRP) composite across the bed joint. FRP composites offer several advantages like high strength-to-weight ratio, and ease of application in terms of labor, time, and reduced curing period. Furthermore, FRP composites are desirable for strengthening old masonry buildings having heritage value because of its minimal interference with the existing architecture. A majority of earlier studies on shear strengthening of masonry available in the literature adopted masonry having the ratio of modulus of elasticity of masonry unit ($E_{mu}$) to modulus of elasticity of mortar ($E_m$) greater than one. Information related to shear behavior of FRP glued masonry composed of masonry units having Young’s modulus lower than mortar is limited. Hence the present study is focused on characterizing the interfacial behavior of brick–mortar bed joint of masonry assemblages composed of solid burnt clay bricks and cement–sand mortar ($E_{mu}/E_m$ ratio less than one), strengthened with FRP composites. Masonry triplets and prisms with bed joint inclined to loading axis (0°, 30°, 45°, 60° and 90°) are employed in this study. Glass and carbon FRP composites composed of bidirectional FRP fabric with equal density in both directions are used for strengthening masonry. Masonry triplets are glued with glass and carbon FRP composites in two configurations: (1) both faces of the triplet specimens are fully glued with GFRP composites; and (2) both faces of the triplet specimens are glued with GFRP and CFRP composites in strip form. The performance of masonry assemblages strengthened with FRP composites is assessed in terms of gain in shear strength, shear displacement, and postpeak behavior for various configurations and types of FRP composites considered. A semianalytical model is proposed for the prediction of shear strength of masonry bed joints glued with FRP composites. A composite failure envelope consisting of a Coulomb friction model and a compression cap is obtained for unreinforced masonry and GFRP-strengthened masonry based on the test results of masonry triplets and masonry prisms with bed joints having various inclinations to the loading axis.

Asphalt pavement constructed with traditional asphalt binder, which features high solar absorbance, is characterized by high surface temperatures during summer. This causes undesirable performance degradation (i.e., due to accelerated rutting, bleeding, etc.) and environmental consequences (i.e., urban heat island effects and volatile gas emission). Thermochromic asphalt binder, which is asphalt binder mixed with thermochromic materials, has been developed by the authors to dynamically control the solar reflectance and modulate the surface temperature of asphalt pavement. The goal is to improve its long-term durability and environmental friendliness. Thermochromic materials are substances that can reversibly change their colors in response to temperature. The binary thermochromic asphalt binder mixture is produced by incorporating thermochromic powders into a conventional asphalt binder. Measurements of spectral reflectance of thermochromic powders indicate that thermochromic materials feature higher solar reflectance at higher temperatures. In this paper, the spectral reflectance of thermochromic powders as functions of wavelength and temperature are fitted with common types of optical mixing models based on experimental data. Optical measurements conducted on the thermochromic asphalt binder mixture show that they feature more solar reflectance than conventional asphalt binders; furthermore, reflectance increases with temperature. The spectral reflectance of thermochromic asphalt binder also increases as the powder content increases. The common types of optical mixing formulas, including those based on Maxwell, Mori-Tanaka, and effective medium theory (EMT), etc., are used to establish the relationship between spectral reflectance of thermochromic asphalt binder and powder content. These optical mixing formulas provide a convenient way to predict the reflectance spectra of thermochromic asphalt binder and will assist its multifunctional design and optimization.

A universal asphalt concrete discrete element method (DEM) model was established in this paper. Coarse aggregates consisting of balls bonded by elastic contact models were simulated using irregular particles. Asphalt mastic consisting of balls bonded by a generalized Maxwell viscoelastic contact model held coarse aggregates together. The generalized Maxwell viscoelastic contact model was developed based on a finite difference scheme using Visual Studio 2005. The relationship between microscale model input and macroscale properties of asphalt mastics and coarse aggregates was derived to calibrate contact parameters of the proposed DEM model. Dynamic modulus tests, static creep tests, bending tests at low temperature, and the corresponding DEM simulations were implemented to contrast the simulation effect of the proposed DEM model and the existing DEM model. Simulation results show that the proposed DEM model exhibits an improved accuracy using a universal mathematical structure. The averaged and maximum relative errors of different property indexes are all less than 5 and 8%, demonstrating the advantage of the proposed DEM model in accurately and comprehensively characterizing low-temperature properties of asphalt concrete. The proposed DEM asphalt concrete model provides a new avenue for studying pavement properties and mechanical mechanisms of asphalt concrete at microscale.

The determination of suction–water content relationship (SWR) is of prime importance in unsaturated soil mechanics. When such a relationship is obtained from continuous drying or wetting process of the same soil sample, it is termed as water retention characteristic curve (WRCC). The relationship obtained from suction measurement of remolded soil samples with different water content is termed as spot SWR (SSWR). Most of the reported studies use drying WRCC (DWRCC) because of the relative ease of its measurement as compared to wetting WRCC (WWRCC). There are not many studies that critically compare measured DWRCC, WWRCC, and SSWR of soils. Such a comparison would help to understand the differences in WRCC attributable to hysteresis and limitations of spot measurements, if any. A simple procedure similar to the field wetting process is discussed in this paper for developing DWRCC and WWRCC on the same soil sample, one after the other. WRCCs and SSWRs of three cohesionless soils are not unique for the range of suction measured in this study. The implication of such nonuniqueness is further investigated by comparing unsaturated soil hydraulic conductivity function estimated based on WRCCs and SSWRs.

Geopolymer concrete is an environment-friendly building material which has attracted increasing interest in many fields as a replacement for conventional concrete. The main objective of this paper is to study the residual behaviors of the alkali-activated fly ash–slag geopolymer concrete (FSGC) under different heating temperatures and cooling regimes. Changes in weight, compressive strength and ultrasonic pulse velocity were firstly investigated. Then the wavelet packet technique was adopted to further analyze the measured ultrasonic signals in frequency domain. Finally, the microstructures were investigated by scanning electron microscopy. The results indicate that an increase in temperature makes the weight, compressive strength, and ultrasonic pulse velocity value of FSGC decrease, especially under extreme heat conditions. The deterioration of specimens cooled by watering is more obvious than that of specimens cooled naturally. Based on the experimental results, it can be concluded that the critical temperature for FSGC is 600°C, but this temperature may change with the contents of fly ash and slag. Also, with the increase of temperature and specimen damage, the higher frequency components of the signal attenuate steadily and signal energy stored in lower frequency bands increases. A wavelet packet energy spectrum-based index is sensitive to thermal damage, which can be used as a supplementary indicator to assess the damage degree of the heated FSGC. After high temperature exposure, FSGC undergoes distinct morphological destruction as confirmed by the developments of microcracks and the damaged aluminosilicate gel matrix.

Alkaline activation of fly ash (FA) was used to improve the mechanical performance of a silty sand, considering this new material as a replacement for soil-cement applications, namely, bases and subbases, for transportation infrastructures. For that purpose, specimens were molded from mixtures of soil, FA, and an alkaline activator made from sodium hydroxide and sodium silicate. Uniaxial compression tests showed that strength is highly increased by the addition of this new binder. The results described a high stiffness material, with an initial volume reduction followed by significant dilation. All specimens have clearly reached the respective yield surface during shearing, and peak-strength Mohr–Coulomb parameters were defined for each mixture. The evolution of the microstructure during curing, responsible for the mechanical behavior detected in the previous tests, was observed by scanning electron microscopy. These results were compared with soil-cement data obtained previously with the same soil at similar compaction conditions. The main difference between both binders was the curing rate, with alkali-activated specimens showing a more progressive and long-lasting strength increase. This was analyzed taking into account the chemical process responsible for the behavior of the mixtures.

Steel furnace slag (SFS) is an industrial by-product that is used as an abrasion-resistant aggregate in asphalt pavement surfaces. However, SFS has found limited application in concrete pavements because of its potential for expansion from hydration of the free calcium and magnesium oxides present in the slag. This study investigated the application of asphalt-coated SFS aggregates, i.e., coarse fractionated reclaimed asphalt pavement (FRAP), as an aggregate in concrete. Autoclave expansion testing of SFS FRAP samples and chemical analyses revealed that the SFS FRAP contains residual free calcium oxide and therefore has the potential to expand, although the presence of the asphalt coating reduced the overall expansion magnitude. The performance of SFS FRAP in concrete at 20% and 50% replacements was similar to concrete with unexpansive dolomite FRAP in terms of strength and fracture properties, though the SFS FRAP may cause higher shrinkage strains and reduced freeze/thaw durability. Therefore, application of SFS FRAP with low autoclave expansion, but available free oxides should be limited for use in concrete but may be suitable for nonstructural applications or temporary roads. With further standardized expansion testing, SFS FRAP may be suitable for use as an unbound foundation material or again as an aggregate in a bound asphalt layer.

For any given environmental conditions the tensile strength of glass is a function of the geometry of the critical flaw and the residual stresses in the vicinity of the flaw. The strength of heat treated glass is conventionally considered to be equal to the sum total of the residual stress and the extrinsic strength of annealed glass. Recent experiments suggest that there is an additional contribution to strength attributable to crack healing. To quantify it, uniaxial and equibiaxial strength tests on both as-received and carefully annealed glass specimens were performed for different edge geometries and edge finishes. The results show that strength recovery attributable to healing is significant, and this strength gain appears to correlate with the quality of the edge finish. Possible explanations of this phenomenon are provided. Independently of healing effects, it was also found that the edge quality has a marginal effect on the mean strength but has a significant positive effect at low fractile values often used in design applications.

The ingress of chlorides into posttensioned (PT) concrete structures is a leading cause of corrosion of the prestressing strands. This reduces the strength, durability, and service life of the structure and may result in catastrophic failure. A structural health monitoring (SHM) method is needed to improve the maintenance procedures associated with this method of construction. To evaluate the potential of acoustic emission monitoring for this application, long term corrosion monitoring tests were performed on specimens that were representative of internal and external posttensioning methods. Corrosion was induced in the specimens by adding chlorides to the grout and by performing wet/dry cycling with NaCl solution. The corrosion process was monitored by half-cell potential measurements (HCP) and acoustic emission (AE). Results show that AE has the ability to detect corrosion damage in the PT specimens with similar accuracy to HCP measurements. Furthermore, intensity analysis of the AE data shows that the damage in the PT specimens can be categorized according to the level of corrosion present. This investigation demonstrates that AE can be successfully implemented to detect, monitor, and quantify corrosion levels in PT concrete structures, and that AE is a promising nonintrusive method to detect and quantify corrosion in the absence of electrochemical techniques.

This paper presents an experimental program investigating the effect of galvanic current on the physical and mechanical characteristics of carbon fiber reinforced polymer (CFRP) composite sheets bonded to a steel substrate. Electrochemical reaction is induced by galvanic interaction between anodes (CFRP-steel interface specimens) and cathodes (metallic strips) linked with an electrolyte (a 3.5% sodium chloride solution). Thirty-five test specimens are exposed to various periods of galvanic current from 0 to 72 h until their corrosion rate is converged. Hydrated ferric oxide forms along the CFRP-steel interface with some concentration in the vicinity of its edge, which accompanies a loss in surface area and mass. The electrochemical reaction imposed by the galvanic current exponentially decays with an increase in exposure time. The initiation of corrosion noticeably affects the load-carrying capacity of the CFRP-steel interface, whereas its propagation is not a critical attribute until substantial corrosion damage takes place. CFRP-debonding is the governing failure mode of the interface, irrespective of the degree of galvanic current exposure. The stress-slip behavior of the interface is influenced by the electrochemical reaction and a geometric discontinuity associated with stress singularity. Corrosion-dependent interfacial fracture energy is probabilistically inferred and used for quantifying the degree of interface deterioration subjected to an aggressive corrosion environment.

The degradation of building materials occurs as a stochastic phenomenon. Service life prediction methods are usually divided into deterministic, stochastic, and engineering methods. Deterministic models are simpler and easier to use, but are unable to capture the random nature of the degradation phenomena. On the other hand, stochastic models are more complex but very efficient in dealing with the uncertainty associated with a building’s performance. In this study, a stochastic approach to the factor method is proposed to predict the service life of rendered façades. The model proposed is based on a survey of the degradation state of 85 rendered façades located in Portugal. The factors that affect the durability of this type of coating are identified and translated into probability distributions. This analysis leads to coherent values, revealing that façades on buildings built with adequate design measures are more durable; façades exposed to adverse environmental conditions are more prone to degradation and are penalized in the quantification of durability factors; private buildings are more prone to suffer degradation (this result is related to the budget available for maintenance). This methodology provides an estimated service life of any given rendered façade through a probability distribution.

Beam fatigue testing of hot-mix asphalt (HMA) in the laboratory has been used for several decades by many researchers around the world. A total of two standard procedures are currently available: one that controls constant haversine deflection and another that controls constant sinusoidal deflection. The literature shows a large variability in shift factors between laboratory and field fatigue results. Also, recent literature shows inconsistent waveforms when a haversine deflection is used, which could be one of the reasons causing this large variability. The paper examines the results of the standard procedures and provides a rational explanation of the differences between them. Because of the inconsistency of the ASTM flexural fatigue test standard, it incorrectly produces a larger number of cycles to failure than the AASHTO test, with ratios of approximately 10, which varies depending on the stiffness of the material. Also, specimens tested according to ASTM flexural fatigue test standard, with twice the input tensile strain of specimens tested according to AASHTO flexural fatigue test standard at the same temperature, produced approximately the same number of cycles to failure. An approximate method is recommended to correct old ASTM flexural fatigue test standard results by assuming that the obtained number of cycles to failure corresponds to approximately 55–65% of the tensile strain that was inputted to the machine. More studies need to be conducted to verify the results using other materials and test conditions.

As road infrastructure development has witnessed a steep increase across the globe, it is adversely affecting the environment attributable to unabated extraction and use of stone aggregates, a fast depleting natural resource. This situation has led to a serious ecological problem and requires alternative techniques for obtaining a sustainable pavement such as use of cold mix recycled asphalt pavement (RAP) technology with bitumen emulsion. Techniques like this have proved that they make a positive impact on both economic and environmental conditions. The main objective of this study is to evaluate emulsified mixtures incorporating RAP, which is a typical task attributable to the complexity by heterogeneity of materials. The study recommendations are on the basis of comparison of laboratory performance of emulsified mixtures: without RAP, as a control mixture; and with RAP, containing 30–80%. The study involved understanding the physical characterization of materials, followed by developing mix designs for both conventional cold mix and mixes with varying percentages of RAP content. Indirect tensile strength (ITS) is used as an indicative measure for cold recycled emulsified mixtures (CREMs) during mix design. Laboratory tests, including tensile strength ratio (TSR), moisture induced susceptibility test (MIST), resilient modulus, rutting, creep, and fatigue tests, were conducted for the performance evaluation of the mixtures with and without RAP. The obtained results indicated that the CREMs are superior to conventional cold mixtures in mechanical performance. Among the varying RAP proportions, mixes with 60% RAP showed optimal results indicating that it is possible to design high-quality bituminous mixes incorporating considerable amount of RAP that meets the desired volumetric and performance criteria.

Physiochemical and rheological properties of asphalt binder are known to directly relate to asphalt pavement performance as it relates to fatigue and low temperature cracking. While other performance criteria such as rutting is also affected by binder properties, the latter is known to be also very sensitive to aggregate skeleton and mixture gradation. To enhance pavement performance, asphalt industry has commonly used various modifiers to improve binder rheological properties both before and after it is exposed to oxidative aging. Among those additives are polymers, ground tire rubber, as well as several organic and inorganic fillers. Inorganic fillers such as nano-clay and silica fume showed to be promising candidates to enhance asphalt rheology and aging behavior. Such enhancements are typically attributed to the presence of silicate platelet and silica particles. Accordingly, this paper investigates the merits of application of mesoporous silica nanoparticles in this paper referred to as nano-silica as an asphalt binder additive to enhance binder rheological properties and oxidative aging resistance. To do so, different percentages of nano-silica were added to neat asphalt binder. Asphalt binder was then exposed to short-term oxidative aging using a rolling thin film oven (RTFO). To study the distribution of nano-silica in binder as well as the change in the chemical, rheological, and morphological properties of asphalt binders due to the addition of nano-silica, the scanning electron microscopy (SEM), Superpave tests, and Fourier transform infrared spectroscopy (FTIR) were conducted. It was found that introduction of nano-silica to asphalt binder can improve the rheological properties and oxidative aging resistance of asphalt binder.

This paper presents a literature review covering the most used parameters and rheological properties for the characterization of the rutting resistance of asphalt cements (AC), or binders. They include the original Superpave parameter $G^{*}/\sin \delta$ and the nonrecoverable compliance $J_{nr}$ obtained in the multiple stress creep and recovery (MSCR) test. To draw typical examples of the differences between the rutting performances of binders as a function of the specification criterion, a $50/70$-penetration grade AC was modified with crumb rubber ($\mathrm{AC}+\mathrm{rubber}$), low-density polyethylene (PE), and linear styrene-butadiene-styrene copolymer (SBS) such that the high PG grade is the same (76-xx) for all the formulations. The rankings of binders from the less to the most susceptible material to rutting showed some similarities for the selected parameters. However, the MSCR test was able to underline marked differences in the rheological responses of the formulations that could not be directly observed for the other procedures, as well as the stress sensitivity of the $\mathrm{AC}+\mathrm{rubber}$. Thus, the MSCR test was recommended as the best protocol for analyzing the rutting potential of binders.

Aggressive environments significantly influence the durability and serviceability of hardened cement and concrete. This paper presents an evaluation of the resistance of ground-granulated blast-furnace slag (GGBS) activated with calcined dolomite, as a novel alkali activator, to 5% sodium sulfate attack and 5% magnesium sulfate attack. Two calcined dolomites, D800 and D1000, were prepared in the laboratory at 800°C and 1,000°C, respectively. The results demonstrated the good potential of using calcined dolomite activated slag in resisting sulfate attack. Immersion in ${\mathrm{Na}}_2{\mathrm{SO}}_4$ (aqueous) led to an increase in strength in both the D800 (D800S) and the portland cement CEM I 52.5 N (PCS) activated slag with a more pronounced effect in the former and a decrease in the D1000 (D1000S) activated slag. Conversely, calcined dolomite activated slag had less strength loss than PCS after ${\mathrm{MgSO}}_4$ attack. The products of sulfate attack and the deterioration processes are also analyzed by a range of tests, including pH, weight change, corroded depth, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). After ${\mathrm{Na}}_2{\mathrm{SO}}_4$ attack, the main product on D800S and D1000S was gypsum with a larger amount in the latter. Gypsum, thaumasite, and M-S-H were the main products of D800S and D1000S after ${\mathrm{MgSO}}_4$ attack. The better resistance of D800S to sulfate attack was attributed to the absence of portlandite in the hydrated paste. Conversely, the presence of portlandite in D1000S led to the inhomogeneous sulfate ions inward progression; hence, the severe deterioration of the sample was observed.

Warm-mix asphalt (WMA) technologies aid in reducing mixing and compaction temperatures for asphalt concrete mixtures, allowing for savings in fuel consumption and extending haul distances and construction season. The reduced temperatures also provide a greener technology as emissions are lowered at the plant and the construction site. Engineering and environmental benefits promoted the rapid implementation of WMA technologies, but concerns remain regarding the difference in mixture performance of WMA versus hot-mix asphalt (HMA) because of the changes in the production process, specifically in terms of moisture susceptibility. This case study evaluates moisture susceptibility through the use of laboratory tests including the wet indirect tensile (IDT) strength test, the tensile strength ratio (TSR), and the Hamburg wheel tracking test (HWTT) analyzed with a novel methodology. The performance of two WMA technologies (Evotherm DAT and foaming) versus a control HMA is analyzed with and without antistripping additives and/or recycled materials after field and laboratory aging. Findings suggest that the WMA mixtures are more prone to moisture susceptibility in their early life as compared with HMA. The incorporation of recycled materials did not show a clear benefit for the WMA, whereas the inclusion of antistripping additives and aging significantly improved WMA in terms of moisture resistance, rendering mixtures with equivalent performance to HMA.

This paper presents the evaluation of the optimum mixing ratio of sand-tire chips (STC) mixtures based on void ratio and shear-strength properties. Locally available sand and tire chips of $20\times 10\mathrm{mm}$ size are adopted. Different STC mixtures, in the range 10–70% by weight of tire chips (TC), are considered, along with pure sand (0% TC) and pure tire chips (100% TC). Specific gravity, density, and large direct shear tests were conducted for various samples. The volume of voids and weight-volume relations were determined from the dry unit weight and specific gravity values obtained for various mixtures. The results showed that the addition of tire chips up to 40% by weight showed significant decrease of void ratio by 43%. Shear-strength properties, like angle of internal friction values, are increased with TC contents up to 30%. Based on experimental results, the optimum percentage of tire chips of the selected size is in the range of 30–40% by weight, which is the equivalent of 50–60% by volume. Further, the STC mixture at the optimum ratio results in lightweight material with 20% less unit weight with better strength parameters and compressibility behavior, which can effectively be used for geoengineering applications.

This paper presents the effects of five different types of superplasticizers on workability and compressive strengths of cement pastes containing nanosilica (NS) and nanocalcium carbonate (NC) particles each at 2% by weight as partial replacement of cement. The NS and NC are dispersed in water containing 1% superplasticizer (by weight of cement) of five different types for 30 min in an ultrasonic mixer at maximum amplitude. Comparison is also made with conventional mechanical dry mixing of NS and NC with cement and ultrasonic mixing of NS and NC in water. Results show that the addition of NS adversely affects the workability of cement pastes more than those containing NC, regardless of superplasticizer types and mixing methods. The measured compressive strengths of cement pastes containing NS and NC dispersed in polycarboxylate ether-based superplasticizer solution are the highest among all five superplasticizer types considered in this study. X-ray diffraction (XRD) analysis results also agree well with the measured compressive strengths.

Compared with austenitic or duplex stainless steels, ferritic stainless steels have no or very low nickel content. Therefore, their cost is lower and more stable than those of austenitic and duplex stainless steels, providing a more viable alternative for structural applications. They are also less affected by gradual yielding than their austenitic and duplex counterparts and thus retain elastic stiffness at relatively high stress levels more like their ordinary carbon steel counterparts. Existing stress-strain models, however, are less accurate in predicting stress-strain curves for ferritic stainless steels than for austenitic and duplex stainless steels. The paper collects a wide range of tensile test data for ferritic stainless steel coupons cut either from steel sheets or cold-formed hollow sections. Using the three basic Ramberg–Osgood parameters, stress-strain models are developed for both flat and corner ferritic stainless steels. The accuracy of the proposed models is verified by comparing their predictions with experimental stress-strain curves.

It is generally accepted that the postpeak strain-softening behavior of concrete in compression is a localized phenomenon that occurs mainly in the compression damage zone. Accurate quantification of the size and slenderness effects on the postpeak behavior of concrete, therefore, depends on the accurate quantification of the inelastic deformations that occur in the compression damage zone. In this study, a novel approach is proposed to separate the two inelastic deformation components, known as the localized crack deformation and the deformation caused by the inelastic strain in the compression damage zone, from experimental stress-strain curves. This new approach allows the utilization of existing test results in the published literature in the model development. Based on two comprehensive experimental databases of confined and unconfined concretes covering a wide range of concrete strengths, a constitutive model for predicting the strain-softening behavior of confined and unconfined concretes is proposed.