Standards for Natural Stone
As expected a number of drafts prepared by TC246 Natural Stone were agreed at the Plenary meeting in Carrara, June 2000). This means that 28 standards from TC246 will have reached or passed the prEN stage. This includes all of the test methods required for the specification standards and the mandates with the exception of slip resistance which is currently covered by TC178, this has been redrafted by TC246 and approved for enquiry at the October Plenary Meeting of TC246. The only area in which delays are continuing to occur is the completion of the drafts specifications for the different product groups (blocks, slabs, cladding, tiles, stairs and monumental masonry) which were discussed at length in Milan in October 2000. Revised versions were prepared by the Secretariat and these were discussed and finally agreed at a meeting in February 2001, these will now be sent for Unique Acceptance Procedure.
TC178 (Paving, Setts and Kerbs) has made good progress with the issuing of the ‘market standards’ BSEN 1341, BS EN 1342 and BS EN 1343, and the submission of the harmonised drafts to CEN for the Unique Acceptance Procedure (UAP). The results of the UAP show that two standards have been approved with a result still awaited on the third one. These are some of the first harmonised standards that have been approved to provide the basis of CE marking for construction products.
The tests and the specification for masonry produced by TC125 have been published and the draft of the harmonised specification has been discussed at a Task Group Meeting in March 2001.
There has been no progress on TC128 SC8 which deals with natural slate and the position remains unaltered with the test methods published and the specification being prepared for formal vote.
Progress of Technical Committees
Technical Committee 125 – Masonry Units
This Committee covers a wide range of masonry materials including natural stone. A separate Task Group (CEN/TC 125 WG1 TG6) is responsible for the drafting of the specification standard.
The main test method drafts are:
BS EN 772-1 Determination of compressive strength
BS EN 772-4 Determination of real and apparent density andof total and open porosity
BS EN 772-11 Determination of water absorption by capillary action
These three drafts have been submitted to formal vote and all have been approved and issued by BSI.
The specification part (EN 771-6) was submitted for formal vote as a ‘market standard’ and to the surprise of many was approved and it is now available as a BS EN. The ‘harmonised version’ has been drafted and a version was discussed at a meeting held in Brussels in March 2001.
The potential conflict between the documents from TC125 and TC246 – where both committees have drafted test methods for water absorption, porosity and compressive strength - has still not been resolved. However, it is hoped that the draft from TC125 will include provision for the acceptance of results from tests carried out in accordance with the test methods of TC246.
This committee includes a Sub-committee (SC8) that is responsible for the preparation of the standards for slate and stone products for roofing.
The requirements for the work covered by this committee are covered by:
prEN 12326 -1 Specification
BS EN 12326-2 Test methods
The test methods have been approved and issued as a British Standard but the final draft of the specification is still to be issued and until it is there is no requirement for the tests to be called up or referred to.
CEN/TC 178 includes standards for clay, concrete and natural stone for paving, setts and kerbs. Working Group 2 is responsible for the standards on natural stone.
The ‘market’ standards relating to stone (BS EN1341, BS EN1342, BS EN1343) were released during March 2000 and the revised ‘harmonised’ standards that include all the requirements of the mandate were sent to CEN in July 2000. It was agreed that they follow the Unique Acceptance Procedure (UAP) which combines a short Public Enquiry with the Formal Vote.
The drafts were commented on by the CEN Consultant (Adam Pinney) and these have now been incorporated into the final versions. Once all three language versions were available the drafts were sent to national standards organisations for approval. The first results were received in April 2001 with EN 1342 and EN 1343 were approved, news of EN 1341 is still awaited. These are some of the first harmonised standards that have been approved to provide the basis of CE marking for construction products.
The drafts being developed by this committee cover the use of natural stone for internal and external cladding, and internal paving. There are three working groups – WG1 is responsible for standards on terminology for natural stone, WG2 for test methods and WG3 for specifications and evaluation of conformity.
The specification parts are:
prEN 1467 Specification for Rough Blocks
prEN 1468 Specification for Rough Slabs
Internal and external cladding
prEN 1469 Specification for Cladding
prEN 12057 Specification for Modular Tiles
prEN 12058 Specification for Slabs for Floors and Stairs
Drafts of these were circulated before the Plenary meeting in June 2000 but it was clear that they still contained a number of mistakes. It was agreed to seek comments on them and that UNI (the Italian Standards Organisation) would revise them for approval at the special meeting Plenary Meeting in October 2000. In the UK they were circulated to the Stone Federation and BSI for comment.
Revised versions were circulated prior to the meeting in Milan on 2nd and 3rd October. These were discussed and further changes were agreed in line with the comments received, the relevant mandates and the current CEN rules.
It was agreed that the three specifications that are mandated (prEN 1469 Specification for Cladding; prEN 12057 Specification for Modular Tiles; prEN 12058 Specification for Slabs for Floors and Stairs) would be redrafted by UNI and circulated by email for approval. However, since there was still no agreement on these drafts a further meeting was held in Milan on 15th and 16th February 2001. Following further comments made at the meeting the three drafts were approved for UAP. The other two specifications (prEN 1467 and prEN 1468) are to be revised in line with the three agreed documents and then these will be submitted to the meeting of TC246 in June 2001.
The test methods have continued to progress and the current status is:
The first seven test methods have now been approved at formal vote and so they are now full European Standards. The standards are:
EN 1925 Natural stone test methods – Determination of water absorption coefficient by capillarity
EN 1926 Natural stone test methods – Determination of compressive strength
EN 1936 Natural stone test methods – Determination of real density and apparent density and of total porosity and open porosity.
EN 12370 Natural stone test methods – Determination of resistance to crystallisation
EN 12372 Natural stone test methods – Determination of flexural strength under concentrated load
EN 12407 Natural stone test methods – Petrographic description
EN 12440 Denomination of natural stones
The next set of standards for formal vote include:
prEN 12371 Natural stone test methods – Determination of frost resistance
(Formal vote due to start June 2000 but still awaiting translations)
prEN 12670 Terminology of natural stones
prEN 13161 Natural stone test methods – Determination of flexural strength under constant momentum
(Formal vote to started June 2000)
prEN 13373 Natural stone test methods – Determination of geometric characteristics on units
prEN 13364 Natural stone test methods – Determination of breaking load around a fixing point
prEN 13755 Natural stone test methods – Determination of water absorption at atmospheric pressure
The following drafts were revised at BRE and they have now been sent for public enquiry:
prEN …(WI 00246012) Natural stone test methods – Determination of the velocity of sound
prEN …(WI 00246014) Natural stone test methods – Determination of abrasion resistance
prEN …(WI 00246015) Natural stone test methods – Determination of Knoop hardness
prEN …(WI 00246016) Natural stone test methods – Determination of thermal shock resistance
prEN …(WI 00246019) Natural stone test methods – Determination of rupture energy (Impact resistance)
prEN …(WI 00246032) Natural stone test methods – Determination of ageing by salt mist
prEN …(WI 00246033) Natural stone test methods – Determination of resistance to ageing by humidity, temperature SO2 action
prEN …(WI 00246035) Natural stone test methods– Determination of the dynamic modulus of elasticity
prEN …(WI 00246017) Natural stone test methods- Determination of slip resistance
The remaining test methods were discussed by TC246 Working Group 2 at its last meeting which was held in Helsinki on 7th and 8th September 2000. The tests are:
pr EN (WI 00246030) Determination of surface finish- It was agreed to examine two methods – one for texture >1mm and a separate one for assessing polishing and honing.
pr EN (WI 00246011) Determination of thermal expansion- No further progress
pr EN (WI 00246018) Determination of static modulus of elasticity- Submitted to UNI for Public Enquiry
pr EN (WI 00246034) Determination of colour- It was decided that this was no longer required.
The next meeting of WG2 is planned for September 2001 in France.