A2.3.1 This annex provides a means to determine the amount of methylene blue dye adsorbed by a sample of finely ground limestone. Methylene blue dye is preferentially adsorbed by clay minerals that may be present in limestone. The amount of dye adsorbed is related to the clay type and content. Certain clays may increase the water demand or affect other properties of cements if present in sufficient quantity in the limestone when used an ingredient in cement. The specification places a limit on the methylene blue index of limestone permitted as an ingredient in blended cement.

This specification pertains to blended hydraulic cements for both general and special applications, using slag or pozzolan, or both, with portland cement or portland cement clinker or slag with lime. These cements are classified into two types: Type IS which is portland blast-furnace slag cement and Type IP which is portland-pozzolan cement. They can also be described according to air-entraining, moderate sulfate resistance, moderate heat of hydration, high sulfate resistance, or low heat of hydration properties. The cement shall conform to the chemical requirements prescribed. In addition, the cement shall undergo different tests to determine the following properties: chemical analysis, fineness by sieving, fineness by air-permeability, autoclave expansion, time of setting, air content of mortar, compressive strength, heat of hydration, normal consistency, specific gravity, water requirement, mortar expansions of blended cement and pozzolan, drying shrinkage, activity index with Portland cement, and sulfate resistance.