Cement designations in BS 8500
BS 8500-2: 2023 Concrete - Complementary British Standard to
BS EN 206, Table 1 provides a list of general purpose cements and combinations.
In this context, a cement is a factory produced Portland cement or a composite
of Portland cement with one, or more additions, and a combination is a blend of
Portland cement with up to two additions combined in the mixer at the concrete
plant. These are prefixed with either “CEM” or “C” respectively. They are
accompanied by roman numerals I to VI which categorise the cement/combination
into broad groups which align with BS EN 197-1 and 197-5 cements. Apart from
CEM I which is Portland cement, these categories are further sub-divided into A
to C relating to the percentage of addition. For example, CEM II/A (6-20%), CEM
II/B (21-35%) or CEM II/C (36-50%). This does not indicate the addition type,
hence the following letter designations.
L = limestone fines
LL = limestone fines (higher purity with a low total organic content)
S = ground granulated blastfurnace slag (ggbs)
V = siliceous fly ash
D = silica fume
P = natural pozzolana
Q = natural calcined pozzolana
M = ternary composition i.e. SL (ggbs & limestone fines)
NOTE the limestone fines (BS 7979) designation “LL” is deemed to satisfy the requirements of “L” and so only the designation “L” is used in BS 8500. Where the cement or combination complies with the requirements for sulfate
resistance, +SR is also included.
As CEM I has been the dominant cement supply in the UK
market, although CEM II/A-L (or LL) has been manufactured for many years
predominately with packed cements. Some ready-mixed companies who have sufficient
silo space can use this as a stand-alone material. The volume of this cement
is expected to grow with the introduction of the updated standard. The concrete
supplier is reliant on the cement manufacture for the percentage of limestone and this is important when combining with other additions.
A concrete supplier producing a CIIA-L is required to establish the
relationship for strength; the procedure is provided in BS 8500-2 Annex B/D
Once it has been determined which cement type is available,
a combined performance category (BS 8500-1, Table A6) can be determined. The
combined performance category (CPC) is an alphanumeric grouping of cements and
their equivalent combinations (A to G, and 1 to 4) by relative durability for
resistance to sulfate attack and chloride ingress.