As the concrete industry continues to evolve, blended cements are becoming an increasingly important part of the conversation around performance, sustainability, and constructability. With more cement options entering the market, the key question is no longer just what comes after Type IL cement, but how the industry can use blended cements successfully in real-world concrete construction.

Blended cements are produced by combining portland cement with materials such as limestone, slag cement, pozzolan, or a combination of these materials. While they may feel like a newer topic, blended cements have been part of ASTM standards for decades. Type IL, also known as portland-limestone cement, was introduced into ASTM C595/C595M in 2012 and has since become a major part of the U.S. cement market. As of June 2025, blended cements made up more than 60% of cement shipments in the United States, with most of that estimated to be portland-limestone cement.

Successful use of blended cements begins with evaluating performance in concrete, not just reviewing cement properties on paper. Characteristics such as fineness or limestone content alone are not enough to predict how a mixture will behave. Testing should consider slump, air content, setting time, strength, finishability, pumpability, bleeding, heat of hydration, shrinkage, durability, and other performance factors.

A practical implementation process includes laboratory testing, field test placements or mockups, mixture adjustments, new submittal approvals, and careful attention to construction practices such as hot- and cold-weather concreting, finishing, and curing. This methodical approach helps producers, contractors, and project teams understand how blended cements will perform before full-scale construction begins.

Additional tools can help teams better evaluate blended cement mixtures. Portable semi-adiabatic calorimeters can measure early-age heat release, helping assess setting behavior, early strength development, and mixture consistency. The float test can also be used to evaluate finishability by measuring how many passes are needed to close holes and achieve a smooth concrete surface. These tests provide useful information beyond traditional slump and strength measurements.

Blended cements can also support lower-carbon concrete goals. One project example used concrete mixtures with 50% replacement of Type IL cement with supplementary cementitious materials for structural members, while still meeting specified strength requirements, including early strength needs for post-tensioning and formwork release.

However, successful use depends on more than mixture design. Communication, education, and buy-in from the entire project team are essential. Blended cement mixtures, especially those with higher SCM contents, may behave differently during placement and finishing. Test placements give finishers and

contractors hands-on experience before construction begins and allow adjustments to be made early. Training programs, such as concrete finisher education and certification efforts, help the workforce understand how changing materials affect the finishing process.

The path forward is clear: blended cements offer strong potential for meeting performance needs while supporting industry decarbonization goals. To use them successfully, project teams must prioritize testing, communication, curing, training, and collaboration from the earliest stages of a project.

Excerpt from original article by Eric R. Giannini, Brett A. Harris, Eric P. Koehler, M. Tyler Ley, Mohammed J. Uddin, Anis Ghanei, James J. Martinoski, and James M. Casilio (published February 2026) Read the complete article