Civil Engineering Reference
In-Depth Information
Table 9.
Amounts of Calcium Hydroxide and Calcium Carbonate Formed
in Mortar Blends Exposed to Carbon Dioxide
Material
Contaminant
Calcium Hydroxide (%) Calcium Carbonate (%)
Unexposed
Exposed
Unexposed
Exposed
Cement
None
5.48
1.83
4.68
10.64
Cement
Cl + SO
4
6.10
1.70
1.70
16.70
Cement
+ Fly Ash
None
3.13
3.71
2.30
5.20
Cement
+ Fly Ash
Cl + SO
4
1.98
4.48
4.48
10.44
Cement
+ Silica Fume
Cl + SO
4
—
7.10
—
13.60
Cement
+ Slag
Cl + SO
4
—
5.30
—
13.20
Admixtures in concrete may remain in a free state, at the surface,
or chemically combine with the hydrating constituents of cement. The air-
entraining action of the air-entraining agent involves adsorption at the air/
water and solid/water interfaces. An anion air-entraining agent, such as
vinsol resin, reacts with Ca(OH)
2
to form a precipitate of calcium salt.
Conduction calorimetry of cement treated with a sodium oleate-based air-
entraining agent indicates that the C
3
S is peak unaffected, but the peaks due
to C
3
A hydration are accelerated.
[90][91]
The ettringite and monosulfate
reactions are retarded, possibly caused by an impermeable layer of Ca
oleate aluminate hydrate salt. In the presence of neutralized wood resins,
high dosages lead to the retardation of C
3
S hydration while the C
3
A
hydration is accelerated.
Unsaturated fatty acids, such as oleates and others used as water-
proofers, affect the hydration of cement. The tricalcium silicate peak in the
calorimetry is unaffected, but the ettringite and monosulfate reactions are
affected substantially.
[91]
A composite concrete material containing polymers and cement
has superior properties to those of conventional concrete. Several types
of polymer concretes have been fabricated and examined for their
