Allied Concrete recycles as much of its process water as possible. Most of our plants capture all the water from the site and use it for mixing consumption. General and cleaning water use is controlled by water blasters; these significantly reduce water.
We also recycle returned concrete as concrete blocks, or put the concrete through recyclers to recover the aggregates. Some plants used recycled crushed concrete as an aggregate. The use of crushed glass as a sand replacement is also being implemented at selected locations.
Click below to view case studies of Recycled Glass being used in different areas:
Crushed concrete as an aggregate in ready mixed concrete production
Allied Concrete has been promoting sustainable practices within our business and with our customers for some time. One such product is recycled crushed concrete (RCC) as an aggregate source.
To date RCC has been used for largely non-structural or non critical applications. The Wellington Zoo Hospital is the first instance where we have supplied RCC concrete in structural applications in New Zealand; this was only possible after extensive research work had been completed. Approximately 60 cubic metres (40% of the total cast on site) of 25 MPa RCC concrete has been supplied to this project, for external retaining walls, ground beams and the ground floor slabs. This concrete was used at a 30% replacement rate.
A year long research programme enabled us to fill an important gap in our understanding of locally produced materials under New Zealand conditions. The aim of this work was to enable designers to use material with confidence in structural applications. The programme was carried out using partial funding from FRST, together with a Masters Student from Auckland University.
In an attempt to determine the upper limits of this material, all mixes reported in the project were based upon 100% RCC as a coarse aggregate rather than the more common replacement level of 30%.
20, 40 and 60 MPa concretes were used to cast tests slabs, which were subsequently crushed to give us recycled aggregates of known strength. These three aggregate sources were then used to produce concretes ranging in strength from 20 to 60 MPa using these RCC materials.
Tests were carried out on fresh concrete to measure slump loss, bleed, air content and wet density on a wide range of mixes, from 20 MPa to 60 MPa, using 20, 40 and 60 MPa RCC for each strength grade.
Compressive and flexural strengths, drying shrinkage, creep, chloride diffusion, porosity and oxygen permeability were also tested.
The use of RCC aggregate has been shown to be practical without the need for modifications to existing procedures especially when allowing for the fact that the test results were on total replacement of coarse aggregate.
The performance of the concrete is well within accepted limits especially for Normal Concrete as defined in NZS 3104.