Preparation of Concrete Surfaces before Waterproofing System

• Form release agents, such as oil, grease, wax, and
  silicones, will transfer from the forms to the surface of the
  concrete during casting. These will cause poor adhesion of
  waterproofing systems.
• Concrete curing compounds may contain waxes, resins,
  chlorinated rubber, or film formers of various types. If such
  materials must be used, the specifier should be certain that the
  materials can be completely removed.
• Admixtures such as water-immiscible chemical curing
  agents are sometimes used in concrete. These should be
  avoided.
• Laitance, dust and dirt, moisture, and grease, and oil can
  inhibit or impair the adhesion of the waterproofing system. These
  must be removed
• Moisture contained within the matrix of the concrete as
  well as surface moisture present from curing or precipitation
  events can impair adhesion of the waterproofing system.
  Where possible, the concrete surface to receive waterproofing
  should be protected from precipitation for a minimum of 48 h
  prior to application of the waterproofing.

Repair of Surface Defects

• Surface defects that may impair adhesion
  include honeycomb, fins, “snots,” tie holes, “bug holes,” sharp
  offsets from displaced forms, rutted cracks, ragged corners,
  deviations in the surface plane, and other similar concrete
  defects, along with spalling and delaminations of the concrete
  surface.
• Fins, protrusions, or similar irregularities should be cut
  back to the surface by chipping, grinding, bushhammering, needle gunning, or wire brushing. Avoid polishing of the concrete surface by these techniques
• Sharp offsets in the surface, such as those caused by
  formwork misalignment, should be cut back to an even surface
  by chipping, grinding, bushhammering, needle gunning, wire brushing, or transitioning with grout or patching mortar. 
• Defective concrete areas should be removed down to
  sound concrete, preferably by chipping; if grinding is
  necessary, care must be taken to avoid “polishing” the surfaces.
  If sizable areas or amounts of unsound concrete are found, a
  structural engineer shall specify appropriate corrective action.
• Cracks exceeding 2 mm [1⁄16 in.] should be investigated to
  determine whether they are still active. Such cracks should be
  chipped or routed out before being patched, and edges should
  be undercut slightly as recommended by the manufacturer of the patching
  material. No feathered edges shall be permitted. Tie holes and
  “bug holes” larger than 16 mm [5⁄8 in.] in diameter or deeper
  than 3 mm [1⁄8 in.], or both, should be prepared similarly for
  patching.
• The areas to be patched, along with a band at least 150
  mm [6 in.] wide surrounding it, should be dampened before the
  patching application to prevent rapid absorption of water from
  the bonding grout and the patching mortar, 
• Immediately after the surface water has evaporated
  from the dampening step, a bonding grout or bond coat,
  consisting of approximately one part of cement to one part of
  fine sand passing No. 30 mesh sieve with an amount of water
  sufficient to obtain a consistency of thick cream, should be
  brushed thoroughly into the surface, 
•  The patching mortar should be made from the same
  materials and in the same proportions as the concrete, with the
  exception of coarse aggregate. (In any case, use no more than
  one part cement to 2.5 parts sand.) Mix the patching mortar
  thoroughly with an amount of water sufficient only to obtain
  the stiffest consistency that will permit placement. Apply the
  mortar as soon as the bonding coat begins to lose the water
  sheen.
• Chemical cleaning may be necessary prior to blast
  cleaning or acid etching, in order to remove surface contaminants such as oil, grease, and dirt. Solutions of 10 % caustic
  soda or trisodium phosphate may be used as well as
  proprietary detergents specially formulated for use on concrete.
  They should be applied with vigorous scrubbing, followed by
  flushing with water to remove all traces of both the detergent
  and the contaminant, until the surface is neutral or only slightly
  alkaline, as indicated by litmus or pH paper. Solvents must be
  avoided because they dissolve the oil, grease, etc., and spread
  the contamination over a larger area.

• Scarification by a mechanical impacting device is used
  on concrete surfaces to remove thick overlays of dirt, previous
  waterproofing membranes, or weak surface material. After
  scarification, water or sand-blasting is required to remove
  aggregates weakened by mechanical impacting. If the scarification process produces a surface too coarse or too uneven for
  proper adhesion, it should be made smooth with patching
  mortar.
• Blast cleaning is an effective method for the removal
  of laitance, dirt, efflorescence, and weak surface material.
  There are three types of blast cleaning methods: dry
  sandblasting, wet sandblasting, and high-pressure water jetting.
  Dry and wet sandblasting are usually the most effective.
  Abrasive cleaning techniques can also be used, provided the
  abrasive used does not contaminate the surface being prepared.
  Oils or greases should be removed prior to blast cleaning. If
  compressed air is used, it must be clean and free of water or oil.
  Care must be exercised to ensure that clean water is used for
  wet-blast cleaning. The concrete surface should be abraded in
  the blasting step to the extent that small aggregate particles are
  exposed. The amount removed should be sufficient to provide
  a strong, sound substrate suitable for the application of
  waterproofing.
• Acid Etching:
  6.5.1 General—Acid etching procedures may be used in
  lieu of mechanical cleaning procedures; however, mechanical
  abrading methods are preferred to acid etching because of
  possible chloride ion contamination (and resultant deterioration) of the concrete unless extreme care is taken and because
  acid etching is not as dependable as mechanical abrasion.
  Because of these factors and the potential hazards involved
  with the use of acid, as well as cleanup and environmental
  considerations, such cleaning should be used only where no
  alternative means of cleaning are possible and should be
  performed only by those experienced in its use.
• Etching Procedure—A 10/90 to 20/80 dilution of
  commercial-grade hydrochloric acid in water is typically
  prepared and applied to the concrete at a rate of 1.0 L/m2 [1
  qt/yd2
  ]. The surface to be etched is normally pre dampened to
  obtain a more uniform acid etch. The acid solution is scrubbed
  into the surface. Foaming will subside in 3 to 5 min, after
  D5295/D5295M − 14
  3
  which the surface should be flushed thoroughly with fresh
  water while scrubbing with stiff bristle brushes, in order to
  remove the salts formed by the acid reaction and to dislodge
  loose particles. A second treatment may be necessary to obtain
  a reasonably clean surface. When the presence of chlorides is
  inadvisable (due to effects on concrete or reinforcing steel), a
  15 % phosphoric acid solution should be used. The application
  and washing techniques are the same. The efficacy of the
  flushing operation should be verified at a number of points
  within the area treated by placing litmus or pH paper on the wet
  surface to determine that the surface is reasonably free of acid
  and chloride residues.