STABILIZATION OF LATERITIC GRAVEL USING PRECIPITATED CALCIUM CARBONATE FOR THE USE OF SUBBASE CONSTRUCTION FOR LOW VOLUME ROADS: A CASE STUDY OF BATU TOWN

Abstract

Lateritic gravel materials do not satisfy the gradation requirement for subbase course as it is mostly composed of larger grain sized particles lacking of fine materials. The two most important factors likely to affect the engineering behavior of lateritic gravel materials were the gradation and the strength of the gravel particles which not satisfied by materials they are using at the moment. This thesis study has been done to check the use of blended precipitated calcium carbonate with lateritic gravel as subbase material for the construction of low volume roads in Batu town based on Ethiopia Roads Authority standard requirements for subbase materials. In the beginning engineering properties of both materials were studied by doing some laboratory tests on each materials differently and later the mechanical stabilization of lateritic gavel was carried out in blending of lateritic gravel with different proportion of Precipitated calcium carbonate. The optimum amount of precipitated calcium carbonate required for stabilization is obtained after the compaction test, as a result the maximum dry density attained was found to be 2.1g/cc after the blending of 30 percent precipitated calcium carbonate with 70 percent lateritic gravel. As the test result revealed the California bearing ratio values of blended materials were 42% which is more than Ethiopia Roads Authority specification requirement for low volume roads subbase. In addition to the improvement of California bearing ratio values the blending of precipitated calcium carbonate with lateritic gravel results in fulfill the Ethiopia Roads Authority specification requirement for gradation as it constitutes fine particles. The correlation of soaked California bearing ratio value and other independent variables like maximum dry density and optimum moisture content developed using Minitab statistical software to be Soaked California bearing ratio = -7.86 + 29.24 maximum dry density – 0.17 optimum moisture content. In conclusion the test results favors the use of blended Precipitated calcium carbonate and lateritic gravel as subbase material for low volume roads that can results in reduced cost road construction, reduced environmental problem caused by Precipitated calcium carbonate on children, improved California bearing ratio value and urban land use.