As Qatars construction activity continues to remain at an all-time high, the country has placed key reliance on the importation of materials that are essential to its ongoing construction projects. Now Qatar has taken a big eco-friendly step in its move to transform construction waste into building materialsnot only resulting in a reduction of costs for these projects but also reducing its carbon footprint and protecting the environment.
Recent industry reports have shown that some of the large-scale infrastructure projects underway in the country are now dealing with the challenge of an unmet demand of high-quality materials and have resorted to imported aggregates for use in asphalt and concrete applications. In addition, the high amount of construction activity has also generated a large amount of construction and solid wastes, which are sent to local landfill sites.
Seeking to address this issue, Transport Research Laboratory (TRL), a leading transport consultancy and research firm, along with a group of stakeholders embarked on a project called, Innovative Use of Recycled Materials in Construction. The endeavour included collaborative partners Qatar Standards, which is a part of Qatars Ministry of Municipality and Environment, Public Works Authority (Ashghal), and Qatar University. This three-year undertaking project focussed on the transformation of waste materials into building materials. The project was funded by the National Priorities Research Program (NPRP), which is administrated by the Qatar National Research Fund (QNRF) at Qatar Foundation.
The Innovative Use of Recycled Materials in Construction project complements Qatars policy towards achieving sustainable development and the move to protect the environmenttwo vital points mentioned in the countrys national vision. The initiative not only looks towards addressing the shortage of locally available aggregates but also aims at increasing awareness on the importance of green construction in Qatar. The project has successfully resulted in the identification of main waste streams in Qatar including recycled aggregates from excavation waste (EW), and recycled concrete aggregate (RCA) being sourced from a landfill site at Rawdat Rashid. Considerable quantities of recycled aggregate were identified, which can significantly contribute to the efforts of reducing relying on imported aggregate to meet the demand for construction applications.
A series of comprehensive laboratory tests were carried out in order to identify the optimum use of EW and RCA as unbound pavement materials and coarse aggregate in structural concrete, non-structural concrete and concrete blocks. Based on the results, optimised mixtures were selected and later used in the construction of full-scale site trials (buildings and roads) to demonstrate how to apply the new recycled materials and mixtures in practice.
The performance of recycled materials in service was observed for a period of two yearssubjecting the project sites under normal exposure conditions such as heat, humidity, aggressive ground conditions, and heavy trafficking. The results were used to update the Qatar Construction Specifications (QCS 2014) and promote green construction of buildings and roads.
The latest edition of the QCS, which was published in 2014, permits the use of recycled aggregates from EW and RCA as coarse aggregate in concrete at up to 20 per cent replacement of imported gabbro for structural concrete and up to 50 per cent for non-structural concrete. Recycled aggregates are now also permitted up to 100 per cent in sub-base applications. Also, excavated limestone waste is permitted as aggregate in asphalt in the lower layers of the pavement, but not in the surface course.
During the project, the recycled aggregate materials were supplied by Qatar Quarry Company Lafarge; the building trials were constructed by the Qatari Arabian Construction Company (QACC); and the trial road is constructed by Boom Construction Company. A key factor to the success of the project is the strategic collaboration between government, industry, research and academia, all of which have expressed support for the governments objectives of sustainable development and green construction.
Industry experts have pointed out that the use of recycled aggregate will help drive in major economic and environmental advantages as compared to the use of imported aggregate. A comparison of the likely costs of local recycled aggregates in Qatar indicated a significant reduction of up to 60 percent as compared to imported aggregates.
Studies of the project also relevantly showed that the use of local recycled aggregate has driven in a reduction of the carbon footprint by at least 50 percent, which can be attributed to the energy saving in the transport and shipping of the imported aggregates to Qatar. Other drivers include the limitations on port capacity and concerns about the quality of imported aggregate.
The implementation of recycling in construction on a large scale would require significant changes to the existing construction practices in Qatar. To address this, codes of practice, standards and guidelines have been developed for sorting out waste at source before sending it to landfill and certifying recycled aggregate by Qatar Standards. These will significantly improve the quality of recycled materials, provide confidence in use, and change the perception of inferior quality of recycled materials. Guidance documents have also been prepared to provide experience on the use of recycled aggregate in different construction applications.
TRL, in collaboration with Qatar Standards, has also recently released a guidebook entitled, ‘Recycled Aggregate in Construction Qatar Experience,’ which seeks to raise awareness and help Qatari construction companies comply with the new set standards. The 225-page book includes a comprehensive data on the construction industry in Qatar and the potential of recycling initiatives supported by a set of statistical tables and charts, photographs and case studies. It also showcases a range of studies that have been conducted in Doha and the UK between 2010 and 2015, focusing on the development of codes of practice and supporting mechanisms to convert the vast quantities of construction waste into high-value construction products.
In addition, Qatar Standards has also updated the Qatar Construction Specification and now includes the move to permit the use of recycled aggregates in a range of applications–including structural concrete, non-structural concrete, concrete blocks, asphalt pavements, road sub-base materials and fill applications. Despite this, the new set of specifications does not force clients and contractors to use recycled aggregates, so the uptake will be determined largely by the cost. TRL is also keen to help those companies looking to make the move to recycled aggregates, offering independent audits to check the quality of the materials before Qatar Standards certification.
Recently, another project in Qatar has been awarded to implement recycled aggregate in real construction projects. The new project will place key focus on the performance of recycled aggregate across a wide range of construction applications and monitor performance in practice. The project team assigned for this task will work with a wider group from the government and construction industry to provide sustainable aggregate. Results of this undertaking will be published and distributed to ensure that stakeholders are aware of recycled aggregates and have confidence in their use.