Texas Transportation Institute (TTI) Senior Research Engineer Tom Scullion recently visited road builders in the Dominican Republic (DR) to help them upgrade their transportation network. This small island nation is upgrading its infrastructure by building their equivalent of the United States Interstate Highway System. The upgrade is over a billion dollar effort. One of the major links under construction is the AutoPista Del Coral, which links major tourist resorts in the east of the island. Under the supervision of TecnoAmerica, the Brazilian contractor Odebrecht is constructing this important roadway.
The DR’s current road system dates back to a time of dictatorship, when all roads literally led to the capital. As a result, finding a direct route from one side of the island to the other has been nearly impossible. The new construction effort aims at expanding the road network and connecting more cities. The new network is aimed at expanding the islands tourist business and also aiding both the agricultural and mining industries.
The local engineers prefer to use cement-treated bases to handle their heavy truck loads and wet climate. Their main concern has been excessive shrinkage cracking, which can severely impact pavement life. Several years ago the DR engineers began following research conducted at TTI by Scullion and TTI Associate Research Scientist Stephen Sebesta.The researchers developed a procedure to alleviate this problem, referred to as microcracking.
Two days after finishing, a cured concrete-treated base is subjected to 2 to 4 passes with a heavy slow moving vibratory roller. This causes the base to develop a network of fine cracks. This crack relief pattern helps prevent wide cracks in the base as the material continues to cure with time. The fine crack pattern also minimizes the risk of cracks in the base reflecting through the asphalt surface layer. The microcracks release pressure like tiny fault lines in a tectonic plate.
“The Brazilian contractor had never seen this technique before and they were concerned that it may impact long term strength gains,” says Scullion. “I had to go down and convince the contractor that this was a good idea. The Dominicans had actually built some test sections with and without microcracking. I helped in processing falling Weight Deflectometer strength data and then met with the contractor to discuss the pros and cons.”
Details on the microcracking procedure can be found in Project Summary Report 0-4502-S: Microcracking for Reduced Shrinkage in Cement-Treated Base.