Journal of Materials in Civil Engineering

The implementation of the Mechanistic-Empirical Pavement Design Guide (M-E PDG) in regions outside the United States and Canada, such as the Middle East and North Africa region (MENA), is still in its early stages due to the scarcity of the design input data required for its use at high reliability levels. Several studies have been carried out to present correlations for obtaining material properties as well as exploring the use of M-E PDG embedded climate files to account for the missing inputs and different environmental conditions. Yet, the main challenge resides in obtaining adequate traffic data and adapting local traffic inputs for M-E PDG default values. This paper presents guidelines for developing truck classification and growth factors from short-term traffic count surveys for countries where historical traffic data are unavailable or insufficient. The case of Lebanon is tackled as a case study for demonstration. The sensitivity of the pavement response to the variation of the extrapolated traffic input data is studied under different climatic and material conditions and validated against recent characterized and categorized traffic data. The results reveal that highway design agencies can process traffic count surveys to convert them into traffic input data as elaborated in the methodology, as the pavement’s performance is not majorly affected by the variations and assumptions used in the calculations of the truck classes. However, the variation in the truck traffic volume, i.e., growth factor, significantly influences the predicted pavement distresses, which necessitates the continuous collection of traffic data to have more representative values for the growth rate estimation. Based on the obtained results, final recommendations are presented for the implementation of the M-E PDG in regions lacking traffic records.

This paper compares experimental results on the stabilization of clayey dredged material (DM) using quicklime (QL), hydrated lime (HL), portland cement (PC), and Class F fly ash (FA). The DM was a clay, high-plasticity soil, dredged from the US Army Corps of Engineers Port Arthur (USACEPA) facility along the Neches River located in Orange and Jefferson Counties, Texas. The soil consists of a large proportion of clay (66%), has high moisture limits (plasticity index: $\mathrm{PI}=52$ and liquid limit: $\mathrm{LL}=80$), and is characterized as a fat clay with silt. Physical properties of the untreated DM, such as unconfined compressive strength (UCS), consistency limits, and compaction behavior, were determined. Stabilizing reagents were mixed in various percentages by dry weight of DM. Results indicate that 12% QL, 6% HL, 6% PC, and 7.5% Class F FA by dry soil weight must be used to meet a minimum benchmark criterion of a PI value below 35, which was established based on Texas Department of Transportation (TxDOT) specifications. Standard compaction tests were carried out in accordance common standards with ASTM D698 to determine the optimum moisture content (OMC) for all mixtures. Stabilized mixtures were prepared at the corresponding OMC, and unconfined compressive tests were run according to common standards. Tests results were compared with the relevant literature, and a linear regression model was developed to predict the PI reduction as a function of initial PI, LL, and stabilizer type and content with good accuracy ($R^2=0.86$). Overall, tests showed that stabilization of clayey DM using lime products, PC, or FA significantly improved the DM physical properties, which could then potentially be used as a local fill construction material that is cost-effective and environmentally friendly and reduces the overall use of cement products.

The curing of soil specimens treated with a liquid polymer soil stabilizer of styrene acrylic family was studied through an extensive laboratory testing program. First, the effect of different curing environments including air, water and heating on the unconfined compressive strength (UCS) of stabilized sand was studied to identify suitable curing environments. Furthermore, a parametric study was conducted through which the liquid content of the specimens (i.e., polymer + water) was varied and the overall performance of treated specimens of sand and sulfate-rich high plasticity clay was assessed. The optimally treated specimens (i.e., with the best curing environment and optimal stabilizer dosage) were evaluated for their (1) short-term performance, (2) swelling potentials of treated high plasticity clay, and (3) durability after 24 wet–dry or freeze–thaw cycles. The results suggested that heating can significantly expedite the curing; conversely, soaking the specimens in water showed a detrimental effect in terms of the resultant strength. The strongest specimens were achieved when no extra water in addition to the liquid stabilizer was added when treating the soil. As to clay, the liquid polymer showcased excellent performance in reducing the swelling potential but the strength of the specimens was highly decreased by to moisture and freeze–thaw cycles.

This paper investigates the utilization of copper mine tailings (MT) as an alternative road base construction material through geopolymerization. Specifically, MT was mixed with different amounts of sodium hydroxide (NaOH) solution at various concentrations from 0 to 11 M, compacted, and then cured at 35°C. After 7 days’ curing, unconfined compression tests were performed on the specimens to determine their unconfined compressive strength (UCS). Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analyses were also performed to study the microstructure and chemical composition of the specimens at different conditions. The study has systematically investigated the effect of two main factors, NaOH concentration and moisture content, on the behavior of geopolymerized MT. The results show that the maximum dry unit weight of the compacted MT is influenced by the NaOH concentration, with higher NaOH concentration leading to larger maximum dry unit weight. The behavior of the final geopolymerized MT depends strongly on the NaOH concentration and moisture content of the initial compacted MT. At a constant moisture content, the UCS of geopolymerized MT increases with higher NaOH concentration up to a certain level and then decreases. This behavior is simply related to the effect of NaOH content or $\mathrm{Na}:\mathrm{Al}$ ratio on the geopolymerization. For specimens prepared at the same NaOH concentration, the highest UCS does not necessarily occur at the optimum water content or the maximum dry unit weight, emphasizing the contribution of geopolymerization to the UCS. Moreover, this study demonstrates that by selecting appropriate moisture content and NaOH concentration, the geopolymerized MT can meet the strength requirements for road base by different state DOTs and the Federal Highway Administration (FHWA) in the United States. However, before the field application of MT in road base construction, a comprehensive leachate study based on the new EPA standard should be performed to ensure that the MT is environmentally safe.

Fly ash bricks are used for load-bearing masonry. The bond development between the masonry unit and the mortar is mainly due to the mechanical interlock of cement hydration products in the brick pores. This paper deals with the investigations in understanding the phenomenon of bond development between the fly ash-lime-gypsum (FaL-G) brick and the mortar. The bond strength of the FaL-G brick masonry and the burnt clay brick masonry was determined. Apart from quantifying the bond strength of FaL-G and burnt clay brick masonry, microstructure analysis of the materials at the brick-mortar interfaces was carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) techniques to establish the evidence and to quantify the chemical bond development between the FaL-G brick and the mortar. The results show that the flexure bond strength of FaL-G brick masonry is an order of magnitude higher than that of the bond strength of burnt clay brick masonry. This is attributed to the chemical bond between FaL-G brick and the mortar, which has been demonstrated in this study.

In practical engineering, sand fills or deposits are often under an anisotropic stress condition. Thus, these soil elements sustain an initial static shear stress before being acted upon by cyclic loading because of traffic, waves, and earthquakes. To experimentally explore the effect of consolidation condition on the undrained cyclic response of saturated sand, a series of triaxial tests were performed on both loose and dense samples under varying consolidation conditions. The results indicate that different densities and consolidation conditions lead to three distinct failure modes: flow liquefaction, cyclic mobility, and residual deformation failure. Given the presence of the limiting values of residual pore pressures, a pore pressure–based failure criterion was used to evaluate the cyclic resistance of sand. It was found that the consolidation stress condition affects the cyclic resistance differently in loose and dense sand. The concept of dissipated energy was then used to delineate the pore pressure development during cyclic loading, and the amount of energy dissipated in sand was closely correlated to its relative density, consolidation stress ratio, and cyclic stress ratio. Moreover, a unique relationship between the residual pore pressure and dissipated energy was obtained for both isotropically and anisotropically consolidated sand with varying densities and cyclic stress amplitudes.

The use of controlled low-strength materials (CLSM) is rapidly expanding in many geotechnical applications as designer backfill, especially foundations subjected to dynamic loading. This paper investigates the effects of incorporating treated oil sand waste (TOSW) in CLSM as a replacement of fly ash and partial replacement of sand on its dynamic properties. Several mixtures of CLSM were prepared with varying contents of cement, fly ash, and TOSW, and their shear wave velocity and geo-mechanical properties were evaluated. The piezoelectric ring actuator (PRA) technique was used for measuring $Vs$ of CLSM and an empirical equation was suggested to estimate shear wave velocity ($Vs$) based on mixture proportions of CLSM. The results suggest that the shear wave velocity was affected primarily by the cement content, while TOSW had minimal impact on it. However, TOSW improved the flowability of the mixture and could totally replace fly ash for that function. It is concluded that TOSW can be successfully incorporated in CLSM mixtures, offering an application to reduce the landfill disposals of oil sands waste while reducing the demand on natural resources.

Various filler materials were evaluated to identify and differentiate chemical reactions from physical particle reactions during hydration within a portland cement system. Laboratory teasting included solubility within a calcium hydroxide environment, heat generation via isothermal calorimetry, and portlandite formation identification via X-ray diffraction. Results indicate that quartz, which is often accepted as inert filler material in portland cement systems, is chemically reactive in highly alkaline environments. The study introduces diamond, a novel, truly nonreactive filler material that allows quantitative determination of the extent of pure physical reactivity, otherwise known as the filler effect, in the absence of additional contributions to hydration due to chemical reactivity. A proposed zero-reaction plot is suggested to evaluate material reactivity with respect to portland cement. Consequences of the zero-reaction plot are further reaching than a filler test; this method can evaluate the exothermic reactivity of amendments to portland cement in a manner that makes comparative analyses uncomplicated.

Crusher run is a type of construction aggregate produced in a quarry by breaking down the rock to various sizes using a mechanical crusher. Scalping is an essential process for a quarry to produce a series of crusher run products with specific grading specifications for various applications. To study the effects of scalping on the direct shear strength of crusher run, large-scale laboratory direct shear box tests were carried out on crusher run specimens scalped to pass 75, 37.5, 19, 9.5, 4.75, and 2.36 mm. Furthermore, to study the effects of scalping on interface shear strength between the crusher run and a geogrid, interface shear tests were also carried out between the crusher run scalpings and a geogrid reinforcement. The direct and interface shear-strength results were then analyzed to investigate the effects of scalping on the direct and interface shear stresses, failure envelopes, direct and interface friction angles, apparent cohesions and adhesions, and interface efficiencies. Sieving analyses were carried out before and after the shear tests to assess the degree of particle breakdown caused by loading and shearing in the direct and interface shear tests. The experimental shear test results show that scalping can cause a pronounced reduction in the direct and interface shear strengths. The results of the sieving analyses imply that the overall particle breakage of the crusher run specimens caused by large-scale direct and interface shear testing was not significant within a normal stress level of 1,000 kPa; however, some large-particle crushing on the top surface of the specimens was observed.

This study examined the effects of softening additives on the moisture susceptibility of recycled bituminous materials using chemical, mechanical, and imaging laboratory investigation methods. Two chemically different rejuvenators, one petroleum-tech (aromatic extracts) and one green-tech (tall oil), and an amine-based warm mix additive were selected as such softening additives. For chemical investigation, the two rejuvenators were examined using saturates-aromatics-resins-asphaltenes (SARA) analysis, Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis coupled with FT-IR (TGA-IR), and nuclear magnetic resonance (NMR). Mechanically, a semicircular bending (SCB) fracture test was conducted to evaluate the moisture damage resistance of the recycled bituminous mixtures treated with the different rejuvenators and the warm mix additive. Laser scanning microscopy (LSM) was also used to acquire noncontact microscale topographical images to evaluate the effect of lower temperatures on aggregate-matrix interaction in the production of mixtures with the warm mix additive. The test-analysis results were then investigated to identify relationships between different features (i.e., chemical, mechanical, and topographical) of the mixtures associated with the different rejuvenators and the warm mix additive. Although additional data and investigations are still necessary to reach more definite conclusions, it appears that specific chemical functional groups in the rejuvenating agents are associated with the rejuvenated mixtures’ moisture sensitivity, and the lower production temperatures used in warm mixtures may lead to a somewhat more porous region between the aggregates and the matrix phase of recycled-rejuvenated bituminous mixtures.

Nowadays, a large amount of steel slag (SS) not only occupies land resources but also pollutes the environment, and the low early strength and poor stability limit the application of SS in the building materials industry. In the study, SS was precarbonated and replaced 30% of cement to prepare a cementitious material. The optimum precarbonation conditions were determined. The hydration properties and microstructure of the precarbonated SS cementitious material were analyzed, and the strength and volume stability were studied. The results showed that the optimum precarbonation condition was carbonated at a water to powder mass ratio of 10% at 75°C for 2 h. After precarbonation, the early hydration rate and activity of the SS cementitious material had been improved. The calcium hydroxide [$\mathrm{Ca}{(\mathrm{OH})}_2$] of the precarbonated SS-cement paste no longer grew into a layered structure, and the total porosity of the paste decreased. The early flexural and compressive strengths of precarbonated SS cementitious material were greatly increased, and the volume stability was improved.

This paper investigates the effects of weak acids (citric acid, boric acid, and trisodium citrate) with dosages of 0.5, 1.5, and 2.5% of MgO weight on compressive strength, water resistance, and drying shrinkage of magnesium oxysulfate (MOS) cement. Hydration products and microstructure of typical samples are studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis-thermogravimetry (DTA-TG), and scanning electron microscope (SEM) facilities. The results show that compressive strength of MOS cement increases with an increasing $\mathrm{Mg}\mathrm{O}/\mathrm{Mg}{\mathrm{SO}}_4$ molar ratio and decreasing ${\mathrm{H}}_2\mathrm{O}/\mathrm{Mg}{\mathrm{SO}}_4$ molar ratio. The addition of citric acid, boric acid, or trisodium citrate significantly enhances compressive strength and water resistance and alleviates drying shrinkage of MOS cement paste. With the incorporation of weak acid, $5·1·7$ [$5\mathrm{Mg}{(\mathrm{OH})}_2·\mathrm{Mg}{\mathrm{SO}}_4·7{\mathrm{H}}_2\mathrm{O}$] phase, which is a new magnesium subsulfate crystalline product with a needlelike crystal whisker shape, forms in cement paste. This substance behaves in a criss-crossing manner and fills in pores and microcracks, inducing the improved performance of MOS cement paste. With optimum dosages of 0.5, 2.5, and 0.5%, respectively, citric acid, trisodium citrate, and boric acid exhibit decreasing improvement effect.

This paper presents a quantitative analysis and prediction of the process of particle breakage, from the initial state of one particle size fraction (PSF) to the ultimate state of stable grading. The effect of particle shape on the research results was analyzed. The one-dimensional confined compaction test was used to study the particle breakage under different compaction scenarios, with $W$ indicating work done during one compaction and $N$ indicating multiple compactions. The entire process was analyzed using the prediction model of the grey system theory. The results from the analysis demonstrate that the prediction model was superior because it simulated the breakage process, which could not be generated by the limited $W$ and $N$. The demarcation lines, where the mass percentage of newly generated PSFs started to decline, were calculated and verified. The process of change in fractal dimensions and relative breakage with $W$ was divided into four stages: intense breakage, fast breakage, slow breakage, and creep breakage. Each stage was analyzed to determine the change in PSFs that supported the impact load. The present studies provide insight into the micromechanism of the effect of impact loads on particle crushing and the breakage priority of different PSFs before it becomes steady.

In recent years, the increased rate of urbanization has led to the generation and release of large amounts of construction and demolition (C&D) waste. From the viewpoint of environmental preservation and effective utilization of resources, it is beneficial and necessary to reuse C&D waste. Recycled concrete aggregate, which is obtained from C&D waste, is currently being considered as an alternative aggregate for structural concrete. Recycled aggregate concrete (RAC), an ecofriendly concrete produced by partial or full substitution of natural aggregates with recycled concrete aggregates in a concrete mix, has drawn much attention recently. Over the last decade, a significant volume of studies has been reported in the literature on the behavior of RACs. This paper summarizes the literature dealing with the mechanical properties (and the parameters affecting them) of RACs produced using coarse recycled concrete aggregates published between 1978 and 2017. In order to provide a comprehensive understanding of the behavior of RAC, this review takes into account more than 200 published studies. The review also discusses the less understood influences of aggregate surface treatment, aggregate moisture state, and concrete mixing on the behavior of RAC. To the best of the authors’ knowledge, this is the first review dealing with all the potential influential factors affecting the mechanical properties of RAC. Hence, this review is expected to help researchers better understand the behavior of this construction material.

The electrochemical behavior of a novel alloy steel (00Cr10MoV) in the conditions of as-received with mill scale and pickled without mill scale in saturated $\mathrm{Ca}{(\mathrm{OH})}_2$ solution was assessed using various electrochemical measurements. Backscattered electron (BSE) images and elemental mapping were employed to characterize the distribution of mill scale and rust layer on the surface of corroded steel in the presence of chlorides. Compared with pickled 00Cr10MoV steel, much lower passivation capability was observed for as-received 00Cr10MoV steel due to the depletion of alloying element Cr in the defective mill scale. However, in the presence of chlorides, the high corrosion resistance of passivated pickled 00Cr10MoV steel was less pronounced. Therefore, it was confirmed that the surface imperfections possibly formed during the pickling process had a negative impact on the chloride-induced corrosion behavior of pickled 00Cr10MoV steel.

This study evaluates the effects of aging on the micromechanical and chemical properties of foamed warm-mix asphalt (WMA) and hot-mix asphalt (HMA) materials. Two asphalt binders were considered. Atomic force microscopy (AFM) was used to examine the micromechanical and adhesion properties of the asphalt binders considered at different aging conditions. In addition, Fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) techniques were used to identify and quantify the changes in the chemical composition of different asphalt binders due to aging. The results of the AFM tests indicated that the reduced modulus values of the asphalt binders increased with the aging of these binders, while the bonding energy decreased. In addition, the results of the AFM, FTIR, and GPC tests suggested that the WMA binders will experience equal or less aging over the service life of a pavement structure as compared to HMA binders. Good correlations were obtained between the micromechanical and adhesion properties of the considered asphalt binders measured using the AFM and their chemical properties obtained using the GPC and FTIR tests.

Concrete deterioration in cold climate regions is a great concern from a durability perspective because of deicing salts and freezing–thawing (F/T) cycles. This study investigates the response, in terms of physicomechanical properties and microstructural features, of concrete made with different types of cement—general use cement and portland limestone cement (PLC)—without or with fly ash and nanosilica to F/T cycles combined with different concentrations of chloride-based deicing salts (${\mathrm{MgCl}}_2$ and ${\mathrm{CaCl}}_2$). The results reveal that the resistance of concrete exposed to deicing salts is a function of physical penetrability (magnitude of intruding chloride), amount of aluminate in the cement, and content of portlandite available for chemical reactions in the hydrated paste. PLC mixtures exhibit better resistance to deicing salts due to synergistic physical and chemical actions of limestone in the matrix. Fly ash concrete has better performance than the reference concretes, especially the mixture containing 30%. When nanosilica is incorporated in concrete, no features of damage could be captured.

Permeability is an important index to estimate the working performance of pervious concrete. The previous studies show that pervious concrete clogs due to the ingress of the sediments and organic particles under the action of water flow. The clogging effect limits the permeability of pervious concrete. Three clogging effect factors were studied through the lab experiments in this paper, including the clogging agent gradations, the upper water heads, and the horizontal flow velocity. In addition to the traditional permeability coefficient testing method, based on Ohm’s law, the electric resistivity method was introduced to quantify the relative permeability before and after adding clogging materials. Besides, the qualitative research was conducted on the effectiveness of the high-pressure water-cleaning method and an analytical study was made on modeling the clogging process. The high-pressure water-cleaning method can significantly alleviate the clogging effect of porous concrete, especially when solving the problems caused by small particles ($d<0.315\mathrm{mm}$). It is found that a clay-sand mixture is the most harmful to the pervious concrete.

Moisture damage is a major problem in every tropical country that may occur in pavement structures during their design life due to inappropriate selection of aggregates and bitumen from a material point of view. Silica content of aggregates and existence of carboxylic acids in bitumen of the hot mix asphalt (HMA) are suspected to play a crucial role in such damage. The application of polymer-modified bitumen (PMB) may be an effective solution against such problems, as suggested by different investigations. However, high tariffs on PMB decreases the interest of construction agencies, particularly for constructing low-budget bituminous pavement. To address this issue, this study uses elastomeric municipal solid waste (MSW) composed of thermoplastic elastomers based on polypropylene (PP) in the form of plastic cups (PCs) to modify virgin bitumen. This research outlines a method to quantify the moisture susceptibility of the virgin and PC-modified bituminous mixes by second durability index (SDI) using a modified Marshall immersion test due to its applicability in wider temperature-fluctuation ranges. A gradual decrease of stability loss in the SDI curve from 0- to 7-day immersion periods is observed due to short chain propagation of PP in bituminous medium up to 2% by weight PC-modified bituminous mix in the wet process. However, experimental results of this investigation show that addition of 2% by weight PCs to the bituminous mix in the wet process gives the lowest moisture damage (i.e., 9.38%), which may lead to a longer life span of the bituminous mix by resisting the moisture damage of the constructed pavement.

A steel slag material demonstrated rapid hardening and a considerable gain in compressive strength upon reacting with carbon dioxide. Two-hour carbonated paste compacts achieved an average compressive strength of 80 MPa, warranting the slag’s consideration as a cement-like binder for building applications. The microstructure of this ${\mathrm{CO}}_2$-activated binder system was examined. The reaction was found to engage the di-calcium-silicate component of the slag to generate a hardened matrix consisting of $\mathrm{Ca}{\mathrm{CO}}_3$ and a low-lime calcium-silicate-hydrate (C─ S─ H) phase. The latter differed in composition and structure from C─ S─ H variants generated from normal portland cement hydration. Raman spectroscopy confirmed bands (330, 510–550, 600–630, and $\mathrm{1,005}{\mathrm{cm}}^{-1}$) consistent with C─ S─ H species having low-lime compositions. High-resolution transmission electron microscope (TEM) resolved lamellar features for C─ S─ H with short basal spacings (averaging 0.73 nm), correlatively indicating superior interlayer cohesion. Moreover, abundant nano-$\mathrm{Ca}{\mathrm{CO}}_3$ crystals were found interlocked within the C─ S─ H phase, forming a dense nanoscale composite matrix. Such a proposed binder system is completely by-product-sourced, thus presenting the potential of eliminating or significantly reducing the carbon footprint of building products.

This study aims to evaluate fracture resistance and self-healing performance of asphalt concrete at low temperatures using a semicircular bending (SCB) test. Three asphalt mixtures with different types of asphalt binder were used. The applied load and crack opening tip displacement (CTOD) were measured to calculate fracture energy and the critical release rate of fracture energy ($J$-integral). The self-healing indexes ($HI\mathrm{s}$) were defined as the ratios of fracture energy, peak load, and $J$-integral obtained before and after healing, respectively. The self-healing performance of asphalt mixture was investigated considering different healing temperatures, healing time, and initial crack lengths (notch depths). The results showed that the styrene-butadiene-styrene (SBS) modified asphalt mixture possessed the highest fracture resistance, as compared to the asphalt mixture modified by rubber compound and the asphalt mixture with conventional ${70}^{\#}$ asphalt binder. The self-healing ability of the asphalt mixture increased with the increase of healing temperature and healing time; while it decreased with the increase of notch length. The optimum healing temperature was determined to be 60°C at the same healing time of 8 h, whereas the optimum healing time was found to be complicated depending on mixture type. Each asphalt mixture exhibited different healing abilities, depending on healing temperature, healing time, and the performance indicator of healing index.

The objective of this study is to correlate asphalt mixtures’ crack resistance with their in situ cracking performance. Ten mixtures were obtained from a full-scale experiment at the Federal Highway Administration (FHWA) Accelerated Loading Facility (ALF), which were constructed with various contents of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), two warm-mix technologies, and two asphalt binder grades. The mixtures’ linear viscoelastic properties were assessed through dynamic modulus testing. Fracture resistance was characterized by the critical strain energy release rate ($J_c$), which was obtained from semicircular bending (SCB) tests at intermediate temperature. The increase in RAP/RAS content was found to enhance mixture’s stiffness while reducing the mix crack resistance. No significant difference in terms of crack resistance was observed between the two used warm-mix technologies. The use of a soft binder was effective in improving the crack resistance of mixtures with a high RAP content. The generic fatigue model from the literature did not correlate well with the ALF test results; modification was achieved by introducing $J_c$ as an indicator of crack resistance into the model form. The resulting $J_c$-based model exhibited an adequate correlation with field performance measured by the ALF test results.

The effect of cyclic loading deterioration on freeze-thaw and carbonation resistances of concrete were experimentally investigated in this study. A novel loading method was designed, which simultaneously considers both mechanical loading and environmental actions for concrete. It shows that with the increase of cyclic compressive loading, the porosity and water absorption of concrete initially decrease but then increase when the stress is above a threshold level because of the cracking initiation caused by cyclic compression. With the increase of concrete porosity, both dynamic elastic modulus loss and carbonation depth obviously exhibit an increasing trend. On the other hand, under the same stress level, the freeze-thaw and carbonation resistances of high-strength concrete are relatively superior to those of low-strength concrete. Compared with the unloaded concrete, the carbonation depth and dynamic elastic modulus loss after mechanical loading below the stress level threshold are lower. This is probably due to the denser microstructure compacted by the compression. However, if the loading level becomes above the threshold level, both the carbonation depth and dynamic elastic modulus loss dramatically increase, which is due to the cracks initiation and propagation after cyclic loading deterioration. Therefore, the combination of mechanical and environmental actions is more severe than a single environmental action without considering the mechanical loading.

Rheology deals with flow and deformation of matter under applied force. The study of rheological response of superplasticized portland pozzolana cement pastes subjected to a stepwise loading at three levels of temperature using Herschel–Bulkley and Bingham flow models is presented here. Rheological tests were done in a temperature-controlled coaxial cylinder viscometer (Brookfield DV-II). Cement pastes were prepared at a water–cement ratio of 0.37 using four types of portland pozzolana cement (PPC) and superplasticizers (SP) of four different families. Saturation dosages of the superplasticizers were obtained through Marsh cone and mini slump tests. Rheological tests were done on superplasticized cement paste mixes for three levels of dosages viz., lower than the saturation dosage, saturation dosage, and higher than the saturation dosage. Cement paste samples were subjected to shear rates ranging from $30$ to $65{\mathrm{S}}^{-1}$ in the viscometer and the resultant shear stress was measured. Rheological parameters were obtained at three test temperatures (15, 27, and 35°C) by fitting the second cycle downward flow curves using Bingham model and Herschel–Bulkley model. These parameters were analyzed and used for modeling through random kitchen sink algorithm. The variation of predicted and measured values of the rheological parameters were compared and validated. It was observed that the model could effectively predict the rheological parameters within the experimental domain.

Laboratory fatigue tests were conducted to investigate the antireflective cracking performance of geosynthetics under different combinations of traffic load and temperature variation (thermal load). Four ratios of traffic load to thermal load were selected and the performance of a geotextile and a glass fiber geogrid were evaluated during the tests. Results indicate that the crack growth rate in asphalt pavements significantly increases as the thermal load increases. However, placing the geotextile or glass fiber geogrid can both retard the fatigue of specimens and the propagation of the crack. Also, the glass fiber geogrid can reduce the crack opening better than geotextile for all the evaluate cases, while the geotextile can reduce the fluctuation of crack opening better than glass fiber geogrid under large temperature variation. Moreover, the antireflective cracking performance of glass fiber geogrid rises as the traffic load increases, while the influence of geotextile on crack retardation is more obvious as the thermal load increases.

The objectives of the work described in this paper are twofold. First, the reuse of high-limestone filler crushed sand in concrete formulated without the use of superplasticizer and to be used for pavement construction is investigated. Then, concrete’s splitting tensile strength is modeled using a new proposed approach. The proportioning study for three types of concrete mixes was conducted based on the compressible packing model (CPM). The results of mechanical tests, primarily compressive and indirect tensile strengths, confirm the possibility of using high-filler content sand as a main component of portland cement concrete (PCC) for the construction of rigid pavements. To model the splitting-tensile strength, and in contrast to existing models which relate this property to the compressive strength, the proposed approach directly relates it to the cementitious matrix strength, to the concrete component proportions, to the cement paste maximum thickness, and to some aggregate parameters. The proposed tensile strength prediction model seems appropriate because it produced relatively low average error when compared with the experimental results.

The Seebeck coefficient of plain cement paste is usually less than $1\mathrm{\mu V}/°\mathrm{C}$. To enhance the thermoelectric performance of cement composites, a kind of ${\mathrm{MnO}}_2$ powder was synthesized and used as a thermoelectric component in this work. The synthesized ${\mathrm{MnO}}_2$ powder was proven to be a kind of effective thermoelectric component in cement paste. The synthesized ${\mathrm{MnO}}_2$ powder possesses a nanorod structure with a diameter of about 50 nm and a length up to 1.4 μm. The measured Seebeck coefficient of the compacted ${\mathrm{MnO}}_2$ powders was about $-\mathrm{5,490}\mathrm{\mu V}/°\mathrm{C}$. The nanorod structured design was proven to be an effective method to increase the Seebeck coefficient of the thermoelectric component in this research. Then the ${\mathrm{MnO}}_2$ nanorods were incorporated into the cement matrix to enhance the thermoelectric effect of cement composites. A relatively high Seebeck coefficient of about $-\mathrm{3,085}\mathrm{\mu V}/°\mathrm{C}$ could be obtained when the content of ${\mathrm{MnO}}_2$ powder was 5.0% by weight of cement, which is more than 1,000 times higher than that of the cement paste without ${\mathrm{MnO}}_2$ powder. And at this content, the electrical conductivity, thermal conductivity, and $ZT$ of cement composites were $1.88\times {10}^{-4}\mathrm{S}/\mathrm{m}$, $0.72\mathrm{W}/\mathrm{mK}$, and $7.596\times {10}^{-7}$, respectively. The thermoelectric effect of the cement composites is enhanced mainly due to the enhanced Seebeck coefficient, while the influence of electrical conductivity and thermal conductivity caused by ${\mathrm{MnO}}_2$ powders is not as obvious as Seebeck coefficient.

Veneer-based structural products, such as laminated veneer lumber (LVL) or plywood, are commonly used in timber construction. When a manufacturer wishes to use new timber species or optimize the use of its veneered stock, the nominal design values of the new products need to be determined from comprehensive and expensive experimental investigations. In an effort to cost-effectively determine these characteristics, this paper introduces a methodology to numerically predict the compressive strength of veneer-based structural products. The method combines a classical elastoplastic approach with a probabilistic strength-prediction model of the wood veneers. The veneer strength is determined from its size and characteristics which can be measured in line during manufacturing. The accuracy of the approach is verified against experimental tests performed on 24 LVL samples manufactured from two different timber species and of various sizes. Results show that the approach accurately predicts the strength of the LVL samples with an overall $\text{predicted}:\text{experimental}$ ratio of 1.05 and low coefficient of variation of 0.08. The methodology is applied to determine the compressive strength distributions of LVL columns and plywood boards manufactured from a new resource, namely early to midrotation (juvenile) hardwood plantation logs. The approach considers three different species, Gympie messmate (Eucalyptus cloeziana), spotted gum (Corymbia citriodora), and southern blue gum (Eucalyptus globulus). The modeled compressive design strength of the new products is found to be of the same order of magnitude of and up to 1.6 times greater than the strength of commercialized LVL columns and plywood boards.

Cross-laminated timber (CLT) is an orthogonally laminated timber panel product made using dimensional lumber. It is gaining traction in the construction industry, as is evident by the increasing number projects using CLT. Currently, CLT panels are manufactured using single species of wood; however, as the product matures, several combinations of species/grades layups may be used to optimize the properties and achieve economic efficiency. The panels using these different combinations of species and grades are called hybrid CLT. For successful integration as a new panel layup in the CLT market, the performance of different connections using the hybrid layup of panels needs to be evaluated. Because hybrid CLT panels can possibly use materials of different densities into which the fasteners embed, fastener performance needs to be characterized according to the existing density profile. A series of laboratory tests are performed to obtain the performance of two different fastener types (a screw and a nail) on seven different layups to provide quantitative information about the performance of single fasteners used for common connection system. Additionally, the existing analytical models for predicting fastener performance under loading are adjusted to account for potential density profiles in hybrid CLT panel applications, and the results are compared to experimental results. Marked effects of face-layer density on the performance of the fasteners under lateral and withdrawal loading are captured. Neither yield mode nor the strengths of the fasteners are affected significantly. Results suggest that the adjusted models can be used to account for the effect of varying density.

Fine ceramic aggregates prepared from various types of tableware bone china ceramic was used in concrete. The raw fine bone china aggregates were evaluated for pozzolanic activity using the Frattini test, saturated lime test, and strength activity index test. The compressive strength results showed that up to 60% of the fine bone china ceramic aggregate (FBCCA) can be used to produce concrete with desirable strength characteristics. The pozzolanic behavior of fine bone china aggregate acts as an accelerator to form calcium silicate hydrate (CSH), improving the microstructure properties of the concrete. Investigations were made by X-ray diffraction analysis (XRD), Fourier transformation infrared spectroscopy analysis (FT-IR), and ${}^{29}\mathrm{Si}$ nuclear magnetic resonance (NMR) spectroscopy. The results revealed that an additional amount of CSH gel can be gained when using fine bone china aggregate.

This paper presents an experimental study that sought to characterize the effect of corrosion and fatigue load on the behavior of reinforcing steel bars. The surface profiles of corroded steel bars and the relationship between fatigue life and corrosion morphology were investigated. First, the corrosion process was accelerated by applying external direct current. Next, fatigue tests were performed on uncorroded specimens and precorroded specimens, and the results are presented and analyzed. A method for calculating the three-dimensional (3D) corrosion morphology coefficient of corroded steel bar is proposed. The fatigue life of corroded bars is significantly reduced because of corrosion morphology, and a logarithmic linear relationship exists between fatigue life and the corrosion morphology coefficient. Considering the corrosion morphology of corroded steel bars, a method is provided to calculate the fatigue life of a corroded steel bar based on the properties of uncorroded steel bar and the 3D surface morphology coefficient of corroded steel bars. The prediction results for corroded steel bars agree well with the experimental observations.

An understanding of the response of pavement materials under repeat loading is required for the mechanistic approach to pavement design. In this study, the response of granular subbase materials for a flexible pavement under simulated traffic loading has been investigated using repeat load triaxial (RLT) testing. Three types of granular materials treated with polyacrylamide (PAM) have been tested to assess changes in engineering performance and response to simulated traffic. Untreated materials have been also tested for comparison. In addition, these samples have been prepared using different compaction efforts to assess the effect of compaction level on performance and response of these materials. The engineering performance of these materials (treated and untreated) in terms of strength and deformation is assessed by conducting unconfined compressive strength (UCS) and RLT tests. Data related to their response under simulated loads have been also collected and used to calibrate an existing plastic strain model to predict the permanent strain response of each soil type from its physical properties. Results indicate that samples treated with PAM yielded higher UCS values and lower deformation characteristics than the untreated samples, with plastic strain magnitude being dependent on the compaction effort used. Furthermore, the model adopted for determining plastic strain has been found to satisfactorily describe the plastic strain response of the RLT experimental test data.

This paper investigates the performance and microstructure of alkali-activated slag concrete (AASC) subjected to different 28-day curing regimes: air, intermittent water curing (7 days in water followed by 21 days in air), and continuous water curing. Three concrete mixes were prepared with fixed contents of slag, desert dune sand, and aggregate and activated by an alkaline solution consisting of sodium silicate and sodium hydroxide. The ratio of alkaline activator solution (AAS) to slag was varied between 0.45 and 0.55. Samples were tested to assess transport and mechanical properties. Test results showed that an AAS:slag ratio of 0.50 provided optimal performance. Intermittent water curing was found to be the most effective curing regime, resulting in a reduction in porosity and sorptivity, and an increase in bulk electrical resistivity, modulus of elasticity, and compressive strength. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to characterize the microstructure. Calcium alumino-silicate hydrate gel was highlighted as the main reaction product, while sodium alumino-silicate hydrate gel was only detected in air cured counterparts.

Nowadays X-ray computed tomography (CT) imaging is being applied in the field of structural engineering. Scanning a concrete specimen by using X-ray tomography provides an insight into the inner structure without the need to destroy the specimen. As an example, the internal structure of cement-based materials is of high importance for understanding and modeling the transport phenomena that influence its durability. Some methods have been applied to observe and quantify the size and distribution of aggregate and cracks. In this study we would like demonstrate some examples of the potential of X-ray CT to study the three-dimensional evaluation of concrete structures and building material. Based on the technical potential of medical CT we believe that our studies provide enough indication for the successful use of CT for concrete and concrete elements to determine aggregate size and distribution, pore or void size and distribution, deterioration due to freeze-thaw cycles and porosity, level of deterioration of concrete due to fire, and level of deterioration of steel prestressing wires due to corrosion.

The effect of curing temperature on hydration of a ternary blend of calcium aluminate cement (CAC), calcium sulfate (C$), and limestone (Cc) was examined. Compressive strength was evaluated at 1, 7, and 28 days. Hydration kinetics and products were assessed using calorimetry, thermogravimetric analysis, and X-ray powder diffraction. It was found that elevating the curing temperature from 5 to 50°C accelerated cement hydration. At 5 and 23°C, the incorporation of limestone caused a transformation of monosulfoaluminate into monocarboaluminate in the hydration product at 28 days. Higher curing temperatures (35–50°C), however, resulted in a collective increase in monosulfoaluminate, monocarboaluminate, and aluminum hydroxide, and led to a significant reduction in ettringite. Higher curing temperatures also led to an increase in aluminium hydroxide but did not form as much hydrogarnet (${\mathrm{C}}_3{\mathrm{AH}}_6$) in the CAC-C$-Cc system as in the CAC-C$ system. This study provides a technical reference for practical design of materials based on the ternary binder system.

In this study, a discrete element approach is used to simulate brickwork. Bricks are represented by blocks with Mohr-Coulomb plasticity and strain softening. The mortar consists of elastic Voronoi blocks connected by elastoplastic contacts. First, the parameters for brick and mortar are calibrated through a series of bending and compression tests conducted on brick and mortar samples, respectively. Then, shear tests on triplets are performed and Brazilian tests on disc samples are investigated by the numerical approach. Compared with results from other researchers, the numerical model can not only reproduce accurate strength values of the samples but is also able to display the damage development and fracture patterns of the brick as well as mortar.

Soil treatment using binders is an important method to enhance the strength, stiffness, and durability of soils. The porosity/binder concept has been developed to help with the mixture design for soil stabilization measures and has been verified for homogeneous mixtures. Unfortunately, in cases in which the base soil is fine-grained, it is typically not possible to obtain perfect mixture homogeneity on site. In such cases the binder typically forms a crust around soil clods. This study examines the applicability of the porosity/binder index to such non-homogeneous mixtures. For this purpose, the unconfined compressive strength of samples produced from homogeneous and non-homogeneous mixtures have been compared. In these mixtures, the addition rate, the dry density, and the water content were varied. It was found that the porosity/binder concept can be used to predict the strength of non-homogeneous field gradations of stabilized soils, provided that the clod size and water content of the laboratory samples resemble the clod size and water content of the material on site. The precision of predictability decreases with increasing variations of water content and mixture homogeneity.