- Why Concrete?
Concrete goes back to ancient times. Roman builders used a basic form of concrete before the beginning of the Common Era. Some of these structures are still standing 2000 years later. Modern Portland cement (a primary ingredient in concrete), consisting of lime, silica (sand), iron, aluminum, and gypsum, was formulated and patented in 1824. Modern concrete is a mixture of Cement, sand, gravel, water, and possible admixtures (chemical additives). (Side floating box - terminology Cement - dry powder added to sand gravel and water. Concrete - wet mixture of Cement sand gravel and water. Often confused and used interchangeably).
Modern concrete is an amazing product. It literally is the foundation of almost all construction today. Concrete strength is measured in PSI, which is a measurement of how many Pounds per Square Inch of pressure is required to cause it to be crushed, or fail. Typical residential construction aims for strengths of 2,500 - 3,000 PSI. High Strength Cement is considered to be strengths above 4,000 PSI. Our shelters are a minimum of 6,000 PSI.