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Frequently Asked Questions

Q. Can I use Firstmix in the USA?
A. Yes. Firstmix allows you to use cylinder strengths and in.-lb units, and caters for air-entrainment.

Q. Can I customize FirstMix to suit local aggregates and cements?
A. Yes. You can incorporate the properties of your local cement types and aggregates into Firstmix.

Q. How close will the strength and workability of the actual concrete be to that predicted by FirstMix?
A. It depends on how close your aggregates and cement are to those used in the tests, on which the DOE method (used by FirstMix) is based.

Q. How easy is it to modify a mix in the light of trial mix or other test results?
A. Very simple. Firstmix Help gives guidance on modifying a mix to meet the required strength or workability.

Q. Can FirstMix cater for admixtures?
A. At present Firstmix only caters directly for air-entraining agents. You could design for a artificially low workability to model the effect of a water reducing agent.

Q. Why do values entered on the Mix Design Form sometimes change slightly when they are displayed?
A. All data in Firstmix is stored in SI units. If you are using In.-lb units or cylinder strengths, values may change slightly because of tiny inaccuracies in the conversion. These errors will be negligible.

Q. Can I allow for entrapped air in concrete?
A. Entrapped air reduces the strength of concrete like entrained air but unlike entrained air does not significantly improve workability. You could determine the free water requirement for no air-entrainment, tick the Specify Free Water Content check box, so that this content does not change, and then specify a percentage of air entrainment equal to the estimated percentage of entrapped air, so that the required free-water/cement ratio is reduced.