Concrete Mix Designs

Mixed designs by Dams for Africa

Concrete pages:

To Simple Mixes
To Construction Concrete
To Heat Cured Concrete

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(1) Three simple mixes are presented showing the proportions by volume of cement, sand and stone, required for building typical rural infrastructure such as a farm reservoirs. Proportions are given for plaster, mortar, and basic concrete (average strength of 25MPa). So for example the concrete may be used for the reservoir's floor-slab, the mortar to construct its wall of bricks/blocks, and the plaster for rendering the wall to improve the water retention of the reservoir.

(2) An Excel based mix design program has been developed for construction concrete. Materials are proportioned by mass to make concrete that may vary in strength from 15 to 65 MPa. Materials include cement, fly ash, concrete sand, filler sand, stone, superplasticizer, water. The program has a list of the inputs that are required, while the mix proportions are stated as outputs. A tutor is imbedded in the cells next the various inputs and outputs explaining what each line item is (only visible in the full excel version). Note that the methodology used in this program is based on ACI standard 211.1-91, adapted here to Excel. The mathematical relationships presented here come from standard strength vs water:cement ratios, as published variously in the literature, but for greater accuracy these relationships may be obtained from the cement supplier's curves, or trail mixes done in the laboratory. Thereafter the program does the necessary interpolation. Note that there are other Excel pages, not in view here, that are required before this program can be made operational. The program retails for $ 150, and can be e-mailed on receipt of payment.

(3) A method for determining the mix proportions for heat cured concrete is given. While much of the program is similar to 'construction concrete' the additional variable of maturity (or inputted heat in deg-hrs) is added, making this a relatively sophisticated program. Initially trial mixes at differing heat regimes are required using the local materials to obtain graphs that establish the various mathematical expressions used in the program. The program retails at $250.