Nele De Belie

Ghent University | UGhent · Department of Structural Engineering

Mechanical properties of Ultra High-Performance Concrete (UHPC) degrade when exposed to elevated temperatures, even more than ordinary concretes due to its dense microstructure. Concerning, in particular, the special application of nuclear power plants, in which UHPC can find a promising use, concrete can be subjected to moderately high temperature...

Although the circular economy principles date back to the late 1960s, only with the recent stimulus from the European Commission and the Ellen McArthur Foundation has this concept gained attention worldwide. The City Hall of Santiago de Cali (Colombia) is implementing a circular economy model through a sustainable construction handbook and its cert...

In this study, the self-healing of cracks in four alkali-activated slag (AAS) systems modified by superabsorbent polymers (SAPs) is studied. The formation of carbonate precipitate is the main healing mechanism and further AAS hydration is inferior. Self-healing ability in water glass-activated slag (WG-AAS) system is the weakest because Ca²⁺ appear...

Ultra High-Performance Concrete (UHPC) is widely acknowledged for its remarkable mechanical properties, owing to its compact microstructure. The response of UHPC to impact forces plays a vital role in ensuring the safety and longevity of structures, specifically in protective buildings, high-performance pavements and offshore concrete structures. I...

The combination of environmental actions and mechanical load, which most structural concretes are subjected to, has a synergetic effect on the durability of concrete. The comparative test conducted by RILEM TC 281-CCC WG4 demonstrated and quantified the effect of an applied mechanical load on carbonation performance of concrete with supplementary c...

This paper presents an integral parametrized framework to calculate the life-cycle inventory (LCI) in lime-based construction materials manufacturing, utilized for implementing decarbonization strategies in the LCI. The calcination operation is identified as the main source of CO2 emissions, with 0.79 tCO2/t CaO being inevitable (65% of total emiss...

Durability of concrete with supplementary cementitious materials (SCMs) is crucial to the longevity of our built environment. Current research on the carbonation performance of concrete focuses on determining changes in microstructure induced by the chemical and physical interactions of CO2 with the cement phase in samples that do not undergo loadi...

A real-case study is presented aiming at contributing to the understanding of environmental and economic sustainability of lime-based mortars, renders and plasters manufacturing in Europe. A Life Cycle Inventory is presented and used for scenario analysis. The Life Cycle Assessment shows that the binders' production dominates the Climate Change, Re...

In the last decades major advances have been made in the development of self-healing concrete which is able to heal its own cracks without the need for traditional repair interventions, thereby increasing its durability and service life. Recently, more and more self-healing technologies have been applied in demonstrator projects. These demonstrator...

With the current demands for more sustainable and durable structures, the search for smarter and innovative building materials plays a crucial role in the further development of the construction industry. The discovery of the synergetic effect between superabsorbent polymers (SAPs) and cementitious materials gave space to uncountable new possibilit...

Hybrid binders emerge as a solution to further decrease the clinker factor in cementitious systems without unfavorable slow strength development.The Portland cement reduction not only produces greener systems, but also makes them more sensitive to carbonation, especially due to the very limited amount of portlandite available. Therefore, the pore s...

For several decades, the cement industry has been actively seeking alternative raw materials to reduce greenhouse gas emissions and energy consumption. In pursuit of partial replacements for clinker, worldwide research has focused primarily on industrial (fly ash, Si-Mn slag, fired clay-based) and agroforestry (rice husk, sugar cane) waste. The com...

Development of new solutions for masonry mortars is heavily reliant on laboratory-based experimental procedures. This study provides insights into the properties of masonry mortars, prepared by four distinct compaction methods, based on existing standards: tamping, tapping, jolting and vibrating. The particular mortar mix under study has been desig...

The ever-changing needs of the end user in the construction industry, together with the increasing awareness about the great influence of the sector on the worldwide sustainability, require some tools to be employed by the stakeholders to drive the market towards conscious and appropriate choices. An example in this regard are advanced cement-based...

Alkali activation may help to increase the early strength and reduce the setting time of mixtures with high contents of supplementary cementitious materials (SCMs). In this research, the effect of sodium sulfate activator on reaction kinetics, compressive strength and pore structure of hybrid systems produced with 70 wt.% ground granulated blast fu...

The tracking of healing on concrete slabs where dense crack patterns are formed under bending is reported using Acoustic Emission (AE) and Ultrasound Pulse Velocity (UPV). Additively manufactured polymeric networks are designed to distribute a polyurethane agent through capillary actions and under pressure to the open cracks, formed in the slabs. I...

This study evaluated the mechanical properties and self-healing performance of cement mortar containing pulverized clinker, calcium sulfoaluminate (CSA), and Na2SO4. Mechanical properties of cement mortar were investigated by measuring compressive strength, and sealing efficiency were evaluated by a hydrostatic permeability test and a nitrogen gas...

Bacteria-based self-healing concrete has become an effective approach to mitigate microcracks in the concrete structure. However, there are still doubts about when to use vegetative cells or spores of Bacillus sphaericus as a healing agent. Thus, this research aims to give recommendations regarding this choice. Spores and cells were encapsulated in...

Extreme environments are aggressive for concrete structures, hence a performance-based design is crucial to guarantee the durability during the service life. Nonetheless, there is a knowledge gap regarding the influence of cracks on standard and self-healing concrete. This research focuses on monitoring cracked self-healing concrete with two commer...

The capacity of hydrated lime to reabsorb CO2 as it hardens has made it a desirable replacement for cement to produce mortars with an overall lower environmental footprint. Still, research into lime-cement formulations remains limited, especially when it comes to their self-healing capacity. Some studies show that hydrated lime can improve self-hea...

The development of circular economy models for the construction sector brings important challenges and opportunities to research and particularly to make knowledge transfer, for example through public policies. Santiago de Cali, third major city of Colombia (South America), is developing a circular economy model policy, which is mainly based on was...

Although steel reinforcements are used to withstand tensile forces in concrete, cracks are an unavoidable phenomenon. The presence of cracks, in fact, increases the risk for lowering the service life and durability of concrete structures. A critical issue occurs when due to splitting forces, cracks appear in concrete along the tensioned rebars whic...

As an alternative to the usage of axenic bacteria to achieve microbially induced calcium carbonate precipitation (MICP), this study evaluates the usage of two non-axenic biomasses as self-healing agents. A fungi-based consortium (Yeast) and heterotrophic nitrifiers (HTN) were harvested from the incubation of agricultural side streams. The character...

Capillary water absorption tests are widely used in uncracked cementitious materials to assess the quality and durability. Due to the easy execution of the test, it is also frequently used to assess the self-healing efficiency of self-healing concrete and mortar. It is established that the presence of a crack significantly increases the water uptak...

Among the various possibilities to tackle the issue of concrete damage within its structural service life, the biomimetic approach has favoured the development of innovative solutions such as the use of 3D printed vascular networks suitably incorporated into concrete structural elements to inject and convey the most suitable healing agent upon crac...

This study focuses on the evaluation of the efficiency of a low-cost macrocapsule, using commercially available pharmaceutical capsules with specific modifications, for self-healing concrete. The macrocapsules were developed by the Belgian Building Research Institute in a previous study. The healing agent is a resin based on alkyd-urethane, a low-c...

Vascular self-healing concrete is an innovative technology that can potentially improve the durability and longevity of concrete structures. However, limited research is available concerning this type of self-healing compared to intrinsic or capsule-based healing. As the rheology and curing properties of a healing agent can dictate the optimal desi...

Lime-based construction materials (LBM) range from concrete blocks to mortars and plasters used in building new structures or to conserve our cultural heritage. However, little interest has been aroused in the scientific community about their sustainability assessment through Life Cycle Assessment. This research presents a case study carried out wi...

Fe-rich slags originating from non-ferrous metallurgy have shown promising properties as a new type of supplementary cementitious material (SCM). However, their combined use with limestone has not yet been investigated in detail. The goal of this study is to elucidate whether this yields a positive effect as observed for aluminosilicate SCMs with l...

Novel hybrid binder concrete mixes with alkali-activated non-ferrous slag (NFS), either alone or in combination with blast furnace slag (BFS), as partial replacement of Portland cement, and containing 50% recycled aggregates, were successfully manufactured. The compressive strength, carbonation resistance, chloride resistance, frost scaling, sorpti...

Fine recycled concrete aggregate (FRCA) possesses substantial limitations for its use due to its significant porosity. Extensive research on the effect of carbonation on the accessible porosity of coarse recycled concrete aggregate is available in the literature, but FRCA information is scarce. The present paper presents results of the effect of ca...

The required depth of concrete removal should dictate the selection of concrete removal technique and removal energy in repair systems. This study presents a new research approach in the investigation of the impact of concrete removal techniques on the substrate, and as a result, the bond with repair mortar. On the other hand, it introduces a remed...

Advanced design of eco-friendly concrete is very urgent in view of the vital fight against climate change. An interesting eco-efficient strategy is the combination of (1) alternative low carbon hybrid binders with a low clinker factor and the inclusion of alkali activators, (2) substituting natural aggregate by recycled aggregate and (3) securing s...

The objective of this work is to study the freeze thaw resistance of supplementary cementitious materials (SCM) based concrete made from non-ferrous slag (NFS) benchmarked with CEM I 52.5 N and CEM III 42.5 B concrete. NFS is synthesized during the production of Cu metal from Cu scraps. The freeze thaw resistance of NFS concrete containing 70% CEM...

Superabsorbent polymers (SAPs) are novel admixtures in cementitious materials in order to have internal curing. Neutron tomography is used to investigate and to visualize the water release by SAPs with different kinetics over time. This gives insight into the time window for effective internal curing as the results are linked to shrinkage and inter...

Cracking of cementitious materials poses severe problems for the mechanical performance and the durability of concrete structures. Self-healing cementitious materials provide a means of countering these issues, but the testing procedures to assess the self-healing efficiency are mostly impractical for in-situ evaluation. This study concerns the eva...

Bacteria-based self-healing is a promising method due to its effectiveness to completely heal the crack. Expanded clay was chosen as a bacteria protector as it can retain a high amount of bacteria liquid in its pores and it is compatible with the mortar matrix. Most researchers employed bacteria in the form of spores to produce self-healing concret...

Early age cracking is a high risk for low water to cement (w/c) concrete known as the ultra-high performance concrete (UHPC). The lack of water to fully hydrate cement particles at the early age, provides a rapid increase of self-desiccation and autogenous shrinkage which might lead to cracking. However, internal curing agents such as superabsorben...

Recent studies highlighted the need to investigate the sustainability of innovative cement-based composites. In this regard, some works focused their attention on the use of Super Absorbent Polymers (SAPs) blended into the concrete matrix also employed to promote the autogenous healing, which can result into extended durability. In this study the L...

SAPs have been widely studied over the past two decades as new admixtures for cementitious materials. Their ability to absorb and retain water from the cementitious mixture allowed them to be successfully used as internal curing agents preventing self-desiccation and reducing autogenous shrinkage. A lot of research has been developed and important...

Nowadays, Ground Granulated Blast-Furnace Slag (GGBFS) is increasingly used together with Portland cement to design low carbon footprint binder systems. Such systems with a low clinker factor are generally connected with a slow strength development. Alkaline activation in hybrid binders can provide a suitable solution to cope with this issue. Among...

In capillary imbibition (or absorption) experiments performed on cementitious materials, a non-linear evolution of water uptake with the square root of time is frequently reported. This anomaly is derived from analytical methods that assume that the pore structure remains invariable during water ingress. A more comprehensive understanding of the tr...

This study examines the effect of recycled aggregates on the stimulated autogenous self-healing of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) when exposed to wet and dry conditions. Recycled aggregates have been produced by crushing four months old UHPFRC specimens with an average compressive strength of 150 MPa. Two different percen...

Crack formation further decreases the durability of structures when chloride ions associated with freezing temperatures are present. Therefore, preventing the entry of aggressiveness is imperative to guarantee the service life. Repair actions might recover the liquid-tightness when cracks occur. A water repellent agent (WRA) and a sodium silicate (...

During carbonation of concrete, calcium hydroxide is consumed which results in a drop of the pH which can cause steel corrosion. In uncracked cementitious materials it can take several years before the carbonation front reaches the level of the reinforcement. However, most structures are cracked allowing for a fast ingress of carbon dioxide at the...

Self-healing concrete is an innovative and promising technology to increase the durability and service life of the structure by limiting the influence of aggressive attacks. However, knowledge on the performance in realistic conditions is limited. This paper presents the benefits of introducing a bacteria-based healing agent in concrete to enable s...

This research focuses on the evaluation of the sustainability of recycled ultra-high-performance concrete (R-UHPC) in a life cycle analysis (LCA) perspective, and with reference to a case study example dealing with structures exposed to extremely aggressive environments. This involves the assessment of the self-healing capacity of R-UHPC, as guaran...

Self-healing is recognized as a promising technique for increasing the durability of concrete structures by healing cracks, thereby reducing the need for maintenance activities over the service life and decreasing the environmental impact. Various self-healing technologies have been applied to a wide range of cementitious materials, and the perform...

The impact of the addition of layered double hydroxides (LDHs) on binding of chloride ions was studied by pore expression experiments. A Mg-Al-NO3 type of LDHs was added to paste samples blended with 3 % NaCl in different proportions (4 % and 10 % by mass of the binder). In addition, the influence of LDHs on the hydration process, morphology and po...

Concrete is currently the most used man-made construction material. Unfortunately it is prone to defects, such as cracks. Crack repair is possible by incorporation of superabsorbent polymers (SAPs) which can fill a crack by swelling and promote formation of healing products. However, SAPs are usually acrylate-based and not biodegradable. Present wo...

In microbial induced calcium carbonate precipitation (MICP) system, yeast extract (YE) is needed for spores germination. The aim of this research is to evaluate the minimum amount of YE in mortar that allows spores of Bacillus sphaericus to germinate with limited negative effect on mortar properties. Two YE concentrations of 2 and 5 g/l were tested...

This paper aims to evaluate mechanical behavior (compressive and flexural strength) of reactive powder concrete (RPC) with ferronickel slag (FNS) as quartz sand replacement. Standard laboratory tests were performed i.e. sieve analysis to determine the particle size distribution of the FNS, slump and density tests as well as compressive and flexural...

In this work, the performance of mortar made with ferronickel slag (FNS) as cement replacement was investigated. The granulated FNS was ground to obtain a fineness higher than cement. To assess the performance of FNS in fresh and hardened mortar, the workability, flexural, and compressive strength were experimentally assessed. Based on the results...

In cold climates, concrete structures suffer from freezing and thawing (FT) effects with de-icing salts used to melt the ice on the roads. Optimization of the mix design could help to minimize its impact, but it cannot be that helpful after crack formation. Cracks are pathways for aggressive substances and allow water expansion during the freezing...

This paper investigates the mechanical response under fatigue cycles in Ultra-High-Performance Con- crete (UHPC) under four-point flexural loading, focusing on the effect of damage recovery triggered by stimulated autogenous self-healing. Thin beam specimens were pre-cracked up to 0.25 mm residual crack opening displacement under monotonic loading...

Superabsorbent polymers have been widely investigated for internal curing in cementitious materials. In most cases, commercial SAPs are used and not enough information is available regarding their chemical composition. Efficient and optimal application of SAPs in cementitious materials depends on chemical composition and its effects on the properti...

In this study, superabsorbent polymers (SAPs) are studied to mitigate the plastic shrinkage in three alkali-activated slag (AAS) systems. Plastic shrinkage cracking tests were performed on fresh AAS pastes, while monitoring the capillary pressure, the internal relative humidity, the setting time, and the compressive strength. The setting time of th...

In this study, non-destructive acoustic techniques were adopted to obtain information about various processes occurring inside cementitious materials. During the fresh stage, acoustic emission (AE) was used to monitor the hydration process of mixtures with and without superabsorbent polymers (SAPs). Results showed that the process of internal curin...

Concrete with self-healing systems, such as vascular networks, results in promoted sustainability and reduced maintenance costs for a structure compared to traditional concrete. 3D printing, or additive manufacturing, allows for complex network topologies to be fabricated, however, the challenge lies in a lack of standards in both self-healing and...

The environmental load associated to Hydrated Lime (HL) products is attributed to the limestone decomposition and the industrial production (combustion in the kiln, the electricity, the transports, etc.). Although the fuel and electricity mix used in the factory can be critical, no records of Life Cycle Assessment (LCA) have been found addressing t...

A numerical method is proposed to determine the semi-carbonated and fully-carbonated depth of concrete subjected to sustained loads. The method modified the diffusivity of each element by multi-axial load levels and stress damages. Based on 1000-day carbonation results of 2D mesoscale concrete, it was indicated that the external load causes highly...

This paper presents the experimental investigation of the self-healing capacity and ability to maintain the structural performance of a Ultra High-Performance (Fiber Reinforced) Concrete (UHPC/UHPFRC), with a crystalline admixture to stimulate the healing, after freeze-thaw cycles. To the aforesaid purpose ultrasonic pulse velocity tests, four-poin...

Carbonation of concrete, in which 0%, 50% and 70% of cement was replaced by blast furnace slag (BFS), under different levels of sustained compressive load (0, 0.25, 0.5 and 0.75 times the breaking load) was investigated. The results show that the carbonation rate first decreases with load level and then above a threshold value (approximately 0.25–0...

This work reports on the self-healing capabilities of mortar specimens with polyurethane encapsulated in two types of cementitious macro-capsules, by comparison with the performance of mortar specimens using the same healing agent encapsulated in glass capsules, as tested in an inter-laboratory testing campaign following a pre-standard procedure. T...

A novel linear reservoir-vascular tubes network is presented in this work and the design efficacy is explored by testing concrete beams loaded on bending and by assessing their damage healing and mechanical recovery. The healing system is composed of additively manufactured polymer components that appear equally effective compared to conventional c...

This study aims to examine the influence of quickly cooled granulated copper slag (QCS) and finely ground slowly cooled broken copper slag (SCS) as basalt aggregate and cement replacement, respectively, in ultra-high performance concrete (UHPC). The UHPC mixtures and cement pastes having a water-to-binder ratio of 0.18 were produced with different...

Economic and environmental factors call for increased resource productivity. Partial or full replacement of Portland cement by wastes and by-products, and natural aggregates by construction and demolition wastes, are two prominent routes of achieving circular economy in construction and related industries. Municipal solid waste incineration (MSWI)...

RILEM TC 267-TRM is studying tests for the reactivity supplementary cementitious materials (SCMs). In the first phase, the lime reactivity (LR) test, which is standardised in Indian standard (IS)-1727, gave promising correlations with 90-days cement mortar strength. In Phase 2, working group 1 has looked at further optimisation and robustness study...

Many (inter)national standards exist to evaluate the resistance of mortar and concrete to carbonation. When a carbonation coefficient is used for performance comparison of mixtures or service life prediction, the applied boundary conditions during curing, preconditioning and carbonation play a crucial role, specifically when using latent hydraulic...

Due to the increasing awareness and sensitivity towards the environmental and economic sustainability issues, the concrete industry has to deliver innovative solutions, in terms of materials, products and structural concepts, to achieve higher durability of engineering feats in real service scenarios. The inclusion of SuperAbsorbent Polymers (SAPs)...