For many years I have been volunteering at Algonquin College with their Engineering Tech program. I’ve been put together with students each year to engage in experiments involving masonry. I choose the topic, we do the work together, and they prepare a report.
Our first year, we studied the effects of different types of salts (magnesium, calcium, sodium, potassium) on four concrete and cement mixtures. After subjecting the samples to water and freezing and then thawing with salts, over three weeks, we crushed the samples and measured the results. Short answer: don’t use salt. It’s a dessicate which helps concrete absorb more water than it would otherwise, and freezing water can rupture concrete.
Since then we’ve examined a variety of subjects within masonry. Most of them are explained in text books, but by doing them ourselves we got to see the actual numbers instead of just reading that, for example, more water in the mix weakens cement, or that soaking concrete in water during curing adds strength.
Masonry is part chemistry and part art, and it was fun to explore the chemistry side. Some years we did three experiments, exploring additives, sealers, the effects of water, even the placement of rebar. I was the only mason involved with the program, maybe someone else will step forward.