Technical Questions

Mixture design and strength submittals

Q. Is there an ACI document that states that the Licensed Design Professional must review mixture design and strength test data? Even though our project specifications call for these submittals, we sometimes encounter a Contractor that fails to submit them. Many of our projects are built in areas without a Building Official, and it’s not always possible to persuade the Owner that the Contractor must provide this information.

A. Yes. ACI documents do contain such language. Submittals are discussed in Section 1.5.1 of ACI 301: “Provide submittals as required by this Specification in accordance with Contract Documents.” Submittals specific to concrete mixtures and strength are described in Sections 4.1.2.1 and 4.1.2.2, respectively. According to these sections, concrete mixture proportions and characteristics must be submitted along with test records used to establish the required average strength. Furthermore, Section 4.1.2.3 lists submittals required for concrete materials, including cementitious materials, aggregates, admixtures, and water (and/or ice).

ACI 301 also provides a mandatory requirements checklist and an optional requirements checklist to assist the Architect/Engineer in supplementing the provisions of this Specification as required or needed by designating or specifying individual project requirements. Mixture proportions, characteristics, and test data used to establish the mixture proportions are part of that checklist. Finally, Section 26.12.1.1 of ACI 318 requires that: “All reports of acceptance tests shall be provided to the licensed design professional, contractor, concrete producer, and, if requested, to the owner and the building official.”

Note that contract documents can be written to require performance submittals rather than prescriptive submittals. According to Section 4.1 of ACI 211.5R, a prescriptive submittal comprises proportions per unit volume of concrete (mass, absolute volume, or both for each material in the mixture); fresh properties (slump, unit weight, temperature, and air content); and hardened properties (compressive strength). In contrast, a performance submittal does not include mixture proportions. Instead, it includes a listing of a mixture’s constituents and each material’s class, grade, type, or applicable ASTM specification. While a performance submittal also includes fresh and hardened concrete properties, the latter may include specific properties other than compressive strength. Appendixes A through C of ACI 211.5R provide examples of a prescriptive submittal for single mixtures from multiple batch plants, a prescriptive submittal for multiple mixtures from multiple batch plants, and a performance submittal.

References: ACI 318-19; ACI 301-20; ACI 211.5R-14

Topics in Concrete: Mixture Proportioning; Quality Assurance; Specifications; Testing of Concrete