Type 1L Concrete: What It Is, and the Problems It's Causing

Over the last few years, the cement in almost all ready-mix concrete quietly changed. Type I/II Portland cement was replaced by Type 1L — Portland-limestone cement (PLC) — and contractors across the country are reporting more scaling, finishing and durability problems because of it. Here's an honest look at what changed, what's going wrong, and what it means for your project.

What is Type 1L cement?

Type 1L, classified under ASTM C595, is made by intergrinding traditional Portland cement clinker with up to 15% finely ground limestone. The goal is environmental: it cuts the embodied carbon of cement by roughly 10%. It has been used in Europe for years, and starting around 2022 and 2023, major U.S. cement producers shifted almost entirely to it — often presenting it to contractors as a "drop-in replacement" for the cement they'd used for decades. Today it makes up the majority of cement supply nationally, which means if you pour concrete now, you're almost certainly getting 1L.

The problems contractors are reporting

The switch has not been smooth. Across the trade — including here in Michigan — finishers and concrete contractors have reported a consistent list of issues with 1L mixes:

• Surface scaling and dusting. The most common complaint: the top layer flakes, pops or powders, sometimes within the first winter.
• Less bleed water and a shorter finishing window. Many finishers describe 1L as "thirstier" — it holds less surface water, so it can dry too fast and leave less room for error during finishing.
• Plastic-shrinkage cracking. That faster surface drying raises the risk of early cracking if conditions aren't managed.
• Increased porosity and a softer surface. More permeable concrete absorbs more water — which matters a lot in a freeze-thaw climate.
• Color and finish inconsistency. Decorative, stamped and exposed work is harder to keep uniform.

The frustration is real enough that some installations have ended up in litigation, and a number of producers have started migrating back toward the older Type I/II cement.

The honest nuance

Here's the part a lot of online complaints leave out: the industry's position is that PLC, poured correctly, performs comparably to the old cement. Their argument is that 1L is simply less forgiving — it punishes the shortcuts (adding water at the truck, rushing the finish, skipping proper curing) that older cement tolerated. There's truth to that. The reality on the ground is somewhere in the middle: the material genuinely behaves differently, the rollout gave contractors little warning, and success now depends heavily on discipline and proper practice. It's an evolving situation, and the verdict isn't fully settled.

What this means for your project

You don't get to pick the cement — it's what's available in the supply. What matters is the contractor's process, which matters more now than it ever did. With 1L, the difference between a slab that lasts and one that scales comes down to controlling the water-to-cement ratio, finishing to the surface rather than the clock, and — critically — proper curing. It also makes protecting your new slab through its first winter non-negotiable: because 1L tends to be more permeable, keeping deicing salt off new concrete is more important than ever.

How we handle it

We've adapted our process for 1L: communicating mix requirements with our ready-mix supplier, holding the water ratio, watching evaporation and the surface during finishing, curing properly, and recommending sealing on driveways and patios. Thirty-five years in, adapting to a new material is part of the job — the goal is the same slab quality you'd expect regardless of what's in the bag. Planning a project? Get an instant ballpark or a free estimate.