Classifications Properties of Lightweight Concrete LIGHTWEIGHT AND INSULATING GROUT ◦ Density:600-1000 Kg/cm^3 ◦ Mechanical resistance: 25-100 Kg/m^2 NON-STRUCTURAL LIGHTWEIGHT CONCRETE ◦ Density:1000-1400 Kg/cm^3 ◦ Mechanical resistance: 100-150 Kg/m^2 STRUCTURAL LIGHTWEIGHT CONCRETE ◦ Density:1400-2000Kg/cm^3 ◦ Mechanical resistance: higher than 150 Kg/m^2 (Richardson) Classified based on the aggregates chosen to be in the mix. give concrete specific properties, such as weight and efficiency. Can end up being up to 88% lighter than traditional concretes. According to ASTM regulations: lightweight concretes are those mixtures that range from 60 to 100 pounds per cubic foot (pcf). Anything that is below 60 pcf is classified as super light weight concrete. (NRMCA)
Leca Clay Aggregates Features Shape: Round Color: shades of black and brown Texture: ◦ Coarse ◦ Spongy cellular/Porus (IMPORTANT!) ◦ This is what makes the clay light weight, because its surface area creates a lower density product Mixes well with concrete Freezing and High temperature Stability Low Density (light) High Resistance to pressure (incompressibility) (Lecaworld) Clay Composition: Clay is typically moist fine grained natural material Shape: No specific shape Texture: Usually sticky and plastic textured Color: Depends on impurities, weathering, and mineralogical composition.(Lecaworld) Clay Leca is used to expand the moisture retentive clay makes more dry, less dense material (can mix better) Gives it higher resistance to pressure as well as a lower density (Lecaworld)
Expanded lightweight concrete process Pyro-processing: Clay to Leca By heating shale, clay, or slate to temperatures in excess of 1800 to 2100 degrees F in a rotary kiln, ceramic aggregates are made. This causes the material to expand into an artificial lightweight aggregate. “Their cellular pore system gives these lightweight aggregates their low-particle relative density” (Lecaworld)
Structural Projects Image from http://floatingbuilding.comhttp://floatingbuilding.com Floor Slabs High Rise Buildings Image from http://www.concreteconstruction.net What is it used for?
Overall There are three purposes for light weight concrete: ◦ Lightweight and Insulating Grout, Non-Structural Lightweight Concrete, Structural Lightweight Concrete Concrete is classified based on the aggregates chosen to be in the mix (gives concrete specific properties) Through a process called pyroprocessing clay is turned into leca, which is then mixed with cement to create Expanded Clay light weight concrete. Benefits and Down sides: ◦ Expanded Clay lightweight concrete can prove to be significantly more expensive than normal weight concrete ◦ Can be an economical solution because less concrete and steel beam material is utilized due to smaller columns being needed for the design to withhold. ◦ Low permiability, concrete more recycleble, used to reduce a dead load It is typically utilized in the construction of high rise buildings, floating structures, floor slabs and bridges. (Geofill, NRMCA, Laterlite, Richardson)