Jonathan Wilkins

I now know far more about cement than I ever wanted to. I've been trying to patch my kitchen floor and achieve a match with the existing concrete. This is trickier than I realized. It didn't make as much difference when I was doing smaller patches such as those adjoining rooms but the middle of the floor is much more sensitive.

A 2'x3' patch in a high traffic area like the middle of the floor requires a lot more strength and the prior owner had redone the kitchen and had removed an island that had contained the stove. To do this they had to cut a large hole in the middle of the floor. Unbeknownst to me before I removed the linoleum, they had taken some short cuts when placing the lino. These included patching cracks with plaster of paris and other unsuitable materials. (Nothing dangerous structurally, just not something I could just seal over and have it look decent.)

Anyway, google and wikipedia came to my rescue and I finally have things under control.

Cement is a term to describe substances that set and bind independently and can join materials. In construction, the term usually refers to portland cement (named due to it's similarity to a type of rock near Portland, UK). There are two main varieties of portland cement, white and grey. White is more expensive due to the ingredients used.

Combining these with fine aggregate (like sand) and water yields mortar. Combining mortar with large aggregate (like gravel) gives you concrete. The strength of mortar and concrete is largely dependent on the amount of water used, but there are strengthening agents that can be added. Pigments can be added to achive desired hues and additives are also available to lighten the color. There are also ingredients available to speed and slow the setting time.

Also, angle grinders rule. Don't use a sander on concrete. Get an angle grinder and a diamond grinding wheel for mortar. They come in handy for all sorts of shit. Like shortening the length of your pliers so you can get in behind a pedestal sink: