Determination of Dynamic Cone penetration Index (DCPI) of Borrow pit Materials for Construction of Low Volume Roads in Dodoma Tanzania.

Abstract

The study for determination of dynamic cone penetration index (DCPI) of borrow pit materials for construction of low volume roads was conducted in Dodoma region in Tanzania. Samples for tests were collected from five borrow pits which are Nkulabi, Zuzu, Mahomanyika, Dinda and Ntyuka. Results of plasticity indices were 14%, 11%, 10%, 16% and 13% for Nkulabi, Zuzu, Mahomanyika, Dinda and Ntyuka borrow pits respectively. Results of grading coefficients and shrinkage products were 33.7 and 148.1 units for Nkulabi, 19.9 and 295.9 units for Zuzu, 32.3 and 56.0 units for Mahomanyika, 25.4 and 391.3 units for Dinda and 32.8 and 111.2 units for Zuzu borrow pits respectively. Results of dynamic cone penetration indices were 5.8 mm/blow, 5.2 mm/blow, 4.7 mm/blow, 6.0 mm/blow and 4.5 mm/blow for Nkulabi, Zuzu, Mahomanyika, Dinda and Ntyuka borrow pits respectively. Specifications require DCPI values of the tested material not to exceed 5.69 mm/blow in order to be suitable for use as gravel wearing course material. Therefore, these results indicate that materials from Zuzu, Mahomanyika and Ntyuka borrow pits have satisfied the requirement hence qualify to be used as gravel wearing course material. However, materials from Dinda and Nkulabi borrow pits have DCPI values above the limiting value of 5.69 mm/blow and therefore they did not meet strength requirements as gravel wearing course material. Based on grading coefficient, shrinkage product and strength parameters which are used for selection of suitable materials, only Zuzu borrow pit materials qualified for construction of gravel wearing course. Therefore, engineering properties of materials from Dinda, Mahomanyika, Nkulabi and Ntyuka need to be improved through blending process.