NRMCA has published a group of five two-page reports on some of the materials used in concrete. These documents approach the specification of materials from the producer's point of view, but that's not necessarily a bad thing. What, why, and how do changes in the specification affect the concrete's properties? There are reports on supplementary cementitious materials, fly ash, minimum cementitious content, water-cement ratio, and aggregate gradation. The next time you're looking at a materials specification it might be worthwhile to compare it to these guides. They are available to download free here.
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