Mechanism of taking up loads for concrete paving blocks 

Paving for concrete blocks comprises closely packed paving blocks in pre-determined patterns and tiny joint spaces between individual blocks are filled with sand. Presence of sand avoids the displacement of a single block unit from remaining blocks. Furthermore the horizontal interlocking provided by the arrangement of paving blocks in special patterns (for example herringbone pattern) stops any single block from moving relative to one another. For example vertical loads acting directly on one concrete paving block aren't only resisted by block itself, but also by blocks adjacent to it. 

Fig: Paving blocks