TABLE 1: Concrete Mix Proportions (kg/m)

Six 100 mm cubes had ±2 mm removed from all external surfaces on a high speed facing machine. This was necessary to remove the distorting influence of different amounts of mould oil and laitance on the surfaces. The cubes were then halved as shown in Figure 1. This resulted in 12 ‘slab’ samples which were divided into 3 groups of 4 slabs each to be treated as follows: Group 1: exposed to carbonic acid water; periodically brushed.