HARD CORE • FREE-TRANSLATOR.COM • Definition of Hard core

... C.A. Wilkes, relates, in laying in situ any metallic or other materials for street roadways, to completing the convenience thereof by roughening or grooving the surfaces. The concrete is laid in a plastic condition upon a bed of hard core, broken stone, or preferably rough concrete. For footpaths the material may be laid in convenient sections, say 4 ft. to 8 ft. square and 2 in. to 4 in. thick; and in order to allow for the expansion of the material during the setting of the sections or subsequent variations ...

— Scientific American Supplement, No. 530, February 27, 1886 • Various