Journal of Materials in Civil Engineering

This paper presents the findings of a research program that developed prediction equations for estimating the flexural strength of degraded paste beams. Deterioration was attributable to calcium leaching from the beam’s four lateral sides. Given that natural leaching is a slow process, an accelerated experiment was performed by using a 6 M ammonium chloride solution. At specified leaching durations, sound and deteriorated beams were tested in flexure using the three-point bending (TPB) test. The leaching depth and the paste’s compressive strength were both measured. Based on the residual rate of compressive strength and the residual rate of the elastic modulus that was obtained from experimental data, the loss of flexural strength with respect to the leached ratio was constructed with a simplified model. The influence of the residual rate of tensile strength on the prediction and the best-fitting curves are presented. The degradation processes between flexural strength and compressive strength are different.

In this study, the effects of asphaltite and long-term aging (LTA) on the mechanical properties of hot-mix asphalt were investigated. The asphaltite entrained as filler at five different proportions into the hot-mix asphalt samples, and the obtained results were compared against the control mixtures. The pure and asphaltite-containing compacted mixtures were exposed to LTA in an oven. Marshall stability, resistance to moisture-induced damage, and resistance to crack propagation tests in accordance with the principles of elastic-plastic fracture and linear-elastic fracture mechanics were carried out on the mixtures. It was determined that the optimal proportion of asphaltite usage as filler with respect to volumetric design is 3% by weight. The test results demonstrated that asphaltite use enhances resistance against permanent deformation, moisture-induced damage, and crack propagation, especially at normal temperatures, albeit at the cost of causing the hot-mix asphalt to exhibit a more brittle behavior. The use of asphaltite would be recommended to reduce the long-term effects of aging in general, specifically on account of the results of the stability, moisture-induced damage, and fracture toughness tests.

The object of this study was to evaluate the effects of several common combinations of binder types and additives on the functionality and durability of permeable friction course (PFC) mixes. Three binder types (i.e., conventional asphalt AR-80 and two polymer-modified asphalt binders) and two additives (i.e., cellulose fiber and hydrated lime) were selected for a 19-mm nominal maximum aggregate size gradation. A series of laboratory tests was conducted to analyze PFC pavement surface performance-related properties, including air-void content, permeability, moisture sensitivity, friction, resistance to raveling, and resistance to permanent deformation. Results showed that using polymer-modified binders instead of unmodified asphalt in the open-graded mixture increased air voids and permeability. Mixes using polymer-modified asphalt or those treated with hydrated lime were shown to increase the mixture resistance to moisture damage, raveling, and rutting. The aging index value was higher for the conventional binder compared to polymer-modified asphalt.

The falling-head method determined using a permeameter cell is commonly used to study permeability ($k$) of soils and facility of fluids to travel through a solid skeleton. A research program was undertaken to evaluate the suitability of such test for assessing permeability of freshly mixed mortars and concrete. Validation of $k$ values with respect to bleeding and surface settlement responses and correlations with permeability calculated using empirical soil models are established. The falling-head method was found appropriate to assess the effect of mixture composition (i.e., binder content, water-to-cement ratio, and chemical/mineral admixtures) on permeability variations. Concrete incorporating coarse aggregates exhibited greater permeability levels than those determined on mortars. Despite the differences in chemical nature between soil and mortar, the actual $k$ values determined by testing were found to be well correlated to those calculated by using several previously reported empirical soil models.

Self-consolidating concrete (SCC) is one of the innovative products in concrete technology that has been developed in recent years. However, many researchers are still trying to optimize the mixture proportions and investigate the incorporation of new materials in SCC. The typical high content of portland cement in SCC is one of the main challenges in optimization of its mixture proportions. This high cement consumption increases the production cost of SCC and, considering the large amount of ${\mathrm{CO}}_2$ emitted during portland cement production, is also undesirable from an environmental point of view. In this study, two approaches were employed to lower the portland cement content in SCC mixtures, namely, adopting a dense aggregate grading and partially replacing portland cement with natural zeolite. Portland cement was replaced by natural zeolite at different percentages to investigate the effect of this natural pozzolan on the fresh and hardened properties of the SCC mixtures. Fresh properties of the SCC mixtures were assessed by slump flow, T50 time, J-ring, and GTM screen stability tests. Compressive strength, electrical resistivity, and rapid chloride penetration tests (RCPTs) were carried out to evaluate the hardened properties of the SCC mixtures. It was concluded that producing a durable SCC mixture containing a low portland cement content of $262.5\mathrm{kg}/{\mathrm{m}}^3$ is possible while keeping the total cementitious materials content at a constant $350\mathrm{kg}/{\mathrm{m}}^3$. On the basis of the fresh-SCC test results, using higher replacement levels of natural zeolite (up to 30%) led to improved segregation resistance but increased the required dosage of high-range water-reducer agent. At hardened state, using higher replacement levels of natural zeolite resulted in lower RCPT values and higher surface resistivity.

In this study, quantitative microstructure-property relationships are mainly used to characterize the damage due to high-strain-rate impact loading and the mechanical behavior of concretes prepared by substituting natural aggregate (gravel) with recycled aggregates having different rigidities (blue brick and rubber). Based on the results obtained, a possible mechanism for microstructural damage in concrete is proposed. It is concluded that the aggregate causes a change in the initial interfacial transition zone (ITZ) condition, and it is this altered ITZ condition that has a major effect on overall mix behavior. The analysis also indicates that there is almost a linear correlation between the roughness values (Ra) of the region near the paste–aggregate interface and the dissipated surface fracture energy values of the specimens. Moreover, three-dimensional topographic images of the specimens constructed using a vertical nanotech scanning interferometer show that the paste region of the gravel specimen has the smoothest profile due to the relatively strong hydrated paste.

The current performance grade (PG) binder specification uses the parameter $G^{*}\sin \delta$ to quantify binder fatigue property, which has long been known to be the weakest part of the specification. The purpose of this study was to identify a better binder fatigue test. Six asphalt binders with a variety of modifiers were characterized using five asphalt binder tests, including the $G^{*}\sin \delta$, elastic recovery test, the multiple stress creep recovery (MSCR) test, the linear amplitude sweep (LAS) test, and the double edge notch tension (DENT) test in this study. Additionally, the push-pull asphalt mix fatigue test was employed to verify these binder fatigue tests. Comparing the results of the binder tests and the asphalt mix push-pull test, this study further confirmed the poor performance of the parameter $G^{*}\sin \delta$ to differentiate binder fatigue resistance. It was also found that neither the MSCR nor the LAS test showed good correlation with asphalt mix fatigue resistance. Finally, it was identified that both the DENT and the elastic recovery binder fatigue tests provided the same ranking as the asphalt mix fatigue test. The DENT test is recommended for characterizing asphalt binder fatigue resistance, because it is more fundamentally based than the fully empirical elastic recovery test. Obviously, these findings are based on laboratory tests only, so further field validation is needed. Additionally, one needs always to keep in mind that the binder alone does not determine fatigue life of a pavement structure, and other factors such as traffic and environment are also important.

In theory, the addition of fly ash microsphere (FAM), which is finer than cement, and condensed silica fume (CSF), which is even finer, to successively fill the voids between cement grains can increase the packing density of the cementitious materials and reduce the volume of voids to be filled with water. This would release more water to increase the flowability at same water/cementitious materials (W/CM) ratio or allow the W/CM ratio to be lowered to increase the strength at same flowability requirement. This study was aimed to evaluate the effects of FAM and CSF on the packing density of cementitious materials and the water film thickness (WFT) in cement paste and investigate the effects of the WFT on the flowability, cohesiveness, adhesiveness, and strength of cement paste. The results showed that adding FAM and CSF can significantly increase the packing density and WFT and thereby greatly improve the overall performance of cement paste.

This paper examines the durability of fiber-reinforced polymer (FRP) nails in treated wood. The FRP nails were exposed to four conditions: (1) accelerated weathering, consisting of exposure to ultraviolet light and condensation; (2) 100% relative humidity (RH); (3) being driven into untreated wood and exposed to 100% RH; and (4) being driven into wood treated with alkaline copper quaternary (ACQ) and exposed to 100% RH. Changes in the physical, mechanical, and chemical properties were examined with weight loss, dynamical mechanical analysis (DMA), and near-infrared spectroscopy (NIR), respectively. Although fasteners exhibited changes after exposure to treated wood, the changes were not statistically different than the changes that occurred in untreated wood or in the humid environment. Under these three conditions, the fasteners gained 2–3% of their starting mass, and the storage modulus also increased by 20% after exposure. The results suggest that moisture is more important than the wood chemistry or preservative chemistry in determining the durability of FRP fasteners in wood.

Calcium carbide residue (CCR) is a waste product from acetylene gas factories, which is rich in calcium hydroxide [$\mathrm{Ca}(\mathrm{OH}{)}_2$]. Because clayey soils contain high amount of natural pozzolanic materials (silica and alumina), CCR can be used as a soil stabilizer. This article presents the engineering properties of CCR-stabilized silty clay to ascertain its performance in pavement base and subbase applications. The input of CCR, which reduces the plasticity index of the clay, increases the optimum water content (OWC) and decreases the maximum dry unit weight (${\gamma }_{d,\max }$) of the stabilized clay. The CCR fixation point, simply obtained from the index test, is proved as a practical indicator for determining the CCR content to obtain the required engineering properties at a particular molding water content. The state of water content controls the densification, chemical reaction, and water absorption capacity. The soaked engineering properties are thus dependent upon the state of water content. For a particular CCR content, the optimum water content is the most appropriate in terms of strength, swelling and collapse behaviors, and bearing capacity. The lower water content is not sufficient for the chemical reaction, while the higher water content yields a higher water/binder ratio. The water absorption is smallest for the CCR-stabilized samples compacted at the OWC. To conclude, the optimal mix proportion is the CCR fixation point at OWC. CCR stabilization is more effective than lime stabilization in terms of engineering, economic, and environmental viewpoints.

The primary distresses of the asphalt pavement are rutting, fatigue cracking, and thermal cracking. Laboratory tests can be conducted to characterize the expected performance of asphalt concrete in the field. This study evaluated the double punch test (DPT) as an alternative test method to characterize the fatigue and rutting of asphalt concrete due to its simplicity. In DPT, a cylindrical asphalt concrete specimen is compressed vertically through two steel punches placed concentrically on the top and bottom. The specimen fails along the diametrical plane due to the tensile strain generated in the tangential direction. Double punch tests were performed at intermediate and high temperatures to characterize fatigue and rutting potential of asphalt concrete, respectively. The DPT results were found to correlate well with fatigue parameters from indirect tensile (IDT) tests for fatigue and flow number test results for rutting, both of which have been reported to correlate well with field fatigue and rutting performance, respectively. The results indicate that the DPT can serve as a viable alternative to evaluate the fatigue and rutting behavior of asphalt concrete.

Laboratory and field experiments were undertaken to investigate the possible application of recycled crushed glass blended with crushed basaltic waste rock as a footpath base material. The laboratory experimental program included basic and specialized geotechnical tests including particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion, pH, organic content, and triaxial shear tests. A field demonstration footpath comprising two sections of recycled glass-waste rock blends with 15% and 30% recycled glass content and a third control section with only waste rock was subsequently constructed on the basis of the outcomes of the initial laboratory tests. Subsequently field tests with a nuclear density gauge and Clegg impact hammer were undertaken, as well as laboratory testing of field samples to assess the geotechnical performance of the trial sections. The field and laboratory test results indicated that adding crushed glass may improve the workability of the crushed waste rock base material but subsequently results in lower shear strength. The blend with 15% glass content was found to be the optimum blend, in which the material presented good workability and also had sufficiently high base strength. Higher recycled glass content (30%) resulted in borderline, though still satisfactory, performance. The research findings indicate that recycled crushed glass in blends with crushed waste rock is a potential alternative material to be used in footpath bases. A separate study is recommended to evaluate the environmental risks associated with the usage of these recycled materials.

This paper presents results of an experimental work carried out to evaluate utilization of recycled materials, such as fly ash and bottom ash (by-products of thermoelectric power plants), and blast furnace slag (by-products of ironworks) as binders and aggregates with high volume in high-strength, lightweight mortar. The effects of high volumes of fly ash, blast furnace slag, and bottom ash on flow characteristics, density, and compressive strength of mortar were investigated. In addition, the water capillary absorption characteristics of mortar regarding moisture transport that may affect the durability of the mortar were studied. It was found that the flow characteristics of fresh mortar were neither changed nor decreased with the increase in the replacement ratio of bottom ash, while these were improved by the use of high volumes of fly ash and blast furnace slag as replacements of cement.