Jordan Journal of Civil Engineering

Comparison of Performance of Base-course Aggregates for Limestone and Sandstone at Varying Moisture and Gradation

Authors:

Khalid Mehmood; Anwar Khitab; Jawad Hussain; Syeda Aamara Asif; Waqas Anwar;

Abstract:

Unbound Granular Materials (UGMs) are widely used as base and sub-base layer materials in flexible pavements all over the world, as these materials are proficient to bear heavy vehicle loads and are inexpensive as compared to bound materials. This paper demonstrates the relationship among resilient modulus 􀜯􀯋, permanent strain and physical properties of limestone and sandstone obtained from Margalla and Sargodha regions of Pakistan, respectively. This research paper investigates the effects of moisture change, percent of fines in gradation curve, stress level and aggregate type on resilient modulus and permanent strain of a flexible pavement. Water can intervene into the unbound base-course layer and may result in premature pavement failure. Thus, it is necessary to investigate the UGM behaviour under optimum moisture content (OMC) towards wet side as well as towards dry side. In order to examine the aggregate properties, basic aggregate tests (i.e., impact value test, specific gravity, soundness and water absorption test) were performed. The basic test results of aggregate used in this research work were under allowable limits. Performance test ( 􀜯􀯋) and permanent strain of designated materials were conducted using Repeated Load Triaxial (RLT) test technique. The results demonstrated that type of aggregate, material gradation, percent of fines in gradation curve and percentage of moisture significantly affect resilient modulus 􀜯􀯋 and permanent strain of unbound layers of flexible pavements. Moisture content has an adverse effect on unbound base-course materials. When moisture increases from OMC towards wet side, 􀜯􀯋 decreases and permanent strain increases. On the contrary, 􀜯􀯋 increases by reducing water content from OMC towards dry side and permanent strain also decreases. Result from RLT test demonstrates that sandstone is more sensitive to moisture as compared to limestone.

Keywords:

Resilient modulus, Unbound granular materials, Moisture damage, Stress level, RLT test, Proctor test, Limestone, Sandstone