• Calabria-Holley, Juliana
• Harris, Jack
• Paine, Kevin A.
• Zhou, Yanjun

Abstract

The University of Bath has developed an innovative fibre cement capable of achieving flexural strengths in excess of 30 MPa. These fibre cements are manufactured by a bespoke method at a low water/cement ratio (less than 0.2). Consequently after hardening there is a considerable quantity of unhydrated cement (a quaternary blend of Portland cement-fly ash-silica fume and limestone) left in the paste. As a result of this it has been considered that after cracking these fibre cements will have significant potential for autogenous healing primarily as a consequence of the hydration of this unhydrated cement and associated pozzolanic reactions. This paper reports on research carried out to test this hypothesis. A number of fibre cements were cast and then cracked after 28 days of curing. The fibre cements were then subject to a number of healing regimes. It was shown that substantial post-crack healing did occur in fibre cements; conventional fibre cements cast at a higher w/c ratio (0.5) were shown not to heal. The precise mechanism of healing was, however, less clear and appears to be due to the leaching of calcium hydroxide and its subsequent carbonation rather than delayed hydration. Reasons for this are discussed in the paper.

Topics

• impedance spectroscopy
• laser emission spectroscopy
• crack
• strength
• cement
• flexural strength
• leaching
• Calcium
• curing