Reference: D. P. Bentz and J.T. Conway, Cement and Concrete Research, 31, pp. 503-506, 2001.
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COMPUTER MODELING OF THE REPLACEMENT OF "COARSE" CEMENT PARTICLES BY INERT FILLERS IN LOW W/C RATIO CONCRETES: HYDRATION AND STRENGTH





D.P. Bentza and J.T. Conwayb

aBuilding and Fire Research Laboratory
100 Bureau Drive Stop 8621
National Institute of Standards and Technology
Gaithersburg, MD 20899-8621 USA
bHolnam Inc.
6211 Ann Arbor Road
Dundee, MI 48131 USA





ABSTRACT

In concretes with water-to-cement (w/c) ratios below about 0.38, a portion of the cement particles will always remain unhydrated due to space limitations within the material. Thus, in many of the high-performance concretes currently being produced, cement clinker is in effect being wasted. This communication examines the possibility of replacing the coarser fraction of a cement powder by an inert filler, to conserve cement without sacrificing material performance. Using the NIST CEMHYD3D cement hydration model, it is demonstrated that for "initial" w/c ratios of 0.25 and 0.30, a portion of the coarser cement particles can be replaced by inert fillers with little projected loss in compressive strength development. Of course, the optimal replacement fraction depends on the initial w/c ratio, suggesting that blended portland/inert filler cements need to be produced with the end concrete mixture proportions in mind. This further implies that a cement/inert mixture of specific proportions will only perform optimally in a limited range of concrete mixture proportions.

Keywords: Blended cements (D), compressive strength (C), hydration (A), modeling (E), particle size distribution (B)



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