Early Entry Concrete Saw

[ajk1]

ACI 360 recommends sawcutting to 1/3 of the slab depth for control joints in steel fibre reinforced slab on grade.
Does anyone know of an ACI or PCA publication that gives a recommendation for depth of sawcut in steel fibre reinforced slab on grade if an early entry saw is used?

 

[Ron]

ajk1....the most significant enhancement that steel fiber gives to concrete is an increase in toughness, including tensile strength. Even using early sawing (Soffcut or similar) I would stay with no less than 25%. I have no written reference for that, just experience.

 

[ajk1]

Ron- thanks. So do you have actual good experience with sawcutting the steel fibre slab to only 25% of its depth using early entry saw? Our floor will be about 225 mm thick and have about 25 kg/cubic metre of 1000 MPa steel fibres.

Unrelated to sawcut depth, but the main advantage of steel fibres is not that they increase the modulus of rupture much (at the normal doaseges) but rather that they provide the slab with signifcant post-cracking strength. If this is accounted for, there can be a dramatic reduction in required slab depth, if the yield line analysis takes proper account of the post-cracking strength.