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Matches in Ghent University Academic Bibliography for { <https://biblio.ugent.be/publication/01GMAZB7XJM8BM9YF4KNQQQXW2> ?p ?o. }

• 01GMAZB7XJM8BM9YF4KNQQQXW2 classification D1.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 promoter F4BFDAEA-F0ED-11E1-A9DE-61C894A0A6B4.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 promoter FAECAB1E-F0ED-11E1-A9DE-61C894A0A6B4.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 date "2022".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 language "eng".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 type dissertation.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 hasPart 01GMAZRRE03SYTP25QP1WD1KKS.pdf.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 hasPart urn:uuid:7cbc9d60-3ad4-4139-b926-ce116a99d8ae.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 subject "Technology and Engineering".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 isbn "9789463556613".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 abstract "Blast furnace slag (BFS), a by-product of the iron and steel manufacturing industry, has latent hydraulic properties and therefore has been extensively used as a supplementary cementitious material (SCM) in the construction industry for decades. In recent years, in addition to its advantages in improving concrete performance, BFS as SCM has gradually attracted more interest due to its advantages for the future low carbon economy. However, concrete containing BFS generally has a weaker carbonation resistance than Portland cement concrete. This Ph.D. thesis focuses on the carbonation behaviour and mechanisms of concrete with different BFS replacement ratios of 0%, 50% and 70% (denoted as PC, BFS-50% and BFS-70%). Accelerated carbonation of BFS concrete and the effect of curing time The carbonation behaviour of concrete was investigated in terms of carbonation rate, phase assemblage and pore structure. The carbonation depth of concrete with different curing times (14 d, 28 d and 84 d) was measured after accelerated carbonation for 14 d, 28 d, 56 d, 91 d and 183 d to evaluate the carbonation rate. During the accelerated carbonation, the temperature, relative humidity and CO2 concentration were maintained at (20 ± 2) ℃, (60 ± 5) %, and 2%, respectively. The phase assemblage of the non-carbonated and carbonated cement paste was compared using Thermogravimetric Analysis (TGA) and X-ray Powder Diffraction (XRD). The pore structure of the non-carbonated and carbonated concrete was compared using Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscope with Backscattered Electron mode (SEM-BSE). The carbonation resistance of concrete with BFS replacement is worse than for Portland cement concrete due to the lower amount of portlandite and coarser pore structure of carbonated BFS concrete. The carbonation rate increases with the increasing BFS replacement ratio. In addition to the coarsened pore structure of the cement paste matrix after carbonation, the greatly weakened interfacial transition zone of BFS concrete plays an important role. However, a proper curing protocol such as a longer curing time can effectively improve the carbonation resistance of BFS concrete. The carbonation rate of BFS-50% after 84 d curing (1.05 mm/d1/2) is close to that of PC (0.94 mm/d1/2). The longer curing time results in less calcium carbonate formation and lower carbonation degree of AFm phases for carbonated cement paste. With the increase in BFS replacement ratio, the carbonation degree of AFm phases decreases while the carbonation of clinkers increases. The pore structure of non-carbonated PC and BFS-50% is densified by a longer curing time, while that of BFS-70% remains unchanged. After the carbonation, the concrete with a longer curing time has a denser carbonated pore structure, which can slow down the further carbonation. In the case of BFS concrete, though still higher than for non-carbonated concrete, the porosity of carbonated concrete with a longer curing time is greatly decreased. Moreover, the carbonation rate at different surfaces of the concrete specimens is found to be different due to the compaction-induced microstructure changes. The carbonation rate at different surfaces shows the following order: top trowelled surface > side cast surface > bottom cast surface. The effect of CO2 concentration on the carbonation The difference between the concrete behaviour under natural carbonation and accelerated carbonation was investigated in terms of carbonation rate, phase assemblage and pore structure. The carbonation depth of concrete cured for 28 days and carbonated at different CO2 concentrations (0.04%, 1% and 2% CO2) was measured after different exposure times. The phase assemblage and pore structure before and after the carbonation were investigated using XRD, TGA, MIP and SEM-BSE. The estimation of the natural carbonation coefficient based on accelerated carbonation tests can lead to inaccurate results as not only the CO2 concentration determines the CO2 diffusion rate. In this thesis, the change in diffusion coefficient during the carbonation results in an underestimation of the natural carbonation coefficient which could cause issues for service life prediction. A higher CO2 concentration leads to a denser carbonated pore structure. It should be noted that carbonation leads to a coarser pore structure for BFS concrete which is opposite to the effect of increased CO2 concentration. Therefore, the extrapolation of accelerated tests to natural conditions is difficult, in particular for BFS concrete. The lower porosity induced by higher CO2 concentrations (accelerated carbonation at 1% and 2% CO2) is mainly attributed to the heterogeneous C-S-H carbonation. The carbonation of inner C-S-H eases the access of water to the clinker phases, leading to a higher reaction degree of clinker and a denser structure. The carbonation of outer C-S-H under natural carbonation, which shows a large amount of silica gel formation, accounts for the increased porosity of BFS concrete. The CO2 concentration influences the experimentally observed carbonation product assemblage. More calcite tends to form under higher CO2 concentrations while metastable vaterite is more likely to form under a lower CO2 concentration. Less well-crystallized calcium carbonate is formed at higher CO2 concentrations of 1% and 2% CO2 due to the higher amount of C-S-H carbonation. The hydrotalcite is more stable at higher CO2 concentrations and carbonates slower. Coupled effect of carbonation and mechanical load on the carbonation of concrete The carbonation behaviour of concrete under sustained compressive load which simulates the on-site concrete carbonation process under service load was investigated. The loading setups which can fit into the carbonation chamber were developed for load application and maintenance during the carbonation. The carbonation depth of concrete after the accelerated carbonation at 1% and 2% CO2 under different sustained compressive load levels (25%-75% of the breaking load) was measured after the exposure time of 28 d. The pore structure of non-carbonated and carbonated concrete was investigated by MIP. The internal crack pattern was investigated by fluorescent resin impregnation and SEM-BSE. The crack propagation on the concrete outer surface during the compressive loading was investigated by Digital Image Correlation (DIC). In addition to PC, BFS-50% and BFS-70%, the effect of fly ash was investigated based on concrete with 30% fly ash (FA-L) at 2% CO2. The sustained compressive load can slow down the carbonation at moderate load levels, but lead to an increase in carbonation rate above a threshold load level. At 1% CO2, the threshold compressive load level for PC is around 0.25, while the threshold load level for BFS-50% and BFS-70% is around 0.5. At 2% CO2, the threshold load level for FA-L is around 0.4. The sustained compressive load shows a greater densification effect on the concrete with SCMs. The difference between the carbonation depth of PC and BFS-50% at moderate load levels is very limited. The densification effect of sustained compressive load which can slow down the carbonation is to a greater extent due to the carbonated zone instead of the non-carbonated zone. The carbonated zone primarily shows a load-induced densification effect and contributes to the slowed-down carbonation rate through autogenous healing of microcracks, ITZ densification and pore densification. In the non-carbonated zone, the densification effect is partially because of the densified interfacial transition zone and large gel pores. However, crack propagation dominates in the non-carbonated zone, especially at a high load level. The increase in the carbonation depth under sustained compressive load above the threshold load level is mainly because of the generation and propagation of microcracks. For PC without initial carbonation, it is attributed to the sharp increase in crack width, while it is attributed to the internal coalesced fine microcracks and superficial cracks for BFS concrete. For PC with initial carbonation during the pre-conditioning, it is attributed to a large number of coalesced cracks both at the outer surface and inside the carbonated zone. Thermodynamic modelling of the carbonation process A simulation of the carbonation process was carried out to better understand the investigated effects of BFS replacement, curing time and CO2 concentration. The thermodynamic modelling was carried out using the Gibbs free energy minimization program GEMS. In addition to the CEMDATA18 database (developed by EMPA, Switzerland) for hydrated solids in the Portland cement system and the default thermodynamic database, K-, Na- and Ca-based zeolites which represent the amorphous aluminosilicate gel formed during the carbonation process and hydrotalcite with different Mg/Al ratios containing CO3 2− , SO4 2− and OH− are included. The evolution of portlandite, C-S-H, ettringite and AFm phases during the carbonation process was calculated. The thermodynamic model developed in this thesis can adequately simulate the carbonation process of concrete with different BFS replacement ratios in terms of chemical changes and phase evolution. The modelled results agree well with the experimental results. The total solid volume of PC is predicted to increase after carbonation. However, due to the lack of portlandite and a higher amount of AFm phases, the total solid volume of BFS-50% and BFS-70% is predicted to continuously decrease during the carbonation process. The anion substitutions in the structure of hydrotalcite during the carbonation are predicted by thermodynamic modelling. A transformation from OH-Ht to CO3-Ht with a decrease in Mg/Al ratio during the carbonation is predicted for all concrete mixes. Before the carbonation, the hydrotalcite in the PC system is predicted to mostly contain CO3 2− due to the excess limestone powder, while the BFS-50% and BFS-70% systems contain mostly OH- ions. During the carbonation, the hydrotalcite of PC is gradually depleted. However, the CO3-Ht is predicted to remain stable even at complete carbonation conditions for BFS- 50% and BFS-70%.".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 author 7EE53126-CD04-11E9-8B81-BA085707D3EF.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 dateCreated "2022-12-15T13:24:56Z".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 dateModified "2024-10-29T15:58:05Z".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 name "Carbonation rate, mineralogy and microstructure of blast furnace slag concrete at different CO2 concentrations and mechanical loading".
• 01GMAZB7XJM8BM9YF4KNQQQXW2 pagination urn:uuid:46e089b0-6504-4d5d-9eb7-1d3b1e383c62.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 publisher urn:uuid:c285896c-61d2-41b0-a6e0-a69ae75a1ee0.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 sameAs LU-01GMAZB7XJM8BM9YF4KNQQQXW2.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 sourceOrganization urn:uuid:588f3415-064b-4fa0-995c-f3fa4500e281.
• 01GMAZB7XJM8BM9YF4KNQQQXW2 type D1.