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Difficulty: MediumConcrete and Masonry Materials

A mason is assembling a reinforced load-bearing wall using hollow concrete masonry units (CMU) and needs to encase the vertical steel rebar placed inside the open cells. Which cementitious material is specifically formulated with high slump and fluid workability to completely fill these structural cavities without leaving air pockets?

  1. A
    Bedding mortar
  2. B
    Gypsum plaster
  3. Masonry groutAnswer
  4. D
    Surface bonding cement

Answer

Masonry grout is the specialized, high-fluidity mixture engineered to fill hollow concrete masonry cores and bond structural rebar.
Masonry grout is specifically proportioned with a high water-to-cement ratio and small aggregates (such as pea gravel or coarse sand) to give it a high slump (typically 8 to 11 inches). This fluid consistency allows it to be poured or pumped into the hollow cells of concrete masonry units, fully surrounding steel rebar and bonding the assembly into a monolithic structural unit.

Step-by-Step Solution

1
Analyze the functional requirement of filling vertical block cavities containing reinforcement steel.
The application requires a fluid, high-slump cementitious mixture that can flow around rebar and fill voids without creating air pockets or honeycombing.
Masonry units create deep vertical channels where regular thick mixes would bridge and fail to fully encapsulate the steel.
2
Differentiate between jointing mortar, structural grout, plaster, and surface coatings.
Masonry grout is specifically formulated with higher water content and fine aggregates to facilitate complete void filling and structural load transfer.
Mortar is formulated to be stiff enough to hold block elevation during placement, while grout is formulated to flow freely.

Key Concept

Distinction between masonry grout (void filling and reinforcement encapsulation) and masonry mortar (unit bonding and jointing)
Estimated Time:50s
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Topics

Concrete and Masonry Materials

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