WHAT IS THE USE OF GROUT IN COLUMN?

[Rovin069]

WHAT IS THE USE OF GROUT THAT USUALLY FOUND UNDER THE BASE PLATE OF THE COLUMN? AND WHY IT IS ALWAYS NON SHRINK? IS THERE ANY OTHER TYPES OF GROUT? THANKS

 

[hokie66]

The grout is just to fill the inevitable gap between the base plate and concrete. Neither concrete or steel is likely to be precisely normal to the axis of the force, or precisely at the correct level, so grout is used to make up this tolerance. It is non-shrink so that it doesn't shrink and allow the column to lower. A sand-cement grout can be used, and often was in the past, but there is an amount, albeit small, of shrinkage in grout which does not have the anti-shrink additives.

 

[charliealphabravo]

Baseplates can be designed without grout but there may be some additional baseplate failure modes that need to be checked.

 

[johnbridge231]

charliealphabravo, that's correct. Eurocode 3, Part 1-8 suggests this as well.

Biaxial Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis

http://www.engissol.com/cross-section-analysis-design.html

 

[EngineeringEric]

They can be used as leveling compound, and non-shrink is specified because if not contractors would use shrinkable-grout to save some money (they would find it somewhere).

the concrete often is not level so there would be localized crushing when loaded by steel, and the anchor bolts would be designed as 'columns', and the base plate would need to be checked to not be fully bearing... But i guess you knew most of that.

 

[JLNJ]

Back in the day cementitious grouts were not as sophisticated as they are now and they would shrink like any cement paste would when it cured. This would reduce the contact area with the base plate. Most times this was probably OK, but with the advent of non-shrink grouts there is no need to worry or design for partial bearing under base plates or machinery.

I always thought the grout was there to make up for the inherent inaccaracy of concrete placement. The tolerance for the concrete finish elevation exceeds the tolerance for the finish base plate elevation.