Interground Limestone Cement: Construction and 2-yr Performance of a Concrete Test Section

Several countries around the world have used interground limestone cement (ILC) for several years in concrete construction. The results from various research projects do not all agree on the influence interground limestone has on the plastic and hardened properties of concrete, but most agree that the variability can be controlled if the limestone content remains at or below 5%. To better understand the performance of ILC, a test section of concrete flatwork was poured in a median in Baxter, Minnesota in October 2004. This test section was constructed with concrete made with and without interground limestone in the cement. The physical and chemical properties of both cements were very similar. Tests of the fresh and hardened properties of both concretes placed in the field suggest very similar properties with slightly higher strengths for the interground limestone cement. The reason for the increased strength of the interground limestone is uncertain but may have been related to a reduced w/cm ratio. The test section is performing well after more than 2 years. Based on this small test section it appears that mechanical properties similar to normal concrete can be achieved using <5% interground limestone in the cement.