Materials and Structures最新文献

Lead–zinc mine tailings are hazardous waste that is produced by mining activities. Poor tailings management can lead to heavy metals leaching into the groundwater or surrounding environment if not properly managed. In this study, lead zinc mine tailings were treated using several activation methods to stabilize their heavy metals. Thus, in this study, several activation methods like mechanical, mechano-chemical, and microwave oven activation were applied to stabilize the heavy metals and reuse them effectively in construction. Toxicity-characteristic leaching procedures were performed to analyze the leaching concentration based on USEPA standard limits. A modified sequential extraction procedure (BCR) was used to determine the detailed distribution of heavy metals. 20% of tailings were replaced with cement. Tailings aggregates used in construction reduce the cost of construction and minimize the emissions of CO₂ to the environment as cement consumption is reduced. Characterizations supported the stabilized structure of concrete after activation methods were applied. Overall, it was concluded that activation methods can treat tailings powders and make them suitable for safe utilization in construction. Mechanical activation (200 rpm), mechano-chemical-activation (Graphene Oxide, 0.03%), and microwave oven activation (high power) for 40 minutes was selected for successful applications for concrete based on tailings due to their better-stabilizing effects and cementous properties.

This project aimed to document the mechanical properties, the bonding, and joint performance of trembling aspen to improve its use in Engineered wood products. It also aimed to study the bending characteristic and investigate the failure behavior of full-size beams made of trembling aspen. Non-destructive and destructive tests were conducted on lamellae of trembling aspen (Populus tremuloides Michx) following the ASTM D198. Full-size beams were manufactured following the manufacturing principles outlined in the CSA-O122, the standard for glulam production in Canada, to evaluate the performance of finger jointing, block-shear and delamination, and to establish the glulam's bending strength. Mechanical tests on trembling aspen assessed a 5th percentile value of 13.8 MPa in tension, and 40.9 MPa in bending with a mean modulus of elasticity of 10,343 MPa. The relationship between dynamic and static modulus of elasticity was analyzed and showed a strong correlation, with low relative error, and its feasibility for machine stress rating. The test conducted on the finger joint shows a characteristic value of bending strength of 31.8 MPa. The block-shear and delamination align with the requirement from the standards CSA-O122. The investigation of the bending performance on the glulam made of trembling aspen achieved a mean strength resistance of 30.3 MPa, once modified to be compared with the values from the standard, is lower than the MOR value required from the standard. In addition to the mean modulus of elasticity determined of 9013 MPa, it is also lower than the value from the standard.

This paper presents phase diagrams for Portland cement-slag-fly ash ternary cements. The study investigates various binder combinations of Portland cement, slag and fly ash, ranging from 30–100, 0–50 and 0–50, respectively. The thermodynamic equilibrium of given ternary cement systems was simulated using thermodynamic modeling coupled with simulated degree of reaction of slag and fly ash that vary with the binder compositions. The obtained results suggest that a 56% substitution factor for supplementary cementitious materials is feasible without significantly altering the formation of C–(A)–S–H. Additionally, it is found that ettringite and straetlingite are stable in the same cementitious material combinations, but ettringite becomes unstable in mixtures that favor monosulfate formation. Overall, this study provides a catalogue for selecting an appropriate proportion of binders to create mixes that complement one another, providing characteristics that are specifically tailored to the application. The results may have important implications for designing and optimizing ternary cement compositions.

This paper investigates the mechanical properties and microstructural characteristics of Controlled Low-Strength Material (CLSM) modified with Alkali Activated Solution (AAS), synthesized by combining NaOH and Na₂SiO₃ in a 1:3.29 weight ratio. The study evaluates the flowability, compressive strength, elastic modulus, and tensile strength of conventional CLSM mixes across different water-to-cementitious material ratios (w/cm), humidity levels, and curing periods. These properties are then compared with modified CLSM mixes produced by partially substituting cement in the mix with AAS. The results indicate that AAS modification enhances flowability and significantly improves both early and long-term compressive strength compared to unmodified mixes. The authors performed Scanning Electron Microscopy analysis to evaluate the microstructural characteristics of both control and modified mixes. Microscopic analysis reveals the formation of unique tubular crystal zeolitic structures in modified mixes, contributing to their improved mechanical properties. However, the study also highlights challenges associated with shrinkage and cracking, particularly under low relative humidity curing conditions. These findings provide valuable insights into the efficacy of AAS modification for enhancing the performance of CLSM mixes and underscore the importance of considering both mechanical and microstructural aspects in the mix design.

Metallurgical sludge waste (MSW), a by-product of mining, energy, and metallurgical industries, has shown potential as a substitute for traditional aggregates. This research article focuses on studying the properties of concrete incorporating MSW itself and recycled concrete aggregate (RCA) containing MSW at both early and late ages. Great emphasis is placed here on the tests carried out one year after concreting. A total of ten concrete mix proportions were prepared with varying amounts of MSW and RCA, including a reference mix. In order to investigate the effects and role of MSW on the durability properties of concrete mixes, several laboratory tests, their numerical evaluation and energy dispersive spectroscopy were carried out. The investigation aims to provide insights into the performance, durability and long-term behaviour of MSW concrete.

The moisture infiltration and transmission processes within the pore structure of asphalt mixtures subjected to wet-dry cycling significantly impair their resistance to water damage, making it essential to investigate the effects on the connectivity characteristics of the pores and assess the reparative effects of microwave heating. Computed Tomography (CT) scanning technology was utilized alongside a void network model to investigate the impact of microwave heating on these mixtures under dry–wet cycles. Parameters such as coordination number, void length, and fractal dimension were analyzed to explore how microwave heating altered microscale void connectivity. It was found that the dense-graded asphalt mixture (AC-13) exhibited relatively weak connectivity, which was slightly enhanced in the stone mastic asphalt (SMA-13), while open graded friction course (OGFC-13) displayed the strongest connectivity, particularly in the intermediate layer, facilitating moisture and air flow. Significant increases in coordination numbers and fractal dimensions were observed during dry–wet cycles, with the largest changes noted for OGFC-13. Microwave heating resulted in a reduction of the total coordination number and average coordination number, with increases of 14.8%, 27.6%, and 43.4% over the initial values, respectively. The self-healing effect was significantly enhanced by microwave heating, especially pronounced in OGFC-13, where the standard deviation of void throat length decreased from 6.2961 to 5.2614 mm. The self-healing effect was manifested in the mixtures as a promotion of reduced void throat length and structural densification. Additionally, the characteristics exhibited following microwave heating, particularly the reduced pore throat length and fractal dimension, highlighted the necessity of selecting OGFC-13 type steel slag asphalt mixtures with enhanced microwave heating self-repair potential.

Ageing results in significant performance deterioration of asphalt, especially in relation to its fatigue and low-temperature performance. This performance deterioration can theoretically be lowered by incorporating antioxidants in asphalt mixtures. Although there are several promising studies that have shown the potential efficacy of antioxidants such as zinc diethyldithiocarbamate (ZDC), no work has comprehensively evaluated its performance. In this regard, ZDC was employed to evaluate its effect as an antioxidant to slow down the ageing related performance deterioration of bitumen and asphalt mixtures. Both ZDC-modified (3% and 5%) and unmodified bitumen and asphalt mixtures were subjected to short-term and long-term ageing. Afterwards, linear amplitude sweep (LAS) tests and low-temperature frequency sweep tests were carried out on the bitumen samples using a dynamic shear rheometer (DSR). Four-point bending (4PB) fatigue tests were carried out at 25 °C, and indirect tensile asphalt cracking tests (IDEAL-CT) were carried out at 25 °C and −10 °C on the various asphalt mixtures. It was seen that properties of long-term aged bitumen and asphalt mixtures measured at low temperature and intermediate temperature could be improved by 13–69% for mixtures and 1–44% for bitumen with the addition of ZDC, compared to the unmodified samples. The ageing-mitigation efficiency of ZDC was more pronounced for the low-temperature performance-based metrics since its performance deterioration rate was significantly reduced. Overall, a comprehensive performance evaluation of the effectiveness of antioxidants at different scales provided robust evidence for the potential extension of this technology to field trials and application.

This recommendation specifies a method for measuring active elastic waves and assessing damage to concrete members such as decks and girders. The method uses elastic waves propagating inside the concrete member. Elastic waves generated near a surface of the concrete member are detected by acoustic emission sensors installed on the opposite side of the member. Elastic waves propagating in concrete are attenuated or diffracted by damage such as cracks and voids, resulting in fewer AE sources than that of intact areas. Thus, it is possible to distinguish a damaged region from others with density of the observed AE source distribution.

In this work, we comprehensively report on the synthesis of octadecylamine (ODA)-functionalized graphene (G-ODA) and compare its performance to those of graphene nanoplatelets (GNPs) and graphene oxide (GO) as asphalt binder modifiers. An exploration into the mechanisms through which asphalt binder properties are enhanced by each graphene-based material has been conducted, identifying the one that demonstrates superior compatibility with asphalt. The study systematically evaluates the performance of each modifier, analyzing viscosity, rheology, anti-aging properties, morphology, and chemical transformations within asphalt binders. Experimental results indicate that all three graphene-based modifiers enhance the high-temperature performance and aging resistance of the asphalt binder, with GO emerging as the most compatible material, exhibiting superior performance across all investigated responses. The rheological properties results show that GO can improve G*/sin(δ) for the unaged binder by about 120%, followed by G-ODA and GNP. On the contrary, multiple stress creep and recovery (MSCR) results indicate that both GO and GNP efficiently reduce permanent deformation, with reductions in Jnr of about 39% and 34%, respectively while the G-ODA shows a smaller reduction of − 10%. Additionally, GO excels in improving elastic response, showing a substantial increase in percent recovery at 297%, compared to 48.4% with GNP and 28.8% with G-ODA. Fourier-transform infrared spectroscopy (FTIR) analysis establishes the absence of evidence indicating chemical interaction between any of the graphene-based materials and asphalt molecules. This suggests that the improvement is solely attributed to physical interaction, specifically through π-π interaction. On the other hand, AFM phase images indicate that all graphene-based materials can alter the morphology of asphalt binders. They increase the projected surface area of the Peri/Catana phases, which can influence the rheological properties of the binder.

Semi-flexible pavements (SFP) are extensively used in high-traffic zones owing to their outstanding resistance against rutting. Nonetheless, interface cracking persists as a prominent issue within SFP composites. This study establishes a finite element model of SFP using a computer vision algorithm to analyze its mechanical properties at the internal interface. Two interface components, namely the aggregate-asphalt and asphalt-grout interfaces, were developed to simulate stress distribution, crack initiation, and extension within the multiphase composite of SFP. The examination of transition zone properties within the asphalt-grout interface shed light on damage morphology and mechanical response. The results demonstrate that incorporating the interface layer significantly enhances the accuracy of force behavior analysis in simulating SFP materials. Furthermore, reinforcing the interface transition zone boosts the overall peak compressive strain strength of SFP materials in tandem with increased interface strength. Moreover, the grout joints and asphalt-grout interfaces within SFP act as vulnerable points where cracks propagate swiftly, leading to the detachment of cementitious grout from the base asphalt mixture.