Shelter

Interesting use of concrete for construction  (source: seier+seier)

Concrete is the most often used construction material of the modern world.  It is simple and economic to make and if the Egyptians had known the secret they could have made it 4000 years ago. To make concrete, first you need to make the cement (or mortar) that holds the concrete together. 

The Romans did this by burning limestone (which is mostly calcium carbonate CaCO₃) to create something called quick lime (calcium oxide CaO). Burning isn't quite the right term because "to burn" usually indicates an oxidation process which involves the "chemical union of oxygen with any substance".  What actually happens in a lime kiln is that the temperature of the limestone is increased to a point above its dissociation temperature.  The earliest lime kilns were really just layers of wood and limestone stacked together and lit like a giant bonfire.  So it is easy to see why it is called burning limestone when it really isn't.

Source: epicture

You don't need to spend lots of money to feel more secure in your home but you do need to have a plan. Most homeowners put little or no thought into home security and, as a result, the thieves benefit. With some observation and careful thought you can create a plan that makes thieves skip your house and move on to something easier. 

The plan starts with the realization that there is no such thing as absolute security. The goal isn't to turn your home an impenetrable fortress. (Although there is something romantic about the idea of living in a castle with a moat.)  The goal is to make your home  an unattractive target for thieves.   This can be done without turning your home into a prison compound or breaking your budget.