Reinforcing materials

The document contains new requirements for headed shear stud reinforcement, headed deformed bars, stainless steel bars, and high-strength steel bars.

Limit set on historical mixture proportion data

ACI 318 now sets a limit of one year on the age of strength test records that can be used to establish a sample standard deviation for proportioning a concrete mix based on field experience.

4x8 testing cylinders

In addition to the traditional 6-inch-diameter by 12-inch-high concrete cylinder, the code now officially recognizes using 4x8-inch cylinders for trial mixtures and acceptance testing. Where 4x8-inch cylinders are used, a strength test is the average of the strengths of three cylinders, instead of two, as 6x12-inch cylinders require.

Defining concrete durability

Under 318-08, licensed design professionals must prescribe new exposure categories and classes for concrete durability requirements. The format of Chapter 4 was revised extensively by introducing exposure categories and classes with applicable durability requirements.

To submit a Problem Clinic question, e-mail, or telephone 773-824-2492.