Cement Types

Shown below are the two basic cement types - Portland cement and Pozzolanic cement. The images represent what you would see if each were viewed under a microscope.
 

Manufactured (or Portland) Cement: Cement made from pulverized “clinker” (kiln-fired limestone)		Pozzolanic (or Pozzuolanic) Cement: Cement made from volcanic ash or fly ash
Portland Cement Crushed (angular) Larger particles Less variation in size Looser matrix		Pozzolan (Fly Ash) Silica (glass) spheres Small particles Varied size particles Dense matrix
The Portland cement that currently defines the industry standard is comprised of a loose matrix of aggregate and kiln-fired limestone. This material is characterized by a loose and open matrix that makes Portland cement-based products very porous. This porosity makes the material susceptible to liquid and gas intrusions which ultimately contribute to the break down of the material’s integrity over time.		The Pozzolanic cements are comprised of fly ash or volcanic ash and a chemical binder. This combination produces a very dense matrix that has a slight porosity, thereby dramatically reducing the material’s susceptibility to gas and liquid intrusion thereby making it a more durable repair material.