IMIESA January 2021

Page 46

CITY OF CAPE TOWN

Innovative use of builders’ rubble

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uilders’ rubble is a valuable construction material and the Solid Waste Management Department at the City of Cape Town (CoCT) has recognised that it has no place occupying valuable landfill airspace. The city is now maintaining separate stockpiles of clean builders’ rubble (less than 10% contamination with other material), which attracts a significantly lower landfill gate fee. However, due to a struggling construction industr y and a perception in the public sector that builders’ rubble is a liability in construction, the large stockpiles of builders’ rubble at the Coastal Park Landfill had grown to approximately 450 000 m3, restricting operations and planning at the landfill. In response, the CoCT prioritised the use of builders’ rubble in the earthworks contract for the construction of its new materials recover y facility (MRF) at Coastal Park.

The process Site sur veys and geotechnical studies revealed that the builders’ rubble stockpiled at the landfill was suitable for the production of 19 mm aggregate, G7 and G9 materials (as per COLTO specifications) for the bulk earthworks and construction of detention ponds and a section of bioswale. Furthermore, material suitable for the

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IMIESA January 2021

production of both sub-base and base material for the layer works of access roads was identified for the above earthworks contract. In response, the tender document was tailored to require the inclusion of builders’ rubble, with pricing requested for both builders’ rubble, which on average was offered at a cheaper rate, as well as commercially available virgin material, thus driving green procurement. Approximately 60 000 m3 of rubble sourced from the Coastal Park stockpile was subsequently used in the earthworks and bulk ser vices contract. Certain portions only required screening to produce suitable aggregate to meet the technical specifications, while other material was screened, crushed and, in some cases, blended to achieve the required grading.

The CoCT found that builders’ rubble is a useful construction material when the quality and per formance of the material is well matched to the application and recommends that municipal construction tenders make provision to favourably consider appropriate builders’ rubble sources. The CoCT’s Green Procurement Action Plan is designed to facilitate the use of recycled or recovered materials in its operations and projects. Further projects at the Coastal Park Landfill, including the construction of a new landfill cell, are also designed to include locally available builders’ rubble. As the CoCT continues to provide waste diversion projects, it hopes to increase the number of citizens participating in this sustainable behaviour.


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Articles inside

Minor concrete defects and their remedies

4min
pages 50-52

Experts in bespoke culverts

3min
page 53

Construction Law

7min
pages 48-49

Towards a water secure future

3min
page 47

Innovative use of builders’ rubble

2min
page 46

Bell beefs up excavator range

2min
page 43

Constructing for and with the community

5min
pages 44-45

The right equipment, the best support

6min
pages 36-37

Built to keep on performing

1min
page 39

Planers at the cutting edge

3min
page 35

The importance of postclosure management

2min
pages 32-33

Tshwane ready to up its waste game

3min
page 30

Hot Seat

6min
pages 28-29

4IR in the waste sector

2min
page 31

Why you should hire from CHPA members

1min
page 34

Meeting demand for high grade bitumen

2min
page 26

NME innovations for Africa

2min
page 27

Environmental Engineering

4min
pages 24-25

Understanding your water consumption

3min
page 20

Behind the scenes of the Kashimbila Multipurpose Dam

6min
pages 14-15

Financing

5min
pages 10-11

Cover Story

6min
pages 12-13

Editor’s comment

4min
pages 5-6

Automatic control valves regulate the levels

3min
pages 16-17

President’s comment

2min
page 7

Upgrading the Midmar WTP

2min
pages 21-22
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