HBMs for base layer

The symbolism of their compressive class (C) is in accordance to CEN EN 14227-1 (2013). The first value corresponds to the characteristic compressive strength (R ) obtained from a cylindrical specimen with H/D (ratio between height and diameter) equal to 2, while the second value corresponds to the characteristic compressive strength (R ) from cubes or cylinders with H/D equal to 1.0 (in fact, 0.8 to 1.21). The characteristic strength (R ) is the 28-day compressive strength expressed in megapascals (MPa). 

HBM can practically be cement-bound granular mixtures (CBGMs) or slug bound mixtures (SBMs) or fly ash bound mixtures (FABMs). The aggregate mixture may be crushed rock materials or gravels. Further information for these mixtures is provided in Section 10.5.3. 

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