10.1.2S urface Abrading
Surface abrading can be accomplished by
1. Mechanical abrading
2. Water blasting
3. Abrasiveb lasting
Of the three methods to produce ar oughened surface, the most technically
effective is abrasive blasting by means of sandblasting or shot blasting
followed by broom sweeping, vacuum cleaning, or an air blast to remove the
abrasive. However, in someinstances this may notbeapracticalapproach.
10.1.3A cid Etching
Acid etching is apopular procedureused for both new and aged concrete. It
mustb er emembered that during this process, acid fumesw illb ee volved
that may be objectionable. Also thorough rinsing is required that saturates
the concrete. Thism ay necessitate al ong drying period, depending on the
coating to be used.
10.2C oating Selection
The coating to be selected willd epend on the physical properties and
conditions of the concrete as wella st he environmental conditions.
Factors such as alkalinity,p orosity,w ater adsorption and permeability,
and weak tensile strength must be considered. The tendency of concrete to
crack, particularly on floors, must also enter into the decision. Floorc racks
may develop as ar esult of periodic overloading or from drying shrinkage.
Dryingshrinkage is not considered aworkingmovement, whereas, periodic
overloading is. In the former,arigid flooring system could be used, whereas,
in the latter,a ne lastomeric caulkingo ft he moving cracks would be
considered.
Selection may be influenced by the presence of substrate water during
coating. If the concrete cannotbedried, one of the varieties of water based or
water tolerant systems should he considered.
When aggressive environments are present, the surfaceprofile and surface
porosity of the concrete mustbetaken into account.Ifcomplete coverage of
the substrate is required, specification of film thickness or numbero fc oats
may needtobem odified. Block fillers may be required. In anonaggressive
atmosphere, an acrylic latex coating may suffice.
Specifice nvironmentalc onditionsw illd ictate thet ypeo fc oating
required. Not only do normal atmospheric pollutantshave to be considered,
but any specific local pollutantsw illa lso have to be taken into account.
Corrosion of Linings and Coatings
518
CAT8247—CHAPTER 10—6/10/2006—12:52—SRIDHAR—XML MODEL B–pp. 515–532
Surface abrading can be accomplished by
1. Mechanical abrading
2. Water blasting
3. Abrasiveb lasting
Of the three methods to produce ar oughened surface, the most technically
effective is abrasive blasting by means of sandblasting or shot blasting
followed by broom sweeping, vacuum cleaning, or an air blast to remove the
abrasive. However, in someinstances this may notbeapracticalapproach.
10.1.3A cid Etching
Acid etching is apopular procedureused for both new and aged concrete. It
mustb er emembered that during this process, acid fumesw illb ee volved
that may be objectionable. Also thorough rinsing is required that saturates
the concrete. Thism ay necessitate al ong drying period, depending on the
coating to be used.
10.2C oating Selection
The coating to be selected willd epend on the physical properties and
conditions of the concrete as wella st he environmental conditions.
Factors such as alkalinity,p orosity,w ater adsorption and permeability,
and weak tensile strength must be considered. The tendency of concrete to
crack, particularly on floors, must also enter into the decision. Floorc racks
may develop as ar esult of periodic overloading or from drying shrinkage.
Dryingshrinkage is not considered aworkingmovement, whereas, periodic
overloading is. In the former,arigid flooring system could be used, whereas,
in the latter,a ne lastomeric caulkingo ft he moving cracks would be
considered.
Selection may be influenced by the presence of substrate water during
coating. If the concrete cannotbedried, one of the varieties of water based or
water tolerant systems should he considered.
When aggressive environments are present, the surfaceprofile and surface
porosity of the concrete mustbetaken into account.Ifcomplete coverage of
the substrate is required, specification of film thickness or numbero fc oats
may needtobem odified. Block fillers may be required. In anonaggressive
atmosphere, an acrylic latex coating may suffice.
Specifice nvironmentalc onditionsw illd ictate thet ypeo fc oating
required. Not only do normal atmospheric pollutantshave to be considered,
but any specific local pollutantsw illa lso have to be taken into account.
Corrosion of Linings and Coatings
518
CAT8247—CHAPTER 10—6/10/2006—12:52—SRIDHAR—XML MODEL B–pp. 515–532