Evening all. I've put in footings for a small retaining wall in a garden The wall is to comprise a single course of hollow blocks, topped with a decorative brick. The footings are have rebar (vertical) for the blocks. I was thinking of saving time by mixing a finer concrete mix (using horticultural grit or pea gravel and sharp sand) not only to fill the block cavities but bed the blocks onto the footings as well. I wondered what the adhesion of concrete is compared to mortar....would an additive help? Comments? Many thanks
you will find it hard to level the blocks if you have any from of stone in the mortar mix. It is best to lay two courses of block and then infill with a concrete mix. Horticultural grit / pea gravel is very expensive compared to traditional aggregate. You should also install horizontal rebar every few courses which should be tied to the vertical rebar and don't forget to fit the weep holes and back fill with clean aggregate as you go
It's only a single course Sospan,so wouldn't think you need the horizontal rebar. Horrible things hollow blocks, lay them, give it a couple of days to harden before filling blocks with concrete.