Portland-limestone cement, or PLC, is engineered with a higher limestone content than portland cement to reduce the carbon footprint of concrete by about 10%. It performs just like the cement you’re used to using, resulting in the same concrete you’re used to having. The same specifications, the same mix design, now with a better carbon profile.
Concrete is everywhere. In fact, other than water, it’s the most-used material on the planet, representing about 50% of all manmade materials (by mass). It’s a versatile, economical construction material that is the basis for everything we build. Foundations. Buildings. Roads. Water and waste storage and delivery structures. Modern society is possible thanks to the versatility and widespread availability of concrete.
Because society places so much concrete each year, even small changes to its formulation can have dramatic effects on the construction industry’s annual carbon footprint. Modifying a concrete mix design to replace higher carbon materials with lower carbon ingredients is an effective strategy. Portland-limestone cement offers an easy way for concrete producers to accomplish this, much like fly ash and slag cement have done for decades. And concrete mixes designed with PLCs are compatible with all supplementary cementing materials (SCMs), so when you substitute PLC for ordinary portland cement, you can continue to use all the other materials you use to make concrete for an even
greater reduction in carbon footprint.
ACCELERATED EARLY STRENGTH GAIN
Almost anywhere you use ordinary portland cement, you can use PLC instead. In the U.S., PLCs have an established track record for transportation infrastructure. Many states have been placing PLC concrete pavements for more than a decade – with good results. From highways to driveways, PLC performs just as well in heavy-duty pavements as it does for residential flatwork. And it’s appropriate for bridge applications, too, from top to bottom, everything from the deck down to the foundation, even including geotechnical work. For buildings, PLC concrete is a natural fit for structural members of any type or size, and it’s also great for exterior finishes and hardscaping. Architects and other designers who are tasked with meeting goals put forth by green rating systems or codes will find PLC an especially useful approach to help them achieve a lower carbon footprint for any project.
EASY TO USE
To help with the transition to more environmentally friendly concrete, cement
manufacturers understand that the switch to PLC must be simple. By optimizing PLCs, they have made it easy for specifiers, producers, and installers to use them. PLC can be swapped in for portland cement at a 1:1 replacement level. This is a big help to ready-mix producers, who can continue operations using their well-established systems with a minimal amount of disruption. In most cases, all that is needed for maintaining fresh concrete behavior is the typical tweaking of proportions or admixtures, similar to changing from one source of cement to another. Anyone who knows how to work with cement and concrete knows how to work with PLC concrete.
Update from ODOT on Supplement 1126 pertaining to Type IL Portland Limestone Cement
On February 10, 2022, Ohio Concrete received the official word from the Ohio Department of Transportation (ODOT) on their acceptance of permitting the swap of Type IL Portland-limestone cement (PLC) as a 1-for-1 for Type I or I/II cement in existing approved ODOT JMFs and not going through the retesting requirement per Supplement 1126 (strength and permeability).
The highlighted areas of this document on page 1 and 2 offers specific details on what will be required for changing an existing JMF over to an ODOT certified Type IL PLC. This states that ‘The ready mix supplier will notify the contractor, Project Engineer, and District Concrete Monitor of the intended date to switch over to Type IL. Do not comingle Type I and Type IL cement on any construction items (i.e., bridge deck, parapet, columns, etc.). Mix designs selected by the contractor must be submitted following the guidance in Supplement 1126.03, prior to use on the contract.’ Further, the ready mix producer is to… ‘adjust batching software to show Type 1L on the computer-generated ticket to track when the substitution is made on the mix design. Handwriting batch information on tickets is not an acceptable practice, unless otherwise approved by the Department in writing.’
Thank you to all that assisted us through this with your mixture performance data and other industry information! Please continue to test and capture the performance results with Type IL testing. We do not know if this decision will lead to a permanent change in the Supplement 1126, but at least for now will make this cement change much easier.
Note that we are also working directly with PCA for further technical announcements on PLC acceptance that will assist on private projects when only ASTM C150 (Type I and/or Type I/II) cements are referenced. Stayed tuned for more on that.