Cement manufacturers are being placed under ever more restrictive regulations regarding emissions and the environment. Still, most US plants are producing cement at near capacity due to the large demand by the concrete construction community. Much of this cement is being utilized in the newer high-performance low water-to-cement (w/c) ratio concretes. Unfortunately, as noted by Taylor [1], for w/c ratios below about 0.38, complete hydration of the cement will not occur. In fact, a portion of the relatively costly cement particles will remain unhydrated and thus serve only as reinforcing fillers. Cement is a rather expensive filler material, so it should be of great cost benefit to the industry to find a solution to this problem.
Previously [2,3], it has been suggested that some of the energy costs related to grinding could be saved by using coarser cements in these low w/c ratio high-performance concretes. In this paper, an alternative solution will be explored, namely, the replacement of a fraction of the coarse cement particles by an inert (and inexpensive) filler. Computer modeling studies using the NIST cement hydration and microstructure development model (CEMHYD3D) will be used to contrast the predicted hydration and compressive strength development of systems with filler replacement to those where the complete original cement particle size distribution is used (no filler replacement). It should be noted that the technology of manufacturing a cement with only the coarse fraction replaced by limestone (or another basically inert filler) or a cement with a reduced maximum particle size would need to be more fully developed. But, such technology could provide benefits in reduced energy and raw material consumption and reduced emissions of carbon dixoide per ton of concrete binder produced.