How to make cement and mortar in the wild (aka survival cement)
In a survival situation, a mixture of mud and grasses can be used to create a substance known as “survival cement”. Survival cement can be used to construct shelters, create cookware, kilns, and to wrap foods for “clay baking”. It takes two ingredients to make cement in the wild – mud and grass.
To begin, find a source of mud that is high in clay content. Mud with high clay content will ball up in your hand and retain its shape when released. The higher the clay content the better the quality of the hardened cement.
Next, harvest grass, preferably dry grass. Cut the grass into segments 6-12 inches long for most projects. Longer lengths can be used for larger projects. Grass can also be layered, with blades parallel to each other, in between the layers of mortar (it acts much like rebar).
Place the clay mud in a container and add water until it becomes squishy (but not runny). It should be wet enough that it can be molded but not so wet that it does not retain its shape. Wetter mixtures are good for mortar (it flows better between bricks and fills cracks and crevices more effectively) while thicker mortar is good for bricks.
Dump the mud on a tarp and place about the same amount of grass as mud on top (about 40%-60% of the mixture should be grass). Step on the mud to mix the grass and mud together. Once thoroughly mixed and flattened, fold the mixture on top of itself repeatedly until you have a ball again.
Next, add more grass and repeat the steps to thoroughly mix the grass and mud together. The resulting mixture should be about 40% to 60% grass.
Use the cement immediately before it begins to dry and set. If you find that you are short on grass and have to harvest more, cover the cement to preserve the moisture content. If you have to add more water, add just a little water at a time.
Cement made in this manner has survived intact for thousands of years (Anasazi used this technique).