Florida DOT Concrete Batchman/Operator Practice Exam - Prep, Study Guide & Practice Test

Aggregates form the bulk of concrete by volume, with the cement paste filling the spaces between them and bonding the pieces together. In a typical normal-weight concrete mix, the paste portion is roughly one-quarter of the volume, leaving about three-quarters for the aggregates. Because of small variations in mix design, water-cement ratio, and any air voids, the practical range for the total aggregate content usually falls around 75% to 85% of the concrete's volume. This is why the range 75% to 85% best fits standard concrete mixes. Too little aggregate would leave too much paste, affecting economy and strength, while too much aggregate would leave insufficient paste to coat and bond the aggregates properly.