The Green Movement

The green movement has caused changes in the concrete industry and possibly huge problems for the painting, coating, flooring or any industry that would require bonding to a concrete surface. The green movement is forcing concrete producers to increase the use of waste products, such as fly ash, a waste ash from burning coal. This leads us to the question: what is Pozzolan Portland Cement or Blast-Furnace Slag Portland Cement, or What is Green Concrete?

Green concrete is concrete made of less Portland Cement, replaced with the addition of Fly Ash, or other pozzolan.

Pozzolans are ashes and soils that, with the addition of water, form cement type abilities similar to Portland Cement.

The American Concrete Institute defines Natural and Artificial Pozzolans as: pozzolan, natural – a raw or calcined natural material that has pozzolanic properties (for example, volcanic tuffs or pumicites, opaline cherts and shales, clays, and diatomaceous earths). Pozzolan, artificial – materials such as fly ash and silica fume.

The problems?
The addition of Fly Ash and Silica fume adds bonding strength to the cement paste and is excellent to a point, but also adds fines to the mix that, with agitation such as steel troweling, move to the concretes surface. These fine particles on the surface of any concrete product retards bonding ability of flooring adhesives, paints coating and even other cement products such as patching compounds. Concrete with high percentages of pozzolans become brittle and lends to excessive crack.