Sound Smarter on the Jobsite: Concrete vs Cement
If you're saying "cement," 99% chance you mean "concrete." Cement is an ingredient in concrete, along with aggregate, water, and any admixtures. Calling concrete "cement" is like calling a peanut butter and jelly sandwich "bread."
So what exactly is “cement?” It’s a chemical binder, that when activated with water, binds together aggregate to make concrete. Historically, cement was mostly lime; today, it’s mostly Portland cement, which was named for the stone it was originally created from in England.
When working on historic structures, it’s very important to use the correct cement - older lime cements are much softer, whereas modern Portland cements are harder - they’ll cause your historic masonry to spall. Not good!
Aggregate, another ingredient in concrete, can be many different things - from fine materials like sand [for making mortar] to chunky materials like stone or even seashells.
And: concrete doesn’t “dry",” it cures! It doesn’t usually reach full strength til 28 days, though it can reach strengths adequate enough to continue construction in far less time, as long as the mix and install are done correctly, and it’s tested before moving to the next step.
And: concrete’s best friend is steel. Concrete is great in compression, but not very good in tension, whereas steel really shines in tension. This is why we add steel rebar [reinforcing bar] to concrete, so that the combined assembly takes full advantage of the characteristics of both materials.
I could do a whole ‘nother post on rebar alone!
And finally, no conversation about concrete and cement is complete without a reminder that Mel Torme has already told us the recipe and procedure for creating concrete, if with a bit of artistic license:
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