A high-strength security wall has been erected out of Echo Prestress’s own pre-stressed, hollow-core concrete slabs at its factory in Chloorkop, Gauteng.
A high-strength security wall has been erected out of Echo Prestress’s own pre-stressed, hollow-core concrete slabs at its factory in Chloorkop, Gauteng. The wall comprises 50MPa concrete which would have even jack hammers struggle to break through it.
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 the ground. It consists of five tiers of interlocking slabs measuring 6m x 1,2m x 150mm, placed horizontally and secured into position between vertical steel columns.
According to Echo Prestress marketing director, Melinda Esterhuizen, it is considerably more economical to use pre-stressed, hollow-core slabs than an in-situ wall offering the same properties, which would take two to three times as long to build with no advantage gained in strength or durability.
“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),” she adds.
Soil conditions typically determine the type of foundation and whether the slab placement should be horizontal or vertical. Where there is clay, collapsible soils and high water tables, horizontal installations are necessary, while better soil conditions are suited to vertical applications.
Wind and impact resistance determine wall height and slab depth, and influence the placement decision as some horizontal installations require piling.
Another consideration highlighted by Esterhuizen is that storm-water drainage must be properly engineered and weep holes, generally 100mm in diameter, should be placed strategically for good drainage.
“The concrete slabs and steel support columns are 100% recyclable and reusable,” she states. “The wall itself has a very long lifespan, is maintenance-free, and except for occasional cleaning and rust protection for the steel columns, no other maintenance is required.”
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