Chemical stabilizers

The frost susceptibility of soils is always of concern in any construction project in the cold regions whether it is in Minnesota, Alberta, the Yukon Territory, or Alaska. Wherever the temperature of the region falls below freezing for a long enough period to cause significant frost penetration of the soil, the problems associated with frost heaving and jacking are of concern. We typically dismiss the problems by specifying "non-frost-susceptible soil" in the design. However, many areas of the north, particularly the far north simply do not have a source of non-frost-susceptible material available. Such materials must be imported from other areas often at great expense. This is a particularly acute problem in remote areas of northern Canada and Alaska where shipping is by barge, and the barge can operate only in the summer. In such areas local materials must often be used to make the project economically feasible. Higher

maintenance costs must be expected of course, but there simply is no alternative.

Modification of local materials to eliminate or reduce their degree of frost susceptibility is an area of research with large potential for cost savings. Danyluk (1986) tested eight possible stabilizing additives. The purpose was to determine if they could be used to alter the soil sufficiently to increase the unconfined compressive strength, permeability, and after-thaw California Bearing Ratio (CBR). Table 4. shows the results of Danyluk's stabilizer experiments.

Although 10% calcium acrylate additive gave the overall best performance, it is considered too expensive to be used on a large scale. Twenty percent Type I Portland cement with 2% calcium chloride provided the best results in the range of materials that could be considered economically feasible on a moderate scale. Cost analysis indicated that it would cost

TABLE 4. Results of Stabilizers in Fine -Grained Soil

	Unconfined
	Compressive		Frost-Heave	After
Stabilizer	Strength	Permeability	Ratio	Thaw
(% by Weight)	Ob/in	(cm 590-X 1Q-5)	Treated/Untreated	CBR
Untreated	13.4	4.5	1.0	0.4
20% Cement	39.2	2.9	1.12	3.1
20% Cement. 2%
calcium chloride	64.0	0.7	0.91	7.2
20% Cement. 2%
sodium sulfate	55.1	0.8	0.85	2.3
20% Cement. 20%
Hydrogen peroxide	31.8	1.4	1.05	4.3
20% Lime	292	8.5	1.11	06
8% Asphalt emulsion	51.6	0.28	0.85	3.7
10% Calcium acrylate	3480	0.09	0.35	21.2
l%Tetrasodium
Pyrophosphate	208	0 12	0.28	26

Danyluk (1986).

California bearing ratio between $18 and $39 per cubic yard FOB Anchorage, Alaska. These prices still make the additive prohibitive for all but limited applications, but may be attractive for smaller scale projects such as around foundations of small structures, driveways and access ramps or where surface conditions are more critical such as airstrips and runways.

More recently work in Alaska has centered on the use of fly ash from coal burning power plants as a stabilizing additive. The lime content of Alaskan coal is high, and although lime is not the most effective additive in Danyluk' s study, it is locally available in Alaska and therefore becomes economically attractive.

Chemical additives for soil modification is clearly a research area that needs more work to find effective and economically feasible materials.

Words and expressions:

Frost susceptibility Морозоустойчивость

Acute problem Острая проблема

Barge Баржа .,

Degree Степень

Additive Добавка

Ratio Соотношение

Lime Известь

Price Цена

Airstrip Взлетно-посадочная площадка

Runway Взлетно-посадочная полоса