Use of Recycled Aggregates in Geotechnical Applications

Dhir, Ravindra K.; Brito, Jorge de; Silva, Rui V.; Lye, Chao Qun

doi:10.1016/b978-0-08-100985-7.00011-x

Cited by 3 publications

(10 citation statements)

References 54 publications

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“…There are three main categories of CDW aggregates: Recycled concrete aggregates (RCA), Recycled masonry aggregates (RMA, sometimes Crushed Clay Masonry-RCM) and Mixed recycled aggregates (MRA-also mixed demolition debris) [15,16]. However, most construction and demolition blends are combined of these types and the portion of each material can affect the properties of the total blend [17][18][19][20][21].…”

Section: Main Types Of Cdwsmentioning

confidence: 99%

“…Additionally, other materials like ceramics can exist in some blends [17]. Moreover, another type of aggregate waste, reclaimed asphalt pavement (RAP) aggregate produced from crushing mixes bounded with bituminous binder, is also a typical substitute material for using in pavement and geotechnical usages [15,22]. The composition of CDW aggregates highly depends on their source and the processing method.…”

Section: Main Types Of Cdwsmentioning

confidence: 99%

“…Around 75% of CDWs were crushed into the gravel fraction and the remaining in the sand fraction. Majority of the RAP batches were considered gravel as per BS 5930, relying on the considered standard [15] (Figure 4). There are several local and global standards and also technical recommendations of different institutions, which fixes the limits for the gradation of materials used in unbound layers of pavements.…”

Section: Size Distributionmentioning

confidence: 99%

“…The average specific gravity of RCAs is relatively higher than that of the other types of recycled aggregates. Lower specific gravity of RA is essentially due to the presence of: (1) adhered cement mortar and its porous nature; (2) bitumen coating (in RAP) which has a density value normally lower than 1.10 kg/m 3 ; or (3) containing masonry and lightweight materials (in CDW) [15]. The results and values of specific gravities for construction and demolition waste considered in different publications are shown in Table 4.…”

Section: Specific Gravitymentioning

confidence: 99%

“…The goal is to determine the optimum moisture content (OMC) at which soils or mixtures of aggregates mixes attain the densest condition, demonstrating their Proctor Maximum Dry Density (MDD). Differences between these test procedures include the weight of the hammer used (2.7 kg for standard proctor and 4.9 kg for modified proctor) and the falling height of the hammer (35 and 45 cm) [15].…”

Section: Compactabilitymentioning

confidence: 99%

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Using Recycled Aggregates from Construction and Demolition Waste in Unbound Layers of Pavements

et al. 2020

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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. A number of tests and evaluations are applied in order to enhance the required quality and durability of the pavements under given traffic volumes traffic loads and climate actions. Today, unbound recycled aggregates (RA) are mainly used in the lower layers, such as subgrade, capping, sub-base and base, but in rural roads they can be adopted also for bound layers, towards the surface of the structure and may be constituents of bound layers and of novel surfacing applications.

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Section: Main Types Of Cdwsmentioning

confidence: 99%

Section: Main Types Of Cdwsmentioning

confidence: 99%

Section: Size Distributionmentioning

confidence: 99%

Section: Specific Gravitymentioning

confidence: 99%

Section: Compactabilitymentioning

confidence: 99%

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Using Recycled Aggregates from Construction and Demolition Waste in Unbound Layers of Pavements

et al. 2020

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Influence of Water Content on Track Degradation at Transition Zones

Zhu

Heitor

2021

Transp. Infrastruct. Geotech.

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This study aims to explore the role of water retention behaviour in the track degradation of the transition zone by examining the influence of water content variation. A model of railway bridge approach transition was built in the PLAXIS 3D to simulate the track degradation under diverse water content scenarios. A wedge-shaped backfill with unbound granular material (UGM) was simulated as a technical solution between the bridge abutment and open track. The most distinctive characteristic of the model is that the direct relationship between soil water content and soil displacement can be explored. To achieve this, the seasonal change in the soil moisture content of subsoil was simulated as the independent variable. The water content variation adopted mimicked the wet season (𝜔= 7.6%), as-compacted (𝜔= 5.6%) and dry season (𝜔= 3.6%) water content conditions. The results indicate that higher soil strains and displacements are obtained for high water contents. This indicates that there is a clear correlation between soil water retention and track displacements. In addition, the results suggest that a reduction in water content in the track substructure can be effective in mitigating in service settlement as overall track stiffness increases as a result. However, this effect is more pronounced at the track level and becomes less importance at higher depth in the formation layer. This study also shows that the bump from the bridge structure to backfill can be mitigated and smooth track geometry from the backfill and the open track can be achieved by manipulating the water content.

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Green Blocks Made of Recycled Construction Waste using Recycled Wastewater

Elgaali¹,

Wazeer²

2021

Adv. sci. technol. eng. syst. j.

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This study tests the feasibility of manufacturing concrete blocks made of recycled materials. The paper is an extension of work originally presented in ASET conference in Dubai. The paper, depicts and analyzes how the characteristics of the blocks (strength/durability) are affected by the presence of recycled concrete ingredients (recycled aggregate (RA)) and recycled water (RW). The recycled materials (RA and RW) were mixed in 16 different configurations; from each one 10 samples were prepared for testing. In each concrete configuration the RA and RW gradually replaced the fresh materials at 25%, 50%, 75%, and 100%. The RA moderately impacted the bearing capacity but significantly impacted the durability. The results show that using recycled aggregate decreases the bearing capacity by 22% (at the 100% replacement), and the recycled water slightly affected the bearing capacity (at the 100% replacement). To boost the durability, the ground granulated blast furnace slag (GGBS) was used, in the concrete mix, instead of the ordinary Portland cement (OPC). The GGBS was used at 3 magnitudes: 25%, 50%, and 75% of OPC. As a result the carbon foot-print footprint (1000 kg/m 3 ) was significantly lowered. Besides, the strength and durability of the blocks are reasonably enhanced. Generally, producing blocks from recycled materials is economical and feasible. The use of GGBS helps to lower the carbon footprint and enhance the strength and durability.

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Use of Recycled Aggregates in Geotechnical Applications

Cited by 3 publications

References 54 publications

Using Recycled Aggregates from Construction and Demolition Waste in Unbound Layers of Pavements

Using Recycled Aggregates from Construction and Demolition Waste in Unbound Layers of Pavements

Influence of Water Content on Track Degradation at Transition Zones

Green Blocks Made of Recycled Construction Waste using Recycled Wastewater

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