{"id":2198,"date":"2014-01-16T10:56:52","date_gmt":"2014-01-16T15:56:52","guid":{"rendered":"http:\/\/www.constructionspecifier.com\/?p=2198"},"modified":"2017-01-17T15:52:02","modified_gmt":"2017-01-17T20:52:02","slug":"protecting-infrastructure-from-major-floods","status":"publish","type":"post","link":"https:\/\/www.constructionspecifier.com\/protecting-infrastructure-from-major-floods\/","title":{"rendered":"Protecting infrastructure from major floods"},"content":{"rendered":"
\"All<\/a>
All photos courtesy Kryton International<\/em><\/figcaption><\/figure>\n

by Jeff Bowman, B.Sc., Greg Maugeri, and Sarah Rippin
\n<\/b>Major flooding has dominated international news in recent years. While it may not be occurring more frequently than it was 50 years ago, due to growing infrastructure, the impact is certainly greater. Since 1949, the U.S. population has doubled, leading to a rapid increase in the construction of the urban environment. Most cities are unprepared for these rare increases in water levels\u2014initiatives to protect infrastructure from major damage too often occurs only after the destruction.<\/p>\n

<\/a>Concrete is the modern world\u2019s most commonly used building material, employed twice as much as other major building materials\u2014steel, aluminum, wood, and plastic\u2014combined.1<\/sup><\/a> Concrete walls naturally protect against structural damage that can be caused by the effects of nature.<\/p>\n

Looking back in history, many century-old structures stand longer than those erected in the last 50 years. This is largely due to reinforcement methods\u2014instead of using solid stone, most U.S. infrastructure contains reinforcing steel embedded within poured concrete. As the priorities of construction methods shift to increase productivity and streamline scheduling, long-term durability often takes a backseat.<\/p>\n

Feeling the effects of flood damage<\/b>
\nIn 2012, Hurricane Sandy ravaged the Atlantic coastline. The ferocious storm was among the worst disasters to ever hit the United States, causing tens of billions of dollars in damages and losses. The storm surged more than 4 m (13 ft) above the average low tide, leaving millions without power, causing severe flooding, and leaving properties destroyed.<\/p>\n

One such flooded building happened to house the server farm for a well-known company\u2019s global financial transactions. The server farm was located in a large warehouse building on West Street in Manhattan, more than two blocks from the Hudson River.<\/p>\n

The most damaging issue in the storm\u2019s aftermath was the street-level power plant running the server infrastructure was dramatically flooded. The mechanical room took 750 mm (2 \u00bd ft) of flooding during the hurricane, which was foreseen by neither owners nor builders when the servers were installed.<\/p>\n

After the waters receded, engineers worked with waterproofing experts to come up with a way to protect the vital systems from potential flooding in the future. They opted to surround critical systems with waterproof concrete half-walls that could stand up to hydrostatic pressure.<\/p>\n

\"For<\/a>
For this Manhattan server room project, the concrete-to-concrete joints of the walls were constructed using the same crystalline technology to fully tank the room. To provide extra protection, a slurry coat containing the same crystalline properties was applied to the outside of the walls.<\/span><\/figcaption><\/figure>\n

Even under normal circumstances, if soil around a below-grade structure\u2019s foundation is saturated with water to 1 m (3 ft) or more above the ground level, the water\u2019s force causes pressure on the concrete. The walls absorb the moisture like a sponge, leading to cracks and ensuing water infiltration, rebar corrosion, and mold. In a flash flood, similar water pressure is applied to concrete structures.<\/p>\n

Waterproofing concrete from the inside out<\/b>
\nThe project team knew waterproofing the server farm would require a robust assembly that could withstand the sudden onset of a large volume of water. Typical concrete structures built in the past 50 years are waterproofed solely on the positive side (i.e.<\/i> wet side) using surface-applied paints or membranes. These surface barriers are vulnerable to damage during construction, which can lead to waterproofing failure. In the case of the server farm, the water pressure of a flash flood (and the debris it carries) could damage a membrane and leave the servers vulnerable at the most critical moment.<\/p>\n

The slow effects of water damage to an aging building can be accelerated by flooding, which adds force to aging materials and pushes moisture into concrete. This moisture stays within the concrete even after the building is cleaned up, and can cause mold and mildew growth over time. The moisture can also collect around the steel reinforcing rebar within the concrete, causing corrosion that spreads throughout the structure. Additionally, the rebar expands as it corrodes, cracking the concrete and adding to the deterioration.<\/p>\n

To make concrete truly \u2018waterproof\u2019\u2014which means both preventing water passage and resisting hydrostatic pressure\u2014many contractors have embraced a long-term, permanent approach. Using an integral system, usually in the form of a powdered admixture added directly to the concrete itself, the entire mass of concrete can be made the waterproofing barrier. The system should include properties which work to protect steel from corrosion, saving structures which incur water damage fewer repair or replacement costs down the road.<\/p>\n

In late 2010, the American Concrete Institute (ACI) published a new report on chemical admixtures for concrete called ACI 212.3R-10, Report on Chemical Admixtures for Concrete<\/i>. This document contains a new chapter focused entirely on permeability-reducing admixtures (PRAs). Chapter 15 embodies research dating back nearly five years, with volunteers from across the industry spending countless hours and untold effort into its development.<\/p>\n

The result is a valuable resource for concrete users, with the greatest value of the new chapter being its clear categorization of permeability-reducing admixtures into two divisions:<\/p>\n