Evaluation of the Performance of Recycled Concrete Aggregate in Fresh Concrete for Manufacturing Fence Posts

Hollingworth, Leigh (2021) Evaluation of the Performance of Recycled Concrete Aggregate in Fresh Concrete for Manufacturing Fence Posts. [USQ Project]

Text (Project)
HOLLINGWORTH Leigh dissertation_redacted.pdf

Download (11MB) | Preview


The continued urbanisation and development driven by population growth around the world is resulting in large quantities of construction and demolition waste and the simultaneous depletion of natural resources. The production of recycled aggregates offers the potential to reduce the impact on landfills and the natural environment by redirecting waste concrete for use in fresh concrete.

Recycled aggregates are generally considered inferior to natural aggregates particularly due to their greater water absorption properties, and the effect this has on fresh concrete mixes, and the creation of an additional interfacial transition zone between the new mortar and the adhered mortar attached to the recycled aggregates.

This study evaluates the performance of recycled aggregates in the production of new pretensioned concrete fence posts with the aim to produce a commercially viable product. A two-stage-mixing-approach was adopted to optimise the performance of the recycled aggregate concrete with 30% replacement of the coarse aggregates. The aggregates were not subjected to any pre-treatment to keep production costs to a minimum.

Comparison was made with commercially produced versions of the posts using the manufacturer’s standard concrete mixture and procedures. Cylinder test specimens were formed from each batch of concrete to enable an analysis of the compressive and splitting tensile strengths. Post samples were subject to four-point bending tests, and details of loads and deflections recorded enabling evaluation of the modulus of rupture and ultimate bending moments.

The results indicate that compressive strength and the ultimate moment of the samples is not significantly affected at the substitution ratio of 30% recycled aggregates at 38 days. Tensile strength was reduced by the addition of recycled aggregates, as was the overall deflection of the sample posts prior to failure. All of the sample posts failed due to flexure cracking, this lead to rupture of the reinforcement in the natural aggregate samples and bond slippage in the recycled aggregate samples.

The manufacture of concrete fence posts using 30% recycled aggregates is not limited by the compressive, tensile or flexural performance, and presents a potentially environmentally friendly alternative to 100% natural aggregate concrete posts.

Statistics for USQ ePrint 51820
Statistics for this ePrint Item
Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Lokuge, Weena
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 03 Jan 2023 02:21
Last Modified: 26 Jun 2023 01:28
Uncontrolled Keywords: concrete, aggregate, waste, construction, recycled, fence posts, cylinder test
URI: https://sear.unisq.edu.au/id/eprint/51820

Actions (login required)

View Item Archive Repository Staff Only