The Concrete Manufacturers Association (CMA) warns that millions of rand is being squandered on concrete block paving (CBP) roads simply because of poor specifications. The association, in an opinion piece published on its website, reports that “in many instances paving is simply specified as being 25MPa with no reference to the SABS mark”. This results in paving failure, mainly in shopping centres, office parks and housing developments – where paved surfaces tend to be regarded as simple, not requiring an engineering design.

The primary reason for non-adherence to SANS 1058:2012 (the new CBP standard), according to John Cairns, civil engineer, independent paving consultant and CMA Technical Consultant, is that a number of industry professionals remain ignorant of the difference between the old and the new CBP standards or, in some cases, are unaware of the change in standard. SANS 1058:2012 criteria is based on tensile strength and abrasion-resistance while the outdated CBP standard is compression resistance-based.

“Many engineers and landscape architects who design paved roads are unaware of the most important specification criteria when using CBP,” says Cairns, “and specify projects based on compression strength and omit to take surface abrasion into consideration.”

According to Cairns, the reason the standard was changed is because, as paving blocks do not crush under load, compression testing is an inadequate performance indicator. “In fact, paving blocks can have extremely high compression strength but poor abrasion resistance,” he says.

“In most instances paving blocks fail either by cracking and splitting or through surface abrasion due to factors such as particle distribution and binder percentages. These properties are addressed in SANS 1058:2012,” Cairns points out. “This lack of awareness is resulting in sub-standard CBP installations and unnecessary remedial expense.” He adds that most paving breakages occur in shopping centres, office parks and housing developments, where paved surfaces tend to be regarded as simple, not requiring an engineering design.

Cairns warns that CBP roads can also collapse if not designed for construction loading. He points out that breaks often occur on housing estates where roads are designed to handle light traffic only. “Roads are usually built before other construction takes place which means they must support heavy-duty trucks and other construction equipment while the estate is under construction. This extra weight obviously causes damage. In addition, damage is caused by sand and stone spillage, particularly at traffic circles where the majority of braking and turning takes place.”

There are several solutions, according to Cairn. Build road bases to handle construction loads, paving them only when construction is complete, or install complete roads before construction commences. If the latter, they should be built with paving blocks to handle heavy-duty traffic. Thereafter, the contractor must ensure the roads are kept free of sand and stone, or assume responsibility if damage occurs.

“By contrast,” Cairn concludes, “industrial CBP surfacing is generally designed correctly, especially where the paving provides a critical functional element such as the working surface of a container yard or steel mill.”

Birkenmayer’s Monika Howarth says that Birkenmayer endorses the use of the new CBP specifications, and that the engineering behind Birkenmayer Block and Brick Making machinery and equipment adheres to the highest standards for high quality blocks and bricks.

“At Birkenmayer we believe in supplying mixing and block and brick making equipment that produces end products of the highest quality,” Howarth says. “We have clients who can bear testament to the durability, reliability and consistency of our equipment. In fact, one of our clients has been using Birkenmayer machinery for over three decades and has publicly stated they will only ever use Birkenmayer block and brick making machinery, further proving our commitment to industry, safety and quality standards.”