ACC Executive Quality Control Engineer Interview Questions, Process, and Tips

Data requirements for a concrete mix design

• Type of cement

• Aggregate size and type

• Water-cement ratio

• Chemical admixtures

• Strength requirements

• Environmental factors

• Curing method

• Proportion of each ingredient

Exposure conditions of concreting refer to the environmental factors that affect the curing process of concrete.

• Temperature and humidity

• Wind speed and direction

• Sunlight exposure

• Rain and precipitation

• Airborne contaminants

• Proximity to saltwater or other corrosive substances

Various methods to determine the workability of concrete

• Slump test measures the consistency of concrete

• Compaction factor test measures the workability of concrete

• Vee-Bee test measures the time taken for concrete to flow

• Flow table test measures the flow of concrete

• Kelly ball test measures the workability of concrete

• Rheometer test measures the viscosity of concrete

Tests on fresh and hardened concrete

• Fresh concrete tests include slump test, air content test, and temperature test

• Hardened concrete tests include compressive strength test, flexural strength test, and water absorption test

• Other tests include density test, chloride ion penetration test, and alkali-silica reaction test

The standard used for concrete mix design is ACI 211.1.

• ACI 211.1 is the standard used for concrete mix design

• It provides guidelines for selecting proportions of ingredients based on desired properties

• Factors considered include strength, workability, durability, and economy

• Other standards such as ASTM C94 and AASHTO M 157 may also be used

The main role of fineness of cement is to increase the surface area of cement particles, which enhances the strength and workability of concrete.

• Finess of cement refers to the particle size distribution of cement.

• A finer cement will have more surface area per unit volume, which leads to better hydration and stronger concrete.

• The fineness of cement affects the workability of concrete, with finer cement requiring more wa...read more

The apparatus used for consistency test of cement is called Vicat apparatus.

• Vicat apparatus is used to determine the consistency and setting time of cement.

• It consists of a plunger, a graduated rod, a frame, and a base plate.

• The test involves measuring the depth of penetration of the plunger into the cement paste.

• The consistency of the cement is determined by the amount of water required to produce a standard penetrati...read more

The standard used for concrete compressive strength test is ASTM C39.

• ASTM C39 is the most widely used standard for testing concrete compressive strength.

• It outlines the procedures for preparing and testing cylindrical concrete specimens.

• The standard specifies the equipment, procedures, and calculations required for accurate testing.

• The results of the test are used to determine the strength of the concrete and its suita

Cracks in concrete can be caused by various factors such as shrinkage, settlement, overload, and weathering.

• Shrinkage due to drying and cooling of concrete

• Settlement due to uneven subgrade or soil movement

• Overload due to excessive weight or traffic

• Weathering due to freeze-thaw cycles, chemical exposure, or erosion

• Improper mixing, placing, or curing of concrete

• Design flaws or inadequate reinforcement