Natural pozzolana and natural calcined pozzolana
Reduction in the embodied carbon of concrete by reducing the Portland cement content can be achieved by partial replacements and ternary blends. Fly ash, GGBS and limestone powder are well established in the market and their proportions to achieve durability are tabulated in BS 8500.
BS 8500 allows for the use of natural pozzolana, although the commercial availability of such products is still to be established in quantity in the UK it is currently being used in some european states (that have adopted this national annex). These materials are covered in;
BS 8615: 2019 Specification for pozzolanic materials for use with Portland cement:
Part 1 Natural pozzolana and natural calcined pozzolana
Part 2 High reactivity natural calcined pozzolana
This British Standard specifies requirements for the production, chemical composition, mechanical and physical properties of pozzolanic materials for use in combination with Portland cement class 42,5N or greater, conforming to BS EN 197-1:2011, as a component of concrete, mortar or grout. It also specifies requirements for marking, provision of information and conformity criteria for the manufacture’s autocontrol system.
Part 1 covers natural pozzolana, defined in clause 5.2.3.2 of BS EN 197-1:2011; and natural calcined pozzolana, defined in clause 5.2.3.3 of BS EN 197-1:2011. Part 2 covers high reactivity natural calcined pozzolana.
BS EN 197-5:2021 introduced multi-component cements as a component of
concrete with a lower proportion of clinker than that allowable by Part
1, example: Composite cement CEM VI.