Processed mineral additive for reducing concrete permeability and increasing strength

Abstract

A concrete additive includes expanded perlite with a volume weighted mean particle size of approximately 10-100 μm. The perlite further includes at least one additional component to improve workability and compensate for the natural tendency of expanded perlite to absorb water from the concrete mix. The additional component can include: water; a superplasticizer such as polycarboxylates, naphthalene sulfonate, and melamine sulfonate; or a hydrophobic compound such as salts of fatty acids, fatty acids, silanes, and siloxanes. The additive can be made in the form of a flowable powder or a flowable slurry. Concrete containing this additive displays superior properties to conventional concrete, including extremely high thermal resistance and high strength, low chloride ion permeability, and good early strength. The expanded perlite is a readily available raw material and the finished concrete is extremely cost effective for applications where a high strength structural concrete must withstand high temperatures.