Paving producers that hold the SABS (South African Bureau of Standards) mark for concrete block pavers (CBP) tested and approved to SANS 1058, have 12 months in which to comply with the revised standard, SANS 1058 2010, which was published officially by the SABS in March.
The revised standard was drafted jointly by the SABS and the CMA (Concrete Manufacturers Association) and replaces the old compression-based standard to include three new performance measures: tensile splitting, abrasion testing and water absorption. According to Hamish Laing, CMA director, SANS 1058 2010 will offer property owners, developers and specifiers a more accurate comparison of performance among the various pavers on the market.
“A revised standard was required because of the critical role that shape and size play in determining the strength of a paving block. The old standard only defined what the compressive strength should be – an average of 25MPa for most applications – but made no reference to shape or thickness required in paving blocks. The diversity in shape and size of CBPs today called for a more relevant performance-based testing regime.
“Before making our recommendations on the revised standard, we conducted research which showed that paving blocks are not crushed under load but rather break up through excessive point or line loads. Our further research on the relationship between the compressive strength and the tensile splitting tests resulted in a thickness factor being taken into account in the revised standard.
“We also found that there is no relationship between compressive strength and abrasion resistance. In the past it was thought that higher compressive strength equated to higher abrasion resistance, but this has proved false. In fact, we found that blocks of 59MPa can have very poor abrasion resistance, whereas those of only 25MPa can have excellent resistance. Subsequent tests demonstrated that even low-grade blocks with a good topping layer can offer high abrasion resistance, proving that topping layers do more than offer colour variation,” says Laing.
The CMA investigated various abrasion resistance testing systems around the world and opted for the Australian/New Zealand test model which proved to be best suited to local performance conditions.
Laing says the water absorption test also forms part of SANS 1058 2010 because CBPs with low absorption rates tend to offer better durability. “Durability is closely allied to strength and abrasion resistance,” he adds. The CMA strongly recommends that specifiers in the public and private sectors adopt the revised standard as soon as possible. Most CMA producer members are already geared to test their products in line with it. Two accredited laboratories have been established to perform independent tests, one belonging to the SABS and the other to CMA member, Soilcon.