Daba Gedafa

The growing demand for high-capacity freight vehicles has heightened the need to evaluate the impact of heavy truck axle configurations on pavement behavior. This study employed a validated three-dimensional (3D) finite element (FE) model to evaluate the structural response of flexible pavements under trunnion and tandem axle configurations at two vehicle speeds (35 and 55 mph), using legal load levels of 60 and 34 kip, respectively. Then, key pavement responses (i.e., tensile strain, stress, and vertical displacement) were assessed. Also, pavement performance (i.e., fatigue cracking and subgrade rutting) was evaluated. The results showed that the trunnion axle generated higher tensile strain, von Mises stress, maximum principal stress, vertical stress, and vertical displacement than the tandem axle. This increase in pavement responses is primarily attributed to the trunnion’s shorter axle spacing, which causes overlapping stress zones and amplifies strain concentrations within the asphalt and subgrade layers. Concerning pavement performance, the trunnion axle exhibited lower fatigue life and lower resistance to subgrade rutting. Vehicle speed was also found to influence pavement response, with lower speeds producing higher stress, strain, and displacement levels for both axle types. Model predictions were validated using field measurements from the MnRoad test site in Minnesota, USA, confirming consistent trends in pavement responses under dynamic axle loading. These findings offer insight into the roles of axle configuration, maximum load, and truck speed in determining flexible pavement performance, thereby supporting better-informed design and evaluation practices.

Carbon dioxide emissions from cement production are a current environmental challenge. This research attempted to evaluate the pozzolanic reaction of residuals from coal-fired power plants, such as coal bottom ash (CBA) and coal boiler slag (CBS), as a supplementary cementitious material to lessen the deleterious effect on the environment. The residues’ fineness modulus and specific gravity were determined using the No. 325 sieve and Le Chatelier flask, respectively. Chemical characterizations were conducted using X-ray diffraction (XRD) and X-ray fluorescence (XRF). The results indicated that the percent passing of both residues was greater than 66%, as the American Society for Testing Materials (ASTM) requires, and their specific gravity was comparable to that of cement. Subsequently, in concrete specimens, 20% of the weight of cement was replaced by CBA and CBS to determine the strength development of fresh and hardened characteristics compared with the control specimens. Experimental findings revealed that by the 90th day, concrete made with CBA achieved 98% of the compressive strength of the control concrete, while the concrete made with CBS reached 79% of the control concrete’s compressive strength. Moreover, CBA-based concrete achieved 97% of the flexural strength of the control concrete, while CBS-based concrete outperformed the control by 2% on the 90th day. A lower severity level of chloride ion penetration by both CBA- and CBS-based concrete was achieved in the rapid chloride penetration test, indicating the durability of the concrete.

Concrete usage is increasing rapidly; subsequently, the industry’s carbon footprint is increasing and impacting the environment significantly. Large amounts of fine and coarse aggregate, including cement, are needed to fulfill the increased demand, leading to increased natural aggregate usage. Therefore, finding a fine aggregate replacement in concrete is essential. Coal bottom ash (CBA) and coal boiler slag (CBS), byproducts of coal-burning power plants with pozzolanic properties, can replace fine aggregate in concrete to reduce global natural material depletion, health hazards, and technical and economic problems associated with power plants’ solid waste. This study was conducted to determine the optimum fine aggregate replacement amount of CBA and CBS in concrete while improving concrete performance. The optimum CBA and CBS content is 50%, which reduces fine aggregate usage in a concrete mix by 50% while maintaining equivalent or better concrete strength than the control. The optimum CBA content has a unit weight lower than the control for all mixes tested in this study, which makes the CBA mix lightweight concrete. The optimum CBA concrete has 15%, 43%, and 42% higher compressive strength than the control after 7 days, 28 days, and 56 days of curing, respectively. On the other hand, the optimum CBS concrete has 12%,16%, and 16% increased compressive strength than the control after 7, 28, and 56 days of curing, respectively. The compressive strength of optimum CBA concrete was higher than the optimum CBS, indicating that CBA concrete yields higher compressive strength than CBS, possibly due to the difference in physical properties, water absorption capacity, and bulk density. Nanoclay increased CBA concrete compressive strength at an early stage and increased the optimum content to 80% CBA. Therefore, using CBA and CBS can significantly reduce natural material usage and environmental harm by reducing CBA waste disposal and improving concrete performance.

Waste Cooking Oil (WCO), Soy Oil (SO), and Wastewater Sludge (WWS) have great potential to increase reclaimed asphalt pavement (RAP) content for economic and environmental benefits. This study explored the effects of SO and WCO on rutting, fatigue cracking, and low-temperature cracking performance of binders and Hot Mix Asphalt (HMA) with high RAP content. The potential effect of WWS on the performance and compaction efforts of high RAP content mixes at a 10 °C (50 °F) lower compaction temperature than the control compaction temperature was also investigated. The results indicated that 85% of the RAP binders can be incorporated while maintaining similar performance compared to the control by using 15% SO or 12.5% WCO as a rejuvenator with 2.5% virgin binder. Adding 1% WWS by weight of the total binder improved the binder’s rheological properties, the mix’s cracking performance, and the mix’s density at lower compaction temperatures.

Cement production requires considerable energy and natural resources, severely impacting the environment due to harmful gas emissions. Coal bottom ash (CBA) and coal boiler slag (CBS), byproducts of coal-fired powerplants having pozzolanic properties, can be mechanically ground and replace cement in concrete, which reduces waste in landfills, preserves natural resources, and reduces health hazards. This study was performed to determine the optimum cement replacement amount of ground CBA (GCBA) and ground CBS (GCBS) in concrete, which was 10% for GCBA and 5% for GCBS. GCBA-based concrete exhibited superior tensile strength, modulus of elasticity, and durability compared to the control. In the Rapid Chloride Penetration Test, 10% GCBA concrete resulted in 2026 coulombs at 56 days, compared to 3405 coulombs for the control, indicating more resistance to chloride penetration. Incorporating 2.5% nanoclay in GCBA-based concrete increased the optimum GCBA content by 5%, and the compressive strength of 15% GCBA concrete increased by 4 MPa. The mortar consisting of the finest GCBA(L1) having Blaine fineness of 3072 g/cm² yielded the highest compressive strength (32.7 MPa). The study discovered that the compressive strength of GCBA and GCBS-based mortars increases with fineness, and meeting the recommended fineness limit in ASTM C618 enhances concrete or mortar properties.

Coal bottom ash (CBA) is a byproduct of coal-burning power plants. This material can be used as a fine aggregate replacement in concrete to reduce global natural material depletion. Concrete usage is increasing rapidly; subsequently, the industry’s carbon footprint is increasing. Using CBA in the construction industry will reduce the technical and economic problems associated with power plants by reducing solid waste. This project aimed to determine if adding new sustainable materials, such as CBA, to concrete will reduce natural raw material usage, energy consumption, and greenhouse gas emissions while improving performance. This study included two projects: comparing increased CBA content to the two-control project and determining the optimum content based on the compressive strength. The optimum CBA content is 50%, which reduces fine aggregate usage in a concrete mix by 50% while maintaining equivalent or better concrete strength than a pure Portland concrete mix without CBA. The air content of the concrete mix containing % CBA decreased with increased CBA content and compressive strength, possibly due to the spacing factor of the voids in the mix and CBA’s porous and fineness behavior. The CBA optimum content had a unit weight lower than the controls for both projects, which makes the CBA mix a lightweight concrete. Using this material can significantly reduce natural material usage and environmental harm by reducing CBA waste disposal and improving concrete performance.

Cement production requires a significant amount of energy and natural resources, severely impacting the environment due to harmful gas emissions. Coal Bottom Ash (CBA) and Coal Boiler Slag (CBS), byproducts of coal-fired power plants, have pozzolanic properties. CBA and CBS can be mechanically ground to obtain Ground Coal Bottom Ash (GCBA) or Ground Coal Bottom Slag (GCBS), which can potentially replace cement in concrete, reducing waste in landfills, benefit the economy, preserving natural resources, and reducing health hazards. This study was performed to determine the optimum amount of GCBA and GCBS that can replace cement in concrete. The fresh, mechanical, and durability properties of the concrete containing GCBA were compared to a control mix consisting of 100% Portland cement. The optimum amount of cement replaced with GCBA and GCBS was 10% and 5%, respectively, based on compressive strength. The GCBA-based concrete's tensile strength, modulus of elasticity, and durability properties were better than the control. The compressive strength of the GCBA and GCBS-based mortars increased with an increase in fineness. GCBA and GCBS fineness should be within the limit recommended in the ASTM C618 standard to enhance concrete or mortar properties.

Extreme temperature variations between winters and summers are part of life in North Dakota. Looking for materials and methods to modify hot asph |

There are five levels of the Highway Performance Classification System (HPCS) of North Dakota: Interstate, Interregional, State Corridor, Distric |

Due to its extreme weather conditions of cold long winters, and hot and rainy short summers, asphalt pavement design and construction in North Da |