How much is concrete?

The first thing to work out is the strength of concrete required, 20 mpa, 25 mpa etc. All foundation work should be 25 mpa, swimming pools 30 to 35 mpa etc. That determines the ratio of cement to sand and aggregate, that then determines the price of concrete, when ordering do not let the driver or workers add water as that reduces the strength again, ask for a slump of 120mm.