Etching Deterioration The point of attack!

Presented by: Alan Smith NPC Annual Conference

February 9, 2018

1 – 3 Years After Placement

Cement Microstructure And Properties

Its mixed, its placed

and finished, its filled.

In The Beginning.

A typical swimming pool cementitious surface consists of a mixture of white hydraulic Portland cement ASTM C150, white sand (typically limestone, quartz silica) and water. The five principle compounds that make up the cement paste when cement and water are combined are tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A) tetracalcium aluminoferrite (C4AF) and Calcium hydroxide (CH). Of these principle compounds, calcium hydroxide (CH) which makes up approximately 24%-27% of the new compounds, is the most soluble. Calcium silicate hydrate (C-S-H) which makes up approximately 60% of the new compounds is the densest and strongest. When all the ingredients are mixed together you have aggregates, cement paste, void spaces shrink cracking and interfacial transition zones (ITZ) that make up the total cement matrix. Interfaces, shrink cracks and transition zones are part of the basic microstructure and properties of all cement products.

Hydration = Chemical Changes

Portlandite is a rare oxide mineral, the naturally occurring form of calcium hydroxide. It is the calcium analogue of brucite. It was named Portlandite because the chemical calcium hydroxide is a common hydrolysis product of Portland cement. Mohs Scale Hardness: 2

Portlandite

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The other polymorphs are the minerals aragonite and vaterite. Calcite has a wide range of applications, such as soil remediation, soil stabilization and concrete repair. Mohs Scale Hardness: 3

Calcite

Larnite is a calcium silicate hydrate mineral of general chemical formula. Larnite occurs as an alteration mineral in metamorphosed limestone and. It occurs in hydrated cement paste Mohs Scale Hardness: 6

Larnite

Calcium Hydroxide Forming Around ITZ And Void Areas.

A Closer Look. Hydration Components

Notice the Calcium hydroxide compounds next to the aggregate in the ITZ .

Calcium Hydroxide | Calcium Silicate Hydrate

Calcium hydroxide is a very porous unorganized large plate like structure. The C-S-H is much denser and organized structure.

Calcium hydroxide fills in around sand aggregate and craze cracks. If on the surface, it will be the first compound etched.

Cosmetic/Surface Failure

ITZ

Localized Attack

The Importance Of The Saturation Index

Negative Positive

Cal Poly Studies

Cal Poly Studies

Industry Collaboration

Industry collaboration: IPSSA, UPA, APSP, Material Manufacturers,

Builders and even a few Plasterers.

Going The Extra Mile

Going the extra mile repeatedly to see if calcium chloride levels or finishing practices have an impact on etching deterioration (spot etch).

Going The Extra Mile

Materials, Technique, Or Water Environment

Etching deterioration in balanced and aggressive pools. Same materials, same finishing technique.

Most Important! Practical Solutions

SOLUTIONS

MATERIALS

• Pozzolans • Quartz • Pebble • Pigments

HAPPY CUSTOMERS

MAINTENANCE

• Start-Up • Saturation Index • Cyanuric adjustment • Test Kits

Selective Rusting in a Swimming Pool Environment

Selective Rusting in a Swimming Pool

Environment

Selective Rusting in a Swimming Pool

Environment