Tarmac Topblock clariry new EU standards

New EU Standards for both aggregate and aircrete blocks set to be introduced in April 2006, are likely to cause some confusion in the construction industry according to Tarmac Topblock.

The new EU Standards for both aggregate and aircrete blocks set to be introduced in April 2006, are likely to cause some confusion in the construction industry according to Tarmac Topblock technical manager, Colin Marshall, who highlights changes in the classification of dimension and strength as the most important developments to overcome when dealing with block specification.

Colin: "Given that this is the first time in 25 years that a change in our manufacturing standards - due to European harmonization - has been thrust on our industry, a period of familiarisation is required for specifiers and users of concrete blocks".

"Replacing the old BS 6073-1, the new standards comprise BS EN 771-3 for aggregate concrete units, and BS EN 771-4 for aircrete units".

"Although these standards are set to unify the block industry throughout the EU, in doing so, they will change the way UK blocks are defined and this is where the confusion may set in." "Currently in the UK the dimensions of blocks are defined in order of length, height and thickness, however with the new standards, customers will be presented with block dimensions in length, width (replacing 'thickness') and height".

"Similarly the new standards will change the way compressive strength is measured and quoted".

"Up to now, in the UK, we have tested compressive strength using blocks that have been saturated and mortar capped".

"However, for the new standards a dry test is required with a choice of unit surface preparation".

"Although fundamentally this change only adds 4% to the current values quoted, the most popular block strengths of 3.5 and 7.0 N/mm2 will be changed to 3.6 and 7.3 N/mm2 respectively".

"Higher strength blocks will also have to be quoted at slightly enhanced levels".

"Building Regulations as well as design codes such as BS 5628-1 are already adopting these modified strengths in the structural guidance they provide in the design of masonry walls, so in practice familiarisation and understanding has already started to take place".

"The only other area that is set to confuse the customer is a new classification placing blocks into one of four groups".

"This has no real significance in the short term but will do so in the future when Eurocodes are adopted".

"The groupings refer to the unit's void content and characteristic strength values are assigned depending on the unit's grouping and compressive strength".

"For customers in the UK, blocks described as solid will become Group 1 units with cellular and hollow blocks (depending on void content) described as Group 1 or Group 2 units".

"Group 3 and 4 units will cover the blocks not commonly used for construction in the UK, so will not feature readily in the ordering process".

"Therefore taking dimensions, strength and groupings into the new definitions for blocks, customers and the industry will have to recognise the need for these and ensure that both specifications and orders for blocks reflect the new requirements".

"Finally from a customers perspective, the revision of a further three tests required by the standard for checking dimensions, determining product density and moisture movement, will have little impact on the information vital to the customer, however manufacturers will have to make this information available and explain how the tests are conducted".

"In order to reduce the potential for confusion, at Tarmac Topblock we will be defining all of the information required by the new standards, with revised literature showing block dimensions and sizes in both the BS6073 and new BS EN standards".

"We will also be highlighting key areas for potential confusion and training staff to explain the impact of the new standards.".

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