Journal of Materials in Civil Engineering

In this study, mechanical properties of glass fiber–reinforced sulfur mortar prepared with dicyclopentadiene (DCPD)-modified sulfur are evaluated. The efficiency of sulfur modification was detected using a differential scanning calorimeter and mortar’s mechanical property measurements. Fiber-reinforced mortars were prepared using DCPD-modified sulfur and glass fibers of lengths 6 and 12 mm with different volume percentages. Splitting tensile strength and modulus of rupture (MOR) increased up to 147.44% and 83%, respectively, due to fiber reinforcement; however, compressive strength did not improve much. Based on mechanical measurements, experimental relations for prediction of splitting tensile strength and MOR in the range of 0–5.21% of glass-fiber volume percentage were derived.

A three-story apartment building on the University of Miami campus in Florida, built in 1947 and scheduled for demolition in the spring of 2011, was used as a research test bed. Two identical strips of the one-way reinforced concrete (RC) slab of the first floor of the building were saw cut and load tested. In parallel with the well-established measurements of load and deflection, a continuous acoustic emission (AE) monitoring was carried out throughout the load test in order to estimate the AE evaluation parameters that relate to RC damage. The analysis of the AE results provides experimental evidence for the validity of AE technology as an assessment tool in the practice of in situ load testing.

Tension cracking is a very important phenomenon in the case of compacted fine grained soils, which are commonly used in earth dams, embankments, and waste containment systems. The strength and permeability of earthen structures can be seriously affected by the formation of tensile cracks. The purpose of this paper is to evaluate the effect of discrete and randomly distributed fibers (DRDF) in improving the tensile strength-strain characteristics of bentonite amended natural silty soil. The authors conducted a series of direct tensile tests on unreinforced and fiber-reinforced soil by using a specially developed tensile test set up in the laboratory. They conducted tests by varying the fiber content and fiber length and studying their effect on tensile strength-strain characteristics and crack formation. The present paper indicates that the blending of fibers improved the tensile strength-strain characteristics and ductility of the soil. The authors carried out a digital image cross-correlation (DIC) analysis of images of top view of the soil captured during tensile tests to obtain the displacement vectors and strain field distribution. As the fiber content and fiber length increased while keeping other parameters constant, there was an increase in the strain at crack initiation and energy absorption capacity of fiber-reinforced soil and improvement in postcracking behavior. Further, they found longer fibers to be more effective in restraining cracks. The results of DIC analysis were found to be effective in reflecting the distinct strain field development at the onset of tensile loading with fiber inclusions of appropriate length and dosage.

Zeolite is a naturally occurring pozzolanic material that can be beneficiated through calcination, resulting in more efficient usage in concrete as a mineral admixture. The present study analyzes the physicochemical characteristics of a natural zeolite and the same zeolite calcined under different conditions. It is seen that optimum pozzolanic reactivity and specific surface area are obtained when the calcination is done at 800°C for 8 min. The water and superplasticizer demands in cementitious binders with zeolite have also been determined. It is shown that mortars and concretes with zeolite, especially with calcined zeolite, perform well in terms of strength and durability characteristics, such as permeability and corrosion, compared to concrete with Class F fly ash (FA) and to plain concrete. In terms of autogenous shrinkage, the performance of natural zeolite is better than that of calcined zeolite and the FA considered. In general, the results indicate that calcined zeolite can be used as a mineral admixture in the production of high-performance concrete, with properties comparable to those of the FA considered, with the exception of the fluidity properties.

This paper deals with the experimental investigation of the use of low modulus vinylon and polypropylene fiber ropes as external confining reinforcements on standard concrete cylinders. Vinylon has a higher modulus of elasticity than polypropylene, whereas the latter has ultrahigh tensile deformation at failure. Ropes require no use of impregnating resins or mortars. The research examines low concrete strength columns in three levels of rope confinement, subjected to monotonic or cyclic loading. The effectiveness of the rope composite reinforcements is assessed by the resulting axial stress versus axial and lateral strain behavior. The elaboration also includes the stress and strain values both at 3% axial strain and at ultimate strain. Suitable fiber rope confinement may improve plain concrete strength by a factor higher than 6.6 and provide an axial strain ductility higher than 40. No column wrapped by polypropylene fiber ropes reaches fiber fracture. The performance of the retrofitted columns is discussed with respect to the fiber-reinforced polymer sheet confinement.

Assessing the volumetrics of hot-mix asphalts (HMAs) is an important aspect of quality-control and quality-assurance procedures. The economic value of HMAs is usually assessed in terms of their mix bulk specific gravity ($G_{mb}$), air-void content, voids in mineral aggregate, and voids filled with asphalt. However, the results for specific gravity can vary with the coring process and method used in the experimental measurements. In light of these concerns, this study focused on the assessment of the dependence of the measured volumetrics of HMA-wearing courses on the testing and coring procedures. A wide range of methods for the measurement of specific gravities and surface texture was considered. Analyses showed that the coring process, measurement methodology, and core diameter can all substantially affect the results of HMA volumetrics measurements; the effects of the selection of the testing technique are not negligible and can be critical. At the same time, results demonstrate that there is potential for reducing the cost and duration of massive coring processes, as well as other negative impacts (e.g., road-surface defects and environmental diseconomies).

The findings of an extensive literature review on the permeability of hot-mix asphalt concrete are detailed in a state-of-the-art report on the measurement and interpretation of asphalt concrete permeability data. The permeability of asphalt concrete is affected by a range of factors with various levels of importance, which are reviewed along with their impact on the coefficient of permeability. Many theoretical, empirical, semiempirical, and numerical models have been developed to predict permeability, using a range of indicators. Some of these models are reviewed and their advantages and shortcomings discussed. Recent advances in X-ray tomography studies are also summarized. The review reveals that field permeability measurements are not reported to match numerically well with laboratory measurements, though there is some correlation. The reviewed test methods for permeability all rely on an assumption of laminar flow that is unlikely in more porous mixtures. Attempts to measure connected air voids improve the chances of obtaining more meaningful correlations between permeability and air voids, regardless of the mathematical model used to link the two quantities. The lift-thickness to nominal maximum aggregate size (NMAS) ratio and/or changes in the binder content has a less significant effect on permeability than changes in the porosity and/or mix gradation. Air void gradients and distributions in compacted asphalt concrete mixtures can now be assessed with X-ray techniques: the distribution of air voids appears to be nonuniform in laboratory-prepared specimens.

Calcium chloride (${\mathrm{CaCl}}_2$) has been used to accelerate strength gain in soil-cement mixtures. While its use in concrete is well established, there are few reports on dosage and temperature controls in soil-cement applications. This article provides laboratory and field data regarding the unconfined compression (UC) strength of soil-cement as a function of temperature, time, and dosage. The results indicate ${\mathrm{CaCl}}_2$ can increase the UC strength of soil-cement mixtures at curing temperatures of 2°C and 21°C while decreasing it dramatically if the initial temperature exceeds 50°C. At a 2°C curing temperature, a dosage of 1% ${\mathrm{CaCl}}_2$ (by weight of cement) increased the average 28-day UC strength from 1,618 to 1,869 kPa ($+15.5\%$) while at 21°C the strength gain was significant at a dosage of 5% ${\mathrm{CaCl}}_2$, increasing the average 28-day UC strength from 1,916 to 2,338 kPa ($+22.0\%$). In general, there is an optimum dosage that varies with temperature and soil type. In terms of field application, it is possible to use conventional construction equipment to wet dose ${\mathrm{CaCl}}_2$ without raising the moisture content by more than 1.5%, a key consideration when in situ conditions are wet relative to target moisture conditions. For the soils tested, the optimum dosages are expected to be closer to that which is specified for cold-weather concreting (e.g., $<2\%$ by weight of cement), rather than much higher values reported in the literature.

Splitting tensile experiments of concrete specimens with different strain rates are conducted by using the Split-Hopkinson pressure bar to verify a previously developed mesoscale dynamic particle element model. In addition, further study is accomplished on the mechanism of strain rate effects on concrete material. Different dynamic fracture patterns and failure modes at different strain rates are evident in the tests and the numerical simulation. The comparisons between the two methods are matched satisfactorily in terms of the complete force-displacement relationship and the fracture profiles of the ruptured specimens. It is concluded that the dispersed patterns of mesocracks under higher strain rates, which require higher frictional and kinetic energies, are the key factors of strain rate effects on concrete. Weibull distribution is also introduced in considering the heterogeneous properties of the three components of concrete and in studying the influence on strain rate effects.

The first purpose of this paper was to find appropriate parameters for the electrochemical chloride removal method; that is, type of electrolyte solution, electric potential and charging duration. The second was to determine the efficiency of the chloride removal at remote areas from the position of installation. The $30\times 30\times 10{\mathrm{cm}}^3$ and $70\times 70\times 7.5{\mathrm{cm}}^3$ concrete specimens were prepared for the first and second purposes respectively. The chloride removal process was performed by applying electric potential between the reinforcement bars embedded in concrete and an external electrode installed on the concrete surface submersed in external electrolyte. With 28 days charging, this method could remove up to 76% of chloride by using the $\mathrm{Ca}(\mathrm{OH}{)}_2$ solution as electrolyte with 15 V DC electric potential. The efficiency of chloride removal decreased as the distance from the position of installation increased. This was consistent with the equation of Nernst Planck which described the movement of chloride ions mobility through the concrete by electric current. As a result, there was a good tendency for using electrochemical chloride removal method to remove chloride ions from reinforced concrete.

Quantitative test technology on the mesoscopic strength of the mineral aggregate contact surface of bituminous-stabilized macadam was studied, which include the shear adhesion strength ${\tau }_a$ between aggregates and bitumen, the cohesion strength ${\tau }_c$ of bitumen binder itself, and the total shear strength ${\tau }_t$ of mineral aggregate contact surface. The HC-40 hydraulic force measurement device and the self-designed test die were used to apply shear load on the contact surface of the mineral aggregate to determine the shear failure load in different kinds of bitumen, thickness of oil film, and temperatures. On the basis of the relationship between the shear adhesion strength ${\tau }_a$, the cohesion strength ${\tau }_c$, shear adhesion failure area $S_a$, shear cohesion failure area $S_c$, the total area of mineral aggregate contact surface $S_t$ and the shear failure load F, then the shear adhesion strength ${\tau }_a$ and the total shear strength ${\tau }_t$ can be calculated by using the property of shear cohesion strength ${\tau }_c$ of bitumen binder. The results show that the shear cohesion strength ${\tau }_c$ of bitumen binder has obvious correlation with bitumen quality and experimental temperature while the shear adhesion strength ${\tau }_a$ between aggregates and bitumen obviously relates to bitumen quality, experimental temperature, and oil film thickness. Confirming the shear strength characteristics of the contact surface is important in the study of the crack and raveling resistance abilities of the mixture.

This paper provides a mechanistic procedure for performance characterization of recycled aggregate systems for use as aggregate base layers. Twelve recycled aggregate systems with different lithologies and known field performance histories were selected for this study. The aggregate sources were selected from seven different states with different climatic conditions to account for the environmental impacts on the performance of the pavements constructed with recycled materials. A comprehensive material testing protocol was followed to characterize the mechanical and physio-chemical properties of the recycled aggregate systems. A shear strength test at different confinement levels and the Canadian freeze-thaw test, Micro-Deval test, and tube suction test were performed on the samples. Analysis of the laboratory tests showed that several recycled systems performed equally or better compared to control systems consisting of virgin aggregates in terms of higher shear strength and higher hardening index. Laboratory test results also showed that recycled concrete (RC) materials typically had superior mechanical properties such as a higher resilient modulus and hardening index compared to recycled asphalt (RA) systems; however, RC systems showed higher frost susceptibility. The laboratory analysis and numerical simulation results presented in this study underscore the significance of climatic conditions and subgrade soil type when a RA system is considered as a viable option.

Particles of natural rockfill materials come in various sizes and shapes, resulting from natural processes, and their mechanical properties are affected by a multitude of interdependent factors. As a result, it is very difficult to investigate an individual factor. Therefore, most studies are conducted by using substitute materials such as glass beads, gypsum rods, wooden rods, steel balls, and metal rods. However, these commonly used materials have properties that are often quite different from natural rockfill materials, e.g., in particle shape, particle strength, modulus, and grading. This paper suggests a more suitable substitute to simulate rockfill materials by using cement ellipsoids in different sizes cast with cement paste. Results from triaxial compression tests show that this kind of proxy material can reproduce the basic behavior of natural rockfill materials.

Accelerated carbonation is a process in which ${\mathrm{CO}}_2$ is intentionally introduced to concrete at an early age for a short period of time to promote rapid strength gain. The accelerated carbonation of portland limestone cement (PLC) was studied to examine the possibility of replacing ordinary portland cement (OPC) by PLC in carbonation curing of precast concrete products. Carbonation behavior was characterized by strength gain, ${\mathrm{CO}}_2$ uptake, pH change, XRD, TG, SEM, FTIR, and ${}^{29}\mathrm{Si}$ NMR spectroscopy. It was found that PLC was a ${\mathrm{CO}}_2$ reactive material. Its ${\mathrm{CO}}_2$ uptake reached 12% based on dry cement mass. In reference to hydrated PLC, the strength of carbonated PLC was 79% higher at 20 h and of close value at 28 days, even though the ultimate ${\mathrm{CaCO}}_3$ content in carbonated PLC was over 40%. The calcium carbonates produced by accelerated carbonation were found to be imbedded in calcium silicate hydrates, forming an intermingled microstructure. The high carbonation reactivity of PLC was possibly attributed to its fine particle size and the existence of limestone powder nuclei for calcium carbonate precipitation. The use of PLC in accelerated carbonation of concrete products can significantly contribute to a net gain in carbon emission reduction.

This paper reports the fracture parameters of bond in stone masonry beams bound with plain and fiber-reinforced mortar. Sandstone blocks were joined together with a modern Type S mortar conforming to the Canadian standard. A companion series was examined employing a hydraulic lime mortar, typically used in the restoration of historical masonry. Based on a previous study, polypropylene microfibers were incorporated at up to 0.50% by volume to achieve superior crack growth resistance. This study evaluated the critical stress intensity factor, the critical effective crack length, and the critical crack mouth opening displacements. The masonry beams were subjected to quasi-static flexure as per ASTM and dynamic bending through a drop weight impact machine that generated stress rates up to ${10}^7\mathrm{kPa}/\mathrm{s}$. The study reveals that there is an improvement in the bond strength due to fibers but a difference in the fracture performance between the Type S and hydraulic lime mortars. Whereas with Type S mortar, fibers promote failure through fracture in the stone block especially under dynamic loading, in the hydraulic lime mortar fiber reinforcement moves the failure plane from the interface to within the bulk mortar.

Self-consolidating high-strength concretes, including palm oil fuel ash (POFA), were produced based on the water/binder (W/B) ratios of 0.25–0.40. POFA was used in the concrete mixtures by replacing 0–30% of normal Portland cement by weight. The freshly mixed concrete mixtures were tested to determine the key fresh properties such as filling ability, passing ability, and segregation resistance. Filling ability was measured with respect to slump flow, $T_{50}$ slump flow time, inverted slump cone flow spread and time, and V-funnel flow time. Passing ability was determined from J-ring flow and L-box flow tests. In addition, sieve and column segregation tests were carried out to quantify segregation resistance. The concrete mixtures were also tested for compressive strength. The experimental results showed that W/B ratio and POFA content had significant effects on the filling ability, passing ability, and segregation resistance of concrete. The filling ability and passing ability of concrete increased with a lower W/B ratio and a higher POFA content. Moreover, the use of POFA greatly influenced the segregation resistance of concrete. The optimum POFA content for filling ability, passing ability, and segregation resistance was 20%, which also produced the maximum compressive strength in concrete.

This paper presents the effect of geometrically similar specimen size on the mechanical properties of cement-based foams. The experimental study also investigates fracture-mechanical parameters under flexural impact. A preformed foam was employed to prepare the specimens using a synthetic foaming agent that was known to achieve a stable bubble structure. The cement-based foams were prepared to a cast density of $475\mathrm{kg}/{\mathrm{m}}^3$ and were examined under compression and flexure. Along with a plain unreinforced mix, polypropylene fiber at a volumetric fraction of 0.2% was used to study the effect of microfiber reinforcement. The tested specimens scaled between one to four times in dimension. Parameters associated with their dynamic-fracture mechanics were evaluated under flexure with the help of a drop-weight impact tester equipped with a high speed imaging system. Bažant’s size effect model and the multifractal scaling model were employed to describe the size effect. It was seen that when subjected to compression, the fiber-reinforced specimens demonstrate a noticeable size effect, whereas, under quasi-static flexure, the more significant size effect was observed for the plain specimens. As expected, fiber reinforcement improved the Mode I fracture toughness at all sizes.

Although widely used by state Departments of Transportation (DOTs) and other highway agencies for characterization of rut resistance and moisture susceptibility of asphalt mixtures, loaded wheel testers (LWTs) are rarely employed to evaluate the fatigue performance of asphalt mixtures because of their inherent problems. In this study, LWT was used to characterize the fatigue behavior of asphalt mixtures. A commonly used type of LWT, an asphalt pavement analyzer (APA), was chosen as a platform and modified to conduct the fatigue testing. A linear variable differential transformer (LVDT) was mounted to the bottom of the specimen to measure the tensile strain on the bottom surface. The tensile stress was calculated by treating the test specimen as a simply supported beam with a vertical load moving on its top. With the stress and strain measurements, theoretical analyses could be made to characterize the fatigue properties of asphalt mixtures. For comparison purposes, two other types of fatigue tests, beam fatigue and direct tension fatigue tests, were also conducted. Four types of asphalt mixtures were tested for their fatigue characteristics using the three fatigue tests. Two types of approaches—stiffness and dissipated energy—were adopted to analyze the fatigue behavior of asphalt mixtures. The results showed that LWT fatigue test was able to differentiate between asphalt mixtures in terms of fatigue behavior. The results from the LWT fatigue test were generally consistent with those from flexural beam and direct tension fatigue tests. The LWT fatigue test has the potential to become a useful tool to rationally characterize fatigue properties of asphalt mixtures and to differentiate good-performing from poor-performing mixtures in terms of fatigue resistance.

Wood guardrail posts are among the most common wood materials currently used in highway construction. Preservative treated hem-fir is an important species for guardrail applications in the western United States. The service life of treated timber post guardrail systems has been estimated to be between 10 and 20 years. However, there is surprisingly little information on performance of timber guardrails. One aspect of the estimate of service life is wood durability. This study assessed the flexural properties, level of decay, and residual preservative levels in chromated copper arsenate preservative treated hem-fir guardrail posts removed from a project near Bellingham, Washington. Increment cores were removed from each post to assess preservative treatment and fungal colonization. The posts were tested for flexure properties in a three-point bending test. Posts that met the American Wood Protection Association standards for preservative penetration tended to have lower levels of internal decay after 20 years in service, and all but six posts retained sufficient flexural properties to meet AASHTO standards.

Rigid concrete overlays have been used for smoothing damaged surfaces and/or restoring or improving the mechanical capacity of bridge decks for many years. However, engineered cementitious composites (ECCs), which demonstrate superior ductility with high strength and improved durability characteristics, are an attractive alternative to conventional overlay materials if a strong mechanical bond is formed between the overlay and the substrate material. An experimental study was performed to evaluate the bond strength between ECC overlay and an ordinary concrete substrate with smooth and rough surface textures. Microsilica concrete (MSC), generally used as an overlay material, was also prepared as a control mixture. ECC and MSC overlay mixtures were cast over the concrete substrate to determine bonding performance. Slant shear and splitting prism tests were performed with MSC and two ECC mixtures. The experimental results show that when ECC is used as an overlay material, bond strength is significantly increased compared to MSC. Under compression loading (slant shear test), the bond-strength properties of layered ECC substrate concrete cylinder specimens were greater than the strength of substrate concrete with compressive strength of around 30 MPa. However, in the case of layered MSC substrate concrete cylinder specimen, failure consistently occurred at the interface.

The effects of firing conditions on the microstructure and physical properties of clay roofing tiles are studied. This research presents the effects of oxidizing and reducing atmosphere on Kanjiža clay material with carbonate content up to 22% by weight and the characterization of the final products. The firing was done both in the laboratory and under industrial conditions. The ${\mathrm{Fe}}^{2+}/{\mathrm{Fe}}_{\text{total}}$ ratio played a decisive role in the sintering process under a reducing atmosphere. The formed glassy phase, with the presence of ${\mathrm{Fe}}^{2+}$, attacked the earth-alkali oxides after the carbonate decomposition and more effectively filled smaller pores. The obtained results justified the benefits of the reducing firing atmosphere with 5% CO, lower porosity, higher frost resistance values, and changed microstructural characteristics

Experimental studies on shrinkage and interior humidity of three series of concrete with three aggregate contents in each concrete under sealing and drying conditions were carried out. The results show that the development of interior humidity of concrete is influenced strongly by the water-binder ratio and curing status of the specimen. In dry conditions, a fast reduction of the interior humidity is accompanied with a fast increase of shrinkage strain of the unsealed specimen compared with that of the sealed specimen. The effect of coarse aggregate on the interior humidity is insignificant. The difference in interior humidity between exposed and sealed specimens decreases with the reduction of the water-binder ratio. For a given age, the autogenous and drying shrinkages decrease with the increase of coarse aggregate content. The addition of coarse aggregate has a more significant influence on drying shrinkage than autogenous shrinkage.

Based on an accelerated asphalt-aging test in the laboratory, the authors evaluated the physical and chemical properties of asphalt at different aging times and temperatures for this paper. They evaluated the properties of the asphalt binder, such as saturates, aromatics, resins, asphaltenes, penetration, softening point, and molecular distribution of the asphalt, by using experimental results from the accelerated asphalt-aging tests. They employed gel permeation chromatography (GPC), Fourier transforms infrared spectroscopy, asphalt constituents fraction analysis, and rheological test techniques to analyze the effects of asphalt from different crude oil sources on antiaging performance. They used asphalt-aging tests to determine the relevant kinetic parameters needed in the aging kinetics equation. They found that the asphalt-aging reaction perfectly fits to the first order kinetics equation, and during the asphalt-aging process, the asphalt had a higher activation energy and a lower reaction rate coefficient. Moreover, the molecular weight ($M_W$) of asphalt increased, whereas the dispersity decreased. The asphalt-aging process was divided into two stages: one stage is from aliphatic sulfide to sulfoxide and the other stage was from benzylic carbon to carbonyl. The aging resistance of asphalt was influenced by the asphalt fraction, wax content, and molecular weight.

In the United States, several states have adopted the Micro-Deval test (MDT) method for evaluating degradation characteristics of aggregates used in road construction. This paper compares MDT aggregate degradation data to those obtained by the Idaho degradation test (IDT) method. Simple linear regression analyses were performed on the aggregate degradation data with the resulting coefficient of determination, $R^2$, values of 0.70 and 0.67 for IDT versus MDT for coarse aggregate and IDT versus MDT for fine aggregate, respectively. Additional models considered are (1) a weighted combination method that relies on the judgment of the engineer and (2) a multivariate regression analysis that does not involve weighting factors. In all the analyses considered, the multivariate regression had the largest $R^2$ value of 0.75. Numerical examples showing correlations between MDT and IDT loss values are presented, followed by conclusions. Analyses used in this project may be of practical use to other state departments of transportation when adopting a new aggregate degradation test method and performing calibration with an existing test method.

Nail connections salvaged from the timber floor diaphragms of two $\sim 100\mathrm{year}$ old unreinforced masonry buildings were pseudostatically tested to determine their hysteretic behavior. The research objective was to establish expected load-slip characteristics of nail connections in historic timber diaphragms to facilitate improved seismic assessment accuracy. A summary of the testing procedure, test results, and performance characterization is presented. Nail connections constructed from Kauri (Agathis australis) timber and wire-drawn nails in the 1890s were found to have an average yield strength of 1.0 kN and an average maximum strength 1.4 kN. Nail connections constructed in 1914 from Rimu (Dacrydium cupressinum) timber and wire-drawn nails were found to have an average yield strength of 0.8 kN and an average maximum strength of 1.0 kN. Both connection types exhibited an average ultimate displacement capacity of approximately 11.4 mm.

Fly ash is becoming increasing used in concrete structures for enhanced durability. This research investigated two types of fly ash in conjunction with four cements. The cements were both high and low alkali, with and without blended silica fume. Mortar and concrete mixtures were prepared containing from 0 to 80% fly ash replacement. Standardized tests were performed for compressive strength, as well as sulfate, chloride, and alkali resistance. High replacement levels performed relatively well in sulfate and alkali resistance, but poorly in regards to compressive strength and chloride resistance. From a durability perspective, 40% fly ash replacement was found to have the best overall performance from these mixtures. Standardized test methods are comparative by nature, and as such cannot replicate the complexity of concrete mixtures and their exposure conditions; higher replacements have been successfully used in practice.