Date of Award
Master of Science
Kolay, Prabir K.
Puri, Vijay K.
Construction and demolition waste concrete has dramatically increased worldwide in the last decade. The social and environmental concerns on recycling of these wastes have consequently increased substantially. Recent technology has greatly improved the recycling process for construction and demolition waste concrete. The current study presents the results of a laboratory study on the performance of portland cement concrete prepared by incorporating different mineral admixtures i.e., silica fume (SF) and meta-kaolin (MK) with natural coarse aggregate (NCA) from quarry and recycled coarse aggregate (RCA) from old concrete pavements. The silica fume (SF) and meta-kaolin (MK) were used as a partial replacement of ordinary portland cement. Natural aggregate was replaced with 100% recycled concrete coarse aggregate by volume. In the present investigation, silica fumes (SF) and meta-kaolin (MK) replacement were 0%, 5.0% individually and few combination of SF and MK. A fixed air entraining admixture (AEA) i.e., 5% and water to cement (w/c) ratio of 0.42 was used to study the effect of the SF and MK on concrete mix. To maintain a desired slump for workability of the concrete mix, a super plasticizer (SP) was also used. All the concrete mixes used 605 lb. of ordinary portland cement per cubic yard. Concrete mix specimens were tested for compressive strength after curing periods of 7, 14, 28 days; splitting tensile strength after curing for 28 days; and flexural strength test after curing for 14 and 28 days. The aim of the study was to design a concrete mix with 100% recycled concrete aggregate with the addition of meta-kaolin (MK) and silica fumes (SF) that has strength equal or greater than the strength of concrete prepared with 100% natural aggregate. Among all tests performed, a combination of 5% meta-kaolin (MK) and 5% silica fumes (SF) mixture with 100% natural coarse aggregate showed better results as compared with the mixture used 100% recycled concrete aggregate. For the same combination of MK and SF, 100% recycled concrete showed highest strength. Results also show that the use of 5% meta-kaolin (MK) and 5% silica fumes (SF) with natural or recycle aggregate showed highest compressive, tensile, and flexural strength compared with concrete mixes prepared without meta-kaolin (MK) and silica fume (SF). With different percentages of SF and MK, the compressive strength for NCA and RCA concrete has increased in the range between 7 to 17% and 4 to 12%, respectively after curing for 28 days. The increase of tensile strength with different percentages of SF and MK ranged between 3 to 10% for NCA concrete and 1 to 4% for RCA concrete after curing for 28 days. Also, the flexural strength result has increased with different percentages of SF and MK in the range between 19 to 40% for NCA concrete and 14 to 25% for RCA concrete after curing for 28 days. Hence, by using mineral admixture or supplementary materials i.e., MK and SF, it was possible to achieve higher mechanical properties of the recycled concrete aggregate containing 100% recycled aggregate.
Available for download on Friday, March 13, 2020
This thesis is only available for download to the SIUC community. Others should
contact the interlibrary loan department of your local library.