Case Studies in Construction Materials最新文献

Bio-oils are increasingly used to enhance petroleum bitumen’s intermediate and low-temperature characteristics regarding their economic and environmental benefits. Research has shown a beneficial impact of nanomaterials on altering bitumen’s high-temperature characteristics. The present study uses a mixture of rice bran oil and nano-calcium oxide to improve the performance of bitumen in all three temperature conditions. Rice bran oil was added to pure bitumen at doses of 3, 5, and 7 % relative to the weight of bitumen. The rheological tests (dynamic shear rheometer, multiple stress creep recovery, linear amplitude sweep, and bending beam rheometer) demonstrated that using rice bran oil in bitumen enhanced its performance at intermediate and low-temperatures but declined its performance at high-temperatures. Therefore, to improve the performance at high-temperatures, the bituminous sample containing 5 % rice bran oil was combined with 1, 3, and 5 % nano-calcium oxide, followed by repeating the rheological tests on them. The samples modified with nano-calcium oxide showed increased friction and shear stress, viscosity, and rutting parameters. Besides, the samples exhibited reduced sensitivity to aging compared to the bio-oil samples. However, the non-recoverable creep compliance and percentage of recovery showed improvements. The fatigue life of bio-oil samples decreased after adding nano-calcium oxide. However, the fatigue life remained higher than the base bitumen sample when adding 1 % nano-calcium oxide. Fourier-transform infrared spectroscopy analysis showed that a new chemical reaction occurred due to adding nano-calcium oxide to bitumen containing rice bran oil. Besides, the scanning electron microscope image revealed that the nano-calcium oxide particles are uniformly and homogeneously distributed within the bitumen sample containing 5 % rice bran oil. Consequently, the mix containing 5 % rice bran oil and 3 % nano-calcium oxide increases the resistance against high-temperature failures and improves the low-temperature performance compared to the base bitumen sample.

Silicate-modified polyurethane (PU/WG) is an effective organic–inorganic hybrid-grouting material that blocks water and reinforces weak formations. In deep high-temperature formations, owing to environmental impacts, PU/WG raw materials are heated before grouting. To elucidate the basic characteristics of PU/WG grouting materials in deep, high-temperature environments, we investigated the effects of raw material temperature on the curing time and strength of PU/WG by considering different mass ratios during the curing time test. Furthermore, the influence of raw material temperature on the micro-structure of PU/WG was analysed from a microscopic perspective using scanning electron microscopy. Energy-dispersive X-ray spectroscopy revealed the composition and curing mechanism of PU/WG. The results indicated that as the raw material temperature increased from 24 to 60°C, the peak strength decreased from 41.65 to 14.51 MPa, and the peak strain decreased from 27.03 % to 8.83 %. Based on the experimental results of the curing time testing and strength test, we established a PU/WG curing time-variation model considering the coupling of raw material temperature and mass ratio and provided an optimisation scheme for the PU/WG strength, which provides effective guidance for grouting time design in high-temperature environments.

During construction at low temperatures, fresh concrete is susceptible to early freeze damage, which can permanently damage the concrete structure. Therefore, this study aimed to enhance the early-age strength and durability properties of the cement paste at −5 ℃ by incorporating calcium nitrite (CN) antifreeze and nano-silica (NS). First, the effects of CN and NS on the fresh properties of the cement paste were measured by setting time and bleeding rate tests. Subsequently, the mechanical properties and chloride content after salt solution erosion were tested for each group of specimens, and the change in slurry densification was further observed by ultrasonic pulse velocity and resistivity tests. Finally, the hydration products and microstructure of the specimens were analyzed using XRD and SEM tests. The results showed that the addition of CN and NS could reduce the setting time of cement paste and avoid the bleeding phenomenon of cement paste under negative temperature environment. The decrease in curing temperature and the use of NS both inhibited the promotion of C₃A hydration by nitrite ions, which led to a decrease in nitrite-AFm content. However, NS can compensate for the reduced nitrite-AFm content by promoting the production of hydrated C-S-H through nucleation and pozzolanic effects. Ultimately, the strength and resistance of the slurry to chloride erosion are improved.

Zeolite foamed asphalt - warm mix mixture (ZFA-WMM) has been applied in large quantities in asphalt pavement, however, a lower construction temperature, residual zeolite water and zeolite minerals have different effects on the cohesion and adhesion properties of zeolite foamed asphalt (ZFA), which indirectly affects the water stability of its mixture. This study analyzed the interface behavior in ZFA-WMM using molecular dynamics simulation. First, the molecular model of ZFA was constructed, and its thermodynamic properties were calculated and compared with experimental values and related simulated values to validated the reasonable of model. Then, the interface models of ZFA-aggregate (quartz and calcite) and ZFA-ZFA were established, simulating the effects of the zeolite mineral dosage, temperature, and interface moisture (residual zeolite water) content on the cohesion and adhesion of ZFA. Furthermore, the occurrence mode of cohesion or adhesion failures in ZFA-WMM were predicted by comparing the ZFA-aggregate adhesion work with ZFA cohesion work. The simulation results indicated that as the zeolite mineral dosage increased, the ZFA cohesion and ZFA-calcite adhesion increased, while ZFA-quartz adhesion first grew and then dropped, reaching its maximum at 9.4 % zeolite mineral dosage. Under the pavement operating temperature range (-15°C∼65°C), higher pavement temperatures are beneficial to ZFA-aggregate adhesion; the cohesion of ZFA first increases and then decrease as temperature rises, reaching its maximum at 25℃. The larger the interface moisture content, the higher the possibility of water separating ZFA from the aggregate surface and the water sensitivity of ZFA-WMM. The ZFA-WMM is prone to adhesion failure, especially at higher zeolite dosages.

In this research, sustainable sand was developed using desert sand with recycled fine aggregate. Developing sustainable sand can solve environmental issues caused by excessive river sand mining. For this purpose, four types of sustainable sand have been developed. The present study has developed a method to optimize desert sand by incorporating recycled crushed sand from demolished concrete. The developed sand properties were well within the ASTM and British standards recommendations. A chemical analysis of SEM-EDS and FTIR was also performed on the developed sand. The 50 % addition of desert sand separately with 50 % recycled crushed sand is effected to reach the fineness modulus well within the specified range (2.4–3.0) set by the standard code. Four concrete mixes were prepared with developed sand using the absolute volume method. The compressive strength increment was evaluated at 3, 7, 28, 56, 91, and 360 days of curing. The developed sand mixes with fineness modulus values 2.6, 2.7, and 2.8 successfully pass criteria 1 and 2 set for this study at 28 days of curing. The prepared mix with the lowest fineness modulus value of 2.4 successfully achieved criterion 1 and failed to reach criterion 2. It shows that the fineness modulus value significantly influences the concrete strength. The flexural strength of all mixes surpassed the standard requirement. The study concluded that desert sand is a useful fine aggregate with recycled crushed sand when utilized at the optimum value. Hence, the developed sustainable sand can replace river sand in concrete production.

While graphene effectively enhances the performance of cement-based materials, its current production methods are characterized by environmental unfriendliness and high energy consumption. To investigate a large-scale and eco-friendly graphene preparation approach, Carbon Nano Sheets (CNS) were synthesized via chemical vapor deposition (CVD). The influence of CNS content on the tensile strength of cement mortar was assessed through the Brazilian splitting test. Concurrently, the mechanism of CNS was examined using acoustic emission monitoring and scanning electron microscope. The experimental results revealed that methane can be effectively decomposed into high-quality CNS at 1080 ℃ when using fly ash, silica fume, and sand as substrates. The Brazilian splitting test revealed that CNS effectively enhances the tensile strength of cement mortar, with improvements ranging from 9 % to 58.7 %. Acoustic emission results indicated that the inclusion of CNS reduces the occurrence of micro-fractures during the failure of cement mortar specimens. Furthermore, nano-mechanical testing and microstructural characterization demonstrate that CNS can reduce micro-cracks and pores in the interface transition zone and hydration products, playing a role in dense hydration products. Furthermore, it can decrease the width of the interface transition zone and enhance the micro-mechanical properties of cement pastes. This study offers a novel approach for the eco-friendly production of cement nano additives.

This study focuses on a novel technique to improve the resistance of cement-based concrete to chloride ion penetration by incorporating NH₂-MIL-125(Ti) metal-organic frameworks (MOF) into the mix. The MOF was produced and assessed against its chloride adsorption capacity. Subsequently, it was added to cement-based concrete in proportions of 1 %, 3 %, and 5 %, by cement mass. The effect of incorporating MOF on the concrete resistance to chloride penetration, reaction kinetics, and compressive strength was investigated. The experimental results revealed that the NH₂-MIL-125 (Ti) MOF effectively removed/adsorbed the chloride ions from sodium chloride solutions, with a maximum removal capacity of 31.5 % after 7 days of exposure. Furthermore, the depth and rate of chloride ion penetration into the concrete were reduced as the mass of MOF incorporated into the concrete mix increased. Yet, the efficiency of the MOF to reduce chloride penetration decreased over time, owing to its saturation by continuous exposure to chloride ions. Furthermore, the addition of up to 5 % MOF, by cement mass, had a limited impact (<10 %) on the concrete compressive strength but did not affect the hydration reaction. Owing to its small particle size, MOF strengthened the cement paste by reducing the volume of permeable voids. Such research findings highlight that MOF could be added to cement-based concrete to enhance its resistance to chloride ingress without significantly impacting its compressive strength. This novel approach can effectively impede chloride penetration, thereby delaying corrosion and extending the service life of concrete structures.

This study provides a comprehensive evaluation of three pavement surface treatments—Re-Ascon, Micro-surfacing, and Fog-seal—aimed at enhancing the longevity of asphalt concrete pavement. Utilizing visual inspection, bearing capacity measurements, and linear regression modeling, this study rigorously assesses the effectiveness of these strategies in real-world road environments. Notably, Re-Ascon emerges as the least damaged method in visual inspection, offering crucial insights into initial pavement conditions. Visual inspections consistently underscore Re-Ascon's outstanding performance in mitigating pavement distress, particularly in addressing cracking. Quantitative analysis using the Surface Curvature Index (SCI) from Falling Weight Deflectometer (FWD) measurements highlights Re-Ascon's superior elastic modulus (E1) and resistance to deflection compared to alternatives. Re-Ascon's 20 % SCI reduction compared to Fog-seal highlights its superior deflection resistance, supported by logarithmic elastic modulus values. Correlation analysis confirms Re-Ascon's resilience, maintaining low SCI even under higher loads and adverse weather conditions. Geographical variations and method-specific influences are revealed through PCI analysis, emphasizing the vital impact of preventive maintenance. The identified PCI threshold of 60 % guides timely interventions for major maintenance, while service life analysis forecasts approximately 3.0, 2.5, and 1.5 years for Micro-surfacing, Re-Ascon, and Fog-seal methods, respectively. In conclusion, this research furnishes critical insights into preventive maintenance methods, advocating a holistic assessment through visual, structural, and predictive perspectives, and emphasizing the need for ongoing research to advance sustainable strategies.

Addressing the dual environmental challenges of dredged sludge disposal and the repurposing of industrial by-products, this study pioneers the application of Calcium Carbide Residue (CCR)-based materials for stabilizing dredged sludge in road subgrade construction. The proliferation of dredged sludge, characterized by high moisture content and pollutants, presents a significant environmental hazard, while CCR, a by-product of acetylene production, poses disposal and pollution challenges. This research endeavors to mitigate these issues by exploring the stabilization potential of CCR when mixed with dredged sludge, aiming to enhance the mechanical properties of materials used in road subgrade construction. Through comprehensive laboratory testing, including unconfined compressive strength assessments, scanning electron microscope analyses, and X-ray diffraction examinations, the study reveals the intricate physicochemical interactions between CCR and sludge. These interactions lead to notable improvements in material strength and moisture reduction, substantiating the efficacy of CCR-based binders in sludge stabilization. The CCR-based binder can make the strength of the stabilized sludge reach 215.4kPa and the water content drop to 32 %. Field tests conducted to assess real-world applicability confirm the laboratory results, demonstrating the treated material's suitability for road construction as per secondary road design criteria and its environmental safety. The research highlights the environmental and engineering benefits of using CCR-based materials for sludge stabilization, offering a sustainable solution to the challenges of dredged sludge management and industrial waste utilization. The findings represent a step forward in waste-to-resource conversion, promoting environmental sustainability in civil engineering practices.

In this paper, a new strategy is applied to synthesize a safe-to-use one-part (OP) alkali-activated binder via controlling the activation rate of blast furnace slag (BFS) and fly ash (FA). The proposed strategy involved creating a reactive powder with a high capacity to interact with water, similar to Portland cement (PC). This was achieved by partially activating BFS/FA in the presence of water, which makes the activated paste in a non-workable form, followed by immediate drying at 80°C for 24 hours and pulverizing to produce one-part (OP) alkali-activated powder. The impacts of sodium hydroxide (NaOH) concentration and water/raw material powder (W/RMP) on the performance of the prepared OP-activated powder and the relevant hardened pastes are addressed. Different contents of hazardous lead glass sludge (LGS) include 5, 10, and 15 wt% were incorporated during the preparation process to evaluate the potential applicability of the synthesized OP-activated powders in the immobilization of hazardous lead (Pb). The obtained results revealed that, regardless of NaOH concentration and W/RMP ratio, all the synthesized OP-activated powders showed a high capability to interact with water, yielding hardened materials with appropriate mechanical properties. However, adjusting NaOH concentration at 10 wt% and W/RMP ratio of 0.1 during the synthesis process has resulted in the formation of OP-activated powders with the highest compressive strength values at all ages. Moreover, this mixture exhibited compressive strength comparable to those of the conventional two-part (TP) alkali-activated binder at the same NaOH concentrations. The proposed strategy presents a high affinity to restrict the free Pb inside the alkali-activated mixtures through its transformation from soluble to insoluble form.