Building with Concrete Home

May 19, 2000

Waterproof concrete: Seeing is believing for NW builders

Caltite, an additive invented more than 40 years ago, has recently become a hit with builders and designers. From the Seahawks Parking/Exposition Hall project to a parking garage at Northgate mall, the material is being used throughout the Northwest.

By RANDY KOOLEY
Glacier Northwest

When an architect at NBBJ investigated the additive "Caltite" three years ago for use in a concrete wall exposed to salt spray on the Alaska coastline, Seattle-based Glacier Northwest was asked to provide the product.

DOT shotcrete tunnel Colorado Department of Transportation specified the Cal-tite System on the state’s Bear Creek Tunnel because it was the only warranted technology. Caltite was used as a tunnel lining to prevent water transmission and deadly icicle formation. The original tunnel lining leaked profusely; however Clatite shotcrete is dry, with no damp spots despite recent rains. The Colorado DOT has expressed interest in using the technology on future tunnel work.

The impressive membrane-free waterproofing and corrosion resistance claims made on the Australian manufacture’s Web site (cementaid.com), however, met with a heavy dose of skepticism from the Product Research and Technology Group at Glacier Northwest.

If available, waterproof concrete would eliminate many of the problems associated with traditional membrane or spray-on coating systems such as improper installation, punctures, weather sensitivity, damage due to back-filling, other trade’s work. But it sounded too good to be true. So, Glacier sent a team of concrete experts on a worldwide tour to investigate the product first hand and get to the bottom of the story.

What they found was that the technology wasn’t new. In fact, Peter Aldred invented it in 1958. Since then, over ten million cubic yards of Caltite waterproof concrete has been used successfully around the world. The team visited sites in Manila, Malaysia, Australia, Hong Kong and the United Kingdom and found that structure after structure built with Caltite was performing as advertised. The team was impressed, but the question remained if the technology would work in the United States.

Arrangements were made to test Caltite concrete in Seattle through a local independent laboratory, Cascade Testing Laboratory in Kirkland. Additionally, a national independent laboratory, CTL in Skokie, Ill. was invited to investigate the performance claims with materials available in the United States.

The extensive test program was structured to verify workability, set time, strength development, absorption, freeze-thaw durability, pumpability, drying shrinkage and permeability. The local testing program confirmed to Glacier’s satisfaction that waterproof concrete using Caltite was not only a reality, but also its performance could be guaranteed.

Glacier signed a North American distribution agreement with Cementaid International and formed a new operating unit named the Caltite Concrete Group. Project specifications by Northwest architectural and engineering firms soon followed and several major projects have utilized the Caltite Waterproof Concrete System.

Caltite at work in the Northwest

The Stadium Exhibition Center features a waterproof roof, built with Caltite concrete. No membrane was used on the entire 150,000-square-feet. Zero leaks confirmed in water testing; and the Caltite system reduced cracking by over 90 percent compared to regular concrete on above decks, according to Glacier. Immediate cost savings versus using membrane: $150,000. Thirty-year cost savings to owner: an estimated $2 million.

Skilling Ward Magnuson and Barkshire(SWMB), a Seattle engineering firm, specified Caltite for the Stadium Exhibition Center project. Turner Construction placed close to 4,000 cubic yards on the parking garage decks that serve as the roof of the exhibition space below without the use of a membrane. The initial construction cost savings were significant, but the real savings are derived by the owner from the reduction in long term maintenance and membrane replacement costs over the service life of the structure.

The Colorado Department of Transportation specified the Caltite System for use in a leaking mountain-pass tunnel that had caused many problems throughout its history, including the unfortunate death of a motorcyclist that hit an icicle in the road that had fallen from the frozen ceiling. Caltite shotcrete was applied to the entire tunnel face by a local contractor to shut down water transmission and remedy the dangerous situation.

In Bellevue at the new Civica Office Commons project currently under construction by Sierra/Wright, LLC, DCI Engineers of Bellevue approved Caltite concrete for a secondary fire-suppression water holding tank located in the interior of the building. The water in the large all-concrete tank is used for the building’s fire-sprinkler system in the event that the main water supply is damaged in an earthquake.

Lease Crutcher Lewis is building a new parking structure for a large national retailer at the Northgate Mall. Caltite is being used to waterproof parking garage decks over the main retail floor space. SWMB utilized the experience they gained on the Seahawk’s structure and replicated it on the design for this new building.

The new Elliot Hotel adjacent to the Washington State Convention Center features a ballroom, and street level shops protected by Caltite concrete. R.C. Hedreen Co. used Caltite waterproof concrete instead of traditional membranes on the pan decks of these mission critical areas of the building to speed up the construction schedule. Stoneway Concrete, based in Renton, delivered the ready-mix out of their Seattle plant.

Caltite’s momentum and acceptance in the U.S. engineering and architectural community is growing rapidly, as they along with building owners and construction firms become familiar with the tremendous cost, time and durability advantages waterproof concrete has over traditional "wrapping" methods of waterproofing.

Projects are under consideration throughout the Western United States from Los Angeles to Denver. The San Francisco Bay area is a particular hotbed of activity with product testing starting at several ready-mix concrete suppliers in mid-May. The California Department of Transportation has begun investigation and taken the first steps towards laboratory testing of Caltite for infrastructure upgrades in the California highway system.

Concrete is a sponge

Waterproof Shotcrete Wall Caltite waterproof shotcrete was used on Pierce County Tacoma Dome II Intermodal Station. The waterproof shotcrete wall has no cracks; Caltite shotcrete was used on permanent 8-inch facing.

Normal concrete has an amazing ability to wick water through its internal capillary network, delivering moisture from the "wet-side" to the "dry-side" of any concrete placement. This capillary suction phenomenon is impressive. Normal concrete in a standard absorption test will absorb three to 6 percent of its weight in 25 minutes. A square foot of wall is capable of absorbing a quart of water in an hour. This capillary suction presents a challenge for owners seeking a dry, habitable space for building occupants. Basements become damp and malodorous, leaking roofs destroy ceiling systems, elevated parking decks drip lime-saturated water on to cars parked below. For building designers and owners this problem of water transmission often becomes a nightmare.

Tried (but not always true) responses

To combat this phenomenon, designers in the United States have used membranes and coatings applied to the exterior of any vulnerable concrete. Membranes and coatings when properly applied by skilled, conscientious, workers offer excellent protection. Unfortunately, these systems present several problems and risks to the owners that use them. Membranes and coatings can have a temporary life span and often require periodic replacement and maintenance. Penetrations in the concrete can be difficult and time consuming to seal. Weather can cause project delays because application is often moisture and temperature sensitive and membranes and coatings are extremely susceptible to damage by other trades or back-filling operations. These problems and others, are why waterproof concrete is so appealing to designers, contractors and owners and the reason Caltite is gaining rapid acceptance.

How Caltite works

When fresh concrete is placed, consolidated and starts to cure the water used for mixing and for making it workable in the field leaves the concrete through a process called "bleeding". As the ingredients in the concrete settle, minute capillary systems are formed in the concrete matrix that allow the water to escape. These capillaries become permanent pathways for water and anything dissolved in the water, like aggressive chemicals, to re-enter the hardened concrete. Also, as water leaves during the curing process the concrete shrinks. The more water used, the more capillaries formed and the more the concrete shrinks. So the first step to making waterproof concrete is getting as much water out of the fresh concrete as possible. Doing this minimizes the formation of capillaries and the amount it shrinks.

To accomplish this the concrete mix is modified from a "normal" concrete by introducing a chemical called superplasticizer to reduce the water required for mixing and creating a mix that has low shrinkage characteristics. The superplasticizer disperses the cement in the concrete and makes it behave like concrete with more water. This mix is commonly referred to in the concrete industry as a low-shrink or "LS" mix.

Underground Caisson Port of Portland Caisson project also used Caltite concrete, which was poured into a mammoth Caisson form, later submerged. The structure will handle sewage outfall from Portland International Airport. According to Port officials, the traditional "membrane wrapping" approach would not have worked because of abrasion during the submersion process.

Caltite is then added as a liquid to the LS concrete at the concrete batch plant at six gallons per cubic yard. This liquid has two distinct waterproofing components that act on the concrete matrix. A hydrophobic component, which impacts the surface tension of water, integrates a water-repellent, non-absorptive material throughout the entire mass of concrete. This material effectively lines all of the capillaries in the concrete. A second capillary and pore-blocking ingredient of suspended polymer-particles form a physical plug when the concrete is subjected to water pressure.

In the field, construction joints and penetrations are sealed with conventional water-stop products such as sodium-bentonite according to standard details provided by the manufacturer. The Caltite Waterproof Concrete System has a ten-year performance based warranty so an on-site quality assurance representative from the Caltite Concrete Group is provided to inspect water-stop installation and monitor product quality, placement, and curing operations.

How to deal with cracks that might appear is usually the first question designers want answered about Caltite. Because Caltite is an LS mix design shrinkage is minimized tremendously. Any crack that occurs and leaks is remedied using proven conventional repair methods such as epoxy injection or routing and sealing with waterproof sealant. Once the crack is sealed, the integral waterproof concrete shuts down other escapes routes and will not allow further water transmission.

This proven concrete technology used in other parts of the world since the 1950’s finally made its way to the North American construction market via the world wide web.

The U.S. engineering community has eagerly embraced the advantages their foreign counterparts have enjoyed by using waterproof concrete for years. Owners and contractors are quickly realizing that there is a faster, reliable, more economical way to deal with a frustrating, costly challenge they have all battled for years. Waterproof concrete is a reality, and it will soon be coming to a building near you.

Building with Concrete home | Special Issues Index