Journal of Materials in Civil Engineering

Steel cable is the key component of prestressed steel structures. However, the thermal expansion coefficients of steel cables have not been adequately evaluated yet. This paper presents an experimental study on this topic. A total of 15 groups of specimens were tested, including steel-wire rope cable, steel strand cable, semiparallel steel tendon cable, and steel rod. The thermal expansion coefficients were measured by a manufactured testing instrument. The examined coefficients of the cables were $1.92\times {10}^{-5}$, $1.38\times {10}^{-5}$, $1.87\times {10}^{-5}$, and $1.195\times {10}^{-5}/°\mathrm{C}$, respectively. Subsequently, a cable-supported beam was further numerically analyzed considering temperature effects. The numerical results showed that temperature has a significant effect on the mechanical behavior of the beam when either steel-wire rope cable or semiparallel steel tendon cable is employed. When steel strand cable is adopted, the temperature effect is moderate. For steel rod, the effect is less. Therefore, the influence of prestress losses because of temperature changes should be considered for different types of steel cables in practical design.

Ultrasonic testing is a nondestructive technique commonly used for in situ condition assessment of wood poles. A transmitter and a receiver are used in a transillumination configuration to measure the first arrival of compressional waves ($P$-waves). The $P$-wave velocity is computed using the distance between the transducers and the travel time. The condition assessment of wood poles is inferred from the comparison of the measured wave velocity and a reference velocity that depends on the wood species. A wave velocity smaller than the reference value indicates a reduction in the strength of the wood. The elastic and mechanical properties of wood (elastic moduli, mass density, and Poisson’s ratios) are random variables that vary significantly for the same wood species; consequently, the $P$-wave velocity in wood poles is also a random variable. A better understanding of wave propagation in an orthotropic material, including the uncertainty in the mechanical properties of wood poles, is required to improve the reliability of ultrasonic tests. This paper presents a new methodology to evaluate the probability distribution of the $P$-wave velocity in wood poles. This methodology is founded on results from numerical simulations, laboratory tests, a simplified model of $P$-wave propagation in an infinite cylindrical orthotropic medium, and the consideration of the uncertainty in the mechanical properties of wood. The condition assessment of wood poles is improved by comparing the measured wave velocities $V_p$ at different receiver locations and the corresponding probability distributions of the wave velocity $V_p$ for sound wood poles.

This paper presents the use of widely available fly ash (FA), rice husk ash (RHA), and palm oil fuel ash (POFA) in Thailand to make glass fiber–reinforced concrete (GFRC). These substitutes were used to replace ASTM Type I portland cement by 0 (control), 10, 20, 30, and 40%. The particle sizes of FA, RHA, and POFA were improved by grinding in a ball mill until 95% of the particles could pass through standard sieve size no. 325. An external-spray-mix machine was employed to produce all specimens with 5% by weight of alkaline-resistant (AR) glass fibers. The GFRC specimens were investigated for water absorption, bending strength, bending strain, and toughness at 7, 28, 56, and 180 days. Throughout this period the specimens were submersed in water at room temperature (25°C). All specimens were prepared and tested according to the BS-EN 1170-5 standard. Test results showed that, for both GFRC panels with and without cement replacement by FA, RHA, and POFA, the limit of proportionality (LOP) increased with an increase in the age of curing, whereas the modulus of rupture (MOR) increased initially and then started to drop gradually. Scanning electron microscopy showed that calcium hydroxide deposition within the filaments of glass fiber made it more brittle. This might be the cause of the reduction of MOR. It is recommended that up to 20% of FA, RHA, or POFA be used to replace portland cement without affecting the physical properties of GFRC, which includes the benefits of lowering cost and helping to reduce ${\mathrm{CO}}_2$ emission.

This study investigated the engineering characteristics of rubber-added lightweight soil (RLS), which consists of dredged soil, crumb rubber, and bottom ash. RLS is considered to be environmentally friendly because it provides a means to recycle dredged soil, rubber, and bottom ash. It can be characterized as a flowable backfill material with a light unit weight, resulting from the slurried mixture with rubber. In this study, several kinds of specimens were prepared with seven different water contents (140–200% at 10% intervals) and five different rubber contents (0–100% at 25% intervals by dredged soil weight) and subjected to flow testing to investigate the flowability of the slurried mixtures. Unconfined compression tests were also carried out to evaluate the mechanical properties of RLS, including bulk unit weight, strength, and secant modulus. Test results revealed that the unconfined compressive strength and unit weight of RLS decreased as rubber content increased, but axial strain at peak increased. Additionally, the stress-strain relationship of RLS exhibited ductile rather than brittle behavior owing to the inclusion of the rubber.

An experimental study for the resistance of mortar paste specimens incorporating 0, 5, 10, 15, 20, 25, and 30% metakaolin (Mk, produced by firing kaolin at 820°C for 2 h) to the magnesium chloride solution was reported. Results confirmed that mortar specimens with a high replacement level of metakaolin showed higher resistance to magnesium solution. The reduction of calcium hydroxide and the increase of secondary calcium silicate hydrate (CSH) in the cement matrix results from the pozzolanic reaction of Mk. The compressive strength values of the blended ordinary portland cement (OPC) mortars specimens improved relative to those containing no Mk, up to 25% by weight OPC substitution, and then decreased up to 30% by weight Mk. Scanning electron microscope microstructures indicate a good improvement for the matrix structure of the blended cement mortars, in which a denser structure was observed.

This study was conducted to investigate rutting resistance of asphalt concrete (AC) mixtures as a function of dynamic modulus and gradation. The flow number (FN) test, the recommended procedure (NCHRP 9–19) for evaluating rutting resistance of AC mixtures, was used to simulate rutting in the laboratory. The FN test involves applying a repeated creep load to AC specimens for 10,000 cycles or until an accumulated strain of 5%. FN tests were conducted at 54.4°C and accumulated strain was monitored for each load cycle. The results were used to determine the onset of tertiary flow (or FN) for 16 AC mixtures (eight surface mixes, five base mixes, and three stone matrix asphalt) produced in Virginia. First-order multiple regression models were developed to describe the relationship among FN, dynamic modulus, and gradation. The results showed FN was strongly correlated to dynamic modulus values at 38°C, and gradation (percent passing various sieve sizes) for the 16 AC mixtures. By using previously published data, the veracity of the relationship of FN as a function of dynamic modulus and gradation was verified for 12 mixtures. The results suggest dynamic modulus and gradation could be considered as potential rutting specification parameters for QC/QA purposes in the field. The results may also be useful for optimizing the laboratory mix design process.

Repair and restoration work of reinforced-concrete (RC) structures is increasing because of the deterioration of aging infrastructures worldwide. Generally, plain mortar and polymer-modified mortar are widely used as repair materials for RC structures. In this study the effect of the combined use of polymers with supplementary cementitious materials (SCMs) on certain mechanical and durability properties (such as compressive and flexural strengths, water absorption, carbonation, and chloride penetration) of modified mortars is evaluated experimentally. The experimental program consists of two parts. In Part I, the effect of SCM slag and silica fume (SF) on the mechanical and durability properties of mortars is evaluated. On the basis of the best performance among different slag and SF contents, Part II of the experimental program is designed, in which the combined effect of polymers and slag/SF on the mechanical and durability properties of modified mortar is evaluated. Results show that the combined slag/SF and polymer-modified mortars (PMMs) exhibited better results than polymer-modified mortar alone. Between the combined polymers and SF/slag-modified mortars, the polymer-modified mortar containing 10% SF exhibited the highest compressive and flexural strengths and the lowest chloride penetration resistance compared to those containing 40% slag. Interestingly, the combined polymer and 40% slag-modified mortars exhibited better performance in water absorption and carbonation resistance than polymer-modified mortar containing 10% SF.

Cement kiln dust, rice husk ash, and their combinations are used variously as stabilizers in different percentages (maximum up to 20%) to develop and evaluate stabilized clayey soils. The influence of stabilizer types and dosages on fresh and mechanical properties is evaluated through Atterberg limits, standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity, and California bearing ratio (CBR) tests. The durability characteristics of 19 developed stabilized soil mixtures are also investigated by studying the influence of water immersion on strength, water sorptivity, and drying shrinkage. Correlations between strength, modulus of elasticity, and CBR are also established. Developed stabilized soil mixtures have shown satisfactory strength and durability characteristics and can be used for low-cost construction to build houses and road infrastructures. The use of locally available soils, rice husk ash, and cement kiln dust (waste from the cement industry) in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

The objective of this study was to conduct a laboratory investigation of moisture susceptibility and rutting resistance of warm-mix asphalt (WMA) mixtures containing moist aggregates by using a foaming technology. Gyration number of various samples, indirect tensile strength (ITS), tensile strength ratio, rut depths of dry and conditioned specimens, and deformation (flow) were measured for all mixtures. The experimental design included two aggregate moisture contents (0 and $\sim 0.5\%$ by weight of the dry mass of the aggregate), two lime contents (1% and 2% lime by weight of dry aggregate), one liquid antistripping agent (ASA) and non-ASA, three foaming water contents (2, 3, and 4%) with control, and two aggregate sources. A total of 42 mixtures were used and 420 specimens were tested in this study. The test results indicated that the aggregate source significantly affects the ITS and rutting resistance regardless of the foaming water content, ASA, and aggregate moisture content. In addition, the ITS and rut depth of some foamed mixtures containing moist aggregate satisfies the demand of pavement performance without additional treatment, although some mixtures need a completely dry aggregate or additional treatments. The mixture with various hydrated lime contents exhibited similar rutting and moisture resistance under dry and wet conditions. The liquid ASA used in this study is not recommended for use in foaming WMA mixtures with moist aggregates, because it is sensitive to moisture.

The objective of this study was to compare the laboratory mechanistic properties of sulfur-modified warm-mix asphalt (WMA) with conventional asphalt mixtures. Three mixtures, two hot-mix asphalt (HMA) and one WMA, were prepared. Mixture One used an unmodified asphalt binder classified as PG 64-22, Mixture Two used a styrene-butadiene-styrene elastomeric modified binder classified as PG 70-22, and Mixture Three was a WMA that incorporated a sulfur-based mix additive and a PG 64-22 binder. A suite of tests was performed to evaluate the rutting performance, moisture resistance, fatigue endurance, fracture resistance, and thermal cracking resistance of the three mixtures. Results of the experimental program showed that the rutting performance of sulfur-modified WMA was comparable or superior to conventional mixes prepared with polymer-modified and unmodified asphalt binders. Results of the modified Lottman test showed that the moisture resistance of the sulfur-modified mixture was comparable to conventional mixes. Results of the fracture tests showed that sulfur-modified WMA is more susceptible to cracking than conventional mixes, given its stiff characteristics. However, given these stiff properties, the higher modulus of sulfur-modified mixtures will reduce the magnitude of strain induced in the pavement. Thermal stress restrained specimen test results showed that the sulfur-modified WMA had greater fracture stress than the polymer-modified mixture. However, there was no statistical significance between the average fracture temperatures for the mixes tested.

The paper recycling process generates a sludge characterized by a high content of cellulose fiber. To understand the behavior of this fibrous material, this article presents an interpretation of the geotechnical behavior of a waste sludge from a paper recycling plant situated in southern Brazil using data from laboratory tests. Engineering properties of compacted paper mill sludges are similar to those of most fibrous organic soils: low hydraulic conductivity upon compression and high compressibility. The waste studied has a water content of approximately 250%, organic content of 48%, mineral charges, and water. The one-dimensional compressibility parameters are indicative of high compressibility. For the determination of the strength parameters of the material, undrained triaxial tests were carried out. An incredibly high effective friction angle (${\varphi }^{\prime }=53°$) was found, probably because of the fibrous nature of the paper sludge. In addition, hydraulic conductivity tests were performed on a flexible wall permeameter. The hydraulic conductivity of the fibrous paper sludge reached values near${10}^{-9}\mathrm{m}/\mathrm{s}$. The results showed that the paper mill sludge is a ductile material with reduced hydraulic conductivity and elevated shear strength that could have multiple applications, such as in the construction of bottom liners, cover liners, and steep side-slope liners for solid-waste landfills.

The strength mechanisms of two kinds of cement-asphalt (CA) mortar, which vary principally in their strength and elastic modulus, were investigated by environmental scanning electron microscopy, calorimetry, and strength tests. The results showed that the asphalt emulsion delayed the early hydration of the cement and the asphalt membrane had a negative effect on the further hydration of the cement, to some extent. The cement products could impale the asphalt membrane, and the cement could hydrate adequately because of the sufficient water supply in the CA mortar. The framework formed by the hardened cement paste was the primary structure skeleton in the CA mortar with a high elastic modulus and the asphalt phase, exhibiting as a filling phase, increased the weak phase of the structure system. For CA mortar with a low elastic modulus, the asphalt phase exhibited as a dominant phase. Two weak structure skeletons, formed by the asphalt membrane and the hardened cement paste, respectively, were responsible for the strength together.

Pseudoductile cementitious composite (PDCC) is an effective and durable repair material for concrete structures. Silane is commonly used to enhance the resistance of concrete to water and chemical penetration. By combining PDCC with silane, a novel repair and/or protection system for concrete structures can be produced. Because silane application may affect the PDCC-concrete interfacial interaction and bond capacity, the effects of silane application on the bond properties of the PDCC concrete repair system were investigated in this study with the direct shear test and pull-off test. Specimens with and without silane treatment were prepared for both kinds of tests. Results show that the direct shear test and the pull-off test can be employed to study the bond properties of the PDCC concrete repair system. The interfacial interaction between PDCC and sufficiently cured concrete is strong even though the concrete has been moistly cured for 4 months when the PDCC is cast. When silane is applied between concrete and PDCC, the PDCC-concrete bond capacity measured in the direct shear test shows almost no change, and the PDCC-concrete bond capacity measured in the pull-off test is reduced.

The paper presents an investigation on the influence of the fineness of fly ash on the carbonation and electrical conductivity of concrete. Fly ash collected from three thermal power stations in India (with a Blaine’s fineness of 200, 255, and $305{\mathrm{m}}^2/\mathrm{kg}$, respectively) were used for this study. The study also involved three replacement levels (15, 25, and 35% of cementitious materials) for each fly ash sample. Accelerated carbonation studies were performed on specimens cured for 3, 7, and 28 days. The electrical conductivity of concrete was evaluated by measuring the charge passed in coulomb (per ASTM C1202) on 28-day-cured specimens. The test results indicated that the carbonation depth of concrete increased as fly ash replacement increased. However, the carbonation resistances of concrete increased with increased fly ash fineness. Furthermore, the carbonation resistance of concrete increased significantly with a prolonged curing time. The coulomb charge passed through the concrete at an age of 28 days was significantly reduced with the incorporation of fly ash, and the magnitude of reduction increased with increased in fly ash fineness and replacement level.

Because of different production technology, the calculation of cold-formed profiles significantly differs from that of hot-rolled profiles. Formation of various section shapes from the basic sheets induces changes in material mechanical properties, which manifest themselves through different yield point, ultimate tensile strength, modulus of elasticity and reduced elongation percentage. Yield stress distribution over the cross section also changes, the largest values are in the corners of the profile. This paper presents testing results obtained from tensile coupons taken from different regions within profiles and compression tests on complex stub columns. Results are shown on cumulative diagrams and compared with those obtained from the base strip coupons. Before testing, a detailed measurement of real geometric properties of profiles was performed to determine the initial geometric imperfections of samples. The obtained results represent important parameters in determining appropriate buckling curves of centrically compressed members made from cold-formed profiles.