Preventing aggregate popouts
In Minnesota, Iowa, and South Dakota, we sometimes see aggregate popouts, particularly in concrete flatwork. Popouts are unsightly surface defects that may appear a few hours to a few weeks […]
Petrography
“Classic” alkali-silica reaction
“Classic” alkali-silica reaction is a reaction between alkalis in cement and reactive silicate minerals in susceptible aggregates. The reaction creates a gel that absorbs water and expands, resulting in the […]
Natural cement in Minnesota and beyond
When we think of cement, it’s usually portland cement, which is made from limestone and clay. In Minnesota, we have to import portland cement because most of the carbonate rock […]
Concrete sample size: how big is big enough?
When you submit a concrete sample for petrographic examination, how big a sample do you need? That is, what’s the appropriate concrete sample size? We’ve discussed in previous posts how […]
Concrete petrography gives a grander view
Many engineers have no idea how informative concrete petrography can be. That’s too bad, because concrete petrography is one of the most useful techniques in forensic engineering. Failure analysis of […]
Can you get a representative sample of concrete?
A representative sample of anything is an unbiased selection from the whole population. It’s a statistical concept that applies to everything from opinion polls to laboratory testing. In principle it […]
Make sure you take good concrete cores
We often receive concrete cores from our clients for petrography or other types of testing. When we haven’t witnessed the coring, we can’t always tell whether a core represents damaged […]
Not All Cements are Created Equal
“We can be using the same kind of technology, the same kind of techniques, but when we use it, we get something different.” Shigeru Miyamoto Have you ever experienced a […]
Volumetric and Hardened Air Contents the Same
Air entrained concrete is still the biggest headache in concrete production. We have recently been discussing comparisons between the pressure meter and the microscope. It may seem counterintuitive, but the […]
Petrographic examination of historic stone-veneer mortar
As a petrographer, I have had the opportunity to examine many historic mortars and historic concretes from around the United States. They silently tell stories about natural elements and sometimes, […]