Date Approved

1-7-2022

Embargo Period

1-12-2022

Document Type

Thesis

Degree Name

M.S. Civil Engineering

Department

Civil and Environmental Engineering

College

Henry M. Rowan College of Engineering

Advisor

Gilson R. Lomboy, D.Eng., Ph.D., P.E.

Committee Member 1

Yusuf Mehta, Ph.D., P.E.

Committee Member 2

Douglas Cleary, Ph.D., P.E.

Keywords

Aggregate Mechanical Properties, Compressive Strength, Concrete Mechanical Properties, Flexural Strength, Recycled Concrete Aggregate (RCA), Resistance to Abrasion

Subject(s)

Concrete; Recycling

Disciplines

Civil and Environmental Engineering

Abstract

Recycled concrete aggregate (RCA) is a crushed concrete with the original aggregates' features and old mortar adhered to the original aggregate which makes it necessary to know the mechanical properties of the RCA. The objectives of this thesis are (a) to characterize RCA from different sources and of different proportions, (b) to measure the mechanical properties of concrete made with 100% RCA as coarse aggregates, and (c) to evaluate how the RCA properties affect the properties of new concrete. The study uses RCA with three types of original aggregates (limestone, dolomite, and granite) in two water-to-cement ratios 0.48 and 0.38 and also includes RCA collected from three recycling plants. The RCAs are graded with either 1 inch or ¾-inch nominal maximum aggregate size (NMAS). The resistance to abrasion, material finer than 75-micrometer, and the RCA's parent concrete compressive and flexural strength were characterized. The compressive and flexural strength of concrete with 100% RCA was determined at 7, 14, 28, and 90 days. The results shows that resistance to L.A. abrasion of RCAs range was between 21% and 43% which is within the natural aggregate acceptable ranges (up to 40%). The impact of particles finer than 75 micrometer on compressive strength was not significant. Also, 90 days compressive strength test of concrete with 100% control RCA in ¾ inch NMAS, and w/c ratio as of 0.38 reached 7,200 psi.

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