Nicaragua Report 2!
Methods of stabilizing road beds
The stabilizing process is a method of strengthening and improving the load bearing capacity of earth. The properties of earth are improved by mixing cement, lime, emulsified asphalt or foamed asphalt into sand or crushed stone. The stabilized earth adjusts water content, forms into a moderate grain size, and the synergy of the cement and lime binds the particles increasing the bonding strength.
The sites undergoing stabilization in Nicaragua are mountain roads, high bridges, two-lane unmade dual carriageways on the outskirts the prefecture capital Matagalpa about 40 minutes by car from Sebaco City, which is 90km northeast of the capital Managua.
Figure 1 shows one example of the stabilizing methods being used in Nicaragua. Stabilizing is conducted on 19cm of compacted crushed stone. The material available locally for stabilizing was crushed stone with a maximum diameter of 20mm. After laying the crushed stone with the grader, it was spread with cement. This was then all mixed with the road stabilizer PM550 and compacted to produce a 20cm thick stable roadbed. For this we used about 6% cement.
When using cement in road stabilizing, the hydration chemical reactions (the chemical reaction when cement mixes with water and hardens) cause the accompanying aggregate and particles of earth to bind together. The binding strength increases and reaches the required strength two weeks after mixing. As shown in the example in the diagram, the unconfined compression strength required should be over 0.7Mpa.
Finally, one layer ofasphaltmixturewill be laid onthestabilized roadbed to give asimplepaving finish.
In Nicaragua, of a total of 19,137 km of road, only 2,033 km are paved. So most are earth roads. On this project the rainy season arrived a few km into the construction, but although construction was interrupted, this road stabilizer activity will surely increase in the future.
Figure 1 An example of stabilization methods in Nicaragua
Preparation for Spreading Cement
Mixing with the PM550
Towns & Roads – Here & There
The only National Stairway
Route 339, Tappizaki, Aomori Prefecture
National Route 339 is 108km long, starting from Hirosaki City, Aomori Prefecture, passing through Tappizaki, made famous in the ballad "Tsugaru wintry scene," and ending at Sotogahama, Higashitsugaru. Located in Tappizaki District, this is the only road of Japan’s 459 roads that is, in part, a “National Stairway Road” and can only carry pedestrians. (A little to the right of Tappizaki is the Tsugaru-Kaikyo Line (Japan Rail) which links to Hokkaido by the under sea tunnel.)
Even road signed as a “National Stairway Road” like in the photo, this has become a popular sightseeing spot for veiwing Hokkaido across the Tsugaru Staits.
The stairway is a fairly steep cobblestone promenade with 362 steps and a total length 338m. In 1975, 20 years after it was designated a national road, the stairway was renovated. Later another road was built to carry vehicles and it was proposed to designate this new road National Route 339, but this faced fierce opposition from local people. Now that the name is well known, this spot has become an important tourist attraction and a great local resource.