ACI Certification Concrete Mix Design 2

Question 1

What does the fineness modulus (FM) of fine aggregate indicate?

Accepted Answer

An index of the overall coarseness or fineness of the aggregate

Answer

FM is computed by summing cumulative percentages retained on a specified series of sieves and dividing by 100; higher values denote coarser material.

Question 2

According to ACI 211.1, as the fineness modulus (FM) of fine aggregate increases, the recommended bulk volume of coarse aggregate per unit volume of concrete:

Accepted Answer

Increases

Answer

Coarser fine aggregate (higher FM) has fewer small particles, allowing a greater volume of coarse aggregate while still maintaining adequate workability.

Question 3

What is the primary purpose of preparing trial batches during concrete mix design?

Accepted Answer

To verify that the calculated mix proportions meet specified requirements under actual conditions

Answer

Trial batches confirm that calculated proportions achieve required fresh properties (slump, air content) and hardened strength before full-scale production.

Question 4

Which ACI document provides the standard practice for selecting proportions for normal, heavyweight, and mass concrete?

Accepted Answer

ACI 211.1

Answer

ACI 211.1, 'Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete,' provides the absolute volume method for mix design.

Question 5

The saturated surface-dry (SSD) condition of aggregate is used as the reference state in mix design because:

Accepted Answer

It requires no moisture correction to batch water calculations

Answer

Aggregate at SSD neither absorbs water from nor contributes free water to the mix, making it the ideal baseline for calculating batch proportions.

ACI (American Concrete Institute Certification) Practice Test

ACI (American Concrete Institute Certification) Practice Test

ACI Certification Concrete Mix Design 2