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Title: Performance of NO2 Sequestered Recycled Concrete Aggregates (NRCA) Incorporated Concrete: Influence of Parent Concrete Properties

Author(s): Erandi Ariyachandra, Sulapha Peethamparan

Publication: Symposium Paper

Volume: 349


Appears on pages(s): 725-741

Keywords: NO2 sequestration, NO2 sequestered recycled concrete aggregates (NRCA), chloride-induced corrosion, chloride diffusion

DOI: 10.14359/51732784

Date: 4/22/2021

The utilization of recycled concrete as an adsorbent to sequester NO2 without additives or catalysts is an innovative, cost-effective, and sustainable approach to capture NO2 from targeted industrial facilities. During NO2 sequestration, alkaline products such as calcium hydroxide (CH) in the adhered old mortar of recycled concrete can react with NO2 to form Ca(NO2)2 and Ca(NO3)2. Thus, the use of NO2 sequestered recycled concrete aggregates (NRCA) as a constituent of concrete can be beneficial since Ca(NO2)2 and Ca(NO3)2-based chemical compounds are widely used as multi-functional admixtures for concrete applications. This study investigates the influence of the properties of the parent (demolished) concrete on the mechanical and durability performance of NRCA incorporated ordinary portland cement (OPC) concrete. Two types of recycled concrete aggregate (RCA) were derived from 2 and 20-year old concrete blocks to produce two types of NRCA—2-NRCA (2-year-old NRCA) and 20-NRCA (20-yearold NRCA) by exposing them to a humidified air/NO2 mixture (at RH = 50% and 23±2°C) for two weeks. NRCA was used as a partial replacement for natural fine aggregate in fresh OPC mixtures at 20% and 40% rates by volume. The influence of NRCA on concrete compressive strength, porosity, and long-term chloride diffusion coefficients were assessed. In addition, open-circuit and potentiodynamic polarization tests were conducted to evaluate the resistance to chloride-induced corrosion of steel in concrete. Control test mixtures containing a commercially available Ca(NO2)2 based corrosion inhibitorwere also tested for comparison purposes. Both types of NRCA enhanced the mechanical and durability properties of concrete compared to control mixtures. Test mixtures containing 2-NRCA showed better resistance against chloride-induced corrosion than concrete with 20-NRCA.