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Concrete Waterproofing with Crystalline Technology

Crystalline chemicals improve concrete durability, lower maintenance costs, and extend building life cycles

January 2006
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By Stanley Stark, FAIA

Continuing Education

Use the following learning objectives to focus your study while reading this month’s Continuing Education article.

Learning Objectives - After reading this article, you will be able to:

  1. Understand how crystalline technology works with concrete to provide high performance waterproofing qualities.
  2. Explain the difference between porosity, permeability and the mechanics by which water is absorbed through concrete structures.
  3. Discuss how crystalline waterproofing technology improves the durability of concrete structures and reduces maintenance.
  4. Identify appropriate crystalline technology product applications for various types of concrete construction.
  5. Analyze how crystalline technology admixtures can impact building life cycle and project construction costs.

Credits: 1.00 HSW

This test is no longer available for credit

From foundations, floor slabs and exterior pre-cast panels, to water treatment facilities and underground urban infrastructure, concrete is one of the most commonly used building and construction materials. However, due to its composition, a mixture of rock, sand, cement, and water, concrete is often susceptible to damage and deterioration from water and chemical penetration.

These deleterious effects can be avoided through the use of crystalline waterproofing technology, which effectively improves the durability and lifespan of concrete structures, thereby reducing long-term maintenance costs. This article explores how crystalline technology provides a high level of performance to concrete mixtures, materials, and structures, and what design professionals need to know in order to specify and understand how this chemical technology will enhance building projects.

The Nature of Concrete

The aggregate base of a concrete mixture is formed by rock and sand. This cement and water mixture creates a paste that binds the aggregates together. As the cement particles hydrate, or combine with water, they form calcium silicate hydrates. The mixture then hardens into a solid, rock-like mass.

Concrete is also a water-based product. To make this mixture workable, easy to place, and consolidate, more water than is necessary for the hydration of the cement is used. This extra water, known as the water of convenience, will bleed out of the concrete, leaving behind pores and capillary tracts. Although concrete appears to be a solid material, it is both porous and permeable.

Water reducers and superplasticizers are used to reduce the amount of water in the concrete mix, and maintain its workability. However, pores, voids, and capillary paths will remain in cured concrete and can carry water and aggressive chemicals into structural elements that will corrode steel reinforcement and deteriorate concrete, thus jeopardizing the structure's integrity.

The Porous and Permeable Nature of Concrete

Concrete is best described as a porous and permeable material. Porosity refers to the amount of holes or voids left in concrete, is expressed as a percentage of the total volume of a material. Permeability is an expression of how well the voids are connected. Together, these qualities allow pathways to form that allow the movement of water into, and through, along with the cracking that occurs due to shrinkage.

Permeability, a broader term than porosity, is the ability of liquid water under pressure to flow through porous material. Permeability is described by a quantity known as the permeability coefficient, commonly referred to as D'Arcy's Coefficient. The water permeability of a concrete mix is a good indicator of the quality of the concrete for durability reasons. The lower D'Arcy's Coefficient, that is, the more impervious, the higher the quality of the material. Nevertheless, a concrete with low permeability may be relatively durable but may still need a waterproofing agent to prevent leakage through cracks.

 

Originally published in the January 2006 issue of Architectural Record.
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