Table 16. Summary of tensile strength data.
3 x 10 7
Percent
Curing
fines
Cement
Tensile strength
Days
passing
content
(kPa)*
40
7
Material
no. 200 sieve
(%)
Before freeze Residual
2 x 10
Hart (SM)
19
5
250
20
15
540
720
Graves (SM)
33
5
76
35
10
221
165
15
460
475
1 x 10 7
180
Sibley (SC-SM)
42
5
610
550
10
710
720
15
1010
1180
DGS (SP-SM)
9
5
400
40
10
790
420
Hyannis (SM)
23
5
69
21
8
4 x 10
10
280
120
0
1.0
2.5
5.0
7.5
15
410
490
Ca(OH)2 (percent by wt.)
Manchester silt
93
5
7
0
Figure 21. Effect of lime content on the permeability
(CL-ML)
10
14
1
of the soilcement mix (1 cm/s =3.3 102 ft/s).
15
25
24
Ikalanian (SM)
35
5
9
1
0.25 was assumed. Again, as with the tensile
10
27
20
strength data, most of the soils had reduced
* 1 kip/in.2 = 6.89 MPa.
strength when only 5% cement was used. Increas-
reason, because the before-freeze tensile
ing the cement content to 10% and above actually
strengths actually increased with increased lime
increased the stiffness of the material by about 10
content.
to 30% after freezethaw cycling. Although the
The resilient modulus tests were done at 5% of
material has a high elastic modulus, the tensile
the tensile strength load level. A Poisson's ratio of
strength data show a reduction of strength at the
same lime content. However, the results were at
Table 17. Summary of resilient modulus data.
optimum moisture content. Changing the mois-
ture content to saturation levels (as occurs during
Cement Before-test*
the thaw periods) may produce lower modulus
content modulus
Thaw modular ratios (%)
values. At low lime content (≤6%), Brandl (1981)
Material
(%)
(MPa)
1-cycle 3-cycle 12-cycle
reported that the permeability of lime treated ML
Hart (SM)
5
1931
0.64
0.30
0.04
soils increased (Fig. 21).
10
17582
0.98
1.00
1.01
15
22629
0.91
0.98
1.03
Graves (SM)
5
1820
--
0.23
0.10
CONCLUSION
10
4599
--
1.17
1.32
15
9494
--
1.17
1.18
We evaluated 11 FAA subsurface material speci-
fications for freezethaw resistance. Most of the
Sibley (SC-SM)
5
11784
1.00
1.08
10
10915
1.04
1.06
1.20
unstabilized materials allowed up to 15% fines
15
14824
0.96
1.13
1.21
passing the no. 200 sieve, with the exception of the
crushed aggregate base, which allowed no more
DGS (SP-SM)
5
21892
0.95
0.02
0.00
10
28056
0.88
0.85
0.69
than 8% fines, and the sandclay base, which al-
lowed up to 25% fines. We came to the following
Hyannis (SM)
5
3234
0.88
0.35
0.25
10
7315
0.91
0.45
0.41
conclusions on the basis of our review of the litera-
15
10977
0.99
1.022
1.04
ture.
With the exception of the P-154 (subbase)
Ikalanian (SM)
5
3592
--
0.50
0.35
10
7460
--
1.06
1.15
and P-209 (crushed aggregate) materials, the
remaining unstabilized soils did not meet
Fairbanks (ML)
5
7522
0.96
1.16
1.17
10
14976
1.00
1.11
1.15
the COE frost-susceptibility requirements of
no more than 3% finer than 0.02 mm
* 1 kip/in.2 = 6.89 MPa.
24
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