ABSTRACT
Further tests were undertaken to determine the amount of reactive material that could be expected to be retained on a cementitious substrate under simulated site conditions. In these tests circular mortar discs 48*5mm were prepared and cured in sealed bags. When cured they were air-dried to constant weight at the required test temperature. The penetrants were then applied and the discs were weighed at intervals during drying at 20 °C, 35 °C and 20 °C in a wind tunnel (air movement 6m/s). From Table 2 it can be seen that only 14% of monomeric silane was retained in the pores of the substrate at 20 °C. If the temperature was raised to 35 °C or if the sample was placed in a wind tunnel then the amount retained was reduced to less than 7%. In contrast 68% of the oligomerous siloxane was retained in the pores at 20 °C and a similar percentage was retained at 35 °C and in the wind tunnel. Thus it can be concluded that under site conditions siloxanes are more likely to be retained in a cementitious substrate and therefore give a more controlled degree of protection. With the inherent variability of concrete and application conditions there must be some uncertainty as to how much protection monomeric silanes can give.
