Nele De Belie

Ghent University, Gand, Flanders, Belgium

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Publications (173)261.8 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper is the work of working group 2 of the RILEM TC 238-SCM. Its purpose is to review methods to estimate the degree of reaction of supplementary cementitious materials in blended (or composite) cement pastes. We do not consider explicitly the wider issues of the influence of SCMs on hydration kinetics, nor the measurement of degree of reaction in alkali activated materials. The paper categorises the techniques into direct methods and indirect methods. Direct methods attempt to measure directly the amount of SCM remaining at a certain time, such as selective dissolution, microscopy combined with image analysis, and NMR. Indirect methods infer the amount of SCM reacted by back calculation from some other measured quantity, such as calcium hydroxide consumption. The paper first discusses the different techniques, how they operate and the advantages and limitations along with more details of case studies on different SCMs. In the second part we summarise the most suitable approaches for each SCM, and the paper finishes with conclusions and perspectives for future work.
    Materials and Structures 04/2015; 48(4). DOI:10.1617/s11527-015-0527-4 · 1.39 Impact Factor
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    ABSTRACT: During the last years, more and more research has been devoted to self-healing in cementitious materials. While most research is still done on carefully prepared small-scale mortar samples with predefined cracks, the healing efficiency should be investigated after exposure of the capsules to the concrete mixing and casting process and for random appearing cracks. In the current study, the resistance of brittle encapsulation materials, containing polyurethane, against the mixing and manufacturing process of concrete was studied. Different methods to protect the capsules were proposed and evaluated. In addition, realistic crack patterns were created in beams with embedded capsules. Non-destructive testing techniques such as digital image correlation, acoustic emission analysis and X-ray radiography were used to evaluate the survivability of the capsules upon mixing and the breakability of the capsules upon crack formation. Evaluation of the crack repair efficiency by performing water permeability tests showed some improvement in water tightness due to self-healing, but the water ingress into the cracks was not completely prevented.
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    ABSTRACT: This paper aims to examine the use of fines generated out of recycled aggregates production as an alternative raw material for Portland clinker kilns with enumeration of possible limitations. Different technical set-ups were used to separate these fines from the recycled aggregates. The relationship between the particle size distribution of the generated fines fraction and their chemical composition as well as the relationship between the final filler (<63 μm) content [wt%] and the water demand of the treated sand fraction were investigated. Numerical simulations were carried out to maximise the fines fractions as raw materials in clinker kilns based on which experimental clinkers were produced. The final clinkers were fully analysed and evaluated on possible mineralogical influences.
    Cement and Concrete Composites 02/2015; 58. DOI:10.1016/j.cemconcomp.2015.01.003 · 2.76 Impact Factor
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    ABSTRACT: Incorporation of living organisms, such as photosynthetic organisms, on the structures envelope has become a priority in the area of architecture and construction due to aesthetical, economic and ecological advantages. Important research efforts are made to achieve further improvements, such as for the development of cementitious materials with an enhanced bioreceptivity to stimulate biological growth. Previously, the study of the bioreceptivity of cementitious materials has been carried out mainly under laboratory conditions although field-scale experiments may present different results. This work aims at analysing the colonisation of cementitious materials with different levels of bioreceptivity by placing them in three different environmental conditions. Specimens did not present visual colonisation, which indicates environmental conditions have a greater impact than intrinsic properties of the material at this stage. Therefore, it appears that in addition to an optimized bioreceptivity of the concrete (i.e. composition, porosity and roughness), extra measures are indispensable for a rapid development of biological growth on concrete surfaces. An analysis of the colonisation in terms of genus and quantity of the most representative microorganisms found on the specimens for each location was carried out and related to weather conditions, such as monthly average temperature and total precipitation, and air quality in terms of NOx, SO2, CO and O3. OPC-based specimens presented the higher colonisation regarding both biodiversity and quantity. However, results obtained in a previous experimental program under laboratory conditions suggested a higher suitability of Magnesium Phosphate Cement-based (MPC-based) specimens for algal growth. Consequently, carefully considering the environment and the relationships between the different organisms present in an environment is vital for successfully using a cementitious material as a substrate for biological growth.
    Science of The Total Environment 01/2015; 512-513:444-453. DOI:10.1016/j.scitotenv.2015.01.086 · 3.16 Impact Factor
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    ABSTRACT: Self-healing concrete has been scrutinized by several researchers and some industrial concrete producers in relation to the remediation of the occurrence of micro-cracks. Such cracks are a quite well known problem that can lead to corrosion of the steel reinforcement and thus to the possible failure of the entire concrete structure. The need to repair these cracks as soon as possible leads to maintenance costs which can be of the order of €130 (direct costs) per m3 of concrete. Recent scientific studies indicate that a Microbial Induced Carbonate Precipitation (MICP), using microbial spores as active agent, can be an alternative for the actual repair methods. However, the production of bacterial spores is yet imposing considerable costs. According to some concrete producers they would be willing to pay about €15 to €20 per m3 of concrete for a bio-based self-healing product. However, the actual cost of spores production and encapsulation represent a total cost which is orders of magnitude higher. This article analyzes the costs for the biological self-healing in concrete and evaluates the industrial challenges it faces. There is an urgent need to develop the production of a bio-additive at much lower costs to make the biological self-healing industrial applicable. Axenic production and a possible non-axenic process to obtain ureolytic spores were analyzed and the costs calculations are presented in this paper.
    Journal of Commercial Biotechnology 01/2015; 21(1):31-38. DOI:10.5912/jcb662
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    ABSTRACT: Energy efficiency in buildings has been a hot topic in recent years and the demand for alternatives regarding heat storage and thermal insulation is high. Materials with a large thermal mass like concrete can be optimized in terms of heat capacity. Useful for this purpose are Phase-Change Materials (PCMs), which show a high heat of fusion with a melting point within the ambient temperature range. In this paper, the effect of encapsulated PCMs on the thermal behavior and setting process of mortar at early age, and on the strength and thermal behavior of hardened mortar were studied. Such hardened PCM-mortar warms up more gradually and expands the thermal comfort in buildings. PCMs delay the setting process and cause a shift of the corresponding heat of hydration peak and reduce the strength. However, the strength remains high enough for many applications. A possible application was studied, related to thermal cracking of insulated concrete sandwich panels, where the encapsulated PCMs show an influence on the thermal properties in a positive way as they reduce strains. PCMs are innovative and promising materials to use in future applications of concrete structures to promote thermal comfort and to reduce thermal cracking.
    Materials and Structures 01/2015; DOI:10.1617/s11527-014-0490-5 · 1.39 Impact Factor
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    ABSTRACT: Up to now, glass capsules, which cannot resist the mixing process of concrete, have been mostly used in lab-scale proof-of-concept to encapsulate polymeric agents in self-healing concrete. This study presents the design of polymeric capsules which are able to resist the concrete mixing process and which can break when cracks appear. Three different polymers with a low glass transition temperature Tg have been extruded: Poly(lactic acid) (PLA) (Tg = 59 °C), Polystyrene (PS) (Tg = 102 °C) and Poly(methyl methacrylate/n-butyl methacrylate) (P(MMA/n-BMA)) (Tg = 59 °C). After heating the capsules prior to mixing with other components of the mix, to shift from a brittle state to a rubbery state, their survival ratio considerably increased. Moreover, a part of the capsules, which previously survived the concrete mixing process, broke with crack appearance. Although some optimization is still necessary concerning functional life of encapsulated adhesives, this seems to be a promising route.
    Cement and Concrete Composites 01/2015; DOI:10.1016/j.cemconcomp.2014.09.022 · 2.76 Impact Factor
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    ABSTRACT: Superabsorbent polymers (SAPs) are particles which can take up a significant amount of fluid. In this paper workability, microstructure and strength properties were compared for mixtures with(out) SAPs and with(out) additional water. SAP particles reduce the flow, cause a densification of the matrix due to internal curing and also reduce the strength due to macro-pore formation. These characteristics need to be taken into account when using high amounts of SAPs in a mixture. The microstructure of mixtures with SAPs and additional water tends towards the one of the reference mixture without SAPs. The strength upon water addition, however, decreases slightly.
    Construction and Building Materials 12/2014; 72:148–157. DOI:10.1016/j.conbuildmat.2014.09.012 · 2.27 Impact Factor
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    Yusuf Cagatay Ersan, Nele De Belie, Nico Boon
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    ABSTRACT: This study focused on identification of denitrifiers that can be used to achieve microbial self-healing concrete. By using heat treatment and minimal medium, 9 denitrifying strains were isolated from soil. Upon identification of the strains, their capability of handling dehydration stress was investigated. Qualifying 7 strains were further investigated at N:P ratio of 70:1. Finally, 2 strains, Pseudomonas aeruginosa and Diaphorobacter nitroreducens, were selected and investigated at pH 7, pH 9.5 and pH 13 with and without protection. As a protective carrier diatomaceous earth and expanded clay were used. Significant activity observed at pH 9.5 and with protection both strains could survive pH 13 for 14 days and reduced 20-30 mg/L NO 3 -in 4 days after the pH adjustment to ~10. Overall, the results indicated that Pseudomonas aeruginosa and Diaphorobacter nitroreducens can resist mild heat, dehydration, starvation and relatively alkali environment, which are the main concerns in use of bacteria for concrete structures.
    Advances in Bio-Informatics, Bio-Technology and Environmental Engineering, Birmingham; 11/2014
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    ABSTRACT: Natural fibres such as flax and hemp fibres are mainly used in the textile industry, but have outstanding mechanical properties. These natural fibres have a great potential as reinforcement in cementitious composites, as an alternative to synthetic microfibres. The multiple cracking capacity of cementitious composites reinforced with natural fibres, however, is inferior due to the hydrophilicity, and the fibres may degrade in alkaline environments. Consequently, a proper mixture design and chemical treatments were investigated to improve fibre characteristics. The application of flax and hemp fibres in cementitious composites was examined, with a focus on inducing multiple cracking under tensile stresses. The mechanical properties of the natural fibres, as well as of the cementitious composites and the degradation of the natural fibres in alkaline environments were studied. Multiple cracking was achieved and further improvements were made by chemically treating the fibres. Mercerization with 2 m% concentration sodium hydroxide (NaOH) resulted in optimal multiple cracking. This multiple cracking resulted in small cracks widths, which allowed optimal autogenous healing when exposed to wet/dry-cycles. Natural fibres were thus found to be a valid eco-friendly alternative to synthetic microfibres.
    3rd International RILEM Conference on Strain Hardening Cementitious Composites, Dordrecht; 11/2014
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    ABSTRACT: While the use of insulated concrete sandwich panels results in more energy efficient buildings, the presence of this insulation layer can induce thermal crack formation. As cracks form a preferential path for aggressive agents to enter and degrade the concrete matrix and as they are not wanted in this application from an aesthetical point of view, they need to be treated. In this study it was aimed to invisibly seal the cracks in concrete sandwich panels in an autonomous way. Therefore, the efficiency of various encapsulated healing agents was compared by inducing thermal cracks in concrete sandwich panels causing capsule breakage and thus release of the agents into the cracks. It was shown that encapsulation of both polyurethane and a water repellent agent can result in a reduction of the water uptake by cracks, however, only in the case a water repellent agent was released, cracks were healed in an almost invisible way. From this study, it was shown that the self-healing approach consisting of encapsulated polymer based healing agents can also be applied in concrete sandwich panels although more research will be needed to meet the specific healing requirements for this application.
    10/2014; DOI:10.1002/suco.201400055
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    ABSTRACT: Superabsorbent polymers (SAPs) have already found their way in many applications. These ‘smart’ polymers undergo major characteristic changes by small environmental variations. In the present work, copolymer networks composed of acrylic acid, acrylamide and N,N′-methylenebisacrylamide have been synthesized using free radical precipitation polymerization. The polymers obtained have been characterized for their chemical structure, moisture (de)sorption and swelling behaviour using, respectively, attenuated total reflectance-infrared spectroscopy, high-resolution magic-angle spinning NMR spectroscopy, dynamic vapour sorption and swelling studies. The results indicated a remarkable moisture uptake capacity at high relative humidities of more than 90 % the original polymer weight with a negligible hysteresis. The latter implies that the SAPs developed are very promising water reservoir candidates, which become useful in concrete-related applications. Furthermore, the swelling data revealed that polymers with a low cross-linking density result in materials with superabsorbent properties. In addition, these SAPs show a pH-dependent swelling behaviour up to 450 times their original weight at pH 12.
    Journal of Materials Science 10/2014; 50(2). DOI:10.1007/s10853-014-8657-6 · 2.31 Impact Factor
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    ABSTRACT: Self-healing strategies are regarded as a promising solution to reduce the high maintenance and repair cost of concrete infrastructures. In the present work, a bacterial-based self-healing by use of hydrogel encapsulated bacterial spores (bio-hydrogels) was investigated. The crack closure behaviour of the specimens with/without bio-hydrogels was studied quantitatively by light microscopy. To have a view of the self-healing inside the specimens, a high resolution X-ray computed microtomography (X-ray μCT) was used. The total amount and the distribution of the healing products in the whole matrix were investigated. This study indicates that the specimens incorporated with bio-hydrogels had distinct improved healing efficiency compared to the reference ones with pure hydrogel only. The healing ratios in the specimens with bio-hydrogels were in the range from 70 % to 100 % for the cracks smaller than 0.3 mm, which is more than 50 % higher than for the ones with pure hydrogel; and the maximum crack bridging was about 0.5 mm (in 7 d), while pure hydrogels only allowed healing of cracks of about 0.18 mm. The total volume ratio of the healing product in the specimens with bio-hydrogels amounted to 2.2 %, which was about 60 % higher than for the ones with pure hydrogel (1.37 %).
    Cement and Concrete Composites 10/2014; 53. DOI:10.1016/j.cemconcomp.2014.07.014 · 2.76 Impact Factor
  • Materials and Structures 10/2014; DOI:10.1617/s11527-014-0430-4 · 1.39 Impact Factor
  • Materials and Structures 10/2014; DOI:10.1617/s11527-014-0431-3. · 1.39 Impact Factor
  • Mathias Maes, Nele De Belie
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    ABSTRACT: Marine environments are very aggressive, since sea water consists mainly of chlorides and sulphates. So, to predict concrete’s durability as exactly as possible it is important to know the combined attack mechanisms as realistic as possible. In this research, the reciprocal influence of Cl- and SO42- was investigated for four mixtures, namely with Ordinary Portland Cement, High Sulphate Resistant cement, and with Blast-Furnace Slag (50% and 70% cement replacement). Chloride penetration depths and diffusion coefficients were measured to investigate the influence of SO42- on Cl- attack. Besides, length and mass change measurements were performed to examine the influence of Cl- on SO42- attack. Since the formation of ettringite, gypsum and Friedel’s salt plays an important role, XRD-analyses were done additionally. It can be concluded that chloride penetration increases when the sulphate content increases at short immersion periods, except for HSR concrete. Concerning the sulphate attack, the presence of chlorides has a mitigating effect.
    Cement and Concrete Composites 10/2014; 53. DOI:10.1016/j.cemconcomp.2014.06.013 · 2.76 Impact Factor
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    ABSTRACT: Dynamic water vapor sorption (DVS) may be used to characterize the pore structure of cementitious materials, but the technique is difficult to interpret as the microstructure is very sensitive to drying and rehydration due to humidity exposure. The removal of interlayer water or chemically bound water can cause microstructural shrinkage. As all drying techniques more or less dehydrate C–S–H and ettringite, they cause a restructuration of the C-S-H. In the present paper, DVS measurements were performed to characterize the changes induced by different drying techniques in the textural and sorption properties of the material, while thermogravimetric analysis was used to elucidate carbonation. The ideal drying technique, which can preserve the microstructure and can remove only the non-bound water, does unfortunately not exist. All drying techniques separately affect the microstructure to some extent. However, these changes are minimized when using vacuum-drying and the solvent-exchange-method with isopropanol as drying techniques.
    Cement and Concrete Research 10/2014; 64:54–62. DOI:10.1016/j.cemconres.2014.06.009 · 3.85 Impact Factor
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    ABSTRACT: Bacterial-based self-healing is a promising solution for sustainable concrete maintenance. In this study, bacterial spores were first encapsulated into hydrogels and then were incorporated into specimens to investigate their healing efficiency. The precipitation of CaCO3 by hydrogel-encapsulated spores was demonstrated by Thermogravimetric analysis (TGA). The mortar specimens with hydrogel-encapsulated spores, showed a distinct self-healing superiority: the maximum healed crack width was about 0.5 mm and the water permeability was decreased by 68% in average. Other specimens in non-bacterial series had maximum healed crack width of 0–0.3 mm and the average water permeability was decreased by 15–55% only.
    Construction and Building Materials 10/2014; 68:110–119. DOI:10.1016/j.conbuildmat.2014.06.018 · 2.27 Impact Factor
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    Didier Snoeck, Peter Dubruel, Nele De Belie
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    ABSTRACT: There are two facts that can be taken almost for granted when applying a cementitious material. One, it will gain the wanted compressive strength and two, it will crack. As cracking can often not be prevented and repair sometimes happens too late, cracking and water ingress should ideally be controlled by taking preventative steps. Superabsorbent polymers (SAPs) can assist to first self-seal a crack upon fluid ingress as their swelling capacity may block a crack from intruding fluids. But also, by releasing their absorbed water, they will promote autogenous healing. In this study, the effect of SAPs on the permeability is investigated by performing low-pressure water permeability and gas permeability tests. Also, the ability of (promoted) autogenous healing is investigated by comparing the mechanical properties after performing repeated four-point-bending tests. Specimens with SAP/C = 0.01 (SAPs versus cement weight) show a reduction in water permeability by a factor 104 and an increase in gas permeability up to 50% compared to specimens without SAPs. There was a regain in strength properties when specimens with SAPs were allowed to heal in wet/dry cycles (75% after 28 days of healing). A cementitious material with SAPs is thus superior to promote self-sealing and self-healing.
    International Conference on Application of Superabsorbent Polymers and Other New Admixtures in Concrete Construction, Dresden; 09/2014
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    International Conference on Application of Superabsorbent Polymers and Other New Admixtures in Concrete Construction, Dresden; 09/2014

Publication Stats

2k Citations
261.80 Total Impact Points

Institutions

  • 1996–2015
    • Ghent University
      • • Department of Structural Engineering
      • • Department of Biochemical and Microbial Technology
      Gand, Flanders, Belgium
  • 2000–2001
    • University of Leuven
      • Department of Civil Engineering
      Louvain, Flanders, Belgium
    • Delft University of Technology
      Delft, South Holland, Netherlands