Date of Award
8-1-2013
Degree Name
Master of Science
Department
Civil Engineering
First Advisor
Kolay, Prabir
Abstract
The use of recycled concrete aggregates in Portland cement concrete and granular road base or sub-base works has increased steadily all over the world in order to conserve the limited natural aggregate deposits. The recycling of the demolished concrete aggregate for the use in concrete or granular pavement works will not only help to protect the environment but also an economical benefit to the user. The main drawback for the bulk utilization of demolished or recycled aggregate is its characterization and proper quality control during its production. The overall objective of this research was to characterize recycled concrete aggregates (RCA) obtained from a demolished foundation structure and to determine its suitability for Portland Cement Concrete (PCC) works and use as a granular road base or sub-base material. Tests were carried out on RCA samples to determine whether it meets the specification for concrete aggregate material or a granular road base and sub-base materials. Several concrete mixes consisting of 10, 20, 30, 40, 60, and 80 % replacement of natural coarse aggregates (NCA) with RCA were prepared and tested for compressive strength after curing periods of 7, 14, and 28 days. The compressive strength of concrete made with various percentages of RCA decreased with increasing RCA content but it increased with curing period for all concrete mixes. The durability parameters of the natural aggregates and RCA samples were investigated by using sulfate soundness, rapid freeze-thaw and micro-deval tests to ascertain their chemical and abrasive resistance. The California Bearing Ratio (CBR) of RCA base was also compared with that of a natural road base material to determine its suitability for road base or sub-base works. In this study, the flakiness and elongation indices of the RCA were found to be better than that of conventional natural aggregates. The RCA base material had lower maximum dry density, higher optimum moisture content, and low California Bearing Ratio (CBR) value compared to the natural crushed rock base (NCRB) material but was found to be a relatively good road base material.
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