Southwest Regional Sales Manager,
National Specifications Manager
L&M Construction Chemicals
Is it possible to improve your non-shrink grout specification and lower your in-place grout cost?
Standard Specification for Packaged Dry Hydraulic Cement (Non-Shrink), can eliminate potential problems on projects.
Non-shrink grouts play a key role in the structural stability of most construction projects. Their function is three fold: to fill the void between the base plate and the concrete foundation completely and permanently without shrinking or separating from either; to transfer all loads from the base plate to the concrete foundation; and to maintain precise
Is it possible to improve your non-shrink grout specification and lower your in-place grout cost? ASTM-C1107, Standard Specification for Packaged Dry Hydraulic Cement (Non-Shrink), can eliminate potential problems on projects.
ASTM-C1107 consolidates ASTM-C827, Standard Test Method for Change in Height at Early Stages of Cylindrical Specimens from Cementitious Mixtures, and U.S. Army Corps of Engineers CRD-C621, Post Hardening Volume Adjusting, specifications under one umbrella and is the recognized specification for cement-based non-shrink grouts.
ASTM-C1107 was initially introduced to the public in 1989. It has since undergone a few revisions and continues to be improved upon. C1107 classifies grouts into three categories: Grade A, volume control of grout caused by expansion before hardening occurs; Grade B, volume control caused by expansion after grout hardens; Grade C, volume control caused by a combination of both mechanisms.
In addition to height change, critical elements of working time (placeability) and compressive strength are measured at varied temperature ranges and at varied consistencies or water content. The grout is tested at the manufacturer's maximum allowed water-to-dry solids ratio and is rated as plastic, flowable, or fluid. Grout consistency is tested both after initial mixing and at the end of the grout's stated working time at the manufacturer's allowed temperature ranges. Compressive strength tests are run at maximum and minimum temperatures both initially and at the end of working time. For compliance, a grout must achieve a conservative 28-day strength of 5000psi (34.5 mPa). Most specifications require higher strength. A good rule of thumb is an over design factor of 1.5 that of the concrete foundation. This would require the non-shrink grout to have compressive strength in the 8000 to 9000psi range.
Although C1107 addresses grout limitations with respect to temperature, consistency, and working time, it fails to set limits for these parameters, allowing manufacturers to do so. A grout with very narrow limits may comply with C1107, but such narrow parameters could result in failure. For example, a product that is non-shrink at 20 degrees C (70 degrees F) may not be at 32 degrees C (90 degrees F). In other words, a grout that is working well on a project in Philadelphia, may not work in Phoenix.
C1107 does not address bleeding. A grout that bleeds free water due to consistency or temperature results in a void under the base plate (or surface) once the water has evaporated.
Though all grouts are tested for height change of the hardened grout at 1, 3, 14, and 28 days in accordance with ASTM-C1107 Standard Test Method of Measuring Changes in Height of Cylindrical Specimens from Hydraulic-Cement Grout, Grade A grouts do not have to meet the hardened maximum expansion required of B and C grouts. The higher expansion allowed for Grade A grouts can result in lower compressive strengths and may not compensate for long-term drying shrinkage. Grade C grouts will perform as long as they have adequate post-hardening expansion to counteract drying shrinkage over a wide temperature range.
Will the grout offer adequate load support when the machine is running or when the precast or columns rest squarely on it? Does the grout shrink in 28 days? Only B and C grouts address post-hardening shrinkage. Specifying a grout material to comply with the most stringent requirements for fluid consistency, working time, and temperature range reduces potential problems on projects that experience those extremes. The following is a short-form specification for non-shrink grout.
Grout shall be prepackaged, non-metallic, and non-gaseous. It shall be non-shrink when tested in accordance with ASTM-C1107 Grade B or C at a fluid consistency (flow cone) of 20 to 30 seconds. Thirty-minute-old grout shall flow through the flow cone after slight agitation, in temperatures of 4 degrees C (40 degrees F) to 32 degrees C (90 degrees F). Grout shall be bleed free and attain 7,500 psi (51.7 mPa) compressive strength in 28 days at fluid consistency. Certified independent test data required.
L&M Construction Chemicals, Inc. non-shrink grouts CRYSTEX, PREMIER, DURAGROUT, and FERROGROUT meet ASTM-C1107 and CRD-C621 in all three grade classifications. However, even the best grouts may fail if not installed correctly. In addition to a good specification and an excellent product, the proper preparation, placement and protection of these materials is critical. I encourage you to review the new "How To Grout" manual now available at L&M. L&M's Engineers are always available to solve your toughest grout challenge.
© 2001 L&M Construction Chemicals, Inc. | ConcreteNews Spring 2001.