Concrete should be a minimum 50°F, adequately cured, possess adequate integrity and not be expelling excess water or hydration. A rule of thumb for cure of new concrete is 28 days cure at 70°F but that is not an assurance that the concrete has achieved adequate physical properties.
The prepared area should extend 2 inches (on all sides) beyond the width of the carbon fabric. In general, the surface must be dry, clean, free from dust, paint, coating, oil or dirt and free from frost. For bumps, fins and protrusions use hammer, sand blasting, pressure washing, shot blasting, grinding or other approved mechanical means to achieve an open-pore texture with a CSP (concrete surface profile) 3 or better per ICI Guideline 310.2R. Surface should be wiped with clean cloth after grinding, blasting, brushing surface to remove dust particles. Uneven surfaces (voids) and mortar joints must be filled with Gateway Composites 777 Fiberlock™ Epoxy Adhesive/Filler Compound. (2 part 1:1 mix ratio). 777 Filler Compound should be pressed into the voids/cracks and feathered for smooth surface. A smooth surface is critical for fabric bonding. Uneven surface can result in voids between fabric and substrate which leads to premature delamination of composite.