Concrete finishing is not a perfect science and there is always room for human error.

  A possible contributor to the problems we are seeing today with 1L Cement mixes could be the fines from the concrete mix working their way to the surface of the concrete because of excessive vibration and/or over-finishing.  At some point, an increase in the fines content of a concrete mixture will be detrimental to the concrete surface. Underhydrated concrete mixes and/or overtreated concrete mixes (i.e., with various chemicals) aggravate this potential even more as finishers find themselves forced to over-work the concrete.  Of course, it would be inequitable to suggest that a concrete finisher make do with, and ultimately be responsible for the performance of, whatever materials and processes are required of it.

 The use of 1L cements and their greater fineness and the use of aggregates having higher fine contents (the specification of which have not been adjusted to compensate for the increased fines of 1Ls) together with insufficient water to adequately hydrate this new level of combined fineness, results in a less-than-ideal concrete mixture for proper finishing.  

 General Comments Regarding 1L Cements. 

When 1L cements were first starting to be adopted, all cement manufacturers were touting that 1L cement would be a direct 1:1 replacement for original Portland cement, without impact on strength or durability.  In fact, some even suggested there would be an improvement in strength and workability of concrete made with 1L cement.  While this seemed unlikely, the market accepted these promises.  At this point, there is no question by anyone in the market – including those same cement manufacturers – that 1L cement performance is simply not the same as original Portland cement.  1L cements have unquestionably negatively affected the strength gain and durability of our concrete. 

Despite this, 1L cement seems not to be going away and may only become more problematic within the next two or three years if the industry moves toward even greater limestone replacement as is currently being suggested.  While this is being championed in the name of carbon reduction, the simple fact is that the industry is actually increasing the amount of cement powder being used in any concrete mix in order to make up for 1L cement strength deficiencies.  This is resulting in greater cement production than in the past.  And, with greater 1L cement powder content in our concrete mixes, we are producing less durable concrete with a reduced service life, which also will require greater cement production to supply the need for more frequent concrete replacement.  The net result is that 1L cements in the U.S. are, in effect, not improving the world’s carbon footprint at all and, in the meantime, Departments of Transportation (and their taxpayers), investors in commercial projects, general contractors and concrete contractors are paying the price. 

Some have argued that “limestone cements” have been used successfully for decades outside of the U.S.  While this may be true, it is important to note that the manufacturing process for those cements is not the same process as that being used to make 1L cements in the U.S. and the requirements and limitations of the relative standards are quite different (see European standard, BS 197-1, as compared to the U.S. standard, ASTM C595).  In the U.S., not only has effective pozzolanic material been replaced with inert limestone having greater Blaine fineness which requires greater water for proper hydration and bonding, but unspecified grinding aids are being used to attain that fineness and other undisclosed materials (such as calcium formate (accelerators)) are being added to the cement to help combat the strength issues of 1Ls, all of which further compromise the cement chemistry and its interactions with water, aggregates and other chemical admixtures.  

Testing at Purdue University in late 2023 showed lacking performance of a variety of traditional admixtures included in the study (made by multiple different manufacturers) when used with 1L cements.  Why is this?  Without full disclosure and evaluation of actual cement contents, there is a big unknown that can have far-reaching effects on other materials and chemicals in a concrete mixture.  There is simply no product available today that can be expected to perform the same that it did before cement chemistries were changed.  

 We strongly encourage concrete contractors to share their experiences with 1L cements and express any concerns about further potential changes in cement chemistries here as well as with their local engineers. 

We can, collectively, find a resolution other than simply holding concrete contractors responsible for all concrete failures.