Pool Plaster Types: Marble, Quartz and Pebble on a Spa Shell

Pool plaster vs pebble and quartz: laboratory and field specification matrix

In the Diamond Brite Installation Manual, marble-based finishes deteriorate due to the weak, soluble nature of marble aggregate and fine cement paste, whereas quartz aggregate is completely insoluble even in highly corrosive acid and polymer modification increases cement hardness.

How heated spa water and negative saturation index attack the cement matrix

Hydrated white cement forms calcium silicate hydrate (CSH) and calcium alumino-silicate hydrate (CASH) alongside soluble calcium hydroxide (CH), and CH makes up approximately 24% to 27% of fully-hydrated white cement.

The Interfacial Transition Zone (ITZ) around lights and PVC pipes contains significant amounts of calcium hydroxide and exhibits a higher water / cement ratio and greater porosity.

Per the NPC Technical Bulletin (citing ANSI/APSP balanced ranges), unbalanced water can dissolve components of the cement/aggregate matrix, resulting in leaching where etched areas appear around aggregate particles, tile inserts, and other interfaces.

Low calcium hardness, low carbonate alkalinity, and/or low pH attack the ITZ, and continued leaching can cause complete dissolution of the cement paste over time in those regions of the coating.

In the King Technology Langelier Saturation Index chart, Saturation Index = pH + TF + CF + AF - 12.1, where the Temperature Factor (TF) rises from 0.0 at 32°F, 0.1 at 37°F, 0.2 at 46°F, 0.3 at 53°F, 0.4 at 60°F, and 0.5 at 66°F to 0.6 at 76°F, 0.7 at 84°F, 0.8 at 94°F, 0.9 at 105°F, and 1.0 at 128°F.

In the same Langelier lookup chart, Calcium Hardness (CF) and Total Alkalinity (AF) factors at readings of 75, 100, 150, 200, 300, 400, and 800 are CF 1.5 / AF 1.9 at 75, CF 1.6 / AF 2.0 at 100, CF 1.8 / AF 2.2 at 150, CF 1.9 / AF 2.3 at 200, CF 2.1 / AF 2.5 at 300, CF 2.2 / AF 2.6 at 400, and CF 2.5 / AF 2.9 at 800.

While APSP acknowledges an acceptable Saturation Index range of -0.3 to +0.5 and states the ideal range is 0.0 to +0.5, the NPC further refines the ideal range to 0.0 to +0.3.

In Laticrete Design Manual Section 11 (Source: ANSI/APSP-11 2009), the formula with cyanuric acid is SI = pH + TF + CF + AF - CYA Factor - 12.1, where 12.1 is a constant applied for Total Dissolved Solids between 0 and 1,000 ppm and -0.3 to +0.5 indicates balanced water.

The National Plasterers Council notes that elevated cyanuric acid levels (CYA) will impact the carbonate alkalinity measurement, that only carbonate or adjusted alkalinity can be used to calculate the Saturation Index, and that higher salt levels can make the water more aggressive.

Under Water Chemistry rules, carbonate alkalinity is calculated by subtracting approximately 1/3 of the CYA (in ppm) from the total alkalinity (in ppm), avoiding a false indication that the water is balanced when it is in a corrosive condition.

When a heated spa shares circulation with a cooler pool through our spillover spa hydraulic loop and check valves guide, Pentair's MasterTemp manual warns that if pH is too low (over acid), item 2 is etching of the plaster alongside brown, blue, green, or almost black stains from corroded metal fixtures, and pH must not be tested when chlorine residual is 3.0 ppm or higher or bromine residual is 6.0 ppm or higher.

Water chemistry operating boundaries across industry manuals

Aggregate exposure methods, thickness tolerances, and commercial light reflectance

In the Diamond Brite Technical Information Sheet, crews must have one workman for every 300 square feet to properly expose Diamond Brite, and the exposure time is limited to approximately one hour.

Diamond Brite details four exposure options: Water Washing With Brushes, Acid Washing with a 25% solution of Muriatic Acid, Wet Acid Wash for 3 days, and Powerwash Exposure using 8 to 10 inches of water, 100% muriatic acid for 1-2 minutes, and a 2500 PSI pressure washer with a 45-degree nozzle held 12 to 18 inches away with 20% overlap.

For River Rok natural pebble finishes, each 80 lb. bag covers approximately 18 - 22 sq. ft. to a minimum thickness of 3/8 inch - 1/2 inch using 1 1/2 to 2 gallons (5.7 to 7.6 L) of water, and Water Washing With Brushes is the only approved exposure technique.

Per the Diamond Brite Technical Information Sheet, many building and health departments require commercial finishes to have a dry Lightness level (CIE L value) of 80.0 or greater and a wet Luminous Reflectance Value (CIE Y value) of 50.0 or greater (measured using ASTM D 4086, ASTM E1477, and ASTM E 1347) to reflect more than 50 percent of visible light.

In the Diamond Brite reflectance table, finishes meeting code 454.1.2.4, 15A NCAC 18A .2514, and the Model Aquatic Health Code (MAHC) threshold of greater than 6.5 include COMMERCIAL WHITE at CIE L 88.28, CIE Y 65.67, wet reflectance 81, and Munsell 9, while ONYX records 44.54, 7.71, 39, and Munsell 2.

Under the ASTM E903 standard test method for total solar reflectance (TSR) from 200 nanometers to 2500 nanometers, River Rok percentage readings are 9.6 for Emerald Black, 40.1 for Lucayan Blue, 66.6 for Imperial White, and 42.5 for Granite.

Pre-plaster substrate preparation, fixture beveling, and waterproof membrane handoff

Under SGM Pool Brite installation rules, crews must undercut existing plaster 2 inches below the tile line to a depth of 3/8 inch, verify that concrete shells have cured at least 28 days, and let SGM Bond Kote cure for at least 6 hours before plastering within 3-5 days.

Under Interior Finish Tolerances, a cementitious coating should have an average minimum thickness of 3/8 inch and an average maximum thickness of 3/4 inch, beveling up to adjoining materials greater than 3/4 inch and beveling down to plumbing, lighting, or adjoining materials that are less than 3/8 inch.

During placement, hot or dry shells trigger check or shrinkage cracking and delamination, so all materials and affected areas must stay above 50°F (10°C) and below 100°F (38°C) for 24 hrs. prior and 72 hrs. after placement while troweling to a final thickness of one-half inch (1/2 inch) (10 mm-12 mm).

When Calcium Chloride is used as an accelerator in Pool Brite, it must be fully dissolved in water and no more than 2% by weight of cement (about 1/2 lb. per bag) can be used, because overuse may cause discoloration.

When Diamond Brite is applied to exposed areas above water, water curing of exposed areas for 7 to 28 days will lessen the occurrence of shrinkage cracking, and blisters due to air trapped during troweling must be eliminated because they will fill with water and may delaminate during freezing temperatures.

For full-tile or glass-mosaic waterproofing assemblies detailed in our waterproof membrane systems under glass mosaic tile guide, Laticrete Design Manual Section 5.4 separates Non-Tiled Pool Finish Types (white portland cement and fine marble dust known as Marcite or Marbleite, quartz based plasters, and small river pebbles) and directs specifiers to DS 386.2 when cementitious waterproofing is installed under plaster.

Before scheduling plaster crews on a new concrete vessel, review our gunite and shotcrete shell thickness and rebar schedules guide to confirm that concrete shells have cured at least 28 days, existing plaster at tile lines is undercut 2 inches to a depth of 3/8 inch, and SGM Bond Kote cures at least 6 hours before plastering within 3-5 days.

Thirty-day startup water chemistry, brushing protocol, and visual acceptance

During the first thirty days (30) of initial startup, pH and alkalinity must be monitored and adjusted (if applicable) every three (3) to five (5) days and other chemicals monitored and adjusted (if applicable) every seven (7) to ten (10) days: First Day sets pH to 7.2 - 7.6, alkalinity to 80 - 120 PPM, and calcium hardness to a minimum of 125 PPM for 3 days (then 200-400 PPM); Second Day adjusts pH to 7.4 - 7.6 and total alkalinity to 80-120 PPM and does not add chlorine; Third Day adds 1.0 - 3.0 PPM chlorine and 30 - 60 PPM stabilizer.

Startup rules require owners to brush the pool walls and floor daily for the first two (2) weeks, do not vacuum the pool with a wheeled vacuum for 14 days, and do not install an automatic pool cleaner for 28 days.

For ongoing maintenance, the National Plasterers Council specifies testing one to two times a week for pH, total alkalinity, and chlorine, and once a month for calcium hardness, stabilizer (cyanuric acid), and TDS.

Under Interior Finish Tolerances, the pool should be full of clean water (ideally in a chemically balanced condition) for visual inspection, which should be conducted in the morning, the afternoon, or on a cloudy day, and should not be made at night.

Interior Finish Tolerances also explain that normal color variation (normal mottling) arises from differences in moisture content and the rate of cement hydration, and normal mottling or shade variation is not considered a failure or defect.

Pre-plaster and startup verification checklist

In the Pentair MasterTemp manual, spa water temperatures should never exceed 104°F (40°C), a temperature of 100°F (38°C) is considered safe for a healthy adult, soaking above 102°F (39°C) is hazardous during pregnancy, and thermostats may err by as much as 4°F (2.2°C).

1. 28-day concrete cure and 2-inch tile undercut: Verify under SGM Pool Brite rules that concrete shells cured at least 28 days, existing plaster is undercut 2 inches below the tile line to a depth of 3/8 inch, and SGM Bond Kote cures at least 6 hours before plastering within 3-5 days.
2. 50°F to 100°F ambient and substrate window: Confirm that all materials and affected areas stay above 50°F (10°C) and below 100°F (38°C) for 24 hrs. prior and 72 hrs. after placement to prevent check or shrinkage cracking and delamination at a final thickness of 1/2 inch (10 mm-12 mm).
3. 3/8-inch to 3/4-inch thickness and fixture bevels: Check under Interior Finish Tolerances that the coating maintains an average minimum thickness of 3/8 inch and an average maximum thickness of 3/4 inch, beveling up to materials greater than 3/4 inch and beveling down to fittings less than 3/8 inch.
4. Fill-water calcium hardness minimum: Verify that initial fill water is above 200 ppm calcium hardness (or above 150 ppm calcium hardness for some high-performance finishes) so soft water does not leach calcium hydroxide from the upper surface and weaken the cement binder.
5. 14-day wheeled vacuum and 28-day cleaner hold: Enforce the curing rule to brush the pool walls and floor daily for the first two (2) weeks, prohibit wheeled vacuums for 14 days, and prohibit automatic pool cleaners for 28 days.
6. One-third CYA carbonate alkalinity adjustment: Apply the rule of subtracting approximately 1/3 of the CYA (in ppm) from the total alkalinity (in ppm) to arrive at carbonate alkalinity, avoiding a false indication that water is balanced when it is in a corrosive condition.
7. After 28 days LSI 0.0 to +0.3 equilibrium: Maintain the schedule after 28 days with LSI between 0.0 and +0.3, Chlorine 1 to 3 PPM (noting above 4.0 ppm may cause corrosion), pH 7.4 to 7.6, Alkalinity 80 to 120 PPM, Calcium Hardness 200 to 400 PPM, Cyanuric Acid 50 to 80 PPM, TDS 300 to 1800 PPM, and Salt 2500 to 3500 PPM.

Frequently asked questions