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The Many Faces of SRWs
By Kurt Mee Commercial Wall Specialist Pavestone Company -- Denver, Colorado






One of the newest technologies eliminates the split face look and replaces it with the look of stacked rock. This process involves specialized production capabilities. With the ability to make multiple blocks in one mold, each block can have its very own unique look. Currently the products are available in four-inch systems. Inset: Natural Impressions(R) Ashlar Stone


Presently, the concrete segmental retaining wall blocks available display several distinctive faces. Due to various factors driving the necessary changes our industry is seeing, future faces of the retaining wall block offer countless possibilities. A look back in time reflects how the concrete segmental retaining wall has evolved to what it is today.

Retaining wall construction dates as far back as 5000-6000 B.C. Surrounded by soil, tree branches were placed in horizontal layers to help maintain the structure. Practice, at that time, instructed facing the mass with sun dried mud "blocks" or rock. Historic examples include the Persians who built great cities on top of retaining walls. The Pyramids of Egypt, the Ziggurats of ancient Mesopotamia (modern day Iraq), and even parts of the Great Wall of China were built on this principle. These construction practices developed the mechanically stabilized earth (MSE) construction commonly used today.

The SRWs have many "facing" personalities. The vertical height of the individual block establishes its overall scale, making it available in three dimensions. The first is the four-inch tall block, sold primarily through home improvement stores and specialty garden centers. These blocks are primarily for the do-it-yourself homeowner who is working on a "backyard lifestyle" project. Work on these projects involves small series of walls for planter beds or level sloping ground in minor applications. The second is the six-inch tall block used for larger landscaping projects. These six-inch systems can actually achieve heights of over fifteen vertical feet, when engineered and designed properly. The third face is the eight-inch tall block. The principle concept of the SRW system is to stabilize the earth behind the block, therefore reducing the lateral loading pressure naturally created by the soils. This provides for less weight in the face mass and allows use for more aesthetic facings.

Over the years, SRWs have seen rapid growth and development in most areas of the country. Their principle use has mostly been in large-scale site developments. Cost of the raw land plus the cost to develop the land are the main considerations in evaluating site viability. Flat land and underdeveloped sites have in most cases been purchased and developed. Now, developers find themselves looking at site properties with many developmental challenges. Multiple grades, expansive on-site soils, poor site drainage and site accessibility are typically encountered. All of these issues involve more capital expenditures in order to make the land usable.






Today, segmental retaining wall (SRW) block systems are designed and engineered under conservative design principles. The ancient rock facings have been replaced with prefabricated concrete manufactured to achieve high levels of compressive strength. For stability, geosynthetics interact with the retained soils behind the block facing. These blocks can be designed to create walls exceeding 70 feet in height and can carry substantial surcharge loadings such as bridges, buildings, and roadways. This type of wall is an MSE wall using high strength modular blocks.


SRWs Today

SRWs were introduced to the United States in the 1970s and, until recently, solution designs have been created mostly by the engineering community. An engineer is contracted by the owner/ developer to design a retaining wall. The engineering of SRWs is principally concerned with the structural capabilities of the product and not the aesthetics. This structural design premise did not lend itself to block face aesthetics. For many years the standard 8-inch by 18-inch straight face block became the status quo for the entire industry.

Fast-forwarding to today, the landscape of the SRW market is changing. Architectural design is one of the new driving forces for the SRW industry. Not satisfied with the looks of the past, architects are demanding more aesthetics to enhance their designs created for individual sites. These designs include multiple shapes and colors to satisfy their architectural desires.

Another factor driving change in the look of concrete segmental retaining wall blocks is the occurrence of graffiti, an epidemic hitting most metropolitan areas. The older straight-faced blocks are a prime target for this graffiti movement. With their vertical look and flat texture creating a "canvas effect". According to the Bureau of Justice, graffiti is the most common type of public property vandalism. The web site, www.graffitihurts.org, states graffiti attracts crime, drains tax dollars, decreases property value and even reduces business growth. Since many retaining walls are in new metro development areas, they become easy targets to graffiti artist. Annually, communities are spending millions of dollars trying to remove this blight.

Working closely with developers, designers, and municipalities, the block manufactures are creating new looks that are less appealing to the "would be" graffiti artist. By utilizing multiple faced products and colors together, designers can achieve new high quality looks for the walls while reducing the incidence of graffiti.

The industry is also working on ways to improve the look of block faces and achieve a more natural stone appearance. If this trend continues, the industry may eventually introduce the same manufacturing process to their tall wall product lines. Once this is achieved, architects will have a unique alternative to conventional SRW systems.

With the site developmental challenges before us in most communities, the SRW future is on solid ground. In addition to this growth, there has been exciting new facing designs to enhance SRW projects. Most SRWs are an integral part of today's developments providing wonderful resources for the private and public sector.






Replacing the old singular block style with the new multiple shape products creates a much less appealing structure to be painted on by graffiti "artists." The surface looks irregular to the "tagger", thereby taking away the smooth canvas appearance created by a straight block system.









Building Blocks

1980s: Decade when segmental retaining walls emerged as a landscape feature.

5000: Psi, the recommended strength for SRWs for New England sites, due to the harsh winters in the part of the country.

4: Feet. This is the height under which the combined weight of a segmental retaining wall can resist the weight of the earth being retained without reinforcement.

Source: Ideal Concrete Block




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November 18, 2019, 11:45 am PDT

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