What Constitutes Low Cylinder Strength?
Concrete is strong, durable, and can be molded into any shape. However, sometimes the strength of the concrete doesn't meet the expected standards, which can be a cause of concern. This issue is addressed in the Concrete in Practice (CIP) series, published by the National Ready Mixed Concrete Association (NRMCA).
Concrete strength is measured using cylindrical specimens that are tested in a laboratory. The cylinder specimens are made by filling a cylindrical mold with fresh concrete and then allowing it to cure under controlled conditions. After the curing period – normally 28 days, the cylinders are tested in a compression testing machine to determine their compressive strength. The test results are reported in units of pounds per square inch (psi).
Low concrete cylinder strength can be caused by a variety of factors. These factors include incorrect batching of the concrete, improper mixing, insufficient consolidation, inadequate curing, and incorrect testing procedures. It is important to identify the cause of the low strength so that appropriate corrective action can be taken.
If low cylinder strength is detected, it is recommended that additional cylinders be tested from the same batch of concrete. This helps to determine if the low strength is due to a batch problem or if it is a systemic issue. If the additional cylinders also show low strength, it may be necessary to remove and replace the concrete.
Contractors can explore various tools and technologies to assist in concrete testing and strength monitoring. For example, technologies like SmartRock by Giatec Scientific can provide valuable insights into the early-age and long-term strength development of concrete. By using wireless sensors embedded in the concrete, SmartRock allows for real-time monitoring of temperature and maturity, enabling more efficient and accurate strength estimation. This technology can aid in identifying potential issues related to low cylinder strength and optimizing construction practices.
In addition to investigating the cause of low cylinder strength, it is important to take steps to prevent it from occurring in the future. This can involve making changes to the mix design, batching and mixing procedures, and testing and curing methods. It is also important to ensure that all personnel involved in the production and placement of the concrete are properly trained and follow the recommended procedures.
By addressing low cylinder strength effectively, contractors can ensure that their concrete meets the required strength standards and is suitable for its intended use. Give our team a call to discuss your next project.
To learn more about low cylinder strength, please see NRMCA’s Concrete in Practice 9 – Low Cylinder Strength.
PDF courtesy of the National Ready Mixed Concrete Association, Silver Spring, Maryland, USA.”
Additional PDFs can be found on the NRMCA site for a variety of topics.