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If you are already familiar with this step, click below to proceed to the response form. Otherwise, read the information below before proceeding.
Enter mixture factors and information
The second step in the COST program is to provide information about the concrete mixtures. This includes
FACTORS AND LEVELS
Each mixture component (or ratio of components in the case of w/c ratio) is a factor that can affect the responses (measured properties). Factors may be variable or fixed.
Fixed factors might be expected to have little or no effect. The level of a fixed factor is held constant in the experiment.
COST always requires that either w/c or w/(c+m) be included as a variable factor. The user must designate the range (low and high levels) of w/c (or w/(c+m)), in terms of mass. Other required information includes the cement specific gravity and cement cost ($/kg).
The other potential factors are grouped in the following categories:
Chemical admixtures include three user-designated types. Required information includes the admixture name, range in terms of dosage (volume in liters per 100 kg of cement), specific gravity, percent solids by mass, and cost ($ per liter).
Aggregates include fine aggregate, coarse aggregate, and one additional (user-designated) type. Aggregate proportions may be designated by either volume fraction (default) or mass. Required information includes the range in terms of volume fraction or mass,
bulk specific gravity, absorption (%), moisture content (%), and cost ($ per kg).
Any factor may be designated as a variable or fixed factor. Instructions on how to do so are provided on the input form for mixture factors.
In most cases, the selection of components and their ranges is up to the user; however, in some cases, some of the factors and levels may be designated in specifications. For example, a specification may have a maximum w/c, or a minimum silica fume content. COST does not provide guidance on the selection of min and max values for the components.
Variable factors are usually the mixture components expected to have most significant effects on the responses. The level of a variable factor is varied in the experiment to assess its effect.
Mineral admixtures include silica fume, fly ash, slag, and one additional (user-designated) type. Required information for mineral admixtures includes range (minimum and maximum values) in terms of percent cement mass replacement, specific gravity, and cost ($ per kg).