Since 1995, the Concrete Technology Unit (CTU) at the University of Dundee has carried out considerable research in the area of sustainability, developing efficient and energy-saving construction techniques and promoting responsible use of natural resources. In particular, projects funded through the DETR’s PII and DTI’s recycling programmes have Incinerator Ashes

Since 1995, the Concrete Technology Unit (CTU) at the University of Dundee has carried out considerable research in the area of sustainability, developing efficient and energy-saving construction techniques and promoting responsible use of natural resources. In particular, projects funded through the DETR’s PII and DTI’s recycling programmes have focused on developing outlets for using recycled materials and industrial by-products in concrete. The work has shown considerable potential for using (i) power generation by-products (coarse pulverized-fuel ash (pfa), and conditioned fly ash, (ii) recycled construction demolition material (recycled concrete aggregate and recycled aggregate), and (iii) recycled industrial/domestic material (incinerator ash, glass cullet, and used tyres) as aggregates, fillers, and cement components in concrete.

All of the projects were designed to provide data and knowledge directly relevant to the concrete construction industry. The work was carried out with the support of Project Steering Committees, of up to 20 members from all sectors of the industry. The outcome was a substantial knowledge base and fundamental understanding, meeting the needs of industry and filling the technical gaps that were restricting use of these materials. The work carried out included:

The research work carried out on these six materials, with Government and Industry funding, have developed fundamental understanding, and significant data and knowledge bases that should allow industry to use these waste materials in concrete. Given the substantial amount of these materials generated each year (Table 1), and the significant quantities that are landfilled, there is an urgent need for industry to be made aware of this knowledge base and for its implementation in practice. This follows Government policy as laid out in the Egan Report [1], and Building a Better Quality of Life [2].

However, to date, uptake of this new knowledge and use of recycled materials and industrial by-products in construction has been disappointing, despite extensive efforts by the CTU and others involved in the projects to disseminate the work, albeit through conventional means. For example: (i) reports, (ii) publications, (iii) awareness seminars and workshops, and (iv) international symposia, have all been used.

The reasons for the limited application of the knowledge and use of these materials are many and varied. However, the response from industry to questionnaires distributed at workshops/seminars/meetings organised by the CTU has revealed that:

As a means to demonstrating the suitability of these recycled materials for specific applications, and removing the barrier between research and practical uptake of knowledge, this web-site contains technical data and documents on each of the six materials and provides a means for feedback and discussion.

REFERENCES

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Fly Ash [3,4]

Two projects were carried out to develop technology for the use of fly ash covered by the recently introduced European standard BS EN 450. The work demonstrated that there was an effect of fly ash fineness on strength, but this could be accounted for by adjustments to the mix design. Tests showed that by applying this technique it was possible to fully utilise fly ash conforming to BS EN 450 as a component of cement through the equivalent concrete performance route described in BS 8500-1.

 

Conditioned Fly Ash [5,6,7]

Projects have studied the potential for using the millions of tonnes of conditioned and lagooned fly ash that have been stored (in stockpiles and ponds) in the UK for a long period of time. Through an understanding of moisture effects on the properties of fly ash, design procedures were developed that enable this material to be used through the equivalent concrete performance route (BS 8500-1) and this has made available a vast source of material for use in concrete as a component of cement, active filler and sand.

 

Recycled Concrete Aggregate [8,9,10]

Considerable work has been carried out to exploit the 70m tonnes of demolition waste produced annually in the UK (much of which is sent to landfill) as a new construction aggregate. Methods have been developed that will allow recycled concrete aggregate to be used in new construction, for both normal and high strength concrete. Further work, considered in the development of British standards, has demonstrated that there are no technical drawbacks to its use. Fundamental practical issues have been resolved, and full-scale demonstrations are currently in progress.

 

Incinerator Ashes [11]

Work has investigated the viability of using incinerator bottom ash, incinerator fly ash and sewage sludge ash, as value-added components in construction applications. It has been shown that there is considerable potential for using incinerator bottom ash in cement bound road bases and concrete masonry units. The potential for using fly ash and sewage sludge ash in cements, as pozzolanic activators and latent hydraulic material, has also been demonstrated. Application issues relating to leaching of environmentally sensitive species and dioxin/furan levels were found to be negligible.

 

Recycled Glass [12]

1.7m tonnes of glass cullet are disposed of each year and this has led to the emergence of a cullet surplus. A recently completed project has shown that finely ground glass cullet undergoes a pozzolanic reaction in the presence of Portland cement, and that there is considerable potential for its use as a cement component. Earlier work [13] has shown that there is no significant threat of damaging alkali-silica reaction with the material, and new project funded by WRAP is investigating best practicable options for using glass cullet [14].

 

Granulated Rubber [15]

A recently completed project has indicated significant potential for using the 37 million tyres taken out of service each year, in the form of crumb rubber, as a reinforcing medium or aggregate, in specialist concrete applications. Data available suggests that crumb rubber has particular application in the production of freeze/thaw resisting concrete, thermal resisting panels, and impact resisting surfaces. Since crumb rubber is a inert material, there are few application issues concerning its immediate use in concrete.

 

REFERENCES

DETR. Rethinking Construction: The report of the Construction Task Force, July 1998

DETR. Building a Better Quality of Life. A Strategy for more Sustainable Construction , April 2000

DOE/PII Project (39/3/185). Use of PFA to EN 450 in Structural Concrete, August 1996, 133pp

DETR/PII Project (39/3/448). Development of a Technology Transfer Programme for the Use of BS EN 450 in Structural Concrete, March 2000, 73pp

DETR/PII Project (39/3/236). Use of Conditioned and Lagoon PFA in Structural Concrete, January 1998, 199pp

DETR/PII Project (39/3/236). Use of Conditioned PFA in Concrete: Strength Development and Critical Durability, January 1998, 199pp

DTI/PII Project. Demonstration Project using Conditioned PFA as a Cement Component in Concrete (in progress)

DETR/PII Project (39/3/327). Recycled Aggregate for Use in BS5328 Designated Mixes, January 1999, 134pp

DETR/PII Project (39/3/478). Resolving Application Issues with the Use of Recycled Aggregate,
March 2001, 171pp

DETR/PII Project. Demonstration Project Utilising Coarse Recycled Aggregates (in progress)

DETR/PII Project. Value-Added Recycling of Incinerator Ashes (in progress)

DTI Project. Realising a High-Value Sustainable Solution to the Glass Cullet Surplus (in progress)

WRAP Project. Best Practiceable Options for using Glass Cullet in Construction (in progress)

EPSRC Project. Suitability of Glass Cullet for use as a Cement Component.

DETR/PII Project. Feasibility of Recycling Rubber Tyres for Use in Concrete (in progress).