BS 7943:1999

Foreword
1 Scope
2 Characteristics of UK aggregates
3 Classification of aggregates
Annex A (informative) precision of the procedure for qualitative and
quantitative petrographic examination of aggregates
Annex B (informative) Gel-pat test for the detection of opaline silica
Annex C (informative) Example of report form
Bibliography
Figure B.1 Typical pat specimen at the end of a test, showing several
           gel growths - specimen immersed in the storage solution
Figure B.2 Typical pat specimen at the end of a test, showing several gel
           growths - specimen removed from the storage solution but kept wet
Figure B.3 Typical pat specimen at the end of a test, showing several gel
           growths - an oblique view of the pat after drying in ambient conditions
Table 1 - Guidance on rock types
Table 2 - Guidance on mineral types
Table B.1 - Detection limits for the gel-pat test

Applies to coarse and fine aggregates as specified in BS 812-104.

This British Standard gives guidance on the interpretation of the results of petrographical examination of coarse and fine aggregates, carried out in accordance with BS 812-104, in terms of the susceptibility of the combined aggregate to alkali-silica reactivity (ASR) sufficient to cause damage to concrete in which it is used. The guidance is not applicable to alkali-carbonate reactive materials.

NOTE 1 Guidance on precision expected from the petrographical examination of coarse and fine aggregates, carried out in accordance with BS 812-104, is given in annex A.

NOTE 2 It is recommended that a petrographical examination be earned out by a petrographer who is a member of the Proficiency Scheme for Aggregate Petrographers.