Government Building, 1 William Street, Brisbane

The new Queensland Government Executive building at 1 William Street, Brisbane currently under construction by Brookfield Multiplex Australasia was experiencing surface damage to part of the carpark entry ramp.

For this reason, a topping stronger than the original concrete was required with the ARDEX epoxy screed being selected by Master Floor Preparers (Qld) Pty Ltd as the most suitable system for this application.

The area to be covered was located in the transition zone to the carpark level at the base of the ramp, approximately 6 metres long by 1.6 metres wide and 35 mm thick.

ARDEX Abapoxy was used as the binder for the topping screed, making up approximately 10% of the mixed material. The filler used was ARDEX A 38 Gravel mix, 0-4mm size. This consistency provided close packing that was required so the topping is better able to resist the anticipated loads, although the mix was subject to the availability of these sand sizes and some variation in both sand size and mix ratio was possible. In addition, the sand had to be both washed and dried.

The binder mix consisted of 2 volumes of Abapoxy Part A with 1 volume of Abapoxy Part B mixed together to achieve a homogenous colour. The blended filler sand was added and mixed with a mechanical mixer to achieve a slump free mortar to ensure all the sand was coated with the epoxy binder.

The concrete had to be dry and mechanically prepared to remove all contaminants such as curing compounds and laitance, in addition to being vacuumed to remove any dust.

The procedure was to apply a bond coat of ARDEX Abapoxy with a brush or roller to achieve a uniform thin coating over the prepared concrete immediately prior to placement of the epoxy mortar.

Puddles were brushed out of the epoxy resin bond coat prior to placement of the epoxy screed mortar, the epoxy mortar had to be compacted during placement to remove air pockets. It was then left to harden overnight prior to allowing access to pedestrian traffic, as well as allowing 7 days for the screed to fully cure before allowing vehicular traffic.