International Concrete Abstracts Portal

Concrete specimens containing iron sulfide-bearing aggregates were investigated under electrochemical acceleration to evaluate potential damage mitigation strategies. Cylinders were prepared with different aggregate sizes, sulfide contents, water-to-cement ratios, cement types, and pozzolanic replacements, and subjected to controlled electrochemical exposure to reproduce field-like deterioration within weeks. Damage progression was monitored using resonance frequency measurements, visual crack quantification, and microstructural analysis. Results showed that higher sulfide contents accelerated modulus loss and crack initiation, with coarser aggregates producing visible cracking and greater stiffness reductions, while finer aggregates largely avoided macrocracking. Higher water-to-cement ratios further accelerated deterioration, whereas lower ratios delayed both onset and propagation. Cement type and pozzolanic additions also influenced deterioration, with all mixtures exhibiting damage under electrochemical acceleration. Specimens containing Type I white Portland cement demonstrated greater resilience against rapid failure, while partial cement replacement with glass powder delayed early crack propagation. These findings demonstrate that electrochemical acceleration provides a reliable platform for evaluating potential mitigation strategies and show how mixture design parameters influence deterioration progression in iron sulfide-bearing concrete, offering insights that support the development of practical approaches to manage this durability problem.

Over the past four decades, significant advances have been achieved in material science and construction technologies for the construction of dams. Among these, MgO concrete, rock-filled concrete, and roller-compacted concrete have been applied on an increasing trend in the construction of concrete dams. The application of these innovative materials and technologies in arch dam construction makes it possible to omit transverse and longitudinal contraction joints, which can speed up construction progress and reduce project costs. This paper discusses the design and construction features of arch dams constructed without contraction joints, highlighting the role of innovative materialsand associated construction methods.

The use of lithium-based admixtures is one of the options to prevent deleterious alkali-silica reaction (ASR) in concrete. In 1992, the Canadian Centre for Mineral and Energy Technology (CANMET) initiated a comparative laboratory-versus-field ASR study. About 700 concrete blocks were cast with various aggregates susceptible to ASR, different binders including supplementary cementitious materials, and lithium-based admixtures. The blocks have been exposed outdoors near Ottawa, Canada, and their expansion has been monitored over time. Out of those, a set of blocks was made with two lithium-based products: lithium hydroxide (LiOH) and lithium nitrate (LiN). They were used with high alkali Portland cement (PC) and in “ternary” concrete systems with PC and Class F fly ashes. The Li-to-(Na+K) molar ratios in the mixtures ranged from 0.37 to 1.10.

This paper presents the expansion of the concrete blocks after 25-30 years of outdoor exposure, for 20 different mixtures. The efficacy of LiOH and LiN to limit the expansion depends on the aggregate type and the dosage. Overall, lithium-based products reduced the expansion caused by ASR. However, there are indications that lithium may only have a retarding effect on ASR expansion - not a prevention effect - at least for some aggregates. Finally, two 30-year blocks with and without Li were cored to better characterize the condition of the concrete. The paper presents the results of in-depth investigations, including the damage rating index and stiffness damage test.

PCEs have become essential ingredients in concrete technology, because they allow the production of modern concrete, characterized by ease of placement, low water-to-cement ratio and high durability. The possibility of modifying the chemical structure of PCEs over a wide range of properties allowed the development of plenty formulations engineered for different applications (ready-mixed, precast concrete industry), types of cement and climate conditions. In PCEs’ technology, the side chain length is a fundamental parameter not only in determining the dispersibility but also the cement hydration kinetic. Longer side chains are used for PCEs with high water reduction capability and low retarding effect, while shorter chains offer more a robust behavior in different application conditions. In the present work three different PCEs were synthesized, characterized by same backbone length, same carboxylic acid to side chain ratio and different side chain length. Several measurements and tests were performed, both in cement paste and mortar. Results confirmed the importance of the side chain length of PCEs in determining the plasticizing effect while the retardation of hydration mainly depends on backbone charge density and distribution. This contributes to clarify the correlation existing among the different parameters determining the functionalities of this fundamental class of admixtures.

Concrete repair is a growing industry that requires trained professionals that can correctly diagnose causes of concrete structural distress and design durable repairs. Concrete repairs often fail because of either an incorrect diagnosis of the distress cause or improper repair design. Education and training in fundamentals of concrete structural evaluation methods and repair design principles can significantly improve the service life of concrete structures. Repurposing and rehabilitation of concrete structures is most often much more sustainable than constructing new structures. This paper gives an example of course learning objectives and course outline for a concrete repair course. Teaching resources available, with an emphasis on relevant free student and teacher resources through ACI to enrich the course curriculum, are also given. For example, ways to integrate the ACI 562 “Code Requirements for Assessment, Repair, and Rehabilitation of Existing Concrete Structures and Commentary” into the curriculum is given. This paper also describes how to integrate case studies into the course curriculum, both through discussion and for practice in design. Lessons learned from past experiences teaching repair are also given.