Robert L. Rowan, Jr. , P. E., ACI
Epoxy grout was not developed as a substitute for long established cementitious grout, but as an improvement for applications involving reciprocating or impact loading, and chemical resistance.
Developed in 1955 by Robert L. Rowan Sr., an independent engineer who had close contact with Shell Chemical. Shell was pioneering in the race to develop stronger thermosetting epoxy resins. I was privileged to assist my father in this exciting development and see its commercial acceptance in the petrochemical industry for such tough applications as high pressure reciprocating process gas compressors and pumps in caustic service.
With extensive engineering experiences in the installation, alignment and maintenance of large horsepower internal combustion engines, compressors, pumps, and turbines, the benefits of a second advanced class of grout was obvious to my father. While the higher compressive strength compared to cementitious grouts was the first advantage that caught potential users eyes, it actually was its greater toughness and ability to take impact or reciprocating loads and immunity to degradation from certain lube oils and chemicals that assured its success in the market place. Since its development in the mid 1950's this excellent class of grout has become the standard around the world for the grouting of dynamic machinery.
Where to use Epoxy Grout
As one might expect from the above, epoxy grouts are used today as the grout of choice for applications such as:
- Internal combustion engines-600 HP & up
- Reciprocating pumps and compressors
- Rock crushers and ball mills
- Debarking drums
- Forging hammers
- Rolling mills
- Gas Transmission or other high pressure pipelines
- Oil and gas processing / refining
- Steel manufacturing
- Paper mills
- Petrochemical plants
New Construction and the Repair Market
Epoxy grouts have now found their way into corporate specifications for new construction, after their initial success as a maintenance material. While certainly suitable for both markets and applications for the equipment listed above, some brief guidelines on the limitations of an epoxy grout would be helpful to engineers and maintenance personnel.
Applications where the base plate temperature exceeds 140° F Epoxy grouts that test at 15,000 psi at room temperature are typically limited (except special high temperature formulations) to use under base plates that are 140° F or less. As the operation temperature increases, the compressive strength reduces to as low as 4,000 or 5,000 psi at 140° F depending on the brand. There is a similar reduction in the modulus of elasticity and an increase in creep (permanent deformation under temperature and loading). Below 140° F, these reductions in physical properties are small enough not to influence performance.
Applications that require grout thickness in excess of 6-8 inches
Grout typically is used at a normal 2-4 inch thickness under equipment bases and soleplates. In repair work these depths can become greater. Using a cementitious or a polymer modified concrete (PMC) that cures in 24 hours to build back the foundation first and then the application of an epoxy grout at a 2-4 inch thickness is better from an engineering perspective and more cost effective. For equipment that does not require critical alignment, deep pour versions of epoxy grout are available.
Review the Engineering Properties
Epoxy grout is an advanced engineered product, and as such the user would be well advised to study the particular physical properties of the brand being considered and not be swayed by the glossy paper or low price. Excellent research data and technical papers can be found on the Gas Machinery Research Council's web site www.gmrc.org.
Published physical properties of manufacturer's literature as well as research papers can be confusing. While all physical properties are important to a certain degree, I would like to simplify the process by sharing with you those properties I generally pay attention to in any initial selection process. These are properties that generally affect the long time service life of the grout installation. My list includes:
- Compressive Strength ASTM C 579
- Elevated Temperature Compressive Strength ASTM C 580
- Creep ASTM C 1188, 600 psi 140 °F (4.4 MPa, 60°C)
- Air entrapment/bubbling
First, some thoughts on the ASTM properties. Most epoxy grouts will have room temperature compressive strengths in excess of 12,000 psi. Typical machine base plate loading probably is less than 1000 psi, and the underlying concrete no more than 5000 psi. This is a case where higher may not be better. The higher the compressive strength property, the greater is the chance of cracking. This old "Rule" applies to concrete as well. Don't choose one brand over another just because of a higher published compressive strength.
If the application is under a base plate that will exceed 140°F ( 60°C), then I will look at the elevated temperature test property.
Creep is another important published property that I will look at if the application involves a hot base plate. Creep is usually not of concern for room temperature applications.
Now to my list of non-test properties. Flowability can be an important property. If you can't place the material under the base plate, completely filling the gap to be filled with grout, you won't get a good installation. A stiff grout that has to be field modified by leaving out aggregate can lead to poor base plate contact, in some brands, because of air entrapment. This is more common than one would think. This property is very brand specific, and sometimes can only be learned by (bad) experience.
Cracking, as stated above, is more prevalent in higher strength epoxy grouts. Even so, all epoxy grouts can crack, and proper installation calls for adding expansion joints at appropriate locations to alleviate the bad effect that cracks might cause. A word of caution. Some epoxy grout manufacturers have added plasticizers to their formula in order to make the product less likely to crack. While this can be good in moderation, and is common in epoxy floor toppings, too much compensation will result in a grout that just might "creep" at room temperature.
Like so many things in life, you can learn a lot by reading (published properties), but the best laboratory is in the field, and the experience you get there. Sometimes a good grout consultant can really be of service.
|About the Author
Robert L. Rowan, Jr., PE, is a licensed professional engineer in the State of Texas and is CEO of Robt. L. Rowan & Associates, Inc., Houston, Texas. His company has been involved for over 50 years in the alignment and grouting of dynamic machinery such as gas compressors, turbines, pumps and rotating machinery. Serving such industries as oil and gas transmission, processing and refining and petrochemical, his company serves as engineering consultants to several major energy companies. Mr. Rowan is considered an expert on the repair of dynamic machinery foundations, and holds several patents on adjustable machine support systems. He has served for the past 4 years as the Chairman of the American Concrete Institute Committee 351 "Design of Foundations for Machinery and Equipment". Additional information can be obtained at www.rlrowan.com or by calling
© 2003 L&M Construction Chemicals, Inc. | ConcreteNews Winter 2002/2003.