Changes

* Add only the very minimum amount of water for workability – this is one of the most important aspects to making strong concrete. The amount of water needed for the hydration process when mixing concrete is a lot less than what is normally added to mixtures in the field, where additional water is needed to increase workability of the concrete. The point is that the less water used, the better, since if too much water is used, the concrete will become weaker. Any excess water not used in hydration will remain in the pores – when this water evaporates, the pores remain – the more water added, the bigger the pores and the weaker the final product. [http://en.wikipedia.org/wiki/Concrete#Chemical_admixtures Admixtures] can be added to the concrete mix in order to reduce the amount of water needed. [http://en.wikipedia.org/wiki/Superplasticizer Superplasticizers] work best by reducing the amount of water that needs to be added when mixing concrete, which results in 35% less shrinkage. The resulting end material is stronger and can reduce the amount of micro cracks in mortar by half compared to normal mortar while resulting in 76% fewer leaks. The amount of [http://en.wikipedia.org/wiki/Plasticizer plasticizer] to be added should not be greater than 2% of the dry material weight. A plasticizer that can be used that is possibly available is household washing up liquid. In hot climates though, more research is needed in the field application of plasticizers, since the reduction of water used (and increased strength of product) may not be that great due to more water needed to prevent drying out between mixing and application.

[[Image:concrete graph.jpg|thumb|right|300px|Concrete strength with curing.<br> Neville, A.M. (1981) Properties of Concrete. Pitman.]]

* 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).