Journal of Materials in Civil Engineering

Concrete structures often suffer from multiple dynamic loads, or prior to being subjected to dynamic loads have already withstood initial loads. The mechanical properties of concrete materials under dynamic loads may be closely linked to initial loading history that concrete suffers. This paper deals with the investigation of the effect of initial static load and initial dynamic load on dynamic compressive failure of concrete materials based on numerical simulations. A meso-scale modeling method was established and a total of 147 three-dimensional concrete cubic models were simulated. It is demonstrated in research results that the strain rate effect of concrete is relatively weak under low strain rates, while the strain rate effect is significantly enhanced under high strain rates. Dynamic compressive strength under different dynamic loads gradually decreases with the increasing initial static load and the increasing strain rate can weaken the influence of initial static load on dynamic compressive strength of concrete. When dynamic load changes in hardening stage, tangent modulus has a sudden increase and compressive stress reaches a new peak strength. A sudden increase of dynamic load in softening stage reverses the postpeak softening to postpeak hardening followed by a second peak strength. Initial dynamic load plays an important role in dynamic compressive failure of concrete, especially under low strain rates. The numerical results compare well with the existing test results.

In this study, a handheld Fourier transform-infrared spectrometer (FT-IRS) is used as the primary equipment to determine the reclaimed asphalt pavement (RAP) content in a mix by quantifying the extent of aging of a fresh mix. Binders of different performance grades and sources were used for laboratory aging and were analyzed to comprehend and compare different aging processes in terms of a carbonyl index ($I_{CO}$). The results show that the $I_{CO}$ of the RAP from 10 different sources varies from 0.0275 to 0.0607. Standard PAV aging produces $I_{CO}$ of only 0.0239, which indicates the significantly higher oxidation reaction in a service life than the laboratory aging. Attenuated total reflectance (ATR)-FTIRS data collection requires a small amount of the binder, which can be extracted in the field in 15 min by following the quick extraction method developed in this study. A spectral analysis of an unaged binder and RAP can predict the $I_{CO}$ in the fresh mix. The predicted and the measure $I_{CO}$ values were found to be in good agreement in two different plant mixes. So, the handheld FT-IRS has the potential to be used as a quality control tool in the field by precisely and quickly detecting the presence of aged RAP in the mix.

Researchers have extensively used simulated soil solutions for investigating corrosion of buried ferrous pipes. However, the literature on the correlation between corrosion rates of pipes in soil and simulated soil solution is very limited. The current paper addresses this gap and presents a model for the correlation of corrosion rates of cast iron in soil and its simulated soil solution using the test results obtained from specimens buried in soil and simulated soil solution of varying pH-controlled for 365 days. The test setup for the specimens in soil closely mimicked the buried environment, while the simulated soil solution was developed using the composition of natural soil. The same three pH values were selected for soil and simulated soil solution test setup. Apart from corrosion rates determination, the quantitative analysis of the corrosion products was performed for the specimens in varying pH environments. Based on corrosion rates measurements, a model for the prediction of corrosion rates of the specimens in the soil as a function of corrosion rates in simulated soil solution, pH, and time was developed. Moreover, detailed statistical analyses, i.e., Pearson correlation, normal distribution, homoscedasticity, correlation, and collinearity statistics, were performed using IBM SPSS Statistics to further interpret the results. The findings of this paper have practical significance for evaluating corrosion assessments of buried pipes in support of service life prediction analysis.

Rapid awareness about sustainability have ensued in recent times, and there has been a remarkable advancement by the construction industry to incorporate different waste materials into cementitious composites. Recent studies by the authors showed that recycled glass (GL) in the form of beads used as aggregate in engineered cementitious composites (ECC) is beneficial to its mechanical properties. However, with different durability issues related to the use of glass in cementitious composites, evaluating the durability properties of ECC mixtures incorporating glass as aggregate is paramount. Therefore, this study was carried out to evaluate the properties of cementitious composites related to its performance in various environments. The permeability response alongside the resistance to alkali-silica reaction (ASR) of different ECC mixtures incorporating different proportions of GL was evaluated. In addition, microstructural observations were made to understand the microstructural properties of the mixtures evaluated. The results from this study show that the use of glass as aggregates in ECC enhanced the durability properties of the composites.

In this study, the effect of adding sodium alginate fibers to enhance the self-healing capability of asphalt mixtures was evaluated. Two fiber types containing two different rejuvenators were synthesized, and their production parameters were optimized. A self-healing experiment was conducted using a three-point bending setup to evaluate the effect of different fiber contents on the healing efficiency and strength recovery of the mixtures. The fracture resistance of the mixtures at intermediate temperature was evaluated using the semicircular bending (SCB) test. Additionally, the rutting and fatigue behaviors of recovered binders were evaluated through rheological tests. The self-healing experiment showed that the asphalt mixture prepared with 15% fiber content by weight of the binder exhibited the best performance. From the SCB test, the highest critical-strain energy release rate ($J_c$) value was obtained at a 5% fiber content for both fiber types. Binder testing showed that binder blends with 5% fiber content had the highest rutting resistance. Linear Amplitude Sweep (LAS) test results also indicated that the binders with 5% fiber content exhibited the best performance against fatigue cracking. Overall, the use of 5% fiber seems to be a promising alternative and should be further evaluated.

In hilly and high-rainfall regions, very sharp curves, lack of skid resistance, and poor visibility form a major cause for road-traffic accidents in India and other similar parts of the world. The construction of pavements with open-graded friction course (OGFC) wearing surfaces in such regions will help enhance road safety due to increased skid resistance, reduced hydroplaning, reduced splash and spray, and better visibility. OGFC mixes demand a high percentage ($>90\%$) of good quality coarse aggregates for adequate stability and load transfer. India is the second-largest producer of steel, and about 12 million t of steel slag (as a byproduct) is generated every year and mainly lies unutilized in open areas, leading to environmental concerns. This study aimed to investigate the design and performance characteristics of OGFC mixes with basic oxygen furnace (BOF) steel slag as the coarse aggregate. Properties of OGFC mixes were evaluated by replacing 0%, 25%, 50%, 75%, and 100% of coarse natural aggregates by BOF steel slag. OGFC mixes were first evaluated for design parameters, including air void content, stone-on-stone contact, Cantabro abrasion loss (unaged and aged), and binder draindown. OGFC mixes with the different percentages of BOF slag were then evaluated for performance through the determination of indirect tensile strength, moisture damage resistance, porosity, and permeability. In addition, the benefits of OGFC mixes in terms of improved skid resistance were found under both dry and wet conditions at different contents of BOF slag. Results showed that steel slag used as coarse aggregate improved the frictional resistance of OGFC mixes. Steel slag-OGFC mixes also showed improved design and moisture resistance parameters compared to the values of these parameters for the control mixes (without slag). A replacement of coarse aggregate with BOF steel slag by 50% on a weight basis is recommended in OGFC mixes for enhanced safety in hilly and high-rainfall regions.

Asphalt extraction and recovery are essential steps before characterizing components and properties of aged asphalt binders for recycling the reclaimed asphalt pavement (RAP). To accurately analyze the aged asphalt, it is essential to evaluate removal efficiency of residual mineral fillers during bitumen extraction and recovery. This study investigated three methods (filtration, gravitational sedimentation, and centrifugal sedimentation) to separate base asphalt and styrene-butadiene-styrene (SBS)-modified asphalt from the mineral fillers using trichloroethylene (TCE) solvent. The removal efficiency was quantitatively evaluated by the index of silicon–oxygen bond based on Fourier transform infrared spectroscopy (FTIR). Furthermore, comparative evaluation and consumption analysis were carried out to assess removal efficiency and energy consumption of the three methods. The results demonstrated that centrifugal sedimentation was the best way to get the cleanest asphalt binder, while gravitational sedimentation was superior in terms of removal efficiency, and thus it can be used to obtain larger amounts of the “pure” aged asphalt for macrotest. The removal efficiencies of the three methods were affected by the types of asphalt and concentrations of the asphalt-trichloroethylene solutions.

Concrete crash barriers are structures provided to channel the road traffic and prevent catastrophic accidents resulting in loss of life. The failure of concrete crash barriers is often due to vehicular impact. Improved impact resistance is essential to increase the service life of concrete crash barriers. Studies have shown that the use of crumb rubber in concrete enhances the impact resistance and toughness of concrete. The addition of fibers assist in improving the toughness resistance of concrete and play a vital role in controlling the cracks. Experimental and numerical studies were carried out to ascertain the impact strength of fiber-reinforced rubcrete crash barrier’s. This paper presents the results of impact tests conducted on M 40 grade concrete, fiber-reinforced concrete, and fiber-reinforced rubcrete crash barrier models. Impact tests carried out on rubcrete, steel fiber-reinforced concrete, and polypropylene fiber-reinforced concrete prisms have led to economic proportions of crumb rubber, steel fibers, and polypropylene fibers for higher energy absorption capacity. The results show that the most economic proportion for crumb rubber that can replace fine aggregates by volume was found to be 15%. For obtaining the minimum cost to energy absorption ratio for steel fiber-reinforced concrete and polypropylene fiber-reinforced concrete, 0.75% and 0.2% of the total volume of concrete should be placed with steel fibers and polypropylene fibers, respectively. Energy absorption studies carried out on the one-third scaled-down model of crash barriers revealed that steel fiber-reinforced rubcrete crash barriers exhibited three folds energy absorption capacity in comparison to the concrete crash barrier. Numerical studies on the finite element models of crash barriers have shown similar trends as obtained in the experimental investigations with respect to energy absorption characteristics of crash barriers.

There is no method for evaluating the shear-fatigue resistance of sealants installed in the supporting layer of ballastless track, and the degradation mechanism of sealants under shear-fatigue loading has not been studied systemically. This study develops a shear-fatigue loading test method, and the adhesive properties of sealants are researched during shear-fatigue loading. The functional-group character at the failure interface is analyzed using infrared spectroscopy, and then the correlation between macromechanical behavior and the micromechanism is discussed. Results show that both maximum loads and failure displacements have a downward fluctuating trend during shear-fatigue loading, and sealants with lower hard-phase content present better shear-fatigue resistance. No new chemical bond forms in sealants, but more soft phases fuse into hard phases, which decreases the microphase separation degree of sealants. The developing rules for the hydrogen bonding index identify a trend similar to that of the mechanical behavior of sealants caused by the orientation of amorphous phases. The hydrogen bonding index degradation of higher $R$ value sealants is deemed more significant, which agrees well with the results of the direct tension test.

This study explored the role of aluminum silicate (AS) on the water stability performance and microstructural properties of magnesium phosphate cement (MPC) composites. Five consecutive dosages of AS were introduced in MPC composites as a substitute for magnesium oxide. It was revealed that MPC composites containing 3% AS exhibited a compressive strength (CS) of around 108.2, 97.1, and 103.4 MPa and a flexural strength (FS) of about 14.9, 13.9, and 14.3 MPa at 28 days in open air, full immersion and cover by wet cloth, respectively, and these results were higher than control and other surrogate mixtures. Additionally, electron microscope, X-ray diffraction, and energy dispersive spectrometer observations confirmed the formation of intermediate crystals along with struvite minerals, which explained the dense microstructure, by reducing the micropores. Moreover, thermogravimetric analysis and differential thermal analysis results demonstrated that crystal water in struvite was lost at around 97.35°C, which was the primary issue behind losing the solid mass of the composite paste in a high heat environment. The outcomes of the study might play a role in field applications of MPC composites blended with AS.

This paper presents the results of an experimental study conducted to investigate the effects of polypropylene fibers and synthetic macrofibers (barchip) with different partial cement replacements on the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC). For this study, 21 mix designs were prepared to contain three different fibers (polypropylene, barchip, and steel) and cured under either of the wet or combined (steam, autoclave, and water) conditions. A total of 282 cubic, cylindrical, and prism specimens were cast to measure their compressive and flexural strengths and determine toughness indices. It was found that the combined curing technique, proposed for the first time in this study, was capable of improving compressive strength in the specimens reinforced with synthetic fibers. Specimens containing barchip fibers as well as those containing steel fibers were found to present deflection-hardening behavior after cracking. Most of the specimens containing silica fume and limestone powder with different types of fibers showed satisfactory toughness indices, indicating their acceptable flexural toughness.

The linear amplitude sweep (LAS) test has been widely accepted for estimating the fatigue resistance of asphalt binders in the last 10 years. This paper proposes a fracture mechanics–based analytical approach for crack initiation and propagation characterization in the LAS test, aiming to more precisely explore the binder crack growth and failure mechanism. Seven unmodified neat asphalt binders and one styrene-butadiene-styrene (SBS) polymer-modified binder are selected in this study. The crack length ($a$), rate of cracking ($\mathrm{d}a/\mathrm{d}N$), stress intensity factor ($K$), and energy release rate ($G$) are the fundamental parameters for the data interpretation approach proposed in this paper. Experimental and analysis results demonstrate that the energy-based failure definition (either from continuum damage mechanics or fracture mechanics) should be utilized to detect the material-dependent failure occurrence in LAS test. The fracture behavior of asphalt binder in the LAS test follows the two-phase crack growth (TPCG) model in terms of the crack initiation and crack propagation. The crack propagation phase further consists of stable crack growth and unstable crack growth. It is found that the fatigue performance of asphalt binder is intrinsically governed and dominated by its resistance to the crack propagation. The SBS binder in this study clearly displays slower crack propagation behavior than other neat binders. Additionally, the traditional fatigue life can also be divided into the crack initiation life and crack propagation life, which is promising to clarify the specific modification contribution to binder fatigue resistance. The two critical crack lengths of initiated crack and propagated crack for a given asphalt binder are found to be correlated to each other, indicating the potential links between the binder crack initiation and propagation behaviors.

Some natural fibers such as jute which have high tensile strength can be applied in natural fiber-reinforced polymer (FRP). Natural cellulose fibers are hydrophilic, resulting in lower reinforcement performance. Heat treatment can reduce water content in natural fibers and possibly improve the properties of natural FRP in terms of enhancing fiber and polymer composite action. This paper presents an improvement of jute fiber–reinforced polymer (JFRP) composites by heat treatment. The heat treatment conditions (i.e., temperature and duration) were considered. Coupons of heated JFRPs were tested to investigate their tensile properties. The application of JFRP on confinement was investigated by compression tests on concrete cylinders with JFRP wrapping. The experimental results indicated that a suitable heat treatment condition of 80°C for 24 h can significantly increase the tensile strength of JFRP coupons and the compressive strength of JFRP-confined concrete. The testing results of concrete confinement can be used to validate the existing predicting equations for confined compressive strength. In addition, a new equation was proposed for the effect of heat treatment of JFRP.

This paper reports the characterization of internal damping ratio ($\xi$) and $Q$ factor of ultrahigh-performance fiber-reinforced concrete (UHPFRC) using acoustic tests for undamaged and damaged samples excited by an impact. Ratio $\xi$ is a nondimensional parameter that measures the material capacity to dissipate vibration, and the $Q$ factor is physically interpreted as inverse attenuation, measuring the undamped characteristics of an oscillator. A servohydraulic testing machine was used for straining the samples cyclically, and at the end of each cycle the acoustic tests were made to measure $\xi$ and $Q$. Furthermore, scanning electron microscopy (SEM) was performed in samples extracted from the damaged specimens. From results, undamaged samples presented average $\xi$ around 0.35% with maximum and minimum values of 0.50% and 0.15%, respectively. The analysis of damaged samples showed that the internal damping gave a small variation in the first two load cycles and achieved 0.8% after the peak stress. Low values of $\xi$ found in the present study suggest that UHPFRC structures are more susceptible to excessive vibrations than normal-strength concrete structures. Moreover, SEM images showed damage mechanisms that are the probable reasons for the increase of $\xi$ after severe loading.

Previous studies focused on the determination and simulation of the bleeding extent of fresh cement paste and provided objective conclusions. However, few studies exist on the influence of bleeding on the final structure of cement paste. This study focused on the microstructure development during the hydration of cement paste with various bleeding caused by the water-cement ratio, the slag replacement, and the superplasticizer. To obtain information on the porosity profile and pore size distribution, the sample was measured using a low-field nuclear magnetic resonance (NMR) with Hahn spin sequence and Carr-Purcell-Meiboom-Gill (CPMG) sequence from top to bottom. The results showed that increasing bleeding thickness leads to a heterogeneous structure from top to bottom in terms of porosity profile and pore size distribution. Moreover, hydration can reduce the difference in the pore structure, especially when the bleeding depth is small. It was also found that the influence of bleeding depth on the pore size distribution of gels pores during hydration is minor compared with that of the capillary pores. Furthermore, detailed discussions on the connections between the bleeding and the final structure are presented in this paper.

The reliability of concrete in complex environments is the basis for improving the reliability of concrete structures. A concrete reliability assessment based on multiple degradation factor is proposed. First, chloride penetration and fatigue damage are selected as two degradation parameters for concrete, and series tests are developed to investigate the surface chloride concentration, diffusion coefficient, and degradation of residual strength under coupled effect of chloride penetration and fatigue. Then, two marginal distribution functions of the durability reliability of the concrete are deduced based on two failure modes. Subsequently, fatigue loading the parameters of different typical copula functions are obtained by using the maximum likelihood method (MLM), and copula function selection is carried out according to the Akaike information criterion (AIC) criterion. The joint distribution function is then derived by fusing the two marginal distribution functions using the selected copula function, and a remaining durability reliability model is obtained. Finally, the proposed model is verified by experimental data. This method should be considered as a reference for the evaluation and reliability calculation of concrete structures.

To explore the effect of the joint contact area and temperature on the dynamic property of rock joints and wave propagation in granite rockmass, an impact test of a jointed granite specimen was conducted with a split–Hopkinson pressure bar. The jointed specimen was composed of an artificially grooved specimen and an intact specimen. The ratio of the joint contact area to the cross-sectional area of the intact specimen was defined as the joint matching coefficient (JMC). The specimens were heat-treated at temperatures of 25°C, 200°C, 400°C, and 600°C. The experimental results showed that with the decrease in the JMC, the nonlinear characteristic of the stress–strain curve for the initial loading segment was more evident for the heat-treated specimen at a constant temperature. Furthermore, the transmitted coefficient, secant modulus, and joint-specific stiffness gradually decreased. For a given JMC, the expansion of the mineral component in the specimen heat-treated at 200°C caused the internal cracks to close, resulting in a larger transmitted coefficient and joint-specific stiffness. For the specimens heat-treated at 400°C and 600°C, the transmitted coefficient and joint-specific stiffness gradually decreased owing to thermal damage. In addition, the deformation of the jointed specimen at different temperatures was mainly caused by joint closure. A smaller JMC or more serious thermal damage led to an increase in the peak value of the joint closure.

The main purpose of this research is to assess the influence of different design parameters on the mechanical performance of high-performance fiber-reinforced concrete (HPFRC) mixtures. Special attention is also paid to achieving deflection-hardening behavior in the presence of a large amount of coarse aggregates. Different mixture design parameters were the initial curing ages (3, 7, 28, and 90 days), ratios of Class F fly ash (FA) to portland cement (PC) (0.0, 0.2, and 0.4), addition/type of nanomaterials [nanosilica (NS), nanoalumina (NA), and nanocalcite (NC)], and combinations of fibers [polyvinyl-alcohol + steel (P, S) or brass-coated microsteel + steel (B, S)]. The experimental program included the evaluation of compressive strength, flexural strength, and midspan deflection results in addition to test parameters recorded under biaxial flexural loading via a series of square panel tests, including peak load and energy absorption capacities. Test results revealed that deflection-hardening response coupled with multiple microcracks can be obtained when large amounts of coarse aggregates are available for all HPFRC mixtures. As expected, experimental results change depending on the different curing ages and FA/PC ratios. The most distinctive parameters affecting the results are addition/type of nanomaterials and the presence of different fiber combinations. In the presence of nanomaterials, all results from the different tests improved, especially for NA and NS inclusions. With slight concessions in flexural deflection results, B fiber is shown to be a successful candidate to fully replace costly P fibers because most properties of B, S fiber-reinforced HPFRC mixtures outperformed those with P, S fibers, both under four-point bending and biaxial flexural loading.

In this study, we investigated the degradation process of metakaolin-based geopolymers exposed to high temperatures up to 1,000°C. The changes in mechanical properties, microstructure, and phase assemblage of the samples were studied, and the results demonstrated that at high temperatures the activator type [i.e., ${\mathrm{Na}}_2{\mathrm{SiO}}_3/\mathrm{NaOH}$ (Na/Na) and ${\mathrm{Na}}_2{\mathrm{SiO}}_3/\mathrm{KOH}$ (Na/K) solution] affected the degradation mechanisms of geopolymer mortars. (Na,K)-based geopolymer specimens demonstrated better thermal resistance at temperatures above 200°C. This was evident from the higher compressive strength, lower porosity, and less cracking tendency of this mixture. Compared to (Na,K)-based geopolymers, more mass loss may result in considerable drying shrinkage of (Na,Na)-based counterparts, which would further lead to the occurrence and development of cracks at $\sim 200°\mathrm{C}$. Above 200°C, the degradation of the mechanical properties of geopolymers could be attributed to crack development and degradation of material properties. Furthermore, compared to their (Na-Na)-based counterparts, (Na-K)-based geopolymers achieved improved chemical stability and did not form new crystalline phases above 1,000°C. Moreover, higher temperature exposure (1,000°C) led to significant sintering of geopolymers, forming a dense and homogeneous matrix and, as a result, improved mechanical properties of specimens. Overall, it showed that when specimens were exposed to different high temperatures, the mutual promoted effects between ${\mathrm{Na}}^{+}$ and ${\mathrm{K}}^{+}$ in geopolymers played a significant role in crack development, sintering, and new crystallization formation in the specimens.

Agricultural by-products are increasingly used in the production of bio-based concrete. Compaction forming technology was used in this study to develop a sustainable biocomposite made from corn stalk (CS) and magnesium phosphate cement (MPC). The goal was to experimentally evaluate the effect of forming pressure (FP), CS content, and fly ash (FA) content on the apparent density, compressive strength, and thermal conductivity of CS-MPC biocomposite (CMB). Furthermore, the microstructure changes of typical CMB samples were analyzed by conducting scanning electron microscopy (SEM) tests. The results indicated that the apparent density and thermal conductivity of CMB were less influenced by the FP, while the compressive strength can be effectively improved by increasing FP. The increase of CS content from 25% to 45% led to a 47% reduction in thermal conductivity and a significant decrease of compressive strength. The inclusion of FA had little influence on the apparent density, but resulted in 9.48% reduction in thermal conductivity by adding 20% FA. The optimum FA content of 10% was recommended as MPC admixture, which can increase compressive strength of CMB by 4.17%. The linear empirical model for predicting thermal conductivity by apparent density was established. The microstructure changes inside CMB showed the bonding properties between MPC and CS, and the corresponding micromechanisms were analyzed. The findings provide a basic theory for using CMB as thermal insulation material in buildings.

The reaction of blast furnace slag in sodium hydroxide (NaOH) solutions of different molarities is evaluated. The compressive strength of the activated slag does not scale with the molarity of NaOH. The primary reaction product in the activated slag is identified with calcium aluminosilicate hydrate [C(A)SH]. While the early reactivity of slag is enhanced at higher alkalinity, and the dissolution of slag increases with the molarity of NaOH, the quantity of C(A)SH in the hydrating system does not scale with the molarity of NaOH in the activated slag. From X-ray diffraction (XRD) analysis, an additional water-soluble, sodium-based amorphous product is identified in the reaction products. The water-soluble product, which does not contribute to strength, increases proportionately with the initial Na content in the solution. At higher molarity, there is a larger proportion of the water-soluble product relative to C(A)SH in the reaction products. The $\mathrm{Ca}/\mathrm{Si}$ ratio and $\mathrm{Al}/\mathrm{Si}$ ratios in the C(A)SH gel are relatively invariant of the NaOH molarity in the activating solution. The compressive strength gain in the alkali-activated slag is determined by the quantities of C(A)SH and the intrinsic sodium-filled water-soluble product.

Thailand is an agricultural country, ranked as the top in the world for the production and export of natural rubber. This study investigated the influence of natural rubber latex (NRL) replacement on the mechanical strength improvement of cement-stabilized soil. Cement contents of 3%, 5%, and 7% by weight of dry soil and NRL replacement ratios of 10%, 15%, 20%, 25%, and 30% by weight of compacting water were used in this research study. The mechanical strengths were investigated via unconfined compressive strength (UCS) and flexural strength (FS) tests. The mechanical strengths improvements were examined through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses. NRL replacement was found to significantly enhance the mechanical strengths of cement-NRL stabilized soil. The optimum NRL replacement ratios providing the highest density, compression, and flexural strengths were found at 20%, 15%, and 10% for 3%, 5%, and 7% cement contents, respectively. At the optimum NRL replacement ratio, the UCS was improved up to 30%, 21%, and 18% for 3%, 5%, and 7% cement contents. While, FS was improved up to 78%, 40%, and 29% for 3%, 5%, and 7% cement contents. Even though the NRL films within the soil-cement matrix improved the cohesion of the soil matrix, it was found to retard cementation bonding. As such, the excessive NRL replacement not only reduced the compactability but also retarded the cement hydration and, hence, the strength reduction. The outcome of this research will promote the usage of NRL as a sustainable alternative to imported synthetic latexes for improving the mechanical strength of cement-stabilized soil for pavement bases.

An iron–carbon electroplated long period grating (LPG) fiber sensor to monitor the passivation, initiation, and propagation of the pitting corrosion of steel bars is characterized in simulated concrete pore solutions. An inner silver is first deposited on the surface of LPG fiber before electroplating the outer iron-carbon layer. The surface topographies of both silver and iron-carbon layers are examined with atomic force microscopy. The corrosion evolution of an iron-carbon layer in different solutions is measured by using electrochemical impedance spectroscopy and linear polarization resistance, and the shift in the resonant wavelength of an iron-carbon electroplated LPG sensor is monitored with a spectrum analyzer. Experimental results show that iron–carbon electroplated LPG sensors can continuously monitor the passivation and initiation of pitting corrosion, while it is not suitable to monitor the propagation of pitting corrosion.

A crude extract from jack beans (Canavalia gladiata) is demonstrated to be an effective source of urease enzyme for biocementation via enzyme-induced carbonate precipitation (EICP). Test tube tests of crude and purified extracts from jack beans, jack bean meal, soybeans, and watermelon seeds show that the crude jack bean extract results in the highest unit yield, defined as urease content per initial mass of source material, among these four plant sources. The efficacy of EICP using crude jack bean extract for biocementation was compared with the efficacy of three commercially available enzymes by biocementation of a granular soil. Unconfined compression tests on the granular soil specimens subject to biocementation via EICP demonstrated that the crude extract and the less purified commercially available enzyme were actually more effective than commercially available highly purified urease enzymes at enhancing soil strength, an effect attributed to the presence of complementary proteins in the less purified enzyme sources. The simple technique used to produce the crude extract from jack beans significantly lowers the cost of EICP, eliminating a major barrier to practical applications, including infrastructure construction and environmental protection.

The aim of this research is using a waste wood–based bio-oil as the modifier of petroleum asphalt and analyzing its modification mechanism. The four components, infrared spectrum, and molecular weight distribution analysis were performed to investigate the chemical performance of control binder and bioasphalts. A conventional petroleum asphalt PG 64-22 was employed as the control binder. The bio-oil with addition of 10%, 15%, and 25% by weight was used to prepare bioasphalts (BMA). Meanwhile, the Gas Chromatograph Mass Spectrometer (GC-MS) and oven heating tests were conducted to explore the chemical compounds and their approximate contents in bio-oil. Results demonstrated that the bio-oil significantly changed the contents of chemical components in asphalt binder by decreasing the contents of saturates and asphaltenes and increasing the aromatics and resins contents. The modification of petroleum asphalt by bio-oil is not only a physical mixing but also a chemical process. Some chemical reactions were deduced between the PG 64-22 and bio-oil based on the infrared spectrum analysis. The added bio-oil converted some large molecules into small molecules. There are various chemical compounds in the bio-oil. Higher content of aromatic compounds and many lightweight compounds can explain the softer quality of bioasphalt and its inferior high temperature properties in comparison to petroleum asphalt.

Moisture damage is a major concern for evaluating the performance of asphalt mixtures. There are different types of experimental methods to determine the effect of moisture on mechanical and durability characteristics of asphalt mixtures. In this study, three different experimental approaches were implemented, including the boiling water test, the indirect tensile test, and the resilient modulus test, as well as the fracture energy analysis to evaluate moisture susceptibility of asphalt mixtures fabricated with different types of fillers including portland cement, limestone powder, and recycled concrete aggregates. Replacing the control filler material with these fillers resulted in improved fracture energy, which shows the stripping rate becomes slower by using them as fine aggregate. The fracture energy ratio of the asphalt mixture containing portland cement has the lowest rate of decrease for freeze-thaw cycles. Also, by applying a two-dimensional registration image-processing method as a low-cost soft-computing technique, an adhesion–cohesion index is introduced for determining the effect of moisture on adhesion between asphalt binder and aggregates as well as cohesion within asphalt mastic. Results have shown that there is a meaningful correlation between adhesion–cohesion index and number of freeze-thaw cycles, tensile strength ratio, resilient modulus ratio, and fracture energy ratio. To predict the adhesion–cohesion index of asphalt mixtures as an output of the image-processing method based on experimental results, a regression model was developed and verified in terms of the aforementioned parameters with an average prediction error of 4.46%.

Due to the declining availability of coal fly ash, there is a need to identify alternative sources of supplementary cementitious materials (SCMs). This article presents an investigation on the reactivity of ground and sieved bio ash that can be used as alternative sources of SCM. The oxide contents of bio ash are similar to Class-C coal fly ash. Accordingly, bio ash was found to have both hydraulic and pozzolanic reactivity. Ground bio ash showed higher heat of hydration and similar compressive strength compared to coal fly ash at the early stage (i.e., up to 7 days) of cement hydration due to the hydraulic reactivity. Grinding the bio ash improved its pozzolanic reactivity by 25% as per the modified Chapelle test. Using bio ash as SCM was also found to increase the ettringite formation in cement matrix. Nevertheless, the potential of excessive expansion of the paste samples due to the ettringite formation was found to be negligible.

This study investigates the relation of quality measures of asphalt mixture properties during production and construction to long-term in-service performance of flexible pavements. Data from flexible pavement sections taken from the Long-Term Pavement Performance (LTPP) program along with the pavement sections of 30 Wisconsin projects were compiled in a single relational database to establish a georeferenced architecture that embraces the natural variability within the database. An in-depth analysis was performed on seven selected projects using two modeling programs that are based on statistical regression and mechanistic-empirical methods. The three research approaches allowed for assessing the effects of the variation in quality measures during construction and production: air void (Va); voids in mineral aggregates (VMA); and in-place density. The analysis showed that the deviation from the standard target for in-place density influences fatigue, longitudinal, and transverse cracking, as well as the International Roughness Index (IRI). The study showed the shortcomings of over-averaging pavement characteristics in the modeling of predicted in-service performance. Last, this study showed that implementing the proposed georeferenced relational database architecture within LTPP would increase the impact of this program.

A novel foam insulation material was prepared using calcined phosphogypsum (CPG) as the raw material and hydrogen peroxide (${\mathrm{H}}_2{\mathrm{O}}_2$) as a foaming agent. Stable foaming of ${\mathrm{H}}_2{\mathrm{O}}_2$ in a CPG-based suspension was achieved. The effects of ${\mathrm{H}}_2{\mathrm{O}}_2$ on the mechanical properties, thermal conductivity, and pore structure of the CPG-based foam insulation materials were investigated. The results showed that, with increasing ${\mathrm{H}}_2{\mathrm{O}}_2$ content, the expansion volume increased but the growth rate decreased. The total porosity and macroscale porosity ($>100\mathrm{\mu m}$) first increased and then plateaued, while the microscale porosity ($<100\mathrm{\mu m}$) first increased and then decreased before plateauing. When the content of ${\mathrm{H}}_2{\mathrm{O}}_2$ was 4%–5%, CPG-based foam insulation materials with low bulk density ($\le 500\mathrm{kg}/{\mathrm{m}}^3$), low thermal conductivity [$\le 0.13\mathrm{W}/(\mathrm{m}·\mathrm{K})$], and acceptable compressive strength ($\ge 0.24\mathrm{MPa}$) were manufactured; these values are similar to those of other thermal insulation materials, such as cement foam and geopolymer foam in low density ranges.

Asphalt binder is very sensitive to temperature and exhibits bonding or lubrication effects at different temperatures. The bonding/lubrication properties of asphalt affect the mixing, compaction, and service performance of asphalt mixture. To analyze the interface bonding/lubrication transformation behavior of aggregate-asphalt systems, the contact-slip test was conducted at different temperatures using a self-developed tester. The maximum slip force was used to evaluate the contact properties of aggregate-asphalt systems. A relational model between the maximum slip force and the temperature was established, and the asphalt content for maximum bonding was proposed. The temperature transition behavior from bonding to lubrication of asphalt was analyzed and delimited, and the critical transition temperature was determined. Test results show that the temperature intervals of lower than 90°C, from 90°C to 150°C, and above 150°C represent the bonding zone, bonding–lubrication zone and lubrication zone, respectively, for the AC-13 aggregate-asphalt system. The critical transition temperature of bonding–lubrication is 120°C. Coarse aggregates are more sensitive to the lubrication effect of asphalt; however, the bonding effect affects the particle system more significantly with an increased content of fine aggregates. The structural stability of an aggregate-asphalt system is more sensitive to the bonding part, so the interface strength formed by the coupling of the contact friction effect of the particle system and the bonding and lubrication effect of asphalt increases first and then decreases with increased asphalt content.

The influence of using residual rock wool fibers on the properties of ferrocement mortar was researched. Rock wool (made from basalt) was used as a volumetric partial replacement of fine aggregate to estimate its effect on different properties of ferrocement mortar. The replacement process included using four percentages of rock wool fibers (0%, 2%, 4% and 6%) with two lengths (5 and 10 mm) to explore the possibility of producing sustainable ferrocement mortar. Two types of curing (water and ${\mathrm{CO}}_2$) were used for these mixtures. Compressive strength, flexural strength, density, absorption, and thermal conductivity was tested for different ages (7, 14, and 28 days). Development in compressive strength, flexural strength, and absorption were about 43% and 80.5%, 18.46% and 36.86%, and $-34.5\%$ and $-39.5\%$ for water and ${\mathrm{CO}}_2$ curing, respectively. This improvement was noticed in some mix proportions, in spite of considering sustainability through used materials and curing methods.

Warm-mix asphalt (WMA) technology and recycling of asphalt pavement, i.e., reclaimed asphalt pavement (RAP), have been becoming more popular in recent years due to their economic and environmental benefits. Similarly, bio-oil rejuvenators seem to be a viable solution when the usage of high percentages of RAP is desired. However, employing a high percentage of RAP in WMA using bio-oil rejuvenator remains very limited. This experimental study investigates the use of high percentages of RAP (i.e., up to 90%) in WMA using bio-oil rejuvenator. To this end, rheological tests including rotational viscosity (RV), multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) were carried out on different combinations of binders. Wheel tracking (rutting), indirect tensile stiffness modulus (ITSM), four-point bending beam fatigue, and moisture susceptibility tests were performed to evaluate the performance of the asphalt mixtures containing different binders. Test results demonstrated that the asphalt mixture with 90% RAP and a bio-oil rejuvenator had 37% higher fatigue life and 4% improvement in moisture resistance.

Porous asphalt pavement can reduce noise and improve road safety and driving comfort on rainy days. The seepage model derived from the one-way gradient flow theory cannot truly reflect the seepage process of rainwater inside the drainage layer. In this study, the drainage performance of porous asphalt pavement with different designs was evaluated using a three-dimensional seepage finite element method (FEM), and the drainage capacity of porous asphalt pavement was calculated using short-term rainfall intensity. The results indicated that the drainage capacity of porous asphalt pavement can be effectively improved by increasing cross slopes, the surface course layer thickness, and the permeability coefficient of porous asphalt mixture. Moreover, the pavement width had a significant impact on the drainage performance of porous asphalt pavement.

Traditional Assam-type wooden houses are a popular housing system in the northeastern Himalayan region of India. Such houses have performed exceptionally well in previous earthquakes. An experimental study on the frames of Assam-type houses has affirmed its excellent performance, which is attributed to its flexible timber members and joints, unique infill-frame connection, and light-weight structure. It is important to evaluate experimentally the physical and mechanical properties of various elements used in the construction of such houses to gain an insight into their lateral load behavior. First, the properties of the Sal (Shorea robusta) and Jam (Syzygium cumini) timber species, commonly used as framing elements in Assam-type houses, were evaluated experimentally. The compression strength and tensile strength were determined in both parallel and perpendicular to grain directions followed by determination of bending strength. The timber specimens exhibited significantly different characteristics in two loading directions. The lateral load behavior of Ikra wall panels used in Assam-type houses was then evaluated by diagonal compression testing. The results obtained from the testing of materials indicate that Ikra panels will be helpful in developing and calibrating the numerical models for predicting the seismic response of traditional Assam-type houses as well as timber-framed structures. Finally, based on regression analysis, simple empirical equations are developed to predict the lateral strength of frames of Assam-type houses.

Laboratory evaluation of elastomer- and plastomer-modified asphalt binders using different grades of asphalt binders and produced asphalt concrete mixes is the subject of this paper. The evaluated polymer modifiers in this study were an elastomer [commercially available styrene-butadiene-styrene (SBS) and a plastomer (functionally modified olefin commercially known as Eastman EE-2)], blended separately with two penetration-grade binders ($60/70$ and $80/100$) at polymer/binder ratios of 2%, 4%, and 6% (by mass). The rheological properties of the polymer-modified binders (PMBs) were tested using a rotational viscometer, dynamic shear rheometer, and bending beam rheometer. The effect of the polymers on the rheological properties of the asphalt binders was investigated before and following standardized short- and long-term oxidative aging. Hot-mix asphalt mixes were prepared and evaluated in terms of the number of performance tests, which included indirect tensile strength, moisture susceptibility, resilient modulus, creep-recovery strain properties, and indirect tension fatigue. Analysis of the obtained PMBs indicated that the addition of the elastomer and plastomer polymers to petroleum asphalts was very useful in obtaining a number of desirable characteristics. The main indicators of such improvements are improved rutting resistance of the unaged and short-term aged binders, and the addition of higher percentages of the polymers resulted in an upward shift of the rutting resistance without impacting the fatigue properties of the binders. The addition of up to 6% of the polymers to the binders raised the performance grade (PG) of the PMBs by at least two grades from their base PG. For the softer binder (i.e., Pen. $80/100$), 6% SBS pumped the PG of the binder three grades up. The introduction of varying amounts of elastomer and plastomer polymers can significantly influence the resultant mechanistic properties of mixtures.

Biocomposite building materials with mineral binders are becoming more topical recently because they can address growing environmental concerns regarding carbon footprints and resource depletion better than traditional building materials. However, these new materials also pose new challenges. There have been issues with the compatibility of plant-origin aggregates (such as hemp-origin aggregates) with commonly used mineral binders due to organic compounds released by these aggregates, and these issues have not yet been extensively studied. Magnesium-based binders are a group of alternative binders that are being used in the production of biocomposites, and although they do not appear to have the same compatibility issues, they too have not yet been widely researched. In this study, the impact of organic compounds released by hemp-origin aggregates on the physical and mechanical properties of binders were tested. The hydration processes of commonly used binders such as cement and lime alongside alternative binders-magnesium cements influenced by released organic compounds were investigated. Organic-compound extracts from hemp-origin aggregates were prepared in a water medium with different pH values. The resulting extracted organic compounds were shown to retard the setting time of hydraulic binders (cement and hydraulic lime) and decrease their compressive strength by more than 50%. Magnesium-cement binders, however, show only slight retardation in setting time and no compressive strength loss. Thus, magnesium-cement binders have demonstrated their superior compatibility with plant-origin aggregates.

The rejuvenator is typically utilized to partially recover the mechanical properties of reclaimed-asphalt pavement (RAP). Although the rejuvenator works effectively in softening the highly aged recycled asphalt and improving workability, the rutting and cracking performance of recycled materials cannot be well guaranteed. In this paper, the potential of generating an asphalt mixture incorporating RAP with both strong rutting resistance and improved cracking resistance is evaluated. Rubber, rejuvenator, and their combination are utilized, respectively, to modify recycled asphalt from field cores, and their basic rheological properties are evaluated. Both Marshall mix design and balanced mix design methods are conducted to design recycled-asphalt mixtures with proper material properties. The effects of RAP content and asphalt content on the performance of recycled-asphalt mixtures are also quantified. Results show that rubber modification can increase rutting resistance and low-temperature resistance of recycled-asphalt binder. Although the application usage of rejuvenator is able to soften the recycled-asphalt binder and decrease viscosity, whereas the inclusion of rubber particles can further increase the resistance to fatigue and rutting of recycled-asphalt binders. It is also found that both the rubber modification and rejuvenator can improve binder’s ability to resist low-temperature cracks. Additionally, the Marshall and balanced mix design methods indicate that increased RAP content always leads to increased rutting stability and decreased fatigue crack resistance, whereas moisture resistance and low-temperature resistance are not clearly affected. The addition of rejuvenator can also improve the low-temperature performance and fatigue resistance of recycled-asphalt mixtures and lessen the high-temperature performance, whereas it does not change its moisture resistance property.

Styrene-butadiene-styrene copolymers (SBS)–modified asphalt mixture is widely used in high grade roads because of its excellent comprehensive performance. However, the black characteristics and high temperature susceptibility of asphalt binder have a great impact on the performance of asphalt mixture. This paper mainly investigates the influence of different types of thermochromic materials on the properties of SBS-modified asphalt mixture, including high- and low-temperature performance, water stability, and the aging effect of the natural environment on asphalt mixture (natural aging). According to test results, thermochromic materials slightly reduce the high-temperature performance of SBS-modified asphalt mixture. All three kinds of thermochromic materials can improve the low-temperature crack resistance of SBS-modified asphalt mixture, among which red thermochromic material with 2% content (named as 2%RTP) is the best. In addition, thermochromic materials of different colors can improve the water stability of SBS-modified asphalt mixture, and black thermochromic material with 2% content (named as 2%BTP) exhibits the best effect on improving the water stability. All three thermochromic materials can improve the antinatural aging property of SBS-modified asphalt mixture.

This research involved a detailed laboratory study of sulfate resistance and drying shrinkage of self-compacting concrete (SCC) mixes made with copper slag. After an initial curing of 28 days, SCC samples were subjected to a sulfate solution for a period of over 1 year. Changes in compressive strength, mass gain, and expansion measurements were reported for SCC samples. Comparative analysis of compressive strength was done with the respective water-cured samples for up to 1 year. Drying shrinkage of SCC was studied for up to 448 days. Statistical significance of the compressive strength of SCC mixes was determined using analysis of variance. No major catastrophic damage was reported. An improvement in compressive strength of SCC mixes was observed from 28 to 90 days. Peaks of Ca and Si under energy-dispersive spectroscopy analysis revealed the development of calcium silicate hydrate layers leading to a gain in strength. No major phase change under X-ray diffraction (XRD) was observed for SCC mixes under normal curing as well as under sulfate attack. Minute expansions were reported for SCC mixes with copper slag. SCC mixes containing up to 60% copper slag gave lower drying shrinkage values than control SCC mix. The results of compressive strength of SCC exposed to sulfate were found out to be statistically significant.

The healing properties of bituminous mixes prepared using reclaimed asphalt pavement (RAP) material are different from those of virgin mixes because the chemical characteristics of RAP binder blends are different (depending on the extent of aging) compared to virgin binders. Very limited research work has been reported in the literature on the healing potential of RAP mixtures. The current study aims to examine the fatigue and healing characteristics of RAP mixtures with varying rest periods between loads. To this end, different blends of RAP and virgin binders (VG30) were prepared at varying proportions (0%, 15%, 25%, 35%, and 45%) of RAP material in mix. The fatigue lives of different RAP mixes were evaluated by varying the rest period (400, 650, 900, and 1,400 ms) between load pulses. The healing potential of the mixes was evaluated in terms of the slopes of the lines drawn between fatigue life and rest period. The fatigue life of a mix increased with increases in the proportion of RAP in the mix. The degree of healing indicated by the slope of log (fatigue life) versus log (rest period) line was found to depend on RAP content and rest period. Mix time lag (between the peaks of stress and strain), a viscoelastic property of the mixes, was determined from the stiffness modulus test. Different rheological and chemical characteristics of the binder blends and the time lag values of the mixes were correlated with the fatigue lives and healing indexes of the mixes. The Superpave binder fatigue parameter ($\mathrm{G}*\sin \delta$) and the mix time lag were observed to have good correlation with the fatigue life of RAP mixes. Surface free energy and different aging indexes of the binders (ICO and ICH) showed good correlation with the healing index of the mixes. Flow (consistency) parameters, such as softening point and viscosity at 60°C, correlated well with the healing index. These correlations are expected to improve understanding of the fatigue and healing behavior of RAP mixes.

To effectively evaluate the contact characteristics of a particle system, an aggregate contact-slip tester was developed in this investigation on the microscopic level. Contact indexes, including the maximum slip force, number of macropeaks, and number of micropeaks, were proposed to quantitatively evaluate the contact characteristics of the particle system. The contact tests were conducted on single-file-size particle systems and three graded particle systems of aggregate. By comparing and analyzing the variation coefficient of parallel tests for different speeds and particle sizes, the key test conditions were determined such as loading rate, sampling interval, and test distance. The validity of proposed indexes was verified adopting the ANOVA method by selecting the six-file-size aggregates and three typical graded mixtures. The results show that the appropriate test conditions of this method are loading rate of $10\mathrm{mm}/\min$, test distance of 80 mm, and sampling interval of $1/45$. Each index has little discreteness and shows a good discrimination to the contact characteristics for the materials with different gradations. The maximum slip force reflects the structure stability of the particle system, and the contact effect of the single-file-size particle system enhances with the increase of the aggregate size. The contact among particles of a graded particle system is more frequent, and the system is in an unstable dynamic microadjustment state under the action of external force. The structure stability of the particle system improves with the increase in the number of coarse aggregates, especially particles with a size of 9.5 mm, which is affected by the interference of fine aggregates adversely. The macropeak number and micropeak number, respectively, reflect the particles’ contact characteristics when the particle system is in a stable state and a metastable state. The more frequent contact does not mean that the structure of the particle system is more stable. According to the ability to form and maintain the stable structure of asphalt mixture, the order of three gradations is open-graded friction courses (OGFC)-13 $>$ stone matrix asphalt (SMA)-13 $>$ asphalt concrete (AC)-13.

Contradictory results have been published on the effect of sea sand and seawater in concrete as opposed to conventional river sand and freshwater. The majority of studies show equivalent, if not better, results when sea sand and seawater are used in concrete, although some studies concluded otherwise. This paper investigates the variations in the chemical and physical properties of sea sand. It has been found that each sea sand sample is unique, which might be the reason for the contradictory findings in the current literature. Chemical properties of sea sand were analyzed using a scanning electron microscope and the physical properties were observed using an optical microscope. The particle size distribution was measured. The short-term mechanical properties of sea sand–seawater concrete were compared with conventional concrete. The concrete samples were cured in natural marine conditions and atmospheric conditions and tested at 7 and 28 days. Sea sand–seawater concrete had a high early compressive strength at 7 days and remained slightly higher than conventional concrete at 28 days. The experimental procedure used all natural, unaltered, concrete constituents and curing conditions.

This study presents the results of laboratory experiments and analyses carried out to evaluate the rheological performance of nanoclay (NC) modified asphalt binders from 10°C to 70°C. A viscosity graded binder, VG-30, was modified using 2%, 4%, and 6% NC by weight of the base binder. The suitability of the NC modification was ascertained using a series of rheological evaluations, including a frequency sweep test (10°C–70°C), linear amplitude sweep (LAS) test (10°C, 20°C, and 30°C), and multiple stress creep and recovery (MSCR) test (40°C, 50°C, 60°C, and 70°C). Scanning electron microscopy (SEM) was carried out on the unmodified and modified asphalt binders to assess the microscopic dispersion of NC in the base asphalt binder. The SEM images demonstrated that with an increase in the percentage of NC, the physical dispersion of the modifier in the base asphalt binder changes. Six percent of the NC was found to form an interlocked phase within the composite asphalt binder matrix. It was found that the $h$-parameter obtained from Cole-Cole plots at individual temperatures offers a better and clearer comparison between the asphalt binders in comparison to the master curves and combined Cole-Cole plots. The analysis using $h$-parameter indicated a higher elasticity and lower temperature susceptibility offered by the NC modified binders. With an increase in the percentage of nanoclay, both the fatigue and rutting performance improved. The value of the $J_{nr}$ decreased while the value of the percentage recovery ($R$) increased with an increase in the percentage of the NC. At the temperature of 70°C, only a 6% NC modified asphalt binder was found to be suitable for standard traffic conditions. The LAS test resulted in a higher value of $A$ and an insignificant increase in the value of $B$ for NC modified binders in comparison to the values obtained for VG-30. No specific trend was observed in the value of $A$ at different CSRs, and it suggested from this study that an average value may be used. The number of cycles to failure for NC modified binders was found to be higher than VG-30. A statistical analysis carried out for different parameters revealed that the NC modification has a significant effect on the performance parameters of asphalt binders at all the test temperatures. A simple framework for the cost-benefit analysis has been proposed in this study, which revealed a 6% NC modification to be the optimum dosage for attaining a higher benefit in comparison to the cost.

Wastewater treatment sludge (WTS) is a by-product of wastewater treatment. Moisture holding capacity, high organic, complex inorganics, and zeolite-like chemical contents make WTS a valuable pavement additive. This study evaluated the impacts of 1.5% WTS on fatigue cracking and low-temperature cracking resistance of asphalt mixes. Reclaimed asphalt pavement (RAP) from North Dakota Highway-17 and I-29 projects were used. Three mixes—0%, 40%, and 60% RAP content—with and without WTS, were considered. The rheology of extracted RAP was tested for high-temperature continuous temperature, intermediate-temperature fatigue cracking resistance using linear amplitude sweep (LAS), and low-temperature cracking resistance using 4-mm parallel plate geometry. Rheology tests were conducted using a dynamic shear rheometer (DSR). Results showed that RAP from Highway-17 was relatively stiffer than the I-29 RAP. RAP mixes modified with 1.5% WTS were prepared at 40°C (104°F) lower mixing temperature than the control. Semicircular bend (SCB) and disk-shaped compact tension (DCT) tests were used to evaluate the fatigue cracking and low-temperature cracking resistance of the mixes, respectively. Results indicated that WTS improved the fatigue and low-temperature cracking resistance of 0%, 40%, and 60% RAP mixes from both RAP sources. The effect of WTS on fatigue cracking resistance increased with RAP content, whereas the effect of WTS on low-temperature cracking decreased with RAP content. Low-temperature cracking resistance of the 40% RAP mix was 24% higher than that of unmodified 0% RAP mix for Highway-17 mixes, and was almost similar for I-29 mixes. This shows WTS can be used as an additive to improve fatigue and low-temperature cracking resistance of mixes with RAP.

Presented is a direct-comparison sulfate resistance study of mortars containing 3% or 6% cement replacement with either colloidal nanosilica (nS) or microsilica (mS), exposed to 6 months of full submersion in a 5% sodium sulfate (${\mathrm{Na}}_2{\mathrm{SO}}_4$) solution. Mortar bar samples measured for linear expansion per current standards indicated that at 6% cement replacement, colloidal nS exhibited on average 75% of the expansion of the microsilica-containing counterpart. At 3% replacement, either form of silica reduced the sulfate attack–related expansion to a similar degree (by $35\%\pm 2\%$) in comparison with the control mixture. Supplemental rapid sulfate permeability (RSPT) and absorption testing current standards supported the expansion results. The 6% nS mortar mixture exhibited the least charge passed and smallest permeable pore volume, which indicated that the nS-containing mortars were physically more impermeable and more resistant to ion transport. Increasing nS replacement (i.e., from 3% to 6%) decreased a mixture’s permeable pore volume, whereas increasing mS had an inverse effect. This countered the benefits of increasing the pozzolanic content in the sulfate attack test. Mercury intrusion porosimetry (MIP) testing also revealed evidence of paste and paste-to-aggregate interfacial zone densification, as well as pore-size refinement, which was further supported by higher increases in compressive strength in mixtures with nS over those with mS.

In recent times, alternative ways to dispose various wastes generated, namely, fly ash, scrap tires, steel or iron slag, and foundry sand, are on the rise. Owing to low unit weight and good hydraulic conductivity properties of waste tires, they are found to be a competent alternative fill material for geotechnical applications. Likewise, fly ash is an accepted foundation as well as a backfill material. In the present study, reinforcing composite material made up of fly ash and granulated waste rubber of a nominal size equal to 9.5 mm is explored for use as a reinforced fill material or as a foundation bed material. Accordingly, the interface shear stress properties of a geosynthetic reinforcement with this new composite fill material are obtained using an interface shear box of dimensions equal to $305\times 305\times 204\mathrm{mm}$ ($\mathrm{length}\times \mathrm{width}\times \mathrm{depth}$). Two different types of geogrids, uniaxial and biaxial geogrids made up of polyester and polypropylene, are used as a reinforcing material. The granulated rubber contents in the mixtures are varied as 0%, 9%, 23%, 37%, 50%, and 100% to study its effect on the interfacial shear strength of geogrid and mixture. In addition, the effects of the type of the geogrid, tensile strength of the geogrid, and area of aperture opening within the grid are studied for a given mix of fly ash and granulated rubber ($50:50$ by total weight of the mixture). The effects of the type of geogrid and tensile strength of the geogrid on the interfacial shear strength are found to be insignificant, while a geogrid with a higher aperture opening area ratio is found to exhibit a high interfacial shear strength. The interaction coefficients of uniaxial and biaxial geogrids with fly ash and granulated rubber mixtures are found to range from 0.74 to 1.16 and 0.74 to 1.18, respectively.