10
Coatings for Concrete
The life of concrete can be prolonged by providing ac oating that willb e
resistant to the pollutants present. These coatings are referred to as monolithic
surfacings. Before selectinga na ppropriate coating, consideration must be
given to the conditionofthe concrete and the environment that the concrete
will be exposed to.P roper surfacep reparation is essential.S urface
preparations can be different for freshly placed concrete than for old concrete.
When concrete is poured, it is usuallyh eld in place by means of steel or
wood formsthat are removed when the concrete is still in its tender state. To
facilitate their removal, release agents are applied to the formsp rior to
pouring. Oils,greases, and proprietary release agents are left on the surface
of the concrete. These must be removed if they willi nterfere with the
adhesion of subsequent coatings.
Quite often, curing compounds area pplied to fresh concrete as soon as
practicala fter the formsh ave been removed. Thesea re liquidm embranes
based on waxes, resins, chlorinated rubber,orother film formers, usually in
as olvent. Pretesting is necessary to determine whether or not they will
interfere with the coating to be applied.
Generally,admixtures that are added to concrete mixesinorder to speed
up or slow downt he cure, add air to the mix, or obtain special effects will
not interfere with surfacet reatments to improve durability.T he concrete
supplier can furnish specificdataregarding the admixtures. If in doubt, try a
test patch of the coating material to be used.
It is essential that water from subslab ground sources be eliminated or
minimized since migration through the concrete may create pressures at the
bond line of water resistant barriers.
As discussed in Chapter 9u nder portland cement coating, when water
is added to portland cement,ac hemical reaction takesp lace during the
hardening. This reaction produces calciumh ydroxide andt ricalcium
silicate hydrate. The alkalinity of concrete is provided by the presence of
calciumo xidef rom the cement.C onsequently,c oncrete attack can be due
to chemicals thatr eact with the portland cement binder andf orm
conditions that physically deteriorate the material. Anym aterial that will
CAT8247—CHAPTER 10—6/10/2006—12:52—SRIDHAR—XML MODEL B–pp. 515–532
515
Coatings for Concrete
The life of concrete can be prolonged by providing ac oating that willb e
resistant to the pollutants present. These coatings are referred to as monolithic
surfacings. Before selectinga na ppropriate coating, consideration must be
given to the conditionofthe concrete and the environment that the concrete
will be exposed to.P roper surfacep reparation is essential.S urface
preparations can be different for freshly placed concrete than for old concrete.
When concrete is poured, it is usuallyh eld in place by means of steel or
wood formsthat are removed when the concrete is still in its tender state. To
facilitate their removal, release agents are applied to the formsp rior to
pouring. Oils,greases, and proprietary release agents are left on the surface
of the concrete. These must be removed if they willi nterfere with the
adhesion of subsequent coatings.
Quite often, curing compounds area pplied to fresh concrete as soon as
practicala fter the formsh ave been removed. Thesea re liquidm embranes
based on waxes, resins, chlorinated rubber,orother film formers, usually in
as olvent. Pretesting is necessary to determine whether or not they will
interfere with the coating to be applied.
Generally,admixtures that are added to concrete mixesinorder to speed
up or slow downt he cure, add air to the mix, or obtain special effects will
not interfere with surfacet reatments to improve durability.T he concrete
supplier can furnish specificdataregarding the admixtures. If in doubt, try a
test patch of the coating material to be used.
It is essential that water from subslab ground sources be eliminated or
minimized since migration through the concrete may create pressures at the
bond line of water resistant barriers.
As discussed in Chapter 9u nder portland cement coating, when water
is added to portland cement,ac hemical reaction takesp lace during the
hardening. This reaction produces calciumh ydroxide andt ricalcium
silicate hydrate. The alkalinity of concrete is provided by the presence of
calciumo xidef rom the cement.C onsequently,c oncrete attack can be due
to chemicals thatr eact with the portland cement binder andf orm
conditions that physically deteriorate the material. Anym aterial that will
CAT8247—CHAPTER 10—6/10/2006—12:52—SRIDHAR—XML MODEL B–pp. 515–532
515