Re-refined Engine Oil Bottoms (REOB) are a waste product from the re-refining process of waste engine oil. There is a large incentive in the world to produce recycled engine oil and the production of REOB in this process is increasing. On the other hand refineries are going through transitions due to economic and regulatory reasons (i.e. IMO 2020) which has an impact on bitumen production process and its properties. As a result, harder grades bitumen are more readily available compared to the softer grades. Moreover, suppliers that are non-refiners are also part of the bitumen supply chain which has led to more variation in bitumen composition and properties. REOB, among other options of blending components, has posed a solution for this problem; making it possible to reach softer grade bitumen by blending the two. The pavement industry is however facing premature failures of pavements, less workable mixtures, earlier deterioration etc. and the question arises whether the diverse sources of blending components like REOB modification of the bitumen could be the cause of them. There exists no unique identification number (for example the CAS number used in the USA) for REOB as a material in Europe, which makes it untraceable when used in bitumen. While one is not obliged to notify contractors of the use of REOB, there also do not exist any guidelines for its use in asphalt mixtures; thus both the identification of REOB in bitumen as well as a clear evaluation of the bitumen properties and performance is wished for.
By using an extensive amount of chemical experimental tools like: Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Fluorescence (XRF), elemental analysis (CHNO+S), iatroscan chromatography (SARA fractioning), Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC) the characteristic properties of bitumen modified with REOB are mapped and identification and quantification of REOB in the bitumen is made possible. This is followed up by performing rheological experiments to map viscoelastic properties of the bitumen, using the Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR). Mechanical performance of the bitumen and asphalt mixtures modified with REOB is evaluated by doing Dynamic Mechanical Analyser (DMA) tests on both cohesive/adhesive behaviour of stone-bitumen film and mastic column tests. Lastly, REOB modified asphalt mixtures are tested with Indirect Tensile (IDT) tests at dry and wet conditions and Cantabro Abrasion tests are done to evaluate impact resistance of the mixtures to simulate ravelling susceptibility.
Using the described approach, this study was able to present a methodology on how to analyse REOB modified bitumen to identify and quantify the presence of REOB and how to evaluate properties and performance of REOB modified bitumen and asphalt mixtures.

The widespread use of traditional bitumen, derived from finite crude oil resources, has led to growing concerns over its environmental impact, long-term availability, and cost. These challenges underscore the urgent need for sustainable, alternative binders in infrastructure applications such as road construction. Although previous research has explored bio-based and recycled waste materials as potential substitutes, these alternatives often fail to meet compatibility, durability, and performance standards.

To overcome these obstacles, this study employs a multifaceted methodology encompassing rheological, chemical, and mechanical analyses, along with environmental assessments. The objective is to develop an alternative binder synthesized from bio-based and waste materials that offers comparable or improved durability and performance. Our findings suggest that the alternative binder presents a viable replacement for traditional, petroleum-based bitumen. This innovation not only enhances the sustainability and circularity of road materials but also mitigates the construction industry's dependence on non-renewable oil resources.

The Netherlands has one of the densest road networks with over 140,000 km of roadways. Fatigue cracking is an important distress in flexible pavements. This form of distress results from the application of repeated traffic loading which causes failure. Fatigue cracking assessment on various base layer asphalt mixtures including reclaimed asphalt pavement materials and recycling agents has been addressed in this research work. This research work aims to develop a method for quantifying and assessing this fatigue characterization including the self-healing mechanism of asphalt mixtures using Visco Elastic Continuum Damage Theory. The self-healing in asphalt mixtures was assessed by incorporating group-rest healing periods in a self-developed laboratory testing method. The reliable self-healing models for asphalt mixtures with recycled asphalt materials and recycling agents based on temperature, damage state, and rest periods were predicted using the damage characteristics curve (C-S). Bottom-up cracking in base layer asphalt mixtures was modeled and studied using finite element modeling software FlexPAVE based on the Visco-Elastic Continuum Damage theory. A vivid assessment of mixtures for fatigue and healing characterization is discussed in this research work.

This research work is interrelated with an ongoing project, which aims at developing a protocol to determine the shift factors for the fatigue life of asphalt mixtures to correct healing and aging. The project runs under the umbrella of Knowledge-based Pavement Engineering (KPE), a joint program among Rijkswaterstaat, TNO, and TU Delft. Dura Vermeer is contributing partner to this MSc graduation research work as well.

This master's thesis addresses a critical gap in the field of road construction by focusing on the limitations of Styrene-Butadiene-Styrene modified bitumen (SBS-MB), a widely-used binder. While SBS-MB offers superior performance, its long-term efficacy is compromised due to various aging processes. Existing rejuvenators are insufficient for restoring the binder's original properties. To remedy this, our research introduces an innovative rejuvenator that provides a more comprehensive restoration of SBS-MB, especially in the reconstruction of the polymer network. The study employs a multifaceted evaluation approach, leading to an enhanced understanding of the rejuvenator's effectiveness and mechanisms of action. Furthermore, we validate the rejuvenator's efficacy using real-world, field-collected materials. The findings not only offer a more effective method for restoring aged SBS-MB but also hold promise for improving the recyclability of Reclaimed Asphalt Pavement (RAP), potentially leading to more sustainable road construction practices, particularly in the Netherlands.

Recycled concrete aggregates (RCA) have been recognized as a sustainable solution to satisfy the demand and address the environmental impacts of the concrete industry. However, construction engineers and contractors still have reservations about RCA due to their heterogeneous origin and lower quality compared to natural aggregates. It is essential to know the properties of the parent concrete, in particular its chemical composition, before demolishing concrete structures in order to identify the source of the raw materials. Despite its importance, this has never been done before. This thesis aims to analyze in-situ chemical composition of concrete and to identify the type of cement used in concrete structures by applying the non-destructive characterization technique of a handheld X-ray Fluorescence (hXRF) analyzer. To achieve this, laboratory experiments were performed to assess important factors in measuring cement paste and concrete surface chemical composition using the hXRF. These examined the impact of different water-to-cement (w/c) ratios, curing age, relative humidity, and carbonation on the chemical composition analysis with hXRF, and to gain valuable insights regarding the oxide concentrations of concrete and the most influential factors in hXRF measurements. The results indicated no impact on the chemical composition measurements with the hXRF despite the w/c ratios, the curing age, and carbonation. It was identified that higher relative humidity conditions than 75% affect the measurements with hXRF. Subsequently, three case studies were considered for the in-situ assessment of chemical composition. Conducting tests with hXRF demonstrated the device’s potential for analyzing concrete characteristic oxides (MgO, Al2O3, SiO2, SO3, CaO, Fe2O3). As a result, it facilitated cement-type recognition and provided valuable information regarding its opportunities and challenges. Drawing on insights from the literature review, laboratory experiments, and in-situ measurements, a guideline for in-situ testing of concrete composition was developed.

In the Netherlands, yearly 33 Mton new concrete (roughly 15 billion m3) is producewhile 12 Mton concrete waste becomes available. Recycling of the yearly 12 Mton concrete waste results in roughly 7 Mton coarse recycled concrete aggregate (CRCA) and 5 Mton fine recycled concrete aggregates (fRCA). Currently, fRCA is not used in structural concrete, but only for low grade applications. This research aims to investigate the effect of recycled concrete aggregates (RCA) incorporation on the performance of structural concrete mixtures. Three streams of fRCA were considered in this research and two deliveries of each source were examined. River sand was replaced by 25% fRCA, which was found to be the optimal amount that does not require cement increase. Both deliveries were used in order to identify potential differences. Additional concrete mixtures with simultaneous replacement of river sand by 25% fRCA and river gravel by 30% CRCA were evaluated. Parallel work was conducted during an 8months internship at TNO, where optimization of mortar mixtures with full replacement of river sand by fRCA was investigated. This was performed by considering the water demand of solid constituents (binder and fRCA) and packing of fRCA. Optical microscopy was used for closer inspection of the microstructure of fRCA. Fresh properties of studied mixtures were measured. Assessment of the mechanical performance of concrete mixtures was expressed by means of compressive strength and elastic modulus. Long term behavior was also investigated by shrinkage deformation measurements up to 95 days after casting. Results show that substantial rise in cement content is necessary for obtaining the desirable flow and high levels of compressive strength, when full replacement of fRCA is performed. Regarding concrete mixtures with 25% fRCA, increase in air content was measured. Entrapped air is strongly dependent on the porosity of adhered cement paste on RCA, content of 00.25 mm fraction as well as agglomeration and presence of impurities in as received fRCA. This affects negatively their mechanical performance. Additional porosity resulting from CRCA incorporation was responsible for further reduction in mechanical properties of concrete mixtures. Mixtures with RCA showed three times higher mass loss at the age of 95 days.

This research focuses on developing architected lightweight cementitious cellular composites (LCCCs) for potential thermal insulation purposes. Specifically, Voronoi cellular structures with different randomness are adopted and used as cellular structure of the LCCCs. the mechanical properties of the developed LCCCs are investigated by experimental and numerical methods. With the help of 3D printing technique, LCCCs are prepared with two mixtures: a reference mortar, denoted as REF and mortar incorporating microencapsulated phase change materials (mPCMs), denoted as PCM14. Mechanical properties of developed structures are first investigated. The compressive behaviour of the LCCCs is investigated at the age of 28 days. In general, the LCCCs show anisotropic compressive behaviour in two loading directions: the compressive strength and stiffness of the LCCCs in the out-of-plane direction is substantially higher than that of the in-plane direction. Comparing to conventional foam concrete with the same density, the out-of-plane compressive strength of the LCCCs is higher than commonly reported cases in literature. Due to the high porosity of the cellular structures, the compressive strength of the LCCCs is significantly reduced comparing to the corresponding constituent materials, as expected. In addition, this strength reduction of the LCCCs made with PCM14 is substantially lower than the that of the REF samples. Interestingly, the relative stiffness (measured stiffness of the LCCCs normalized by their porosity) of the mPCMs incorporated LCCCs is even higher than the constituent material E-modulus. Furthermore, the critical role of air voids on the compressive behaviour of the LCCCs is identified. The thermal conductivity of the LCCCs is investigated by numerical models using commercial software Abaqus and ANSYS. It is found that the thermal conductivity of the LCCCs is comparable with the conventional foam concrete of the same density. The geometry heterogeneity of the LCCCs has a minor effect on determining the thermal conductivity of the LCCCs. Moreover, increasing porosity or reducing thermal bridge on the heat transfer direction can dramatically improve the thermal insulation performance of the LCCCs. It is found that the natural convection of the air within the cellular pores and the radiation has less notable effect on the thermal conductivity of specimen. Comparing to the REF, PCM14 has enhanced thermal insulation performance. In the end, using extrusion-based 3D concrete printing technique, the LCCCs with mPCMs has been successfully printed as an implement of manufacturing LCCCs as a construction-scale brick. In general, the developed LCCCs have high porosity gives good insulation properties as well as good compressive strength. This gives them great potential to be used as novel lightweight thermal insulation materials for construction.

In floors without dilation joints drying shrinkage cracking can occur. Shrinkage reducing agents (SRAs) can reduce the amount of drying shrinkage and improve the durability of the concrete structure. The mechanism of shrinkage reduction and the influences on the hydration process and development of mechanical properties of the SRA Sika Control 40 were researched. Shrinkage reducing agents lower the surface tension of water which reduces the capillary tensile stresses and ultimately reducing the drying shrinkage. Experiments were performed on cement paste samples to investigate influences on the hydration process of cement (surface tension, rate of hydration, porosity, shrinkage, flexural and compressive strength). In addition experiments were performed on concrete samples to investigate the influences of applying shrinkage reducing agents on the mechanical properties of concrete (compressive strength, shrinkage, elastic modulus). Overall, the experimental results showed that applying Sika Control 40 is an effective method for reducing drying shrinkage when concentrations of 1.56 w% and 2.61 w% are used. The shrinkage reducing agent has positive effects on the surface tension, weight loss and drying shrinkage for concentrations of 1.56 w% and 2.61 w% of cement. It has negative effects on rate and degree of hydration, porosity, pore size distribution, compressive and flexural strength for concentrations of 1.56 w% and 2.61 w%. The elastic modulus lacks adequate data to observe a trend, however the results are within the range of expected values for concrete for mixtures 156 and 261. , An SRA concentration of 0.52 w% of cement resulted in unpredictable and contradicting results.

Existing reinforced concrete (RC) structures can be strengthened using Strain Hardening Cementitious Composites (SHCC). The ability of SHCC in exhibiting a ductile response under tensile load due to strain­-hardening after crack initiation makes it a viable material to be used in, both, construction and retrofitting of concrete structures. The main objective of this research is to study the shear behaviour of SHCC-strengthened RC beams using NLFEA. The shear behaviour of benchmark RC beams is analysed first. The analysis of the selected RC beams analysed using Damage-based shear retention function results in accurate predictions of peak load if a fine mesh size resulting in 30 or more elements in the height of the beam is used. However, the failure type is predicted inaccurately for both coarse and fine mesh sizes due to lack of consideration for aggregate interlock in Damage-based shear retention function. The analysis of the selected RC beams using Al-Mahaidi shear retention function results in accurate predictions of peak load if a coarse mesh size resulting in 20 elements in the height of the beam is used. The failure type is also predicted accurately using Al-Mahaidi shear retention function with the stated mesh size. The consideration for aggregate interlock implicitly in Al-Mahaidi shear retention function in the form of shear retention factor allows for accurate prediction of both peak load and failure type. After analysing the shear behaviour of RC beams, the shear behaviour of a reinforced SHCC beam is analysed using Al-Mahaidi shear retention function since it can predict both failure load and failure type accurately for RC beams. In comparison with experiment, the peak load for the reinforced SHCC beam is underestimated and the failure type is also incorrectly modelled. Use of embedded reinforcement results in excessive cracking along the reinforcement, causing convergence issues at a load lower than the experimental peak load. Such excessive cracking is not observed in RC beams since cracks more localized in concrete as compared to SHCC, which exhibits multi-cracking behaviour. Therefore, the shear behaviour of selected reinforced SHCC beam using Al-Mahaidi shear retention function is not accurately modelled. After the analysis of shear behaviour of concrete and SHCC separately, their behaviour is studied in the form of SHCC-RC hybrid beams. The solution strategy consisting of Al-Mahaidi shear retention function is used, and different types of hybrid interface are modelled. The results show that peak load and failure type are accurately predicted when a numerically perfect bond is modelled at hybrid interface for hybrid beams exhibiting no debonding during experimentation. This is in case of a mesh size resulting in 20 elements in the height of beam used. The peak load and failure type, however, are inaccurately predicted when delamination is modelled at the hybrid interface for hybrid beams failing due to delamination during experimentation, irrespective of the mesh size considered. This is due to the inability of the Coulomb friction interface model in recognising significant delamination at the hybrid interface as a reason for the failure of the hybrid beam.

3D concrete printing is an additive manufacturing method that uses a printing robot to build 3D concrete elements. In the last decade, several 3D concrete printing techniques have been developed and extensive research has been conducted on suitable concrete mixes, the printing process and the material and mechanical properties of the finished product. However, certain challenges have remained unresolved. Two of these challenges are the low tensile strength and the limited ductility of the printed concrete. As concrete is a brittle material that is weak in tension, traditional structural concrete elements make use of steel reinforcement to ensure tensile strength. The incorporated steel rebars are designed to take over the tensile stress when the concrete cracks. With the linear elastic and eventually plastic behaviour of steel in tension, the steel provides a ductile behaviour to the rein- forced concrete. This ductile behaviour is required to comply with modern building regulations, as it ensures structural integrity and safety by timely warning in case of overload. However, for printed concrete the incorporation of steel rebar reinforcement is not evident.
The use of Strain-Hardening Cementitious Composites (SHCC) in the field of digital concrete printing is one of the many possible ways to incorporate reinforcement into printed structural concrete elements. However, just like regular printable concrete, the bond between subsequently printed layers has shown to be a point of concern. The research presented in this master thesis focusses on the interlayer bond of these printable SHCC’s and more specifically on developing improvement methods for this interlayer bond. To better comprehend the origins of problem a thorough literature study was performed on the following topics: printing facilities, 3d printing compatible mix designs, (printable) SHCC, anisotropy and research on related interlayer bond improvement methods. On the basis hereof an experimental research was designed and conducted on various methods unrelated to the SHCC mixture and their effect on the interlayer bond. The methods can be divided in three groups: nozzle types, surface modification by brushes and incorporation of vertical steel reinforcement. In total 7 parameters were designed and tested: three nozzles, two brushes and two steel reinforcements. Tensile interlayer bond tests were performed to assess the influence of the parameters on the interlayer bond strength. To make sure that the overall strain hardening capacities of the material were not negatively influenced by the interlayer bond improvement methods the research also included compressive tests in two directions and uni-axial tensile tests parallel to the printing direction. Finally, the research was extended with a concise CT scan analysis on porosity and reinforcement bonding. Results show that the type of nozzle has significant influence on all mechanical properties. Sur- face modification by brushes tend to result in SHCC elements that have higher interlayer bond, but a reduced strain-hardening capacity. Specimens with interlayer steel reinforcement completely lose strain-hardening capacity in printing direction. In general, it is concluded that there is potential in designing methods to improve the interlayer bond of printed SHCC.

Strain Hardening Cementitious Composite (SHCC) is a new type of concrete that is able to control the crack-width in concrete structures. The application of this material in the tension zone of hybrid concrete structures is thus of interest in practice. The interfacial behavior for these hybrid structures is something that is of importance for the composite action. Therefore, a study is performed to investigate the behavior of the interface in hybrid SHCC-concrete beams. This is done by performing an experimental study on beams with a joint at midspan. Several parameters such as the interface roughness, coupling reinforcement cover, curing method and protruding reinforcement have been investigated. The hybrid SHCC-concrete beams are tested in a four-point bending configuration to obtain a constant-bending moment region along the interface. The crack propagation along the interface and through the SHCC/concrete has been evaluated with the use of Digital Image Correlation (DIC). Furthermore, also a numerical analysis has been performed using DIANA FEA based. The numerical analysis was used to help to determine the experimental campaign. Furthermore, also several experimental samples have been modelled to study the behavior of the beam in more detail and to make recommendations for future modelling of the interface. Based on the experimental results, the influence of the interface roughness resulted in an increased bond at the interface. This is both seen in an increased bearing capacity and a reduction of the interface and joint opening at equal loads. The profiled interface and holed interface resulted in an increased capacity due to the mechanical interlocking at the interface. The bearing capacity of these samples increased by 78.4% and 54.7% respectively compared to the reference sample (13.9 kN). In case of the profiled sample, no delamination of the interface occurred as the sample failed due to a horizontal crack at the level of the coupling reinforcement. This can be attributed to the localized tensile stresses at the reinforcement level. The last sample with a different interface roughness consisted of epoxy and sand (1-2 mm). For this sample, the bearing capacity increased by 51.8%. The failure of this sample was a combination of interface delamination (initially at the joint) and a horizontal crack through the coupling reinforcement. For all the samples with a different interface roughness, no yielding of the coupling reinforcement occurred. Several beams with a smooth interface have also been tested by adjusting the reinforcement cover, curing method and applying protruding reinforcement. The influence of the reinforcement cover didn’t have an effect on the bearing capacity. However, the interface and joint opening reduced significantly as the eccentricity of the reinforcement bars also reduced. Furthermore, also the effective height increased resulting in lower reinforcement stresses. The influence of a different curing method was investigated by placing the sample in a humidity-controlled (50 %) room to investigate the effect of shrinkage. The results showed that the bearing capacity remained similar to the reference samples. This can be attributed to the fact that the bond internally was still good, caused by the restraint of the reinforcement bars. However, the deflection of the beam increased as a result of the reduced stiffness by the shrinkage induced cracks. Finally, one sample consisted of stirrups at a distance of 50 mm from the joint to take up the tensile stresses at the interface (e.g. due to reinforcement eccentricity). The results showed an increase in bearing capacity by 102.7% compared to the reference sample. However, also in this case, no yielding of the coupling reinforcement occurred. The failure of the sample is also caused by the delamination of the interface. Furthermore, as a result of this delamination, fracture of the top part of the SHCC occurred at the location of the protruding reinforcement due to the rotational restraint of the stirrup. The 2nd part of the study consisted of a numerical analysis. A Coulomb-friction model with an interface tensile strength cut-off is used to model the interface. Based on this, a good correspondence between the experimental results and FE results is found in terms of the bearing capacity and failure mode for the sample with a smooth interface(delamination). However, the crack propagation of the flexural cracks through the concrete and SHCC was substantially different.
The sample with a profiled interface has also been modelled in Diana FEA. This is done by implementing the profiled interface manually in the FE model. The model showed a good correspondence with the experimental results in terms of bearing capacity and interface and joint opening. The crack propagation in the concrete is also similar to the experimental results. The model however doesn’t show any flexural cracking in the SHCC layer as a result of the limitation of DIANA FEA. Also, an additional study is done to replicate the behavior of this beam using a smooth interface. Based on this model, it is recommended to use a perfect bond at the interface. For both these models, the FE model wasn’t able to replicate the strain hardening behavior of SHCC. This is due to the limiting material models in DIANA.

A combination of conventional concrete members with innovative material such as Strain Hardening Cementitious Composite (SHCC) in the tensile zone, can exhibit better crack-width control. This is attributed to the bridging effect by the Polyvinyl Alcohol (PVA) fibers used in SHCC in combination with the special material composition containing fine particles. This hybrid combination is able to satisfy the Serviceability Limit State (SLS) criteria for crack-width control by eliminating the requirement of additional reinforcement. Optimisation of micro-cracking of SHCC requires an investigation to study the influence of the interface in SHCC-Concrete hybrid beam and the type of fiber used in SHCC. This master thesis research is a continuation of the previous Msc. thesis study performed by Zhekang Huang [1] on the experimental flexural behaviour of reinforced concrete beams with a layer of SHCC in the tension zone. Variation in the bond interface property such as smooth interface profile, partially debonded, completely debonded and grooved interface profile are investigated to study their influence on the bearing capacity and crack-width control. To assess the impact of the type of fibers on crack-width control, commonly used PVA fibers are replaced with High Modulus Polyethylene Fibers (HMPE) based on pre-study. All hybrid beams are tested experimentally in a four-point bending set-up to generate cracks within the constant moment region and Digital Image Correlation (DIC) is performed to evaluate the crack patterns and the crack-widths. Numerical analyses of the beams are performed using Finite Element Analysis software Diana {version 10.3} with the modelling of similar interfaces and material properties used in the experiments. From the obtained results, it is observed that for all the beam specimens tested, varying the interface property did not have a significant impact on their bearing capacity as the interface within the constant moment region is only varied and the surface outside this region is bonded. For beam specimens with partial and completely debonded interface in the constant moment region, it is observed that the initial stiffness is reduced but the overall bearing capacity remains the same. Within the constant moment region, varying the interface property resulted in different crack patterns. The profiled and smooth interfaces, despite exhibiting different crack patterns, reached the maximum allowable crack-width of 0.3 mm at similar load steps of 69 KN and 71 KN respectively. This is because a sufficient bond at the interface is developed and as a result, due to local adhesion, the surface roughness plays a minor role. The beam specimens with completely and partially debonded interfaces localised at a much earlier load step of 45 KN and 50 KN respectively. This is because the stress generated in the SHCC layer is higher due to the severely cracked concrete layer on top. The beam specimens with smooth interface and HMPE fibers in SHCC perform similar to the beams with smooth interface and PVA fibers in SHCC. This is because of the additional constraint created due to the conventional concrete layer at the top in the SHCC-concrete hybrid beam. Despite the higher flexural capacity of the SHCC layer containing HMPE fibers, the concrete layer crushes much before the SHCC layer fails, thus, compromising the performance of the hybrid beam. By reducing the interface stiffness properties, an effort is made to reproduce the behaviour of specimen beams in four-point bending test through numerical modelling on Diana FEA. However, the prediction of the number of cracks formed and the crack-widths is inaccurate for all the beam specimens modelled. This is because the material models and interface properties available on Diana FEA to the authors knowledge, are insufficient in replicating the experimental cracking behaviour.

An exploration into the stability of 3D printed thin-walled concrete elements during manufacturing is presented. The failure mechanisms, material parameters and analysis methods are presented. Self-buckling is the dominant failure mechanism, where the Young's modulus plays an important role. Material experiments to assess the Young's modulus are performed and presented. Predictive analysis methods to evaluate the printability of objects are discussed, where finite element modelling and the mechanistic model of Suiker are compared.

The crumb rubber modified bitumen (CRMB) has been utilized in pavement industries to mainly reduce the environmental impacts of the wasted tires by turning unwanted scrap tires into new bituminous materials. However, the relatively high viscosity compared to the conventional asphalt is the major drawback of the CRMB. The higher mixing and working temperatures are thus required in order to achieve the desired workability of the CRMB. This results in more asphalt fume emission, higher energy consumption, and more harmful working environments for workers. Warm mix asphalt (WMA) technologies have been intentionally developed to lower the manufacturing and working temperatures of the asphalt by reducing the viscosity of the asphalt binder. Many studies suggested that coupling CRMB with WMA additives can promote better working conditions and minimize environmental issues of the CRMB.
In this study, experimental works were carried out to evaluate rheological and performance-based properties of the CRMB containing WMA additives in order to investigate the effect of the crumb rubber modifier (CRM) content and WMA additives (wax-based and chemical-base WMA additives) by using only one dynamic shear rheometer (DSR). The performance of the studied binder at high, intermediate, and low road service temperatures were investigated by performing Multiple Stress Creep and Recovery test, Linear Amplitude Sweep test, and 4-mm Dynamic shear rheometer test, respectively. Moreover, the Fourier Transform-Infrared Spectroscopy and the storage stability test were also performed to investigate the effects of the CRM dosage and the WMA additives on the aging susceptibility and the high-temperature storage stability of the binders. The results show that the incorporation of crumb rubber modifier can clearly improve the overall performance (rutting, fatigue damage, low-temperature thermal cracking resistances), and aging resistance of the asphalt binder in a bitumen-level. The high-temperature storage stability of the CRMB became more stable at the higher dosage of the CRM. Moreover, it was found that the wax-based WMA additive can only enhance the high-temperature rutting resistance but negatively impacted the fatigue and low-temperature damage resistances of both neat and CRM binders. The effect of the chemical-based additive on the neat and CRM binders are different as it improved the performance over the whole service temperature of the neat but lowered the damage resistances of CRMBs. Additionally, the addition of both WMA additives decreased the high-temperature storage stability of the CRMB.

The performance of concrete is usually governed by its "strength" and "stiffness" properties. As most of the concrete structures are usually designed to last in service for a period of about half a century, it is important to understand the development of these "strength" and "stiffness" properties over the course of time. Based on the standard codes and practices, these properties are assumed to continuously increase with age assuming standard conditions (moist curing environment and temperature of 20° C), or at least remain constant in case of other curing conditions. However, few studies [27] [13] have reported a reduction in the trend of the strength and stiffness properties with time for the ordinary concrete of different strength mixes, when exposed to drying at different relative humidities after an initial moist curing period. Moreover, such decrease in trend has also been reported for a Geopolymer concrete upon drying at controlled lab conditions (20° C and 50%RH) after an initial moist curing period of 28 days [35]. It is not clear if the reduction in the trend observed is only temporary as a result of the imposed shrinkage deformations and eigen stresses, or if it is a permanent reduction as a result of microcracking. In this regard, it is aimed to understand the uncertainty in the development of the strength and stiffness properties of particularly the ordinary concrete mixes, which have been used across the world for a long time. Accordingly, it is hypothesized that a similar reduction upon drying in the trend of mechanical properties as reported by Prinsse [35] for a Geopolymer might also occur for the ordinary concrete mixes of various grades, which are cured and tested in the same way as the aforementioned Geopolymer concrete. Based on that, parameters such as the curing conditions, specimen size and the grade of concrete mix are assumed to influence the trend and a comprehensive literature study is performed in order to understand the influence of these assumed parameters on the mechanical properties - namely the compressive strength, splitting strength and elastic modulus over time. From the literature study, it is understood that there is some uncertainity in understanding the trend which is aggravated by the complex inter-dependency between the assumed parameters. Accordingly, an experimental program is set up to firstly verify whether there is a similar reduction in trend like the Geopolymer concrete and secondly to give more clarity on the complex inter-dependency between the assumed parameters. Further, the development of eigen stresses is understood to play a huge role in the trend of the measured mechanical properties over time and their influence might vary for the different tests. However, due to its temporary occurrence and larger testing frequency days, they are difficult to capture in the experiments. Accordingly, a FEM tool known as "FEMMASSE" is used, which can simulate the concrete behaviour by incorporating the heat and moisture models. Apart from considering the material effects like hydration, FEMMASSE can also capture the eigen stresses developed as a result of the thermal and moisture gradients. The software mostly finds application in the design of bridges and tunnels. Although, in this research study, the main purpose of using FEMMASSE is to firstly capture the shrinkage induced eigen stresses by simulating the tests at smaller intervals and secondly single out the influence of the studied parameters in order to give more clarity on the obtained experimental results. The obtained experimental results indicate no major reduction in the trend of the studied mechanical properties in time as compared to the Geopolymer concrete. With regard to the studied parameters, it is found that for the chosen curing regime (28DM regime), the trend of both compressive and splitting strength is seen to be affected by the development of the eigen stresses. Interestingly, for the trend of splitting strength, a general pattern of increasing and stabilizing behaviour is observed which seems to be dependent also on the specimen size. However, due to the lack of knowledge of the actual magnitude of the eigen stresses coupled with other phenomena like the size effect and current state of hydration, it becomes challenging to explain the trend merely on the basis of experimental results. In this regard, the use of numerical tool FEMMASSE is shown to help understand the experimental results at greater depth. Owing to the limitations of the software, only the tensile tests are simulated. Initially, it is understood that the attainment of the hygral equilibrium is dependent on the specimen size and the type of concrete,with the smaller specimen sizes and lower strength mixes reaching the equlibrium relatively quickly. The model is then extended to simulate the tensile tests - splitting and flexural and direct tension tests. It is concluded that drying after a moist curing period of 28 days affects the these tensile tests differently. In case of the splitting tests, drying results in the temporary increase of the strength owing to the apparent prestressing at the core of the specimen, with the gradual stabilization of the trend as the specimen attains moisture equilibrium. This trend of temporary increase and gradual stabilization is dependent on the specimen size with the smaller specimens stabilizing at a relatively quicker time due to the faster attainment of the moisture equilibrium. However, in case of the flexural and direct tensile test, drying results in the temporary reduction in the flexural strength due to the reduction in the tensile capacity at the surface, followed by an increasing trend as the specimen starts attaining hygral equilibrium. This indicates that the surface failure tests like the direct tension and flexural are negatively affected (temporarily) by drying as compared to the interior failure tests like splitting test which is positively affected (temporarily) by drying. From the research study, it is evident that there are no major reduction in the trend of strength and stiffness properties over time obtained experimentally until the period of 155 days. However, the presence of the eigen stresses, which not captured in the experiments, does influence the trend of the measured material properties over time. As long as these eigen stresses are present, the material strength determined experimentally might be deceptive, as evident from the simulations of the tensile tests performed in the study. It is understood that unless there is hygral equilibrium (no eigen stresses) across the specimen, the measured material properties might underestimate the actual material strength in case of the flexural and direct tension tests and overestimate in case of the splitting tensile tests. In the engineering practice, especially in mass concrete structures, the eigen stresses could be present throughout the service life of the structure. Thus, the experimentally obtained material strength used for designing the structure might be deceptive due to the influence of the eigen stresses.

In spite of the fact that there are many advantages of alkali activated materials (also called geopolymers) over the cement-based materials, geopolymer concrete has been used in the past for construction purposes on a very limited level. Among the many advantages of geopolymers compared with the cement-based materials is less CO2 emission, it uses byproducts as a binder, less energy consumption during its production, more durable as a material, fast setting time and high strength development. This work is an attempt to exert some light on the usability and applicability of geopolymers in the field of construction with concentration on its use in the 3D printing. The main aim of this study is to propose a design methodology for geopolymer paste mixture to be used in 3D printing process. For achieving this goal, one paste mixture design was selected among six ones on the bases of longer workability/flowability, suitable extrudability and specific setting time. These six designs have different binder ratios. The selected mixture design, named S20, was tested further to find out its suitability for 3D printing process. This S20 mixture was tested on compressive strength, setting time, rheological properties, open time, buildability and 28 days tensile bonding strength of two layers. To find the best suitable design, modifications were done on the S20 mixture by changing the ratios between the used alkaline solutions Na2SiO3 and NaOH (0.25 was selected). These alkaline solutions played a major role in delaying the initial setting time for rheological tests (90 minutes were selected) and the extrudability for the 3D printing process. Another factor for the best design is the Acti-gel as an additive. This additive has a direct link with the buildability, extrudability and viscosity when added with different percentages. The best selected percentage of the Acti-gel was 0.75% for this mixture design. The open time and the 28 days tensile bonding strength tests were selected to be 33 minutes and 1.32 MPa respectively. Comparing the measured plastic viscosity to the open time test, the extrudability of the mixture is not anymore valid beyond 8.8 Pa.s plastic viscosity. This short open time of 33 minutes for such geopolymer mixture design needs a fast-performing 3D printer. This might help in achieving construction projects within short time.

W/C is a fundamental parameter for concrete mix design, it defines the properties in the fresh and hardened state as well as the durability of the material. Nevertheless, once the concrete has hardened, it is very difficult to estimate the W/C in the original mix design, so far only 2 methodologies has been accepted as a standards. Because of this, the aim of the research is to use 4 methodologies, circular polarization microscopy (CPL), thermogravimetric analysis (TGA), UV light microscopy and scanning electron microscopy (SEM) + Powers and Brownyard approach to estimate the W/C of different concrete samples from a Round Robin Test done by the Applied Petrography Group (APG). The results showed that all the techniques have a correlation with the W/C. The CPL on its own and in combination with the UV light can be a feasible technique to estimate this value. Furthermore, since there were several techniques, it was decided to choose which one gave the best results using three guidelines, representativeness, reproducibility and reliability. The technique with the highest score was the combination of CPL+UV light.

The increasing traffic load has led to the use of polymer modifiers in bituminous mixes in order to improve the performance and the durability of the pavement structures. Epoxy is a thermoset material which ensures enhanced fatigue performance and improved mechanical characteristics when used to modify bituminous materials. However, unlike conventional modification techniques, a series of experimental methods have to be conducted to evaluate the chemical- related phenomena occurring during the binder production and their effects on the performance of the epoxy modified bitumen. For this reason in this thesis, the utilization of epoxy modifiers was investigated at binder level.
Initially, the chemical hardening (curing) process of epoxy modified bitumens (EMBs) was investigated by means of Fourier Transform Infrared (FT-IR) spectrometer and Dynamic Shear Rheometer (DSR). Different combinations of hardening conditions for three epoxy modification levels were studied. Properties, such as modulus and viscosity, were utilized to determine the workability of EMB. At the same time, by using the FT-IR spectrometer, the functional groups of EMBs during the chemical reactions were identified for the understanding of polymerization in the epoxy components.
Additionally, the DSR device was utilized to determine the fatigue and tensile strength of EMBs. It was found that, with increasing the content of epoxy modifier, the fatigue life and tensile strength were increased significantly compared to an unmodified binder.
Finally, the age hardening (aging) of EMBs was evaluated at different time intervals. For the simulation of short-term aging on EMBs, a short-term oven aging method (STOA) was used. For long-term aging, simulations were performed in a pressure aging vessel (PAV) under constant pressure and temperature. The results of chemical characterization and rheological properties of the aged EMBs were obtained by using DSR and FT-IR and were compared to the unmodified bitumen.

A series of accelerated corrosion tests were done by SGS INTRON (commenced by Combinatie Aanpak Maastunnel, constructor of the Maastunnel project) to investigate for a proper repair material for the deteriorated concrete floor in the Maastunnel at Rotterdam. Five types of fiber reinforced mixtures with different tensile behavior ranging from SHCC (strain-hardening cementitious composite) to ON06 (similar tensile behavior as normal concrete) were designed. Different cracking behavior was observed due to the different tensile behavior in the repair mortar. It is of utmost importance to investigate if the cracking behavior can be simulated by numerical modeling and if in the future, the parametric analysis might be performed without large experimental series.

Two types of numerical models are implemented in this master thesis, namely the lattice model and the continuum model. The lattice model can simulate the crack pattern of different materials in the accelerated corrosion test. The continuum model cannot show the behavior of decreasing number of cracks with decreasing fracture energy in the strain-softening materials due to the bifurcation problem brought by its incremental solution method. However, the lattice model shows the trend to underestimate the crack width of the strain-softening material. The continuum model has better performance in predicting the crack width. Also, the lattice model can predict the influence of the repair mortar-substrate bond strength on the crack pattern. Meanwhile, the continuum model always shows a complete failure in the repair mortar-substrate interface.
The boundary conditions at the bottom edge are observed to influence the direction of the bottom cracks. The edges of the specimen are kept free in the experiment. However, the repaired area is constrained by the surrounding concrete in reality. This indicates that the laboratory test may not represent the cracking behavior of the concrete floor in the tunnel accurately. SHCC is observed to be more sensitive to the repair mortar-substrate bond strength than material with lower stain capacity. Extra caution on the bond quality is advised while applying SHCC in a concrete repair system.

From the material point of view, with increasing fracture energy and strain capacity, more but thinner cracks can be performed in the accelerated corrosion test. SHCC material can perform the distributed crack pattern with a maximum crack width of 0.1mm which is ten times smaller than normal concrete. This behavior of SHCC is very suitable for being applied to a concrete repair system. The distributed cracks with smaller crack width can effectively limit the possibility of further corrosion. Besides SHCC, some strain-softening (under direct tension) materials can also show the deflection-hardening behavior in the bending test and produce the distributed crack pattern. SHCC and fiber reinforced concrete with deflection-hardening behavior in the bending test are suggested to be used in the concrete repair system.

Asphalt concrete stiffness is currently only determined by tests in The Netherlands. A prediction model can be useful for mix design and verification purposes. In this paper existing asphalt concrete stiffness prediction models have been analysed. A database with 7 mixes has been build to assess these models. A study was performed on the relevance of binder and composition parameters for predicting asphalt concrete stiffness. Finally, a new model is proposed.