Incorporating fibers into reinforced cement concrete significantly enhances the structural suitability under impact and seismic loads by augmenting the stiffness and energy-saving efficiency of the material. Concrete cracks activate the vital fiber behavior called the bridge effect, enhancing the structure's strength and ductility. Since adding fibers to the concrete mix does not reduce water content but rather impairs workability due to the friction generated between fibers and the mixed paste, resulting in fiber balling. This phenomenon diminishes the performance of fiber-reinforced concrete. Adequate distribution and dispersion of fiber in the mix increases the strength and thus avoids the occurrence of fiber balling. According to reviews, nylon fiber dosages ranging from 1.5% to 3% result in effectively performing nylon fiber-reinforced concrete, which exhibits sufficient strength, durability, and flexibility. In this study, experiments have been conducted to better understand the behavior of nylon fiber-reinforced concrete at elevated temperatures by using 17 mm, 25 mm, and 50 mm nylon fiber at 1.5% and 3% dosages. When comparing different temperatures, such as normal temperature condition and elevated temperature conditions (400 °C and 800 °C), always 1.5% dosage has shown the best result for compressive strength and split tensile strength. Here, 3% dosage of nylon fiber has shown reduced mechanical strength because of the effect of fiber balling. As far as compressive strength has taken into account in three temperature cases (normal temperature, 400 °C and 800 °C), 1.5% dosage and 50 mm length of nylon fiber has achieved the most effective strength result. Besides, when split tensile strength has been concerned, 1.5% dosage and 25 mm length of nylon fiber have given the best result compared to other lengths and dosage in three temperature conditions.
This study investigates the sustainability and performance of M20 and M30 grade concrete incorporating Ground Granulated Blast Furnace Slag (GGBFS) and Pond Ash as partial replacements for Ordinary Portland Cement (OPC) and fine aggregates, respectively. Replacement levels were varied between 10% and 50%, and their effects on workability, strength, and durability were analyzed using Multiple Linear Regression (MLR) and Principal Component Analysis (PCA). Concrete mixes with up to 40% replacement demonstrated enhanced workability (R² = 99.96%, MAPE = 0.85%), attributed to improved particle packing and reduced internal friction. However, beyond this threshold, workability declined due to increased porosity and water absorption. Compressive strength (CS), flexural strength (FS), and split tensile strength (SPT) showed a diminishing trend with higher replacement levels. Model for compressive strength achieved an R² of 97.21% and MAPE of 3.21%, while flexural strength model had an R² of 99.68% and MAPE of 1.13%, indicating high predictive accuracy. Durability assessments revealed a decline in water absorption ( R² = 88.05%, MAPE = 5.45%) and acid attack resistance (R² = 99.83%, MAPE = 0.58%) with increasing GGBFS and Pond Ash content, primarily due to increased porosity and altered microstructural characteristics. Microstructural analysis confirmed reduced hydration density and weaker bond formation at higher replacement levels. Economically and environmentally, the use of GGBFS and Pond Ash reduces carbon emissions and reliance on natural resources, providing cost-effective and sustainable alternatives for concrete production. The findings highlight that optimal replacement levels (up to 40%) achieve a balance between sustainability and mechanical performance, contributing to sustainable development in construction.
Recycled aggregates have gained popularity in the recent decade. In this paper, central composite design and response surface methodology as an analytical approach were implemented to determine experimental design and prepare models of concrete properties made by recycled aggregates in the lab. Three important factors were chosen: the compressive strength (fc) of parent concretes, the rate of substitution of parent concretes, and the amount of cement. In contrast, compressive strength (fc), tensile strength (ft), and water absorption of recycled concrete were considered target responses. Statistical analyses reveal that models were acceptable with R2 values. Both statistical and experimental studies represent that fc, ft, and water absorption of concrete mainly relied on fc of parent concretes. The increase in the fc of parent concretes from 19 MPa to 36 MPa led to the rise in the fc of new concretes from 27 MPa to 38 MPa. In addition, when the substitution rate changed from 8% to 92%, fc of concretes changed from 26 MPa to 30 MPa. Recycled concretes with higher strength could be generated if the fc of parent concrete is high enough, mainly because of the better bond between paste and aggregates. The optimization of multiple responses reveals that a high percentage of parent concretes with high fc could be used in concrete mixtures without a considerable fall in mechanical properties.
The state of bridges in Indonesia is concerning, with only 1.2% of the 18,990 national bridges classified as being in good condition. A significant number of bridge failures stem from inadequate maintenance, highlighting the urgent need for a structured and effective quality management approach. This research develops a Work Breakdown Structure (WBS)-based Quality Management System (QMS) framework specifically for concrete bridge maintenance to enhance performance and ensure adherence to national standards. The QMS encompasses three main stages—inspection, maintenance, and rehabilitation—comprising 10 activities systematically aligned with bridge maintenance requirements. Quantitative findings from expert validation showed high suitability of the QMS framework, with average scores of 4.0 to 5.0 across content, format, and performance effectiveness. Statistical analysis with 33 respondents revealed a strong positive correlation (r = 0.768) between the QMS and key maintenance performance indicators such as structural safety and bridge importance, explaining 54.9% and 59.9% of the variance, respectively. Qualitative insights emphasized the enhanced organization and durability of maintenance processes, supported by 10 Standard Operating Procedures (SOPs), work instructions, and checklists. This study's novelty lies in integrating WBS into QMS for concrete bridge maintenance, providing a structured methodology for achieving consistent and high-quality outcomes. The implementation of this framework is anticipated to significantly improve the safety, reliability, and sustainability of bridge infrastructure in Indonesia.
The utilization of composite castellated beams in structures is common due to the increased bending strength and stiffness of the beam. However, the presence of openings in castellated beams reduces their shear strength. The increased bending strength allows these beams to be used over longer spans; however, the reduced shear strength makes shear force effects more pronounced in such beams. In this study, a comparative analysis of the behaviors of composite beams with castellated and solid-web has been conducted using finite element method. Nine composite castellated beams and nine solid-web composite beams, both with equal heights and cross-sectional areas, were modeled based on castellated configurations. The AISC Design Guide 31 (DG31) provides a method for calculating the ultimate bending capacity of composite castellated beams but neglects the contribution of the upper T-shaped section of the castellated beam. In this study, the focus is on innovatively comparing the load-carrying capacity of composite castellated beams with the AISC DG31 results, highlighting how finite element analysis reveals higher capacities than those predicted by DG31 by 17% to 31% across specimens. It is observed that the load-carrying capacity of castellated specimens is 2% to 5% lower than that of specimens with solid-webs. This difference may increase up to 22% with local failure in the web-post if the first openings of the beam are placed too close to the supports. Notably, the research demonstrates that the web openings in castellated beams have a minor effect on load-carrying capacity, suggesting that despite reduced shear strength, these openings do not significantly impact the overall capacity, particularly when placed thoughtfully in structural design.
