Performance Enhancement of Concrete Produced with Treated Demolition Waste Aggregates

  • Qusai Al-Waked

Student thesis: Doctoral Thesis

Abstract

Recently, the utilisation of recycled aggregate from construction and demolition waste in civil engineering applications has proved to be an eco-friendly approach to overcome the current environmental concerns. Nevertheless, the poor quality of recycled aggregate and the high uncertainty of recycled aggregate concrete structural performance have limited its utilisation in structural applications. The current literature showed only a few studies on the use of treated recycled aggregate from construction and demolition waste and its effect on the different engineering properties of concrete.

The main thrust of this research is to evaluate the effects of different enhancement and treatment methods in enhancing the mechanical properties, durability properties, and microstructure of concrete produced with 100% recycled aggregate from construction and demolition waste, with the overall aim of promoting the use of recycled aggregate in the construction industry. In view of this, an innovative regime of various treatment methods, batching techniques, and their combinations were developed to enhance the engineering properties of recycled aggregate and recycled aggregate concrete. This research studied the geometrical, physical, and mechanical characteristics of the supplied recycled aggregate. It examined the effects of various treatments on Aggregate Impact Value and Water Absorption properties of recycled aggregate. It also investigated the effects of different treatments methods, batching techniques, and their combinations on mechanical performance (workability, density, compressive strength, flexural strength, tensile splitting strength, and modulus of elasticity), durability (water absorption, resistance to freeze-thaw, and resistance to sulphate attack), and the microstructure of recycled aggregate concrete.

The treated recycled aggregate demonstrated an enhanced Aggregate Impact Value of 15% and reduced Water Absorption of 3% compared to the untreated recycled aggregate with 17% and 6.1% Aggregate Impact Value and Water Absorption, respectively. The enhanced recycled aggregate concrete mixes showed an increase in the 28-day compressive strength of up to 46MPa suitable for structural applications, compared to the control untreated recycled aggregate concrete that exhibited 35MPa. The enhanced recycled aggregate concrete mixes also achieved enhanced tensile splitting strength, flexural strength, elastic modulus, and sulphate and freeze-thaw resistance. The improved engineering performance of the treated recycled aggregate concrete is attributed to the strengthened interfacial transition zone, better overall interlocking of the treated recycled aggregate with the new cement paste, filled-up pores and micro-cracks, reduced porosity, and compacted dense microstructure. The application of the proposed innovative regime of enhancement methods is anticipated to promote the use of recycled aggregate in the construction industry and provide a better and deeper scientific understanding of the performance of concrete produced with 100% treated recycled aggregate from the construction and demolition waste for structural applications.
Date of AwardAug 2022
Original languageEnglish
Awarding Institution
  • University of South Wales
SupervisorJiping Bai (Supervisor), John Kinuthia (Supervisor) & Paul Davies (Supervisor)

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