B. Aytekin Turkoglu
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5 records found
1
Journal article
(2026)
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Marija Nedeljković, Wim Ekkelenkamp, Burcu Aytekin, Penny Pipilikaki, Sonja Fennis, Jeannette van den Bos
This study advances understanding of how selective demolition combined with advanced recycling techniques affects the quality of recycled concrete aggregates (RCA) from Dutch infrastructure concrete under industrial conditions. A 60-year-old highway viaduct in the Netherlands was selectively demolished, including T-beams, columns, abutments, and foundations. Powder, fine, and coarse RCA fractions were produced from these preselected members using a conventional impact/rotor crusher and two advanced recycling technologies (Smart Liberator and Mangeler) and compared with RCA obtained from unknown-origin concrete rubble. Experimental relationships were established between adhered mortar content and key physical, mechanical, and chemical properties of RCA across particle size fractions. Selective demolition combined with advanced recycling produced materials with substantially improved performance. Fine RCA (0–4 mm) exhibited water absorption values of 2–6%, compared to approximately 8% for fine RCA from unknown-origin concrete rubble, while coarse RCA (4–22 mm) reached 1.5–4%. These improvements were accompanied by the high-performance characteristics of RCA produced using the Smart Liberator, including a Los Angeles abrasion value of approximately LA15 and particle density up to 2610 kg/m3. The results highlight the importance of both parent concrete selection and the choice of comminution technique in achieving high-quality RCA. Unlike conventional high-energy impact crushing, advanced recycling relies on controlled friction, shearing, and selective abrasion, which preserves aggregate integrity and allows efficient removal of adhered mortar. The resulting RCA exhibits mechanical and physical performance comparable to natural aggregates and meets Eurocode 2 requirements. This study demonstrates, at full industrial scale and within a single reinforced concrete structure, how selective demolition combined with advanced recycling enables direct control over adhered mortar content and aggregate performance, narrowing the gap between conventional RCA and natural aggregates for high-performance structural applications.
...
This study advances understanding of how selective demolition combined with advanced recycling techniques affects the quality of recycled concrete aggregates (RCA) from Dutch infrastructure concrete under industrial conditions. A 60-year-old highway viaduct in the Netherlands was selectively demolished, including T-beams, columns, abutments, and foundations. Powder, fine, and coarse RCA fractions were produced from these preselected members using a conventional impact/rotor crusher and two advanced recycling technologies (Smart Liberator and Mangeler) and compared with RCA obtained from unknown-origin concrete rubble. Experimental relationships were established between adhered mortar content and key physical, mechanical, and chemical properties of RCA across particle size fractions. Selective demolition combined with advanced recycling produced materials with substantially improved performance. Fine RCA (0–4 mm) exhibited water absorption values of 2–6%, compared to approximately 8% for fine RCA from unknown-origin concrete rubble, while coarse RCA (4–22 mm) reached 1.5–4%. These improvements were accompanied by the high-performance characteristics of RCA produced using the Smart Liberator, including a Los Angeles abrasion value of approximately LA15 and particle density up to 2610 kg/m3. The results highlight the importance of both parent concrete selection and the choice of comminution technique in achieving high-quality RCA. Unlike conventional high-energy impact crushing, advanced recycling relies on controlled friction, shearing, and selective abrasion, which preserves aggregate integrity and allows efficient removal of adhered mortar. The resulting RCA exhibits mechanical and physical performance comparable to natural aggregates and meets Eurocode 2 requirements. This study demonstrates, at full industrial scale and within a single reinforced concrete structure, how selective demolition combined with advanced recycling enables direct control over adhered mortar content and aggregate performance, narrowing the gap between conventional RCA and natural aggregates for high-performance structural applications.
Journal article
(2026)
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Burcu Aytekin, Patrick Holthuizen, Marija Nedeljković, Erik Schlangen, Oguzhan Copuroglu
This study evaluates how parent concrete characteristics and crushing techniques influence the physical, microstructural, and mechanical properties of RCA. Four parent concretes from an end-of-life viaduct (beam, column, abutment-wall, and foundation) were characterized for cement paste microstructure and volumetric composition prior to recycling. Two crushing techniques were applied: a conventional high-energy Impact Crusher (IC) and the vibration-based Smart Liberator (SL). Feature importance analysis showed that RCA behaviour reflects a combined influence of processing technique and parent concrete. RCA produced from concrete with higher air-void content (≈4%) facilitated mortar detachment and exhibited the lowest water absorption (≈1.7%) and fastest saturation rate (∼3 days). Conversely, RCA derived from concrete with a dense, cohesive, and well-hydrated paste retained more attached cement paste, resulting in the highest water absorption ('7%) and slowest saturation (∼6 days). Despite exhibiting similar compressive strengths, these two parent concretes produced fundamentally different RCA morphologies and absorption behaviours, highlighting the governing role of W/C ratio–related properties, such as capillary porosity and hydration degree, together with paste volume and air-void content in determining RCA quality. The crushing technique also played an important role in defining coarse RCA morphology and surface texture. The IC produced angular particles with irregular surfaces and localized microcracking, especially in dense, low-porosity concretes. These stress-induced defects increased surface roughness and open porosity, raising water absorption and reducing abrasion resistance. In contrast, the SL applies selective attrition and shear along the aggregate–paste interface, removing attached mortar without fracturing the aggregate core and yielding smoother, denser particles with minimal internal damage.
...
This study evaluates how parent concrete characteristics and crushing techniques influence the physical, microstructural, and mechanical properties of RCA. Four parent concretes from an end-of-life viaduct (beam, column, abutment-wall, and foundation) were characterized for cement paste microstructure and volumetric composition prior to recycling. Two crushing techniques were applied: a conventional high-energy Impact Crusher (IC) and the vibration-based Smart Liberator (SL). Feature importance analysis showed that RCA behaviour reflects a combined influence of processing technique and parent concrete. RCA produced from concrete with higher air-void content (≈4%) facilitated mortar detachment and exhibited the lowest water absorption (≈1.7%) and fastest saturation rate (∼3 days). Conversely, RCA derived from concrete with a dense, cohesive, and well-hydrated paste retained more attached cement paste, resulting in the highest water absorption ('7%) and slowest saturation (∼6 days). Despite exhibiting similar compressive strengths, these two parent concretes produced fundamentally different RCA morphologies and absorption behaviours, highlighting the governing role of W/C ratio–related properties, such as capillary porosity and hydration degree, together with paste volume and air-void content in determining RCA quality. The crushing technique also played an important role in defining coarse RCA morphology and surface texture. The IC produced angular particles with irregular surfaces and localized microcracking, especially in dense, low-porosity concretes. These stress-induced defects increased surface roughness and open porosity, raising water absorption and reducing abrasion resistance. In contrast, the SL applies selective attrition and shear along the aggregate–paste interface, removing attached mortar without fracturing the aggregate core and yielding smoother, denser particles with minimal internal damage.
Conference paper
(2025)
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Marija Nedeljkovic, L.S. Gómez Jaramillo, Patrick Holthuizen, Burcu Aytekin, Erik Schlangen, Sonja Fennis
Demolition and replacement of the existing transportation infrastructure have increased significantly due to ageing and growth of traffic loads. Consequently, a significant amount of demolition waste of unknown origin is produced. Without knowledge about parent concrete quality only a limited amount of recycled concrete aggregates is used in high-grade applications. This paper presents the framework for selective demolition of a highway bridge by systematic non-destructive concrete quality assessment. Surface chemical composition of concrete structural members was tested with handheld X-Ray Fluorescence Analyzer. In total, 3 columns, 23 beams, one foundation slab and one abutment were assessed. Their compressive strength was estimated using developed conversion curves based on results from rebound hammer and ultrasonic pulse velocity tests and their correlations to cube compressive strength test results. Beams were classified as a high strength (> 80 MPa) members. Columns, foundations and abutments were of a strength lower than 75 MPa. Ordinary Portland cement and silicious aggregates were identified by their chemical composition for nearly all accessible concrete members surfaces. The concrete chemical composition serves as a criterion for future application of fine recycled material. Members were sorted based on strength before demolition. This approach is essential to maximize the potential of the recycled concrete.
...
Demolition and replacement of the existing transportation infrastructure have increased significantly due to ageing and growth of traffic loads. Consequently, a significant amount of demolition waste of unknown origin is produced. Without knowledge about parent concrete quality only a limited amount of recycled concrete aggregates is used in high-grade applications. This paper presents the framework for selective demolition of a highway bridge by systematic non-destructive concrete quality assessment. Surface chemical composition of concrete structural members was tested with handheld X-Ray Fluorescence Analyzer. In total, 3 columns, 23 beams, one foundation slab and one abutment were assessed. Their compressive strength was estimated using developed conversion curves based on results from rebound hammer and ultrasonic pulse velocity tests and their correlations to cube compressive strength test results. Beams were classified as a high strength (> 80 MPa) members. Columns, foundations and abutments were of a strength lower than 75 MPa. Ordinary Portland cement and silicious aggregates were identified by their chemical composition for nearly all accessible concrete members surfaces. The concrete chemical composition serves as a criterion for future application of fine recycled material. Members were sorted based on strength before demolition. This approach is essential to maximize the potential of the recycled concrete.
Journal article
(2025)
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Burcu Aytekin, Patrick Holthuizen, Marija Nedeljković, Erik Schlangen, Oguzhan Copuroglu
The concrete recycling industry faces significant challenges due to the uncontrolled mixing of parent concretes with varying properties during demolition, resulting in inconsistent recycled concrete aggregate (RCA) quality and limiting its potential for use in new concrete production. Existing literature typically characterizes parent concrete solely based on compressive strength, neglecting other critical parameters. Consequently, RCA is often labelled as inherently heterogeneous, without fully considering the variability introduced by mixed-source demolition. This study introduces an novel protocol for systematic parent concrete characterization, combining an Artificial Intelligence (AI)-based segmentation approach with complementary techniques like polarized light and fluorescence microscopy (PFM). The proposed methodology quantifies critical properties of parent concrete, including water-to-cement (W/C) ratio, cement and aggregate content, air void content, and aggregate gradation. This enables a detailed evaluation of parent concrete variability, providing the basis for selective demolition strategies that reduce RCA heterogeneity and enhance the predictability of its properties. To illustrate its applicability, the protocol was applied to structural components of a Dutch viaduct, including prestressed beams, heavily reinforced columns, foundations, and abutment-wall. Results revealed significant differences in estimated water-to-cement ratios, ranging from 0.29 ± 0.03 in beams to 0.38 ± 0.03 in abutment walls, while hydration degrees varied between 0.80 ± 0.08 and 0.93 ± 0.02, indicating differences in cement maturity. Cement content ranged from 316 ± 11 kg/m³ in foundations to 390 ± 10 kg/m³ in beams, and air void content ranged significantly from 0.9 % in abutment walls to 4.3 % in foundations. Microstructural composition also differed substantially: paste volume ranged from 17 % to 27 %, and coarse aggregate content from 37 % to 52 % depending on the component. These quantitative differences confirm that structural concretes, even within the same structure, exhibit substantial internal variation. As such, uncontrolled demolition leads to the mixing of materials with fundamentally different properties—supporting the argument that RCA heterogeneity is not intrinsic, but largely a result of conventional demolition. This reinforces the value of the proposed protocol in identifying material variability and informing targeted demolition to enhance the predictability and uniformity of RCA.
...
The concrete recycling industry faces significant challenges due to the uncontrolled mixing of parent concretes with varying properties during demolition, resulting in inconsistent recycled concrete aggregate (RCA) quality and limiting its potential for use in new concrete production. Existing literature typically characterizes parent concrete solely based on compressive strength, neglecting other critical parameters. Consequently, RCA is often labelled as inherently heterogeneous, without fully considering the variability introduced by mixed-source demolition. This study introduces an novel protocol for systematic parent concrete characterization, combining an Artificial Intelligence (AI)-based segmentation approach with complementary techniques like polarized light and fluorescence microscopy (PFM). The proposed methodology quantifies critical properties of parent concrete, including water-to-cement (W/C) ratio, cement and aggregate content, air void content, and aggregate gradation. This enables a detailed evaluation of parent concrete variability, providing the basis for selective demolition strategies that reduce RCA heterogeneity and enhance the predictability of its properties. To illustrate its applicability, the protocol was applied to structural components of a Dutch viaduct, including prestressed beams, heavily reinforced columns, foundations, and abutment-wall. Results revealed significant differences in estimated water-to-cement ratios, ranging from 0.29 ± 0.03 in beams to 0.38 ± 0.03 in abutment walls, while hydration degrees varied between 0.80 ± 0.08 and 0.93 ± 0.02, indicating differences in cement maturity. Cement content ranged from 316 ± 11 kg/m³ in foundations to 390 ± 10 kg/m³ in beams, and air void content ranged significantly from 0.9 % in abutment walls to 4.3 % in foundations. Microstructural composition also differed substantially: paste volume ranged from 17 % to 27 %, and coarse aggregate content from 37 % to 52 % depending on the component. These quantitative differences confirm that structural concretes, even within the same structure, exhibit substantial internal variation. As such, uncontrolled demolition leads to the mixing of materials with fundamentally different properties—supporting the argument that RCA heterogeneity is not intrinsic, but largely a result of conventional demolition. This reinforces the value of the proposed protocol in identifying material variability and informing targeted demolition to enhance the predictability and uniformity of RCA.
Blast furnace slag-based alkali-activated concrete with treated municipal solid waste incineration (MSWI) bottom ash as coarse aggregate
Mechanical properties, freeze-thaw resistance, and environmental impact
Journal article
(2025)
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Boyu Chen, Ivana Mariam Paul, Luiz Miranda de Lima, Patrick Holthuizen, Shan He, Burcu Aytekin, Yu Zeng, Guang Ye
Municipal solid waste incineration (MSWI) bottom ash (BA) is widely available and has been increasingly explored for sustainable concrete production. While it is commonly used in Ordinary Portland Cement (OPC)-based concrete, its application in alkali-activated concrete (AAC) remains rare. This study developed a new AAC using MSWI BA as coarse aggregate to evaluate whether this represents a more sustainable application pathway compared to its use in conventional concrete. To address issues associated with metallic aluminum (Al) in MSWI BA, a NaOH-based pre-treatment was applied to reduce its content and minimize surface cracking and volume expansion in AAC. The incorporation of treated MSWI BA increased the overall porosity of AAC. The interfacial transition zone (ITZ) surrounding MSWI BA exhibited characteristic microstructural features. While previous studies suggested that MSWI BA-induced porosity may enhance freeze-thaw resistance in OPC concrete, the opposite trend was observed in AAC. The increased pore volume, irregular pore shapes, and MSWI BA-related microcracking reduced freeze-thaw durability. Despite these challenges, the developed AAC retained mechanical performance within strength class C30/37 and achieved a substantially lower carbon footprint compared to OPC and CEM III/B concretes. Leaching assessments further confirmed that the developed AAC complied with environmental standards and did not release harmful contaminants. Overall, these findings demonstrate that MSWI BA is a promising coarse aggregate for AAC.
...
Municipal solid waste incineration (MSWI) bottom ash (BA) is widely available and has been increasingly explored for sustainable concrete production. While it is commonly used in Ordinary Portland Cement (OPC)-based concrete, its application in alkali-activated concrete (AAC) remains rare. This study developed a new AAC using MSWI BA as coarse aggregate to evaluate whether this represents a more sustainable application pathway compared to its use in conventional concrete. To address issues associated with metallic aluminum (Al) in MSWI BA, a NaOH-based pre-treatment was applied to reduce its content and minimize surface cracking and volume expansion in AAC. The incorporation of treated MSWI BA increased the overall porosity of AAC. The interfacial transition zone (ITZ) surrounding MSWI BA exhibited characteristic microstructural features. While previous studies suggested that MSWI BA-induced porosity may enhance freeze-thaw resistance in OPC concrete, the opposite trend was observed in AAC. The increased pore volume, irregular pore shapes, and MSWI BA-related microcracking reduced freeze-thaw durability. Despite these challenges, the developed AAC retained mechanical performance within strength class C30/37 and achieved a substantially lower carbon footprint compared to OPC and CEM III/B concretes. Leaching assessments further confirmed that the developed AAC complied with environmental standards and did not release harmful contaminants. Overall, these findings demonstrate that MSWI BA is a promising coarse aggregate for AAC.