Grouting refers to all work to be carried out to properly fill the space between concrete surfaces and base plates of equipment, steel structures or concrete prefabricated elements. In concrete foundations (particularly machine foundations) grouting is used to achieve adequate transfer of horizontal and vertical forces. Generally grouts are used for repair works, bonding of concrete surfaces and to act as a medium of force transfer from objects (equipment, machine, superstructure, etc) to the foundation.
Types of Grout
Based on material type, a grout is differentiated in two main categories.
- Cement Based grouts
- Epoxy grouts
Cement Based Grout
As described by the name, these grouts are simply developed using cementetious materials. Cement may be Ordinary Portland Cement or any other type of cement as per requirements. Cement grouts may be sanded or non sanded. according to the requirement and use of grout mix design of grouts may change.
Epoxy grouts are resin based bonding chemicals mixed with hardener to fulfill the grouting requirements. epoxy grouts are free from water and water proof material. These have normally more compressive strength than cement based grouts, therefore recommended for foundations of heavy equipment and/or when foundation has to bear vibrations.
Non-shrink grouts have distinctive property that its volume after 28 days of hardening is not lesser than the initial volume. This property prevents non shrink grout from shrinkage and subsequent crack development. Foundation experts recommends use of non-shrink grouts for maintaining top of grout (TOG) level of foundations. The type of non-shrink grout is normally specified on the drawing, if drawing is not providing the information for required type, then specifications or site engineer recommendation shall govern. If any aggregate is required the it must be non metallic, as metallic aggregates initiates cracking in concrete.
A non-shrink grout can be cement based or epoxy grout.
Selection of Grout Type for Foundations
The following are some guidelines for the selection of grout material in foundations.
Cement-based non-shrink grout
Cement–based grout are recommended to use for grouting of major steel structures and stationary equipment. The minimum compressive strength shall be around 25 to 35 N/mm² (MPa) for lightly loaded foundations. All grouts shall be non-corrosive, non-staining and resistant to effects of moisture.
Epoxy-based non-shrink grout
Epoxy-base grout shall be used for grouting foundation for rotating or vibrating machinery and heavy equipment. The minimum compressive strength recommended by experts is 65 to 75 N/mm² (MPa).
Storage & Handling
Non-shrink Cement – Based Grout and Epoxy Grout aggregate are normally available in sound dry bags and Epoxy Grout liquid components in sealed hardener and resin containers. Manufacturers recomends storing the grout in a dry, weatherproof area and within the temperature range of 4 ºC to 32ºC. The total storage time for non-shrink grout should not be more than 10 months (300 days Approximately)
Applicable codes and standards
ACI 351.1 R-12
Grouting between Foundations and Bases for Support of Equipment and Machinery
British & European standards
Code of practice for foundations
Chemical admixtures for concrete, mortar and grout – Admixtures for concrete