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This paper evaluates the long-term mechanical properties (up to 1 year) of alkali-activated slag concrete produced with recycled coarse aggregate (AAS-RA) and natural coarse aggregate (AAS-NA). The AAS-RA achieved a compressive strength of 35.20 MPa at 28 days and improved to 37.52 MPa at 365 days. This corresponded to a reduction in strength of 12.2% at 28 days and 7.7% at 365 days when compared with AAS-NA concrete. The flexural strength of both AAS concretes decreased with age, displaying a 10% and 11.8% drop after 1 year for AAS-NA and AAS-RA concretes, respectively, compared with that achieved at 28 days. However, the splitting tensile strength remained constant for the entire period. Furthermore, the elastic modulus of both AAS concretes decreased between 28 and 90 days; however, beyond 90 days, AAS-RA concrete maintained a constant elastic modulus while AAS-NA showed further decreased with time, such that by 365 days the AAS-NA had a 10% lower value than the AAS-RA concrete. This is attributed to alkali activation continuing beyond 90 days, producing additional C-A-S-H/C-S-H gel. This resulted in the combined effect of disjoining pressure and self-desiccation, which increased propagation of cracks and crack widths at later ages. However, in the AAS-RA there was also an increase in bond strength between the C-A-S-H gel and old cement paste (C-S-H gel matrix) on the recycled coarse aggregate, which resulted in a greater elastic modulus for the AAS-RA concrete. Experimentally observed long-term mechanical properties were compared with the predicted values in Australian and American Concrete Institute (ACI) codes. However, further studies are required to identify specific amendments required for these codes for the design of structural members manufactured from AAS concrete with recycled aggregate.
Ominda Nanayakkara; Chamila Gunasekara; David W. Law; Jun Xia; Sujeeva Setunge. Alkali-Activated Slag Concrete with Recycled Aggregate: Long-Term Performance. Journal of Materials in Civil Engineering 2021, 33, 04021167 .
AMA StyleOminda Nanayakkara, Chamila Gunasekara, David W. Law, Jun Xia, Sujeeva Setunge. Alkali-Activated Slag Concrete with Recycled Aggregate: Long-Term Performance. Journal of Materials in Civil Engineering. 2021; 33 (7):04021167.
Chicago/Turabian StyleOminda Nanayakkara; Chamila Gunasekara; David W. Law; Jun Xia; Sujeeva Setunge. 2021. "Alkali-Activated Slag Concrete with Recycled Aggregate: Long-Term Performance." Journal of Materials in Civil Engineering 33, no. 7: 04021167.
The utilization of industrial and agricultural by-products for the production of alkali activated concrete (AAC) has the potential to yield significant benefits towards sustainability goals. To be a viable material, the construction industry requires a construction material that achieves the requisite strength and the other property requirements as specified in codes and standards while demonstrating improved sustainability criteria. Fly ash and Rice Husk Ash (RHA) are abundantly available waste products, principally located in Asian countries. Currently, a significant proportion of these materials are disposed of in landfills, lagoons and rivers but offer potential to utilize in AAC. Hence, the identification of variables associated with fly ash and fly ah-RHA blended AAC by utilizing fly ash and RHA is vital. This study quantifies the environmental and economic factors by assessing the Greenhouse gas (GHG) emission, environmental impacts and benefits, and cost analysis of utilizing fly ash and RHA in AAC compared to Portland Cement (PC) concrete. Alkaline activator is a key component responsible for the highest GHG emission, cost and environmental impact amounts obtained for fly ash geopolymer and blended alkali-activated concrete compared with PC concrete. Alkali activators contribute to 74% of the total GHG emission, while heat curing contributed only 9% to the total GHG emission. The addition of 10% RHA to alkali-activated concrete showed a slight benefit for the analysis. Utilization of waste fly ash and RHA is responsible for providing significant benefits in terms of fresh and marine water ecotoxicity by avoiding waste disposal at the dumpsites, rivers, and storage lagoons.
Sarah Fernando; Chamila Gunasekara; David W. Law; M.C.M. Nasvi; Sujeeva Setunge; Ranjith Dissanayake. Life cycle assessment and cost analysis of fly ash–rice husk ash blended alkali-activated concrete. Journal of Environmental Management 2021, 295, 113140 .
AMA StyleSarah Fernando, Chamila Gunasekara, David W. Law, M.C.M. Nasvi, Sujeeva Setunge, Ranjith Dissanayake. Life cycle assessment and cost analysis of fly ash–rice husk ash blended alkali-activated concrete. Journal of Environmental Management. 2021; 295 ():113140.
Chicago/Turabian StyleSarah Fernando; Chamila Gunasekara; David W. Law; M.C.M. Nasvi; Sujeeva Setunge; Ranjith Dissanayake. 2021. "Life cycle assessment and cost analysis of fly ash–rice husk ash blended alkali-activated concrete." Journal of Environmental Management 295, no. : 113140.
Incorporating recycled plastic waste in concrete manufacturing is one of the most ecologically and economically sustainable solutions for the rapid trends of annual plastic disposal and natural resource depletion worldwide. This paper comprehensively reviews the literature on engineering performance of recycled high-density polyethylene (HDPE) incorporated in concrete in the forms of aggregates or fiber or cementitious material. Optimum 28-days’ compressive and flexural strength of HDPE fine aggregate concrete is observed at HDPE-10 and splitting tensile strength at HDPE-5 whereas for HDPE coarse aggregate concrete, within the range of 10% to 15% of HDPE incorporation and at HDPE-15, respectively. Similarly, 28-days’ flexural and splitting tensile strength of HDPE fiber reinforced concrete is increased to an optimum of 4.9 MPa at HDPE-3 and 4.4 MPa at HDPE-3.5, respectively, and higher than the standard/plain concrete matrix (HDPE-0) in all HDPE inclusion levels. Hydrophobicity, smooth surface texture and non-reactivity of HDPE has resulted in weaker bonds between concrete matrix and HDPE and thereby reducing both mechanical and durability performances of HDPE concrete with the increase of HDPE. Overall, this is the first ever review to present and analyze the current state of the mechanical and durability performance of recycled HDPE as a sustainable construction material, hence, advancing the research into better performance and successful applications of HDPE concrete.
Sonali Abeysinghe; Chamila Gunasekara; Chaminda Bandara; Kate Nguyen; Ranjith Dissanayake; Priyan Mendis. Engineering Performance of Concrete Incorporated with Recycled High-Density Polyethylene (HDPE)—A Systematic Review. Polymers 2021, 13, 1885 .
AMA StyleSonali Abeysinghe, Chamila Gunasekara, Chaminda Bandara, Kate Nguyen, Ranjith Dissanayake, Priyan Mendis. Engineering Performance of Concrete Incorporated with Recycled High-Density Polyethylene (HDPE)—A Systematic Review. Polymers. 2021; 13 (11):1885.
Chicago/Turabian StyleSonali Abeysinghe; Chamila Gunasekara; Chaminda Bandara; Kate Nguyen; Ranjith Dissanayake; Priyan Mendis. 2021. "Engineering Performance of Concrete Incorporated with Recycled High-Density Polyethylene (HDPE)—A Systematic Review." Polymers 13, no. 11: 1885.
The long-term creep and shrinkage behaviour of two High-Volume Fly Ash (HVFA) concretes incorporating nano silica with 65% and 80% replacement of cement has been investigated. This comprised a detailed analysis of the microstructure, pore structure and chemistry of the two HVFA systems up to a period of 450 days. The compressive strength and modulus of elasticity of HVFA-65 concrete increased from 32 to 73 MPa and 30.3 to 40.5 GPa, respectively between 7 and 450 days. The HVFA-80 concrete achieved compressive strength values of 22 and 71 MPa and elastic modulus values of 28.9 and 37 GPa. After a total loading period of 450 days, HVFA-65 and HVFA-80 concretes displayed creep parameters, which were significantly below the values predicted by AS 3600, ACI 209 and CEB-FIP standard model equations. After a total drying period of 450 days 28-day cured specimens showed significantly reduced shrinkage compared to 7-day cured specimens. On the other hand, HVFA-80 concrete displayed higher shrinkage compared to the HVFA-65 specimens throughout the period. All specimens except for 7-day cured HVFA-80 concrete were within the maximum permissible shrinkage of 800 microns recommended for Australian construction practices. HVFA-65 concrete showed a denser microstructure and a stronger, better packed interfacial transition zone (ITZ) compared to HVFA-80 at all ages. The XRD and FTIR analysis data identified the formation of hydration products including C-S-H and C-A-S-H which contributed towards both the strength gain as well as the creep and shrinkage properties displayed by the HVFA concrete by minimizing the total porosity and pore size.
Charith Herath; Chamila Gunasekara; David W. Law; Sujeeva Setunge. Long term creep and shrinkage of nano silica modified high volume fly ash concrete. Journal of Sustainable Cement-Based Materials 2021, 1 -21.
AMA StyleCharith Herath, Chamila Gunasekara, David W. Law, Sujeeva Setunge. Long term creep and shrinkage of nano silica modified high volume fly ash concrete. Journal of Sustainable Cement-Based Materials. 2021; ():1-21.
Chicago/Turabian StyleCharith Herath; Chamila Gunasekara; David W. Law; Sujeeva Setunge. 2021. "Long term creep and shrinkage of nano silica modified high volume fly ash concrete." Journal of Sustainable Cement-Based Materials , no. : 1-21.
Despite extensive in-depth research into high calcium fly ash geopolymer concretes and a number of proposed methods to calculate the mix proportions, no universally applicable method to determine the mix proportions has been developed. This paper uses an artificial neural network (ANN) machine learning toolbox in a MATLAB programming environment together with a Bayesian regularization algorithm, the Levenberg-Marquardt algorithm and a scaled conjugate gradient algorithm to attain a specified target compressive strength at 28 days. The relationship between the four key parameters, namely water/solid ratio, alkaline activator/binder ratio, Na2SiO3/NaOH ratio and NaOH molarity, and the compressive strength of geopolymer concrete is determined. The geopolymer concrete mix proportions based on the ANN algorithm model and contour plots developed were experimentally validated. Thus, the proposed method can be used to determine mix designs for high calcium fly ash geopolymer concrete in the range 25–45 MPa at 28 days. In addition, the design equations developed using the statistical regression model provide an insight to predict tensile strength and elastic modulus for a given compressive strength.
Chamila Gunasekara; Peter Atzarakis; Weena Lokuge; David Law; Sujeeva Setunge. Novel Analytical Method for Mix Design and Performance Prediction of High Calcium Fly Ash Geopolymer Concrete. Polymers 2021, 13, 900 .
AMA StyleChamila Gunasekara, Peter Atzarakis, Weena Lokuge, David Law, Sujeeva Setunge. Novel Analytical Method for Mix Design and Performance Prediction of High Calcium Fly Ash Geopolymer Concrete. Polymers. 2021; 13 (6):900.
Chicago/Turabian StyleChamila Gunasekara; Peter Atzarakis; Weena Lokuge; David Law; Sujeeva Setunge. 2021. "Novel Analytical Method for Mix Design and Performance Prediction of High Calcium Fly Ash Geopolymer Concrete." Polymers 13, no. 6: 900.
Civil engineers face significant challenges in the safe design and construction of durable road infrastructure in the presence of expansive soils. These problematic soils exacerbate undesirable serviceability concerns induced by pavement distress. Soil stabilisation has been recognised as a sustainable approach to alleviate the problematic nature of expansive subgrades. Road pavements constructed on top of expansive subgrade soils are generally under unsaturated conditions, where the moisture variations can significantly impact the pavement response. However, current pavement design and modelling frameworks overlook unsaturated soil behaviour by adopting simplified approaches. This study examines the hydraulic behaviour of expansive clayey soils stabilised with non-traditional and traditional chemical based additive. Tests were conducted to determine the state variation and stabilisation influence on the soil water characteristic curve using the dewpoint potentiometer for an expansive subgrade commonly found in Melbourne geology. Results show that the stabilisation has strong influence on soil hydraulic characteristics at various initial state conditions tested. Experimental data have been applied to illustrate the significance of incorporating realistic hydraulic response using a simulated practical application in road pavements. The research highlights the significance of incorporating accurate hydraulic characteristics for simulating and assessing the response of pavement constructed with stabilised unsaturated subgrade soils.
Jaspreet Pooni; Dilan Robert; Filippo Giustozzi; Chamila Gunasekara; Sujeeva Setunge; Srikanth Venkatesan. Hydraulic characteristics of stabilised expansive subgrade soils in road pavements. International Journal of Pavement Engineering 2021, 1 -18.
AMA StyleJaspreet Pooni, Dilan Robert, Filippo Giustozzi, Chamila Gunasekara, Sujeeva Setunge, Srikanth Venkatesan. Hydraulic characteristics of stabilised expansive subgrade soils in road pavements. International Journal of Pavement Engineering. 2021; ():1-18.
Chicago/Turabian StyleJaspreet Pooni; Dilan Robert; Filippo Giustozzi; Chamila Gunasekara; Sujeeva Setunge; Srikanth Venkatesan. 2021. "Hydraulic characteristics of stabilised expansive subgrade soils in road pavements." International Journal of Pavement Engineering , no. : 1-18.
The potential application of alkali-activated material (AAM) as an alternative binder in concrete to reduce the environmental impact of cement production has now been established. However, as the production and availability of the primarily utilized waste materials, such as fly Ash and blast furnace slag, decrease, it is necessary to identify alternative materials. One such material is clay, which contains aluminosilicates and is abundantly available across the world. However, the reactivity of untreated low-grade clay can be low. Calcination can be used to activate clay, but this can consume significant energy. To address this issue, this paper reports the investigation of two calcination methodologies, utilizing low-temperature and high-temperature regimes of different durations, namely 24 h heating at 120 °C and 5 h at 750 °C and, and the results are compared with those of the mechanical performance of the AAM produced with untreated low-grade clay. The investigation used two alkali dosages, 10% and 15%, with an alkali modulus varying from 1.0 to 1.75. An increase in strength was observed with calcination of the clay at both 120 and 750 °C compared to untreated clay. Specimens with a dosage of 10% showed enhanced performance compared to those with 15%, with Alkali Modulus (AM) of 1.0 giving the optimal strength at 28 days for both dosages. The strengths achieved were in the range 10 to 20 MPa, suitable for use as concrete masonry brick. The conversion of Al (IV) is identified as the primary factor for the observed increase in strength.
Muhammad Rahman; David Law; Indubhushan Patnaikuni; Chamila Gunasekara; Morteza Tahmasebi Yamchelou. Low-Grade Clay as an Alkali-Activated Material. Applied Sciences 2021, 11, 1648 .
AMA StyleMuhammad Rahman, David Law, Indubhushan Patnaikuni, Chamila Gunasekara, Morteza Tahmasebi Yamchelou. Low-Grade Clay as an Alkali-Activated Material. Applied Sciences. 2021; 11 (4):1648.
Chicago/Turabian StyleMuhammad Rahman; David Law; Indubhushan Patnaikuni; Chamila Gunasekara; Morteza Tahmasebi Yamchelou. 2021. "Low-Grade Clay as an Alkali-Activated Material." Applied Sciences 11, no. 4: 1648.
The deposition of textile waste into landfill has reached an unsustainable level and raises serious environmental issues across the world. Transforming textile waste into fiber reinforcement in cementitious composites offers a sustainable resolution toward a circular textile economy. This article presents a comprehensive review of environmental concerns, recycling routes for textile waste, together with an in-depth review of the engineering properties of concrete incorporating recycled textiles. In general, the incorporation of these recycled fibers from textile waste enhances strain capacity, crack control, durability, and energy absorption of concrete via dual effects: bridging action (direct mechanism) and refinement of pore distribution (indirect effect). An improvement in compressive strength can be achieved by the utilization of a small dosage of recycled fibers or recycled fiber fabrics in concrete (strength < 40 MPa). Finally, the cost and environmental benefits for eco-efficient building application are also evaluated to draw the attention of researchers toward these potentially recyclable waste materials.
Nghia P. Tran; Chamila Gunasekara; David W. Law; Shadi Houshyar; Sujeeva Setunge; Andrzej Cwirzen. Comprehensive review on sustainable fiber reinforced concrete incorporating recycled textile waste. Journal of Sustainable Cement-Based Materials 2021, 1 -22.
AMA StyleNghia P. Tran, Chamila Gunasekara, David W. Law, Shadi Houshyar, Sujeeva Setunge, Andrzej Cwirzen. Comprehensive review on sustainable fiber reinforced concrete incorporating recycled textile waste. Journal of Sustainable Cement-Based Materials. 2021; ():1-22.
Chicago/Turabian StyleNghia P. Tran; Chamila Gunasekara; David W. Law; Shadi Houshyar; Sujeeva Setunge; Andrzej Cwirzen. 2021. "Comprehensive review on sustainable fiber reinforced concrete incorporating recycled textile waste." Journal of Sustainable Cement-Based Materials , no. : 1-22.
Drying shrinkage deformation due to moisture migration is a major concern in cementitious materials and can lead to a high probability of cracking, resulting in a deterioration in long-term performance and serviceability. In this paper, the primary mechanisms of drying shrinkage, mitigation strategies and the research gaps are elucidated to provide a comprehensive understanding of the factors influencing drying shrinkage and identify research strategies to assist in the development of novel shrinkage-resistant concrete. The use of shrinkage-reducing admixture is identified as the high-efficiency methodology. This reduces the surface tension of the liquid in the capillary pore, resulting in a 20–50% drying shrinkage reduction when applied with a dosage up to 3%. It can achieve even greater efficiency by combining the admixture with expansive agents to provide synergistic effects, giving mitigation of drying shrinkage of up to 80%. Replacing cement with supplementary cementitious materials, up to 35%, is also an effective approach to mitigate drying shrinkage, giving a reduction between 5–42%. The reinforcing effect of novel carbon-nanotubes, albeit at a small dosage (0.1% w.t), can effectively strengthen the C–S–H gel matrix, resulting in a drying shrinkage reduction of 15–21%. Introducing internal restraints using fibres or aggregate also demonstrates high effectiveness for drying shrinkage mitigation. Furthermore, coupled CO2-water curing or coating the concrete surface to prevent moisture loss provides an innovative approach to drying shrinkage reduction at an early age (50–70%). Finally, to avert time-dependent deformation, the use of superplasticizer (less than 1%) based on the polycarboxylate polymer is suggested.
Nghia P. Tran; Chamila Gunasekara; David W. Law; Shadi Houshyar; Sujeeva Setunge; Andrzej Cwirzen. A critical review on drying shrinkage mitigation strategies in cement-based materials. Journal of Building Engineering 2021, 38, 102210 .
AMA StyleNghia P. Tran, Chamila Gunasekara, David W. Law, Shadi Houshyar, Sujeeva Setunge, Andrzej Cwirzen. A critical review on drying shrinkage mitigation strategies in cement-based materials. Journal of Building Engineering. 2021; 38 ():102210.
Chicago/Turabian StyleNghia P. Tran; Chamila Gunasekara; David W. Law; Shadi Houshyar; Sujeeva Setunge; Andrzej Cwirzen. 2021. "A critical review on drying shrinkage mitigation strategies in cement-based materials." Journal of Building Engineering 38, no. : 102210.
Adaption of reclaimed resources within the construction industry, in order to move towards environmental sustainability and a carbon neutral society is essential. To address this issue this study focused on the investigation of the long term performance, carbon emissions and coast savings of Alkali-activated slag (AAS) concrete incorporating recycled coarse aggregate (AAS-RA) up to one year of age. The performance and sustainability aspect of AAS-RA concrete was then compared with AAS concrete incorporated with natural quarry aggregate (AAS-NA) and PC concrete, respectively. Both AAS concretes achieved similar compressive strength of approx. 40 MPa and tensile strength of approx. 3.3 MPa after one year. Hence, full replacement of quarried coarse aggregate using recycled aggregate in AAS concrete did not display any evidence of an adverse impact to the strength characteristics. However, the 7-day and 28-day water cured AAS concretes demonstrated 32% and 16% higher drying shrinkage at one year in excess of the maximum permissible limit specified in AS3600. Both AAS concretes displayed high water absorption but low chloride permeability and sorptivity. A highly porous external surface layer interconnected with numerous capillaries and microcracks is hypothesised to be the reason for the high water absorption. Gel formation densified the microstructure and filled the capillaries in the bulk matrix, which in turn resulted in the lower permeability and secondary sorptivity. The AAS-NA and AAS-RA concretes displayed 43.5% and 52% carbon emission reduction compared to an equivalent strength of PC concrete having similar binder content.
Ominda Nanayakkara; Chamila Gunasekara; Malindu Sandanayake; David W. Law; Kate Nguyen; Jun Xia; Sujeeva Setunge. Alkali activated slag concrete incorporating recycled aggregate concrete: Long term performance and sustainability aspect. Construction and Building Materials 2020, 271, 121512 .
AMA StyleOminda Nanayakkara, Chamila Gunasekara, Malindu Sandanayake, David W. Law, Kate Nguyen, Jun Xia, Sujeeva Setunge. Alkali activated slag concrete incorporating recycled aggregate concrete: Long term performance and sustainability aspect. Construction and Building Materials. 2020; 271 ():121512.
Chicago/Turabian StyleOminda Nanayakkara; Chamila Gunasekara; Malindu Sandanayake; David W. Law; Kate Nguyen; Jun Xia; Sujeeva Setunge. 2020. "Alkali activated slag concrete incorporating recycled aggregate concrete: Long term performance and sustainability aspect." Construction and Building Materials 271, no. : 121512.
The long-term impact on creep, drying shrinkage, and permeation characteristics of an innovative concrete produced with manufactured geopolymer coarse aggregate (GPA) has been investigated and compared with quarried Basalt aggregate concrete. Microstructure and pore-structure development up to 1 year were examined through scanning electron microscopy, nanoindentation, and X-ray computed tomography. Compressive strength and elastic modulus of GPA concrete varied from 34.6 to 50.8 and 18.5 to 20.5 GPa, respectively, between 28 and 365 days. The 1-year creep strain of GPA concrete was 747 microstrain while the calculated creep coefficient was 0.97, which is significantly lower than the creep coefficient predicted by AS 3600 and CEB-FIP models. Moreover, the 365-day drying shrinkage is 570 microstrain, which is also lower than the maximum permissible limit specified by AS3600. The GPA concrete displayed high water absorption, but lower air and water permeability compared to Basalt aggregate concrete. This is attributed to a porous surface layer with large number of capillaries increasing the water absorption of GPA concrete through capillary suction. The discontinuity in the pore network coupled with a condensed interfacial transition zone formed in GPA concrete could be the reason for lower permeability. Overall, the long-term performance of the GPA demonstrates a potential as a lightweight coarse aggregate for concrete, with the added advantage of reducing the environmental impact utilizing fly ash from coal-fired power generation.
Charitha Seneviratne; Chamila Gunasekara; David W. Law; Sujeeva Setunge; Dilan Robert. Creep, shrinkage and permeation characteristics of geopolymer aggregate concrete: long-term performance. Archives of Civil and Mechanical Engineering 2020, 20, 1 -15.
AMA StyleCharitha Seneviratne, Chamila Gunasekara, David W. Law, Sujeeva Setunge, Dilan Robert. Creep, shrinkage and permeation characteristics of geopolymer aggregate concrete: long-term performance. Archives of Civil and Mechanical Engineering. 2020; 20 (4):1-15.
Chicago/Turabian StyleCharitha Seneviratne; Chamila Gunasekara; David W. Law; Sujeeva Setunge; Dilan Robert. 2020. "Creep, shrinkage and permeation characteristics of geopolymer aggregate concrete: long-term performance." Archives of Civil and Mechanical Engineering 20, no. 4: 1-15.
Due to the large contribution of cement production towards CO2 emission and rising concerns regarding climate change, substitution with alternative binders has become an established alternative to improve sustainability. Aluminosiliceous polymeric materials, known as geopolymer or alkali activated materials, have been proven to achieve a performance as good as and even superior to ordinary Portland cement (OPC). Various source materials have the potential to be used for the geopolymer synthesis depending on the local availability, among which fly ash, slag, and metakaolin have received most attention. A less established alternative is low grade clay, whether as the natural clay or the waste of construction work. These have the potential for geopolymer production due to their composition and abundance worldwide. However, due to the impurities present in these low-grade clays and slower dissolution rates, the synthesised geopolymers generally display lower mechanical performance. In this research, four different clays collected form construction sites in Melbourne, Australia, were characterised, and the optimum clay selected based on the amorphous content, specific surface area, and fineness. Furthermore, a relatively low energy-demand calcination regime was applied to the chosen clay, 550° C for 1 h. For the untreated clay-based geopolymer, a 7-day compressive strength of nearly 32 MPa was achieved, which increased to approaching 50 MPa after calcination at 550° C. A range of microscopy techniques, EDS, XRD, XRF, zetametry, 27Al MAS NMR, and computerised tomography were applied to characterise the microstructure and reaction kinetics of the synthesised geopolymer.
Morteza Tahmasebi Yamchelou; David Law; Robert Brkljača; Chamila Gunasekara; Jie Li; Indubhushan Patnaikuni. Geopolymer synthesis using low-grade clays. Construction and Building Materials 2020, 268, 121066 .
AMA StyleMorteza Tahmasebi Yamchelou, David Law, Robert Brkljača, Chamila Gunasekara, Jie Li, Indubhushan Patnaikuni. Geopolymer synthesis using low-grade clays. Construction and Building Materials. 2020; 268 ():121066.
Chicago/Turabian StyleMorteza Tahmasebi Yamchelou; David Law; Robert Brkljača; Chamila Gunasekara; Jie Li; Indubhushan Patnaikuni. 2020. "Geopolymer synthesis using low-grade clays." Construction and Building Materials 268, no. : 121066.
Fly ash is commonly used as a partial cement replacement material, but this is limited to replacement levels of 30% or less, with significant quantities of fly ash still not utilized globally. There has been significant recent research into High Volume Fly Ash (HVFA) concrete to enable the utilization of fly ash and to reduce CO2 emission by reducing cement demand. This comprehensive review summarizes up to date literature on HVFA concrete with more than 50% of cement replacement using ASTM Class F low calcium fly ash. Firstly, the available HVFA literature in which only fly has been used to replace cement, is categorized based on the replacement level and the mechanical and durability property results are summarized. Secondly, the remaining literature is categorized based on the different material additions to modify the HVFA concrete and the results are compared. The summarized results are discussed to elucidate the mechanisms underlying the reported results. The effect of each material addition on the HVFA concrete properties are also discussed to identify potentially more suitable additives for future development. Overall, this paper will provide an understanding of the current state of HVFA concrete research and the gaps in research for the development HVFA concrete containing higher replacement levels and achieving the required performance. Hence, summarised knowledge would significantly be beneficial to design prospective research towards a sustainable cement-free concrete using industrial waste.
Charith Herath; Chamila Gunasekara; David W. Law; Sujeeva Setunge. Performance of high volume fly ash concrete incorporating additives: A systematic literature review. Construction and Building Materials 2020, 258, 120606 .
AMA StyleCharith Herath, Chamila Gunasekara, David W. Law, Sujeeva Setunge. Performance of high volume fly ash concrete incorporating additives: A systematic literature review. Construction and Building Materials. 2020; 258 ():120606.
Chicago/Turabian StyleCharith Herath; Chamila Gunasekara; David W. Law; Sujeeva Setunge. 2020. "Performance of high volume fly ash concrete incorporating additives: A systematic literature review." Construction and Building Materials 258, no. : 120606.
Quarry aggregate reserves are depleting rapidly within Australia and the rest of the world due to an increasing demand for aggregates driven by expansion in construction. The annual production of premix concrete in Australia is approximately 30 million cubic meters, while 3–5% of concrete delivered to site remains unused and is disposed of in landfill or crushing plants. The production of coarse aggregates using this waste concrete is potentially a sustainable approach to reduce environmental and economic impact. A testing program has been conducted to investigate mechanical performance and permeation characteristics of concrete produced using a novel manufactured coarse aggregate recycled directly from fresh premix concrete. The recycled coarse aggregate (RCA) concrete satisfied the specified 28-day design strength of 25 MPa and 40 MPa at 28 days and a mean compressive strength of 60 MPa at 90 days. Aggregate grading was observed to determine strength development, while low water absorption, low drying shrinkage, and higher packing density indicate that the RCA concrete is a high-quality material with a dense pore structure. The rough fracture surface of the aggregate increased the bond between C-S-H gel matrix and RCA at the interfacial transition zone. Furthermore, a good correlation was observed between compressive strength and all other mechanical properties displayed by the quarried aggregate concrete. The application of design equations as stated in Australian standards were observed to provide a conservative design for RCA concrete structures based on the mechanical properties.
Chamila Gunasekara; Charitha Seneviratne; David W. Law; Sujeeva Setunge. Feasibility of Developing Sustainable Concrete Using Environmentally Friendly Coarse Aggregate. Applied Sciences 2020, 10, 5207 .
AMA StyleChamila Gunasekara, Charitha Seneviratne, David W. Law, Sujeeva Setunge. Feasibility of Developing Sustainable Concrete Using Environmentally Friendly Coarse Aggregate. Applied Sciences. 2020; 10 (15):5207.
Chicago/Turabian StyleChamila Gunasekara; Charitha Seneviratne; David W. Law; Sujeeva Setunge. 2020. "Feasibility of Developing Sustainable Concrete Using Environmentally Friendly Coarse Aggregate." Applied Sciences 10, no. 15: 5207.
Green materials are considered as one of the prominent elements in designing an environmentally sustainable construction project. Studies have highlighted cement replacement is a popular method of reducing greenhouse gas (GHG) emissions and replacing virgin materials in concrete. These options incur cost implications through sophisticated designs and technologies. The importance of maintaining a balance between environmental and economic benefits of a green design is critical for the decision making stakeholders in a construction project. However, designers often lack the resources and tools to initiate informed decision making for the optimum selection of a green material. In order to systemize the optimising process, the current study suggests a multi-objective optimisation based decision making framework for optimising the cement replacement materials in concrete. The study aims to present a sustainable criterion optimisation framework that could well be adopted to assess the sustainability of green materials in concrete production. A case study using fly ash geopolymer concrete in Melbourne demonstrated a reduction of 3.63% to 41.57% and 23.80% to 30.25% can be achieved for GHG emissions and production cost respectively if the developed optimisation based framework is implemented. The scenario results highlighted around 3% to 8% GHG and cost increase if material is not available locally. A similar approach can be utilised to optimise the environmental and cost savings of other cement replacement materials. Further studies are encouraged on comparing environmental and cost savings of other cement replacement materials using the developed framework. The framework will be valuable for designers in making decisions on sustainable cement replacement materials.
Malindu Sandanayake; Chamila Gunasekara; David Law; Guomin Zhang; Sujeeva Setunge; Dennis Wanijuru. Sustainable criterion selection framework for green building materials – An optimisation based study of fly-ash Geopolymer concrete. Sustainable Materials and Technologies 2020, 25, e00178 .
AMA StyleMalindu Sandanayake, Chamila Gunasekara, David Law, Guomin Zhang, Sujeeva Setunge, Dennis Wanijuru. Sustainable criterion selection framework for green building materials – An optimisation based study of fly-ash Geopolymer concrete. Sustainable Materials and Technologies. 2020; 25 ():e00178.
Chicago/Turabian StyleMalindu Sandanayake; Chamila Gunasekara; David Law; Guomin Zhang; Sujeeva Setunge; Dennis Wanijuru. 2020. "Sustainable criterion selection framework for green building materials – An optimisation based study of fly-ash Geopolymer concrete." Sustainable Materials and Technologies 25, no. : e00178.
Enzyme-based soil stabilizers have been successfully used in ground applications for the last 30 years. However, the successful application of a given enzyme-based additive is case specific and depends on soil type, soil condition, and operational loads. As a result, contractors incur a substantial cost in terms of time and money for preliminary lab tests, which may determine the suitable mix proportions to utilize in the field application. A sound understanding of the stabilization mechanism of these additives can minimize these costs and yield optimum benefits from the stabilization process. This paper investigates the stabilization effects of a novel enzyme-based additive, commercially known as Eko Soil, that is being applied to construct unpaved roads in Australia and worldwide. The aim of this research is to identify the optimized mix proportions of the additive by unveiling its mechanism of stabilization for a fine-grained field soil, which is dominant in Victoria, Australia. A series of experiments were conducted under a 4-stage test program that included macroscale mechanical tests and microscale imaging tests to unveil stabilization effects and the mechanism of stabilization. The identified mechanism has facilitated enhancement in the efficiency of enzyme-based soil stabilization significantly compared to the strength of nonstabilized soil. The research will substantially benefit the road construction industry by not only replacing traditional construction methods with economical/reliable approaches, but also providing insight on the optimum additive amount required to stabilize road pavements based on this stabilization mechanism.
Rintu Renjith; Dilan J. Robert; Chamila Gunasekara; Sujeeva Setunge; Brian O’Donnell. Optimization of Enzyme-Based Soil Stabilization. Journal of Materials in Civil Engineering 2020, 32, 04020091 .
AMA StyleRintu Renjith, Dilan J. Robert, Chamila Gunasekara, Sujeeva Setunge, Brian O’Donnell. Optimization of Enzyme-Based Soil Stabilization. Journal of Materials in Civil Engineering. 2020; 32 (5):04020091.
Chicago/Turabian StyleRintu Renjith; Dilan J. Robert; Chamila Gunasekara; Sujeeva Setunge; Brian O’Donnell. 2020. "Optimization of Enzyme-Based Soil Stabilization." Journal of Materials in Civil Engineering 32, no. 5: 04020091.
This study investigates strength development, reactivity and environmental/economic benefits of blended High Volume Fly Ash (HVFA) concrete mixes utilizing 65% and 80% cement replacement utilizing a combination of fly ash and hydrated lime, with and without nano-silica. The carbon and non-carbon emissions are considered as environmental impacts while life cycle costs from cradle-to-gate, which is from material extraction to production, are considered for comparison of the economic benefits. The compressive strength of the HVFA mixes increased with the addition of nano-silica. The HVFA–65 and HVFA–80, without nano-silica, achieved 25.0 MPa and 14.5 MPa at 7 days, respectively, and 42.7 MPa and 29.5 MPa at 28 days. With the addition of nano-silica the HVFA–65 ns and HVFA–80 ns concrete had compressive strengths of 37.5 MPa and 28.8 MPa at 7 days and increased to 47.1 MPa and 40.1 MPa at 28 days. Incorporating 3% nano-silica into HVFA concrete increased the early age hydration reaction. This is attributed to the reaction of the C3A and C4AF phases and the formation of monosulfoaluminate, which contributed to the early age strength gain. The majority of Ca2+ ions were consumed during the initial hydration, with few Ca2+ ions remaining for the subsequent hydration reaction with the C3S phase. The HVFA concrete mixes displayed between 51 and 60 % carbon savings and a reduced Global Warming Impact. The non-Greenhouse Gas emissions, i.e. SO2 and NOx, reflects minor savings in the Acidification Impact (AI) and Photochemical Oxidant Formation Impact (POFI) environmental impact indicators. Further, HVFA concrete incorporated with hydrated lime shows a 10% cost reduction compared with Portland Cement concrete.
Chamila Gunasekara; Malindu Sandanayake; Zhiyuan Zhou; David W. Law; Sujeeva Setunge. Effect of nano-silica addition into high volume fly ash–hydrated lime blended concrete. Construction and Building Materials 2020, 253, 119205 .
AMA StyleChamila Gunasekara, Malindu Sandanayake, Zhiyuan Zhou, David W. Law, Sujeeva Setunge. Effect of nano-silica addition into high volume fly ash–hydrated lime blended concrete. Construction and Building Materials. 2020; 253 ():119205.
Chicago/Turabian StyleChamila Gunasekara; Malindu Sandanayake; Zhiyuan Zhou; David W. Law; Sujeeva Setunge. 2020. "Effect of nano-silica addition into high volume fly ash–hydrated lime blended concrete." Construction and Building Materials 253, no. : 119205.
This study investigates low cement quaternary blend HVFA concrete mixes utilizing up to 80% cement replacement using fly ash, hydrated lime and nano-silica. The optimized concrete mixes achieved a compressive strength of 55 MPa and 48 MPa, for HVFA-65 and HVFA-80 concretes, respectively. Additional fly ash and hydrated lime dosage in HVFA concrete increased the rate of hydration of the C3A and C4AF phases but decreased the hydration of the C3S phase. This resulted in lower early age strength development in the HVFA concrete than occurs in PC concrete but significantly higher than for fly ash and hydrated lime alone. The addition of the nano-silica resulted in an increase in C–S–H gel incorporation of tetrahedrally coordinated aluminium (AlIV) into the HVFA concrete and the substitution of Si by Al in the C–S–H gel, leading to an increase in compressive strength in the HVFA concrete. Early age carbonation was increased with a higher of fly ash percentage. However, the reaction products dissolved in the pore water to form calcium bicarbonate with time.
Chamila Gunasekara; Zhiyuan Zhou; David W. Law; Massoud Sofi; Sujeeva Setunge; Priyan Mendis. Microstructure and strength development of quaternary blend high-volume fly ash concrete. Journal of Materials Science 2020, 55, 6441 -6456.
AMA StyleChamila Gunasekara, Zhiyuan Zhou, David W. Law, Massoud Sofi, Sujeeva Setunge, Priyan Mendis. Microstructure and strength development of quaternary blend high-volume fly ash concrete. Journal of Materials Science. 2020; 55 (15):6441-6456.
Chicago/Turabian StyleChamila Gunasekara; Zhiyuan Zhou; David W. Law; Massoud Sofi; Sujeeva Setunge; Priyan Mendis. 2020. "Microstructure and strength development of quaternary blend high-volume fly ash concrete." Journal of Materials Science 55, no. 15: 6441-6456.
Muhamed Khodr; David W. Law; Chamila Gunasekara; Sujeeva Setunge. Reactivity and Performance of Alkali-Activated Yallourn Brown Coal Ash. ACI Materials Journal 2020, 1 .
AMA StyleMuhamed Khodr, David W. Law, Chamila Gunasekara, Sujeeva Setunge. Reactivity and Performance of Alkali-Activated Yallourn Brown Coal Ash. ACI Materials Journal. 2020; ():1.
Chicago/Turabian StyleMuhamed Khodr; David W. Law; Chamila Gunasekara; Sujeeva Setunge. 2020. "Reactivity and Performance of Alkali-Activated Yallourn Brown Coal Ash." ACI Materials Journal , no. : 1.
A comprehensive experimental study has been conducted to investigate the geopolymerisation and compressive strength development of mortar made from brown coal fly ash from two separate locations in the storage ponds of an Australian power plant. The specimens gave similar compressive strengths but had significantly different material and performance characteristics despite being from the same storage location. The Loy Yang‒A (LYA) geopolymer mortar demonstrated an approx. 30% strength increase while Loy Yang‒B (LYB) gave an approx. 18% strength drop over the period from 7 and 90 d, though both geopolymer mortars initially achieved a similar 28-d strength of approx. 23 MPa. The LYA ash had almost double the alumina content compared to LYB and a higher proportion of AlVI compared to the LYB. The lower alumina content coupled with the low quantity of AlVI in the ash and its lower conversion to AlVI during geopolymerisation is identified as the primary reason for the reduction in strength observed in the LYB geopolymer. The increase of Q4(3Al) during geopolymerisation and some conversion to Q4(4Al) coordination over time resulted in the increase in the compressive strength observed in the LYA mortar. This strength increase of LYA mortar is further correlated with an increase in Quartz phases coupled with a reduction in the Moganite phase. Formation of sodium carbonate due to atmospheric carbonation of unreacted sodium hydroxide in Loy Yang geopolymer additionally contributed to the strength development of LYA geopolymer.
Muhamed Khodr; David Law; Chamila Gunasekara; Sujeeva Setunge; Robert Brkljaca. Compressive strength and microstructure evolution of low calcium brown coal fly ash-based geopolymer. Journal of Sustainable Cement-Based Materials 2019, 9, 17 -34.
AMA StyleMuhamed Khodr, David Law, Chamila Gunasekara, Sujeeva Setunge, Robert Brkljaca. Compressive strength and microstructure evolution of low calcium brown coal fly ash-based geopolymer. Journal of Sustainable Cement-Based Materials. 2019; 9 (1):17-34.
Chicago/Turabian StyleMuhamed Khodr; David Law; Chamila Gunasekara; Sujeeva Setunge; Robert Brkljaca. 2019. "Compressive strength and microstructure evolution of low calcium brown coal fly ash-based geopolymer." Journal of Sustainable Cement-Based Materials 9, no. 1: 17-34.