Projects / Programmes
Use of recycled aggregate in concrete and mortar for high-grade applications
| Code |
Science |
Field |
Subfield |
| 2.01.01 |
Engineering sciences and technologies |
Civil engineering |
Building materials |
| Code |
Science |
Field |
| T270 |
Technological sciences |
Environmental technology, pollution control |
recycled aggregate, concrete, mortar, high-grade applications
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
16432 |
PhD Lucija Hanžič |
Civil engineering |
Head |
2007 - 2008 |
0 |
Organisations (1)
Abstract
Demolition of buildings and other structural objects results in large quantities of demolition debris. Disposal of demolition debris in landfills is considered as one of the environmental problems of modern society. Hence, principles of sorting, recycling and reusing basic kinds of demolition debris (e.g. wood, asphalt, bricks, glass, concrete, metals) are being adopted in civil engineering practise. Nevertheless, recycled ceramic waste is presently used only as aggregate for low-grade applications and it will not be possible to reuse such materials in the next recycling cycle. Therefore, the problem of disposing demolition debris is only postponed. In recent years demolition of structures like building frames and bridge beams resulted in a new generation of recycled aggregate, which has much better properties then usual recycled aggregate. This kind of aggregate could be used for production of high-grade materials (like concrete) and be recycled for the second or even the third time. Therefore, the proposed postdoctoral project will study the possibilities for production of recycled aggregate concrete with normal compressive strength (30 to 80 MPa), which could be used for high-grade applications. Hitherto performed research studies have already shown, that fine fraction of recycled aggregate (< 4 mm) should be excluded in concrete production and natural sand should be used instead. In order to act in compliance with »Zero Waste« concept, alternative possibilities for reuse of fine fraction will have to be considered. Hence, properties of mortar made of fine fraction of recycled aggregate will be studied. In addition to standard tests of aggregate, concrete and mortar, specialized tests of microstructure (optical and electronic microscopy), of moisture transport (neutron radiography) and of binding properties of fine fraction of recycled aggregate (low frequency dielectric spectroscopy) will be carried out.
Significance for science
The domain of engineers is to implement the findings of basic sciences into serviceable products. However, in the last two decades it became clear that our planet cannot sustain current exploitation rate of natural resources nor can it digest the accumulating waste. It is a task of a modern engineer to find solutions to these problems. Construction industry produces large quantities of waste, much of it being concrete rubble. Concrete used for structural elements is produced of high quality aggregate and in order to implement sustainable development concepts it should be used for high grade applications in the second life cycle as well. There is a lot of research dealing with the use of recycled aggregate (RA) in concrete, the latter being quite a complex composite material so this study only adds some new aspects to the knowledge in the field.
Study showed that it is essential to take specific properties of RA into account during mix design. Mix design method based on two chief free parameters, namely water-cement ratio and volumetric fraction of excess cement paste (overfill) was applied and proved very efficient. Mixes with strength of 65 MPa were produced without special mixing procedure and with normal dose of cement. The study is a good foundation for further work aimed to produce self-compacting concrete (SCC) using RA. The majority of present concrete production is aimed to classic vibrated concrete because SCC mixtures are prone to variations of properties. When SCCs are produced natural aggregates of good quality are used. However, it is expected that concrete production will shift towards the SCC mixtures in the future and then it will be necessary to use RA due to the reasons given above.
In the second part of the study focus was on fine fraction of RA which cannot be used for concrete production and is therefore still regarded as waste. Fine fraction of RA was used for production of cement-based mortars and positive results, especially in respect to its water retention capability, were obtained giving thrust to further research work.
Significance for the country
The focus of the study was on two aspects of demolition and construction waste (CDW) management, namely (i) an overall survey of situation in the field of CDW management in Slovenia and (ii) the study of concrete and mortar produced of recycled aggregate (RA).
The first part of the study yielded some important conclusions which should be incorporated into the CDW management strategy in Slovenia. These conclusions are as follows: (a) At present too much emphasis is put on recycling of CDW. Although “Reuse” of components is stated as the first option, it is rarely implemented. Quantities of reused materials are not treated as a separate entity in SI-Stat report therefore the progress can not be measured; (b) The “Reduce” concept is not incorporated in Slovenian legislation and regulations. It is not yet understood that the majority of CDW is a result of improper design and architects and construction engineers do not feel responsible for waste generation; (c) In order to implement the “Reduce” concept it is necessary to educate architects and civil engineers. Not only should Slovenian universities introduce special subjects on sustainable development and environment protection to their programmes, but should also incorporate these ideas in existent subjects.
The second part of the study showed that when specific properties of RA are taken into account the coarse fractions can be used for production of concrete (RAC – Recycled Aggregate Concrete), whereas fine fractions can be used for production of mortar (RAM – Recycled Aggregate Mortar). The study was carried out in collaboration with a couple of Slovenian construction companies (especially CPM and Projekt) and in addition students were involved in research activities. There is still a lot of work to be done but encouraging results will hopefully inspire current and future practitioners who were involved in the study to use RA for high grade applications as well. This would make a contribution to a sustainable use of Slovenian resources.
Most important scientific results
Final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Final report,
complete report on dLib.si
