Lightweight Concrete vs. Regular Concrete

Ingredients

• Regular concrete is made by mixing sand, gravel and water with cement. Cement itself is a mixture of lime, iron oxide, magnesium oxide, alumina and silica baked in a kiln and turned into a powder. Once set, concrete is a dense, hard material. Lightweight concrete replaces the sand and gravel with volcanic materials, plastic waste and similar substitutes.

Handling

• Regular and lightweight concrete have different physical characteristics. Regular concrete is known for its density, about 150 pounds per square foot, while the lightweight version can have 120 pounds or less per square foot. Most lightweight concrete is also injected with foam made from polystyrene that thins out the wet concrete, making it easier to pour, though certain types require careful moisture control when wet. As the lightweight concrete dries, the foam disintegrates, leaving hard cement with tiny air holes that help with heat insulation. Regular concrete, on the other hand, insulates poorly. You can also drive nails into lightweight concrete more easily than traditional concrete.

Environmental Concerns

• Traditional concrete is not particularly environmentally friendly. Large amounts of carbon dioxide are emitted while processing cement. And petroleum products used to coat concrete forms in interior applications can produce emissions, though mineral oil or wax can be used instead. While the use of polystyrene is in lightweight concrete is of environmental concern, alternative options include waste materials.

Other Considerations

• Concrete can lose some of its structural integrity over time when cracks form. Lightweight concrete is particularly resistant to cracking, due to the flexibility creating by a mix of lightweight materials and cement. The relationship between these two elements is known as the "contact zone," which is particularly strong in lightweight concrete, contributing to its integrity. Lightweight concrete is also less permeable than its traditional counterpart, also due to the strong contact zone.