The effects of variability in physical and chemical properties of crushed brick recycled aggregate when used in medium strength concrete

Moran, Thomas (2016) The effects of variability in physical and chemical properties of crushed brick recycled aggregate when used in medium strength concrete. MEng dissertation, University of Portsmouth.

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    A large amount of waste is sent to landfill which has the potential to be reused as recycled aggregates on a much larger scale than what is currently achieved. A potential opportunity exists to utilise recycled aggregates in concrete as a coarse aggregate replacement, but currently this is not carried out on any real beneficial scale. The wide range of reasons stated for this include varying quality and consistency of source material, potential strength loss, workability issues due to absorption, availability concerns, contamination issues and limitations set in standards. All of these reasons lead to a low confidence level of the industry regarding suitability of recycled aggregates within concrete.
    This project focuses on two of the many issues stated above, comparing variation between two sources of recycled aggregate at two replacement levels and examining the effect on fresh and hardened concrete properties. Achieved through casting of fifteen concrete cubes and performing associated tests. Results recorded were mixed, overall Raymond Brown performing remarkably better than Chambers Group considering it contained a higher proportion of crushed brick. Results were generally better than what was recorded in previous literature. Investigation was hindered by amount of material gained from only two sources especially as Chambers Group required the recycled stone and brick to be mixed to meet required proportions, therefore limited conclusion can be made regarding variability as only 2 sources compared.
    Combined with investigating the effect of gypsum contamination on delayed ettringite formation causing deleterious expansion. By varying gypsum content within mortar bars and regularly measuring expansion comparing against a known critical limit at 6 months. Generally promising results were recorded indicating that slightly higher levels than 1% of gypsum can be included without causing critical expansion but experiment would vastly benefit from being repeated on a larger scale implementing lessons learnt.

    Item Type: Dissertation
    Departments/Research Groups: Faculty of Technology > School of Civil Engineering and Surveying
    Depositing User: Jane Polwin
    Date Deposited: 17 Aug 2016 16:20
    Last Modified: 17 Aug 2016 16:20

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