The choice of a concrete mix depends on the need of the project both in terms of strength and appearance and in relation to local legislation and building codes.
The design begins by determining the requirements of the concrete.
These requirements take into consideration the weather conditions that the concrete will be exposed to in service, and the required design strength.
The compressive strength of a concrete is determined by taking standard molded, standard-cured cylinder samples.
These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes.
Air-entrained concrete is produced using air-entraining portland cement, or by the introduction of air-entraining agents, under careful engineering supervision, as the concrete is mixed on the job.
Properly designed SCC can save time and labor without sacrificing performance.
Two important properties specific to SCC in its plastic state are its flowability and stability.
The high flowability of SCC is generally attained by using high-range water-reducing (HRWR) admixtures and not by adding extra mixing water.
The stability or resistance to segregation of the plastic concrete mixture is attained by increasing the total quantity of fines in the concrete and/or by using admixtures that modify the viscosity of the mixture.
5.3 It is difficult to produce self-consolidating concrete that is both flowable and nonsegregating using coarse aggregates larger than 25 mm [1 in.].
Therefore, this test method is considered applicable to self-consolidating concrete having coarse aggregate up to 25 mm [1 in.] in size.
Many factors need to be taken into account, from the cost of the various additives and aggregates, to the trade offs between the "slump" for easy mixing and placement and ultimate performance.