In summer 2016, SAME published a special issue of The Military Engineer commemorating the service and contributions of military engineers in the Vietnam War. To accompany the publication, we are featuring on Bricks & Clicks a special series entitled TME Looks Back: Vietnam featuring past articles, photos, and other material that first appeared in the magazine during the 1960s and early 1970s.
Taming the Sands of Cam Ranh
By By Lt. Col. James M. Mueller, Corps of Engineers, United States Army
The Cam Ranh Peninsula, Vietnam, composed of a series of sand dunes covered with sparse, low scrub, lies at 12 degrees north latitude, 109 degrees 15 minutes east longitude, and juts into the South China Sea. Lying in a generally north-south direction, the peninsula connected to the mainland at the northern end, and forms an inner harbor of some 40 square kilometers of protected water with depths to 24 meters. The southern top of the land has a formidable range of granitic mountains that average some 100 meters above sea level, and are covered with scrub and some gnarled trees. Nestled within this range is a small, fresh-water lake, the level of which varies with the season.
When the first American troops1 landed at Cam Ranh Bay in early June 1965, they were faced with the immediate problem of providing trafficable surfaces for military forces, since Cam Ranh Bay, the most accessible sheltered harbor in Vietnam, was to become a major logistic center. Only one narrow unpaved road existed on the entire peninsula.
The dune sand of Cam Ranh peninsula is fine, smooth grained, and of uniform size (Figure 1). Angularity is completely lacking and the sand shifts with the monsoon much the same as dry powder snow. Rock placed on the surface soon disappears under traffic. Four-wheel-drive military vehicles can maneuver fairly well, but six-wheel-drive vehicles have extreme difficulty because of the washboarding effect of the rear dual wheels. Standard mud and snow tires are being used, because there are no special sand tires available. An economical method of stabilization had to be developed promptly with the local materials at hand.
To provide roads on the unstable sand, tests were conducted on sections of heavily traveled routes leading to the ammunition supply point and the depot. Sections were 500 meters long and 10 meters wide.
Section I consisted of 100 percent in-place sand. This was mixed with 10 percent Portland cement and sufficient fresh water to provide optimum moisture content for mixing by a road-material mixer. The soil was compacted with a 13-wheel, rubber-tire roller, then with a smooth-wheel roller, and was moist-cured for seven days. A CBR of 90.7 percent at 0.1-inch penetration was obtained after 23 days.
Section II consisted of 40 percent in-place sand and 60 percent coral fines. This was treated with a 6 percent RC-3, cutback further with 1 part gasoline to 2 parts asphalt by volume. The mix was blended by the material mixer to a depth of 10 inches, bladed, and compacted by a rubber-tire roller. A CBR of 12.7 percent was obtained after 31 days of curing.
Section III was 40 percent in-place sand and 60 percent coarse beach sand from the mainland (Figure 2), treated with straight 6 percent RC-3. The mix was blended to a 6-inch depth, bladed and compacted by a rubber-tire roller. A CBR of 13.6 percent resulted after 31 days.
Section IV, composed of 40 percent in-place sand and 60 percent granitic quarry screenings, also was treated with a straight 6 percent RC-3 asphalt, and similarly compacted. The result was a 12 percent CBR after a 31-day cure.
Section V consisted of 100 percent in-place dune sand. It was treated with 6 percent RC-3, and half of the section was tilled to 6 inches and half to 10 inches. CBR’s of 5.8 percent and 6.8 percent were obtained, respectively, after 31 days.
Section VI was of 100 percent coral fines. Combined with it was 10 percent Portland cement mixed by the road-material mixer to a 10-inch depth. This was watered to optimum moisture content, and compacted by rubber-tire and smooth-wheel rollers. A CBR of 117.5 percent was obtained after 23 days.
Section VII was a strong coral section of 12 inches of fines overlaid with 6 inches of crushed coral, watered, and compacted.
Section VIII consisted of decomposed granite mixed with Portland cement to a depth of 8 inches. One bag of cement was placed every 5 feet laterally and every 4 feet longitudinally. Spreading was done by a grader and mixing by the road-material mixer. Moist curing was continued for seven days.
Section I (sand/cement): The surface of this section wore rapidly under traffic but proved to be a very good base course. When overlaid with hot mix, cold mix, or double bituminous surface treatment it stands up well under heavy traffic with few maintenance problems.
Section II (sand/coral fines/asphalt): Under heavy traffic this combination showed only minor deflection and cracking. Under light traffic such as in cantonment areas, it stands up well with only minor maintenance.
Section III (sand/beach sand/asphalt): This appears to have no structural advantage over the Section II mix. The availability of beach sand compared with mined coral was a slight advantage to operations, but the length of haul, some 13 kilometers, rules out the use of course beach sand from the mainland.
Section IV (sand/quarry screenings/asphalt): Although the strength developed was comparable to that of Section II and III, the materials were more readily available. For light traffic this combination is satisfactory, provided it is maintained at the regular intervals.
Section V (sand/asphalt): This section was displaced severely under traffic and failed completely in a very short time. The excessively smooth, uniform sand could not be sufficiently strengthened with an asphaltic binder.
Section VI (coral/cement): This section proved to be an extremely strong base course. When protected by a wearing surface, this provides an all-weather, heavy duty road.
Section VII (coral fines/crushed coral): This combination compares favorably in strength with that of Section VI, and is less expensive. The road to the ammunition supply point was built entirely of coral. A 3-inch hot mix wearing surface was applied to prevent traffic from abrading the coral and causing a serious dust problem. Some 1,500 tons of traffic daily have had no deleterious effect on this road.
Section VIII (decomposed granite/cement): A very substantial base course resulted from this combination. All depot roads are being constructed of this material, some being overlaid with cold mix, others with hot mix asphalt. The only difficulty has been excessive “bleeding” of the cold mix under the high ambient temperatures (120 degrees Fahrenheit), requiring constant blotting.
For heavily traveled roads, the stabilization methods considered satisfactory are those used for Sections I, VI, VII, and VIII.
For lightly traveled areas, the combinations used for Sections III, IV, and VI are satisfactory.
The method used for Section V was found to be completely unsatisfactory.
[reprinted from TME / July-August 1966]