International Concrete Abstracts Portal

This study presents a comprehensive review of eco-friendly materials and advanced repair techniques for rehabilitating reinforced-concrete (RC) structures, emphasizing their role in promoting sustainability and enhancing performance. By evaluating fifty-five research programs conducted between 2001 and 2024, the study focuses on emerging materials such as geopolymers, natural fibers, and fiber-reinforced composites, highlighting their mechanical properties, environmental benefits, and potential for integration into traditional RC systems. The review is thematically organized into four areas: (1) Sustainability and Environmental Impacts, (2) Material Innovation and Properties, (3) Repair Techniques and Efficiency, and (4) Structural Performance. Key findings reveal that these materials not only reduce the carbon footprint of construction but also significantly improve structural durability, corrosion resistance, and long-term performance under varying environmental conditions. Specifically, geopolymer concretes exhibit low CO₂ emissions and superior bond strength; bamboo and flax fibers offer strong tensile capacity with renewable sourcing; and MICP techniques deliver self-healing functionality that reduces dependency on chemical-based crack sealants. Additionally, the use of recycled and bio-based materials further contributes to cost-efficiency and environmental resilience, fostering circular economy principles. By synthesizing findings across these domains, this study provides practical insights into how eco-friendly materials can simultaneously address environmental, structural, and economic challenges in RC repair. The study underscores the importance of adopting innovative repair methods that incorporate these sustainable materials to address modern civil engineering challenges, balancing infrastructure longevity, sustainability, and reduced environmental impact.

The scaling of concrete parking aprons under F/A-l 8 and B-l aircraft asso-ciated with chemical attack from spilled lubricants and heat has been repro-duced in the laboratory. Two different series of tests involving the refluxing of lubricants, water and concrete were performed. The first involved reflux ing ground concretes, and the second, refluxed concrete-coated cylinders. Series 1 tests identijed if the replacement materials were suspect to attack, and Series 2 ‘was designed to measure strength loss of ordinary portland cement- (OPC) coated specimens, as well as replacement materials. Over 10 different coatings and 10 different inlay replacement materials were tested and compared to OPC control specimens. It was found that OPC lost 55 percent of its strength after 7 days, whereas neutral pH cements showed no reaction (Series 1 tests) and no strength loss (Series 2 tests). Only polyvi-nyl alcohol and polyacrylic acid coatings showed a significant reduction in attack (40percent) of all the coatings tested.

This report reviews the state of the art in design, construction, and mainte-nance of joints in concrete structures subjected to a wide variety of use and environmental conditions. In some cases, the option of eliminating joints is considered. Aspects of various joint sealant materials and jointing techniques are discussed. The reader is referred to ACI 504R for a more comprehensive treatment of sealant materials, and to ACI 224R for a broad discussion of the causes and control of cracking in concrete construction. Chapters in the report focus on various types of structures and structural elements with unique characteristics: buildings, bridges slabs on grade, tunnel linings, canal linings, precast concrete pipe, liquid-retaining structures, walls, and mass concrete.

The Department of Defense has seen an increase in airfield concrete apron distress in the form of surface scaling when exposed to cyclic heat, spilled lubricants, and/or hydraulic fluids. Chemical analysis of the damaged concrete reveals that the spilled fluids are undergoing hydrolysis (breakdown) accompanied by the consumption of calcium hydroxide, and hydrated silicate and aluminate phases. The damage was reproduced in the laboratory on 3 ft by 4-in. (10.2-cm) thick slabs during 5 weeks of exposure to lubricants and cyclic heat. Use of penetrating sealants, coatings and/or neutral pH concretes are suggested for pavements exposed to this environment.

The movements at the expansion joints of prestressed concrete pavements and at the contraction and expansion joints of dowled reinforced concrete pavements were measured every 3 hr for some taxiways of an airport during different months of the year. The widths of lanes and spacing between expansion joints were the same for both types of pavements. The results are reported for eadings taken during a 1 year period. Due to concrete shrinkage, the contraction joints of the dowled concrete pavements started to open after a few days from casting. However, it took several moths for many of these contraction joints to open for full slab thickness. At that times, these joints started to act patially as expansion joints and decreased the movements due to temperature variation at the actual expansion joints of the dowled pavements. On the other hand, the daily and seasonal movements at the expansion joints of prestressed concrete pavements were considerably larger tha the corresponding ones for the dowled concrete pavements. During the fist few months after casting, the ratio between daily slab length changes at the expansion joints in prestressed and reinforced concrete pavements having the same length between the expansion joints and subjected to the same temperature variations was about 2:1. Later on, this ratio increased rapidly, when the contration joints of the dowled pavements opened for full slab thickness and satred toabsorb a large part of the individual slab length changes, thus releasing the expansion joints from taking the full slab movement. The performance of different types of poured-in-place joint sealants, poured during various times of the day, was also checked during this study. While the sealents gave satisfactory results at the contraction and expansion joints of dowled concrete pavements, their use in prestressd concrete pavemens, even with short lengths, was not ucessful. The bond between the joint sealant and the sides of the prestressed concrete slabs, although improved by using lubricant adhesiv, was not sufficant to resist he tearing forces caused by the continious large movement of prestressed concrete pavements.