Aggregate concrete blocks will have to comply with a new European Standard –BS EN 771-3- from April 2006 when the current standard BS 6073-1 is withdrawn. The Concrete Block Association (CBA) has participated in the development of BS EN 771-3 to ensure it meets the needs of designers as well as constructors and regulators.
Although it is not expected to have any direct impact on the type and use of aggregate block products that are currently used, there are nevertheless some changes that effect the way that products are tested and specified.
Compression Tests
One of the key changes will result from the way that blocks will be tested for compressive strength. The new definitive test calls for blocks to be tested dry with a choice of methods for capping the blocks. Compared to the BS 6073 method of requiring blocks to be tested in a saturated condition a higher apparent blocks strength will result, in fact about 4% higher for common block strengths such as 3.5 and 7 N/mm2. Thus 3.5N blocks will be re-classified as 3.6 N/mm2 and 7N/mm2 blocks will become 7.3N/mm2. Current design codes such as BS 5628:Part 1 are being updated to reflect these changes so there is a logical connection between manufacturing specifications and the requirements of designers.
Product Dimension Consistency
A small but important change is that the dimensions of blocks will have to be declared in the order of length, width and height, as opposed to the current order of length, height and width. The reason for this change is purely to ensure consistency of declaring product dimensions across a range of European product standards. Those responsible for measuring and ordering blocks will need to familiarise themselves with this change.
To assist specifiers and users of aggregate blocks in the implementation of this new standard, the CBA has produced an informative guide ‘Understanding BS EN 771-3: Aggregate concrete masonry units’.
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