Glossary of Terms Relating to Cement Concrete, Part 7: Mixing, Laying, Compaction, Curing and Other Construction Aspects
1973 Edition

The glossary defines key terms associated with concrete mixing as follows:

• "Amount of Mixing" (Clause 2.12): Refers to the extent of mixing action carried out in the mixer. For fixed mixers, this is indicated by mixing duration, whereas for transit mixers, it is quantified by the number of drum or blade revolutions post-contact of cement with water and aggregates.

• "Mixing": The process of thoroughly blending cement, aggregates, water, and admixtures to produce a uniform concrete or mortar mix.

• "Mixer Types": Include stationary mixers where mixing time controls the process, and truck mixers where drum revolutions are the key metric.

Standardizing these definitions helps prevent ambiguity and ensures consistent quality in concrete production and placement.

According to IS 6461 Part 7, the following curing methods are defined:

• "Curing" (Clause 2.118): The practice of maintaining adequate moisture and temperature in freshly placed concrete for a specified duration to facilitate hydration and hardening.

• "Membrane Curing" (Clause 2.216): Application of liquid compounds such as bituminous emulsions or resin suspensions, or non-liquid coverings like plastic sheets or waterproof paper, to form a barrier preventing water loss from the concrete surface.

• "Steam Curing" (Clause 2.313): Exposure of concrete to steam at atmospheric or elevated pressures and temperatures ranging from 30°C to 215°C to accelerate the hydration process and strength development.

These methods are critical for ensuring proper concrete durability and performance.

IS 6461 Part 7 provides definitions related to joint types, including:

• "Warping Joint": Designed to accommodate deformation of concrete slabs caused by temperature and moisture gradients. These joints usually incorporate bonded steel or tie bars to maintain slab integrity while allowing movement.

• Other related joints include contraction joints, control joints, and expansion joints, each serving specific roles in controlling crack formation and accommodating structural movements.

Clear terminology in this regard aids in the correct design and implementation of joints to preserve concrete durability and structural performance.

The glossary distinguishes surface finishes as follows:

• "Finish" (Clause 2.168): The overall texture and smoothness of a concrete surface after compaction and finishing operations.

• "Rubbed Finish" (Clause 2.272): A smooth surface achieved by abrasive removal of surface irregularities.

• "Coating" (Clause 2.76): Materials applied by brushing, spraying, or other methods to protect, seal, decorate, or smooth the concrete surface.

• "Swirl Finish" (Clause 2.324): A nonslip textured surface created by a rotary trowelling action.

These classifications help specify surface treatments based on their texture, application method, and functional purpose.

IS 6461 Part 7 defines several common concrete defects:

• "Pattern Cracking" (Clause 2.238): Fine surface cracks forming patterns caused by volume changes near or below the surface leading to tensile stresses.

• "Craze Cracks" (Clause 2.114): Fine, random surface cracks resulting from shrinkage in cementitious materials.

• "Checking" (Clause 2.70): Shallow, closely spaced surface cracks due to drying shrinkage.

• "D-cracking" (Clause 2.128): Progressive fine cracks near slab edges and joints caused by freeze-thaw action and poor quality aggregates.

Understanding these terms assists in diagnosing and preventing concrete durability issues.