ISSN: 1546-962X
Published Online: 28 December 2005
Page Count: 7

Relationship Between Indentation Hardness and Water to Cement Ratio of Hardened Mortar and Concrete

Cong, DX
Senior Petrographer, Wiss, Janney, Elstner Associates, Inc., Austin,Texas

Reed, MH
Senior Petrographer, Wiss, Janney, Elstner Associates, Inc., Northbrook,Illinois

Powers, LJ
Consultant, Wiss, Janney, Elstner Associates, Inc., Northbrook,Illinois

Shotwell, BL
Consultant, Wiss, Janney, Elstner Associates, Inc., Twinsburg,Ohio

Brown, BD
Materials Specialist, Buehler, Etd., Lake Bluff,Illinois

(Received 6 December 2004; accepted 14 September 2005)

Abstract

Accurately estimating the water-to-cementitious materials ratio (w/cm) of hardened concrete is one of the most difficult tasks frequently requested of concrete petrographers. Different methods have been developed and implemented with varying degrees of success. To increase the reliability of estimated w/cm, the indentation hardness of laboratory prepared specimens of neat paste, mortar, and concrete was evaluated using a Buehler semi-automatic testing machine. Preliminary results indicate good correlations between the average indentation hardness measured on the Rockwell HRL scale and the w/cm of the specimens. The data demonstrate a potential for using these correlations to estimate the w/cm of hardened concrete. Testing protocols, sample preparation requirements, and the effects of aggregate and of the composition of concrete mixtures (portland cement and fly ash content) are illustrated. Directions for future work are also discussed.

Keywords:
Rockwell indentation hardness, water to cement ratio, mortar, concrete, paste, fly ash

Paper ID: JAI13060
DOI: 10.1520/JAI13060
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