Utilisation of aggregate materials in road construction and bulk fill (original) (raw)
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Journal of Cleaner Production, 2021
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Catalogue of Pavements with Recycled Aggregates from Construction and Demolition Waste
Proceedings
Construction and Demolition Waste come from debris generated during construction, renovation and demolition of buildings, roads, and bridges. Recycling and reuse are essential in terms of sustainability, mainly from an environmental point of view. Although the recommendation of the use of these recycled aggregates is currently included in some technical specifications, its use is still not widespread due mainly to the lack of knowledge on their technical application. This work is a compilation of the recommendations proposed in the “Catalogue of road pavements with recycled aggregates”, supported by the construction of experimental stretches. It proposes different structural sections for road pavements by using recycled aggregates.
Using Recycled Aggregates from Construction and Demolition Waste in Unbound Layers of Pavements
Sustainability
Pavements are an expensive part of transportation infrastructures, as their construction and maintenance require large amounts of resources and materials every year and all over the world. A sustainable solution for considering environmental concerns about roads and pavements, in general, is utilizing recycled materials for their construction. This has been shown to lower the carbon footprint of the construction sector and to result in natural resource conservation, in reduction of harmful emissions and in minimization of overall costs for pavement construction and maintenance. One of the main groups of recycled materials which has attracted much attention since the end of the last century is construction and demolition waste aggregates (CDW). This paper reviews the completed studies referring to the use of the construction and demolition waste aggregates in unbound layers of pavements and compare the in-hand results from various engineering assessments of these aggregates and mixes...
Construction and Building Materials, 2012
This paper evaluates the behaviour and the environmental impact of a mixed recycled aggregate from non-selected construction and demolition waste (CDW) in field conditions. For this purpose, one experimental unpaved rural road with two sections was built. Sections were formed with a poor subgrade (A-6) and two structural layers: the first section consisted of a base course and a surface built using a natural aggregate and a low quality mixed recycled aggregate, respectively, and the second section, which was used as a reference, consisted of a soft crushed limestone aggregate. The materials were previously characterised in the laboratory. Control compaction ensured that the materials were correctly set in place, and the bearing capacity of each fill layer was measured. The structural performance of the pavement was determined using a falling weight deflectometer, and the changes in the international roughness index and the bearing capacity over time were studied. The results show that the non-selected CDW can be recycled using a simple treatment to create low quality recycled material with a low embodied energy that can be used as an alternative to natural aggregates in unpaved rural roads. According to the technical specifications, the total sulphur compound (SO 3) and the soluble salts content can rise to 3.9% and 3.3%, respectively, without posing a sulphate leaching risk or a reduction in the quality of this type of work. This study is important for increasing recycling rates of non-selected CDW and will support sustainable development in the building sector.
The Use of High Waste Dust In Unbound and Hydraulically Bound Materials for Road Bases
… Conference on the Built Environment and …, 2008
The principal aim of this project is to reduce the demand for the extraction and use of primary aggregates and the associated environmental impacts. This will be achieved by technical development of alternative aggregates mainly limestone waste dusts to replace some of the coarse and fine aggregate fractions in unbound base materials used beneath the road, highway and airfield blacktop or concrete wearing and base courses. The construction industry is the major consumer of primary aggregates and unbound base materials is one large source of consumption. Currently, the UK aggregate market is estimated at 270 million tonnes, recycled and secondary aggregate 65 million tonnes and demolished and crushed waste at 40 million tonnes. Unbound base materials for pavement absorb more than 135 million tonnes of aggregates. It is clear that even small replacement rates will have a significant impact on primary aggregate demand. To monitor the effect of adding limestone dust on resilient modulus of the potential mixes studied in this project, which is a very important parameter in pavement design, samples containing 5, 10, 15 and 20% limestone dust added to Stancombe Type 1 road base materials and tested using LJMU Triaxial Machine. The results show that control samples, which contain no limestone dust, were the strongest and samples containing 20% dust were the weakest, both presented an unbound material behaviour. However, it was decided to reclaim the reduction in the strength of the samples containing 20% limestone dust by adding 4 and 9% pulverized fuel ash (PFA) activated with 1 and 2% hydrated lime respectively as the aim of the project is to use high amount of limestone dust. Interestingly, the results show an increase in new materials resilient moduli of approximately 420%. This means that the new materials can be considered as hydraulically bound materials, i.e. 'concrete-like' materials. The paper will present an interesting comparison of material mechanical properties for all the samples tested in the laboratory and on the road trial sections.
Materials, 2016
Social awareness aims to increase practical skills, such as sustainable development, which seeks to increase the use of different types of waste in construction activities. Although insufficient attention is sometimes given to these actions, it is essential to spread information regarding new studies in the field of waste recycling, which encourages and promotes waste use. Reusing and recycling construction waste in the creation of buildings and infrastructure are fundamental strategies to achieving sustainability in the construction and engineering sectors. In this context, the concept of waste would no longer exist, as waste would become a material resource. Therefore, this study analyses the behaviours of two unbound mixed recycled aggregates (MRA) in the structural layers of an unpaved rural road with low traffic (category T43). The sections were built on inappropriate soil (A-7-6) with a high degree of free swelling. The experimental road consisted of three sections: the first was made with natural aggregates (NA) that were used as a control, the second was composed of MRA in the subbase and NA in the base, and the third section was completely composed of MRA. The materials were characterised in the laboratory. The behaviours of the structural layers in the experimental road were determined by controlling compaction ("in situ" density and moisture) and measuring the deflections and load capacity (deflectometer) during the 18 months after construction. The results show that the sections made with recycled aggregates meet the technical specifications required by General Technical Specifications for Road and Bridge Works (PG-3). Therefore, the water-soluble sulphate content and Los Angeles abrasion coefficient limits can be increased for recycled aggregates without compromising the quality of this type of road with low traffic. To the best of our knowledge, this is the first study regarding the use of unbound MRA made from construction and demolition waste (CDW) in the construction of an unpaved rural road with low traffic on an expansive clay subgrade.
International Journal of Pavement Engineering, 2013
With the increased awareness of building sustainable transportation systems, recycled materials and industrial byproducts increasingly are being used in highway construction, especially as base materials. When compared to traditional base materials, such as crushed aggregate, recycled materials and industrial byproducts often display unique properties. However, the physical properties of recycled materials and industrial byproducts have yet to be fully characterised for the purpose of pavement design. This study evaluated the mechanical properties of a full-depth reclaimed pavement material (RPM) and RPM stabilised with high carbon/high calcium fly ash, and compared these with properties of a conventional crushed aggregate. It was found that RPM exhibited higher modulus than the traditional base course material (crushed aggregates) did. However, RPM also showed higher plastic strain than crushed aggregate, indicating a higher potential for rutting in RPM base. Adding high carbon/high calcium fly ash significantly increased the California Bearing Ratio (CBR) and resilient modulus and lowered plastic strain of RPM. The strength and stiffness of field-mixed RPM stabilised with fly ash was significantly lower than that of laboratory-mixed mixtures, as indicated by different measures, i.e., CBR, resilient modulus and unconfined compressive strength (UCS). Data obtained in this study, along with other data obtained from similar studies, indicate that there are good correlations between resilient modulus and CBR (R 2 ¼ 0.96), as well as between resilient modulus and UCS (R 2 ¼ 0.94) for recycled base materials stabilised with fly ash. However, there is still a need for more testing to further verify the proposed relationships. Nonetheless, the proposed relationships constitute the first such relationship proposed and can be useful in pavement design. Additionally, it is shown that flexural strength is about 20% of UCS as it is recommended for materials stabilised with other cementitious materials.
DEStech Transactions on Materials Science and Engineering, 2017
Unbound aggregates are becoming increasingly scarce and expensive due to the loss of rock quarries and gravel mines to other land uses; therefore, it is important to engineer and optimize aggregate gradations for the targeted end-performance. This paper is aimed at validating in the laboratory a newly introduced gradation design concept intended for controlling structural assembly strength (stability) and drainage characteristics (field drainability). Aggregate gradation optimizations were studied for blending and mixing proportions of fine granite tailings (FGT), a typical crushed granite mining byproduct that has long been considered "waste" materials, and coarse crushed granite aggregates (CCGA). To this goal, one of the common quarry byproduct wastes (i.e., FGT), was mixed with CCGA in varying percentages to explore their potential use for building pavement foundations. Large-scale monotonic triaxial compression tests were performed to investigate the effects of blending proportions on the stress-strain behavior. Based on the test results, the optimum aggregate gradations recommended by the new gradation design concept provided enhanced stability without compromising drainability. The new gradation design concept, hence validated in this study with produced optimum gradations, is expected to achieve sustainable and beneficial unbound aggregate applications for cost-effective longlife pavements.
Use of Recycled Fine Aggregates from C&DW for Unbound Road Sub-Base
Materials, 2020
Fine recycled aggregates are produced in large quantities when crushing Construction and Demolition Waste (C&DW). Even if coarse recycled aggregates are commonly used for road foundations, fine particles are often rejected as they are considered detrimental for the long-term behaviour of foundations. Physicochemical, mineralogical and mechanical characterizations (through X-ray diffraction, X-ray fluorescence, the chloride and sulphate contents, Los Angeles abrasion, micro-Deval resistance and static plate load tests) were performed on raw and treated fine recycled materials for understanding both the effects of the preparation, the compaction and the freeze–thaw cycles on the properties and the evolution of fine particles. Special attention was provided to the shape analysis of fines by means of image analyser. The results showed that the main characteristic parameters to be considered are the sieving curve and the proportion of grades. The mixes containing the highest quantity of ...