Echo Prestress has erected a security wall built with its own prestressed hollow-core concrete slabs at its prestressed hollow-core factory in Chloorkop, Gauteng. Constructed in two sections, the wall is 275m long and at its highest point, reaches 5,4m. A 0,6m section of the wall is buried below ground. The walls comprise five tiers of interlocking slabs measuring 6m x 1.2m x 150mm, which were placed horizontally and secured into position between vertical steel columns.
Echo Prestress marketing director, Melinda Esterhuizen, says there are several advantages to this type of walling, speed of construction, being one of the major considerations, cost being another.
“The current cost of building a security wall using prestressed hollow-core slabs, is approximately half that of an in-situ wall offering the same properties; an in-situ wall would take two to three times as long to build with no advantage gained in strength or durability. Moreover, precast walling has no requirement for shuttering or propping, onsite curing, formwork or grouting, and the construction rate is approximately 50 linear metres per day (eight hours),” says Esterhuizen.
The Echo wall comprises 50MPa concrete which means even jack hammers would struggle to break through it. “Intruders cannot scale it, dig under it or break through it without making a great deal of noise and taking a very long time.” Esterhuizen advises that soil conditions determine the type of foundations required for this type of walling and whether the slab placement should be horizontal or vertical.
“Clay, collapsible soils, high-water tables and so on require horizontal installations, whereas better soil conditions are best suited to vertical applications. Some horizontal placements may also require piling. “Wind resistance and stormwater drainage are other design considerations and so is impact resistance which determines maximum wall height and slab depth. Stormwater drainage must be properly engineered and weep holes, generally 100mm in diameter, should be placed strategically for good drainage. Esterhuizen added that precast security walls also have some green attributes.
The concrete slabs and steel support columns are both 100% recyclable and reusable. The wall itself has a very long life span, is maintenance free, and other than occasional cleaning, no other maintenance is required. However, the steel columns do need rust protection.”
Esterhuizen concluded by saying that a key to the success in constructing this type of security wall is a very close working relationship between the design, engineering and construction professionals. Echo offers design solutions for both precast flooring and security walling applications. Contact Melinda Esterhuizen on (011) 589 8800 or 083 605 0077.