Concrete mix design follows ACI 211.1 (normal weight) or ACI 211.2 (lightweight). CDOT requires trial batches with strength verification at 7 and 28 days. Mix design parameters: w/c ratio per durability requirements, minimum cement content per exposure class, air content 4.5-7.5% for freeze-thaw exposure. Maximum aggregate size: 1.5 inches for general use, 3/4 inch for bridge decks. Alkali-silica reactivity (ASR) mitigation per CO ASR policy using SCMs or lithium-based admixtures.
All work under this section shall comply with CDOT current standards and applicable AASHTO, ASTM, and federal requirements. The Engineer has authority to accept or reject materials and workmanship that do not conform to the specifications.
Source: CDOT Materials Testing Manual, 2024 Edition. Pages 9–10 of 25.