Building Material: Cement or Concrete
The National Institute of Standards and Technology (NIST) has taken a significant step in understanding and addressing a common issue that plagues homeowners and structural engineers alike - the unintentional chemical reactions causing cracks in concrete, often referred to as "concrete cancer."
NIST's team of experts, who boast a century-long history of studying concrete, have been delving into the intricacies of alkali-silica reactions (ASR). These reactions, when certain aggregates react with alkalis, lead to the formation of an expanding gel inside the concrete that exerts pressure outward and creates hairline fractures across the surface. Over time, this process can cause severe cracking and structural damage[1].
In a groundbreaking study, NIST researchers have recreated the ASR phenomenon under controlled laboratory conditions. They built concrete samples with aggregates known to cause ASR and accelerated the reaction by maintaining the samples at about 24°C (75°F) and 95% relative humidity. This sped up a process that normally takes years to occur within months. They then applied mechanical stress using hydraulic presses to examine how ASR-induced cracks impact the concrete's strength[1].
The key findings from NIST's research include:
- ASR causes internal expansion due to gel formation, leading to microcracks that develop into larger fractures.
- The damage progresses slowly but worsens over time, eventually compromising structural integrity irreversibly.
- Experiments quantifying the mechanical impact demonstrate that different amounts of ASR gel correlate with varying reductions in strength under stress.
- The research helps regulatory agencies like the Nuclear Regulatory Commission evaluate safety and consider mitigation strategies for concrete with ASR damage[1].
This research represents one of the most detailed scientific studies of unintentional chemical reactions causing concrete cracking and helps deepen understanding of how to predict, monitor, and possibly mitigate these damaging processes in concrete infrastructure.
Concrete, often referred to as "liquid rock," has been a staple in construction since ancient times, playing a significant role in the foundations of modern society. From Roman aqueducts to the Sydney Opera House, concrete's versatility and durability have made it a go-to material for construction projects. Despite being ancient, concrete remains the subject of ongoing research, with NIST's expertise making it uniquely equipped to tackle scientific questions about concrete and its performance[1].
It's essential to note that concrete is not inherently gray or bland; it can be used in creative and visually striking ways. The term "concrete" refers to a building material composed of cement, aggregate, and water, making it a versatile material that can be molded into various shapes during its liquid state.
As we continue to rely on concrete for our infrastructure, understanding the underlying mechanisms of its behaviour will be crucial in maintaining its structural integrity and ensuring its longevity. NIST's research is a significant step towards achieving this goal, providing valuable insights into the prevention and mitigation of concrete cracks caused by unintentional chemical reactions.
[1] Source: NIST (2025). Detailed Study of Alkali-Silica Reactions in Concrete: Understanding, Predicting, and Mitigating Damage. Retrieved from https://www.nist.gov/news-events/news/2025/08/detailed-study-alkali-silica-reactions-concrete-understanding-predicting-and-mitigating-damage
- This groundbreaking study by NIST on alkali-silica reactions in concrete could have critical implications for various industries, as medical-conditions, technology, and science all rely on the structural integrity of critical infrastructure.
- The research conducted by NIST on unintentional chemical reactions causing concrete cracking, such as alkali-silica reactions, demonstrates the importance of technology and science in the upkeep and maintenance of critical infrastructure, as medical conditions and other unforeseen circumstances necessitate resilient structures.
