Changes

Concrete production and drought

No change in size, 23:24, 4 June 2012

→‎Construction, operations and maintenance

* Use clean gravel – impurities will weaken the concrete.

* Use aggregate (gravel) of 5-20mm for non-porous concrete and 5-10mm for porous concrete. Aggregate can be graded using 2 locally-made sieves of 5mm and 20mm – discard any aggregate that remains on the 20mm sieve or that falls through the 5mm sieve. The reasons for having a maximum size is to do with workability, but also that the maximum size is not greater than the “cover” of concrete over a reinforcing bar – if a stone would span the distance from outer edge to reinforcement, this can become a zone ofweathering where water can get in to corrode the reinforcement.

* Reinforce lower side of flat slabs as concrete does not work well under tension. Reinforcement can be avoided if making dome shape structures (e.g. cover to rainwater tank, or dome latrine slab).

Winona

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