An ACI Education Bulletin. Describes types of aggregates normally used in concrete, aggregate properties affecting performance of the concrete, tests used to measure aggregate properties, and methods used to obtain test samples. Both normal weight and lightweight aggregates are discussed. In presenting aggregate properties and test methods, the bulletin covers grading, specific gravity, absorption and surface moisture, unit weight, particle shape and surface texture, abrasion resistance, soundness, chemical stability, and harmful substances. Also includes a bibliography, glossary, and metric conversion table.