Ladder wire vs mid wall bond beam

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The following describes the differences between (1) #4 rebar in a horizontal filled cell every 48″ versus 9-gauge W1.7 ladder wire every 16″ laid horizontally every  16″ in a mortar bed ie. every other course.

The surface area of the rebar or wire bonding to the surrounding strength of the grout (rebar) and mortar (wire) must be defined as follows. For each vertical 48″ rebar there is one course of block with grout creating a mid wall bond beam OR three rows of ladder wire placed in a mortar bed between the concrete masonry units.

A #4 rebar 48″ on center circumference formula is 2 pi r or computed as 2 x 3.14 x 0.125 = 0.785 then multiply by 16 for a 16″ block length = 12.56 per square inch.

A 9-gauge W1.7 circumference is 2 pi r or computed as 2 x 3.14 x 0.057 = 0.357 then multiply by 2 (connecting wires to make the ladder) then multiply by 3 (3 separate rows of placement) then by 16 for a 16″ block length =  34.36 per square inch.

Typically the minimum mortar strength is 2000 psi for Type S.

The grout should be specified a minimum of 2000 psi.

The yield strength of #4 40k rebar is 40,000 psi.

Although the ladder mesh has a surface bonding area 3 times greater than the rebar, the latter being deformed has better mechanical contact.  The ladder wire mesh relies on adhesion and works for crack resistance which is why it can be substituted for the rebar.

Reference source: Structural Magazine article