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The impregnation of the exterior surface of a masonry wall with a water repellent is a common intervention in (historic) building renovation and maintenance. Such treatments, whilst degrading at the surface with time under influence of ultra violet light, remain effective below the surface several decades after their application. During renovation works of masonry previously treated with a water repellent, the question arises whether it is necessary to repeat the hydrophobic treatment of the entire masonry after repointing. Opposing opinions exist with this regard, but no research clearly supporting one or the other. This research investigates for the first time the effect of hydrophobic treatment when applied on previously treated and repointed masonry walls. Small masonry walls were subjected to rain periods in the laboratory and their water uptake and drying behaviour were studied. Moreover, this laboratory research was followed by 30 months of outdoor exposition of the masonry specimens. The following cases were considered: (1) wall treated with water repellent, (2) wall treated with water repellent, followed by repointing but without new water repellent treatment, (3) wall treated with water repellent, followed by repointing and retreatment. This was done for three different types of pointing mortar: ordinary Portland cement and natural hydraulic lime with standard sand, and natural hydraulic lime with sand with one grain size. The results show that, after prolonged rain periods, the water uptake by repointed but not retreated masonry is comparable to that of untreated, non-hydrophobic masonry, whereas drying is considerably slower. This leads to a high saturation degree in repointed but not retreated masonry, which, in turn, increases the risk of damage to the masonry by e.g. frost. Therefore, retreating repointed hydrophobic masonry should definitively be considered., Heritage & Architecture

Salt crystallization is a major cause of weathering of mortars, including plasters and renders. In the last decade, the use of mixed-in salt crystallization inhibitors in mortars has been proposed as a solution to improve the durability of this material with respect to salt decay. Laboratory characterization and accelerated weathering tests have shown encouraging results. However, data on the long-term behaviour of these mortars when applied on-site were missing until now .In this research the durability with respect to salt decay of a lime-based plaster and a salt accumulating plaster has been assessed. These plasters, with and without sodium ferrocyanide, a well-known inhibitor of sodium chloride crystallization, have been applied to an interior brick masonry wall with a high salt (sodium chloride) and moisture load and monitored for a period of 4 years. Monitoring included visual and photographic observations of the damage as well as measurements of the moisture and salt content and distribution, both in the wall and in the plaster. Moreover, the content and distribution of the inhibitor in the plaster after 4 year exposure was measured, to gain insight into the dissolution and transport of the inhibitor. The results of the research clearly show that the inhibitor is able to significantly reduce the occurrence of salt-induced decay in the lime-based plaster, in comparison to the plaster without inhibitor. No conclusions can be drawn in the case of the salt accumulating plaster, as no decay has developed yet in this case. Two issues related to leaching of the inhibitor and surface discolouration have emerged. These are discussed and possible solutions are proposed., Heritage & Technology

In the Netherlands, beside cement replacement with more green cement types, there is also an urgent need for alternative materials for natural sand in new concrete in order to make it circular. Furthermore, the recyclers have raised questions regarding upscaling and the potential of fine recycled concrete aggregates (fRCA) in structural concrete elements since the availability of recycled construction rubble is increasing. The variations in their chemical and physical properties and lack of standards for their quality evaluation is the main reason for not yet using fRCA in new concrete. In this paper, an in-depth characterization of different fRCA is performed in order to define their chemical properties. The properties can be eventually related to concrete mix design and performance (next step), so that fRCA can be classified as a material that can be used in more advanced applications. This is achieved with a multi-level chemical characterization of individual and total fractions (0-0.25 mm, 0.25-4 mm and 0-4 mm) for finding type and content of the original sand and cement phases and potential contamination of selected fractions. The tests include quantification of element composition with X-ray fluorescence (XRF), qualitative and quantitative phase analysis with X-ray diffraction (XRD) and Rietveld method. In addition, cement paste content, chlorides and sulfates of each type of fRCA was measured in order to evaluate contamination of studied material. It was shown that fRCA from different origins have similar chemical and mineralogical composition and contain comparative chloride content. The chemical composition testing can provide a first line control regarding composition and potential contamination of fRCA. After that, it can be decided which additional tests are necessary to be done in order to evaluate the suitability of fRCA for replacement of primary natural fine aggregates in new concrete., Materials and Environment

An important input parameter for numerical models that simulate cracking of the concrete cover due to reinforcement corrosion is the Elastic modulus of corrosion product (Ecp). Despite its relevance, Ecp is subject of significant variations according to the values reported in the literature, which vary from less than 100 MPa up to 360 GPa. Furthermore, Ecp values proposed in most of the present literature are representative of the corrosion product generated by anodic accelerated corrosion or extracted from the steel/concrete interface (SCI), which might differ from that formed in real corroding structures. Therefore, this study aims to investigate the Elastic modulus of naturally-generated corrosion product present at the SCI through nano-indentation conducted on six reinforced concrete polished sections. The polished sections were obtained from six 20-year-old reinforced concrete prisms cast with different cement type (CEM I, CEM II/B-V, CEM III/B, CEM V/A), same water/binder ratio (0.55) and which were previously exposed to NaCl solution wet/dry cycles. This study revealed that the range of Ecp did not considerably vary between corrosion products formed in different concrete mixes. However, corrosion product was microscopically found to consist of overlapping bands with different Ecp, varying for up to around 70 GPa between each other. Through Environmental Scanning-Electron Microscopy (ESEM) and Energy Dispersive Xray Spectrometry (EDS) analysis of the indented locations, it was found that Ecp is highly dependent on the presence of interfacial cracks and inversely proportional to the concentration of Si and Ca, representative for corrosion product mixed with the surrounding concrete. Furthermore, higher concentration of Fe leads to higher Ecp. Based on this study, an average range of values for Ecp between 80-100 GPa can be suggested for use in numerical models for corrosion induced cracking, regardless of cement type of the structure under investigation., Materials and Environment

Compatibility of repair materials in conservation is a widely desired goal, but difficult to achieve. In this research, the compatibility of four commercial stone repair mortars, commonly used in conservation practice in the Netherlands and neighbouring countries, is discussed. In order to do so, they have been characterized in laboratory. The composition of the repair mortars, their content of soluble salts, porosity and pore size distribution, hygric dilation and flexural and compressive strength were measured. The effect of curing was assessed by comparing specimens cured in laboratory and under outdoor conditions. The effect of 3 years outdoor exposure on the curing and weathering of the mortars was evaluated. The results show that the composition of the selected mortars varies significantly, even though, based on their technical information sheets, they appeared to be similar. Consequently, their moisture transport properties differ significantly. As expected, both the type of binder and the porosity were shown to affect the mechanical properties of the mortar: the mortar based on an inorganic polymer binder showed the highest mechanical strength; the most porous, lime- or lime-cement-based mortars, showed the lowest mechanical strength. Based on compatibility criteria defined in literature and the results obtained in this research, an attempt was made to assess the technical compatibility of the selected mortars with building stones commonly used in the Netherlands. It was found that some requirements are hard to be fulfilled and not all requirements can be fulfilled at the same time. Besides, technical sheets of commercial mortars are often incomplete; therefore repair mortars can hardly be selected based only on the properties reported by the producers., Heritage & Technology

In the Netherlands, beside cement replacement with more green cement types, there is also an urgent need for alternative materials for natural sand in new concrete in order to make it circular. Furthermore, the recyclers have raised questions regarding upscaling and the potential of fine recycled concrete aggregates (fRCA) in structural concrete elements since the availability of recycled construction rubble is increasing. The variations in their chemical and physical properties and lack of standards for their quality evaluation is the main reason for not yet using fRCA in new concrete. In this paper, an in-depth characterization of different fRCA is performed in order to define their chemical properties. The properties can be eventually related to concrete mix design and performance (next step), so that fRCA can be classified as a material that can be used in more advanced applications. This is achieved with a multi-level chemical characterization of individual and total fractions (0-0.25 mm, 0.25-4 mm and 0-4 mm) for finding type and content of the original sand and cement phases and potential contamination of selected fractions. The tests include quantification of element composition with X-ray fluorescence (XRF), qualitative and quantitative phase analysis with X-ray diffraction (XRD) and Rietveld method. In addition, cement paste content, chlorides and sulfates of each type of fRCA was measured in order to evaluate contamination of studied material. It was shown that fRCA from different origins have similar chemical and mineralogical composition and contain comparative chloride content. The chemical composition testing can provide a first line control regarding composition and potential contamination of fRCA. After that, it can be decided which additional tests are necessary to be done in order to evaluate the suitability of fRCA for replacement of primary natural fine aggregates in new concrete.

An important input parameter for numerical models that simulate cracking of the concrete cover due to reinforcement corrosion is the Elastic modulus of corrosion product (Ecp). Despite its relevance, Ecp is subject of significant variations according to the values reported in the literature, which vary from less than 100 MPa up to 360 GPa. Furthermore, Ecp values proposed in most of the present literature are representative of the corrosion product generated by anodic accelerated corrosion or extracted from the steel/concrete interface (SCI), which might differ from that formed in real corroding structures. Therefore, this study aims to investigate the Elastic modulus of naturally-generated corrosion product present at the SCI through nano-indentation conducted on six reinforced concrete polished sections. The polished sections were obtained from six 20-year-old reinforced concrete prisms cast with different cement type (CEM I, CEM II/B-V, CEM III/B, CEM V/A), same water/binder ratio (0.55) and which were previously exposed to NaCl solution wet/dry cycles. This study revealed that the range of Ecp did not considerably vary between corrosion products formed in different concrete mixes. However, corrosion product was microscopically found to consist of overlapping bands with different Ecp, varying for up to around 70 GPa between each other. Through Environmental Scanning-Electron Microscopy (ESEM) and Energy Dispersive Xray Spectrometry (EDS) analysis of the indented locations, it was found that Ecp is highly dependent on the presence of interfacial cracks and inversely proportional to the concentration of Si and Ca, representative for corrosion product mixed with the surrounding concrete. Furthermore, higher concentration of Fe leads to higher Ecp. Based on this study, an average range of values for Ecp between 80-100 GPa can be suggested for use in numerical models for corrosion induced cracking, regardless of cement type of the structure under investigation.

The elastic modulus of corrosion product (Ecp) has been reported with significant variations in the literature. This study aims to investigate the Ecp of naturally-generated chloride-induced corrosion products formed in different concrete mixes. Microstructural characterization was conducted through nano-indentation, electron microscopy and Raman spectroscopy. The corrosion products were mainly composed of a goethite matrix with portions of maghemite, independently of the concrete composition. Microscopic analysis suggest that layers of corrosion products grow at different times and under different physico-chemical conditions. Our measurements showed that Ecp varied between 80−100 GPa, which can be suggested for numerical models of corrosion induced cracking., Materials and Environment, Novel Aerospace Materials

In circular concrete design, beside cement replacement with more environmentally friendly cement types, there is also an urgent need for sand replacement with fine recycled concrete aggregates (fRCA). The variations in physical and chemical properties of fRCA and lack of standards for their quality evaluation are the main reasons for not yet using fRCA in new concrete. In this study, an in-depth characterization of different Dutch fRCA is performed in order to examine suitability of fRCA as an alternative material for river sand and define indicators for fRCA quality. These indicators eventually can be related to concrete mix design and performance, so that fRCA can be classified as a material that can be used in structural concrete elements. This is achieved with physical, chemical and mineralogical characterization of individual and total fractions (0–0.250 mm, 0.250–4 mm and 0–4 mm). The physical properties such as grading, density, surface area, water absorption and cement paste content of fRCA were tested. The chemical analyses include quantification of element composition with X-ray fluorescence spectrometry (XRF) and carbonate content with thermogravimetry and mass spectrometry (TG-MS). Potential contamination (chlorides and sulfates) and reactivity of selected fractions were evaluated. In addition, qualitative and quantitative phase analyses with X-ray diffraction (XRD) combined with Rietveld refinement method were performed and supported by optical polarizing-and-fluorescence microscopic (PFM) study. Based on combined experimental approaches, characteristic quality indicators were defined for fRCA. These indicators showed that fRCA were uncontaminated and nonreactive. Despite fRCA were from different origins, they had similar chemical and mineralogical composition and contained comparative chloride content. In contrast, the content and surface area of fine fraction (0–0.250 mm) and particle size distribution of fRCA varied with the source. With this it c, Materials and Environment

In the Netherlands, beside cement replacement with more green cement types, there is also an urgent need for alternative materials for natural sand in new concrete in order to make it circular. Furthermore, the recyclers have raised questions regarding upscaling and the potential of fine recycled concrete aggregates (fRCA) in structural concrete elements since the availability of recycled construction rubble is increasing. The variations in their chemical and physical properties and lack of standards for their quality evaluation is the main reason for not yet using fRCA in new concrete. In this paper, an in-depth characterization of different fRCA is performed in order to define their chemical properties. The properties can be eventually related to concrete mix design and performance (next step), so that fRCA can be classified as a material that can be used in more advanced applications. This is achieved with a multi-level chemical characterization of individual and total fractions (0-0.25 mm, 0.25-4 mm and 0-4 mm) for finding type and content of the original sand and cement phases and potential contamination of selected fractions. The tests include quantification of element composition with X-ray fluorescence (XRF), qualitative and quantitative phase analysis with X-ray diffraction (XRD) and Rietveld method. In addition, cement paste content, chlorides and sulfates of each type of fRCA was measured in order to evaluate contamination of studied material. It was shown that fRCA from different origins have similar chemical and mineralogical composition and contain comparative chloride content. The chemical composition testing can provide a first line control regarding composition and potential contamination of fRCA. After that, it can be decided which additional tests are necessary to be done in order to evaluate the suitability of fRCA for replacement of primary natural fine aggregates in new concrete., Materials and Environment

An important input parameter for numerical models that simulate cracking of the concrete cover due to reinforcement corrosion is the Elastic modulus of corrosion product (Ecp). Despite its relevance, Ecp is subject of significant variations according to the values reported in the literature, which vary from less than 100 MPa up to 360 GPa. Furthermore, Ecp values proposed in most of the present literature are representative of the corrosion product generated by anodic accelerated corrosion or extracted from the steel/concrete interface (SCI), which might differ from that formed in real corroding structures. Therefore, this study aims to investigate the Elastic modulus of naturally-generated corrosion product present at the SCI through nano-indentation conducted on six reinforced concrete polished sections. The polished sections were obtained from six 20-year-old reinforced concrete prisms cast with different cement type (CEM I, CEM II/B-V, CEM III/B, CEM V/A), same water/binder ratio (0.55) and which were previously exposed to NaCl solution wet/dry cycles. This study revealed that the range of Ecp did not considerably vary between corrosion products formed in different concrete mixes. However, corrosion product was microscopically found to consist of overlapping bands with different Ecp, varying for up to around 70 GPa between each other. Through Environmental Scanning-Electron Microscopy (ESEM) and Energy Dispersive Xray Spectrometry (EDS) analysis of the indented locations, it was found that Ecp is highly dependent on the presence of interfacial cracks and inversely proportional to the concentration of Si and Ca, representative for corrosion product mixed with the surrounding concrete. Furthermore, higher concentration of Fe leads to higher Ecp. Based on this study, an average range of values for Ecp between 80-100 GPa can be suggested for use in numerical models for corrosion induced cracking, regardless of cement type of the structure under investigation., Materials and Environment

Compatibility of repair materials in conservation is a widely desired goal, but difficult to achieve. In this research, the compatibility of four commercial stone repair mortars, commonly used in conservation practice in the Netherlands and neighbouring countries, is discussed. In order to do so, they have been characterized in laboratory. The composition of the repair mortars, their content of soluble salts, porosity and pore size distribution, hygric dilation and flexural and compressive strength were measured. The effect of curing was assessed by comparing specimens cured in laboratory and under outdoor conditions. The effect of 3 years outdoor exposure on the curing and weathering of the mortars was evaluated. The results show that the composition of the selected mortars varies significantly, even though, based on their technical information sheets, they appeared to be similar. Consequently, their moisture transport properties differ significantly. As expected, both the type of binder and the porosity were shown to affect the mechanical properties of the mortar: the mortar based on an inorganic polymer binder showed the highest mechanical strength; the most porous, lime- or lime-cement-based mortars, showed the lowest mechanical strength. Based on compatibility criteria defined in literature and the results obtained in this research, an attempt was made to assess the technical compatibility of the selected mortars with building stones commonly used in the Netherlands. It was found that some requirements are hard to be fulfilled and not all requirements can be fulfilled at the same time. Besides, technical sheets of commercial mortars are often incomplete; therefore repair mortars can hardly be selected based only on the properties reported by the producers., Heritage & Technology

The elastic modulus of corrosion product (Ecp) has been reported with significant variations in the literature. This study aims to investigate the Ecp of naturally-generated chloride-induced corrosion products formed in different concrete mixes. Microstructural characterization was conducted through nano-indentation, electron microscopy and Raman spectroscopy. The corrosion products were mainly composed of a goethite matrix with portions of maghemite, independently of the concrete composition. Microscopic analysis suggest that layers of corrosion products grow at different times and under different physico-chemical conditions. Our measurements showed that Ecp varied between 80−100 GPa, which can be suggested for numerical models of corrosion induced cracking., Materials and Environment, Novel Aerospace Materials

In circular concrete design, beside cement replacement with more environmentally friendly cement types, there is also an urgent need for sand replacement with fine recycled concrete aggregates (fRCA). The variations in physical and chemical properties of fRCA and lack of standards for their quality evaluation are the main reasons for not yet using fRCA in new concrete. In this study, an in-depth characterization of different Dutch fRCA is performed in order to examine suitability of fRCA as an alternative material for river sand and define indicators for fRCA quality. These indicators eventually can be related to concrete mix design and performance, so that fRCA can be classified as a material that can be used in structural concrete elements. This is achieved with physical, chemical and mineralogical characterization of individual and total fractions (0–0.250 mm, 0.250–4 mm and 0–4 mm). The physical properties such as grading, density, surface area, water absorption and cement paste content of fRCA were tested. The chemical analyses include quantification of element composition with X-ray fluorescence spectrometry (XRF) and carbonate content with thermogravimetry and mass spectrometry (TG-MS). Potential contamination (chlorides and sulfates) and reactivity of selected fractions were evaluated. In addition, qualitative and quantitative phase analyses with X-ray diffraction (XRD) combined with Rietveld refinement method were performed and supported by optical polarizing-and-fluorescence microscopic (PFM) study. Based on combined experimental approaches, characteristic quality indicators were defined for fRCA. These indicators showed that fRCA were uncontaminated and nonreactive. Despite fRCA were from different origins, they had similar chemical and mineralogical composition and contained comparative chloride content. In contrast, the content and surface area of fine fraction (0–0.250 mm) and particle size distribution of fRCA varied with the source. With this it c, Materials and Environment

An important input parameter for numerical models that simulate cracking of the concrete cover due to reinforcement corrosion is the Elastic modulus of corrosion product (Ecp). Despite its relevance, Ecp is subject of significant variations according to the values reported in the literature, which vary from less than 100 MPa up to 360 GPa. Furthermore, Ecp values proposed in most of the present literature are representative of the corrosion product generated by anodic accelerated corrosion or extracted from the steel/concrete interface (SCI), which might differ from that formed in real corroding structures. Therefore, this study aims to investigate the Elastic modulus of naturally-generated corrosion product present at the SCI through nano-indentation conducted on six reinforced concrete polished sections. The polished sections were obtained from six 20-year-old reinforced concrete prisms cast with different cement type (CEM I, CEM II/B-V, CEM III/B, CEM V/A), same water/binder ratio (0.55) and which were previously exposed to NaCl solution wet/dry cycles. This study revealed that the range of Ecp did not considerably vary between corrosion products formed in different concrete mixes. However, corrosion product was microscopically found to consist of overlapping bands with different Ecp, varying for up to around 70 GPa between each other. Through Environmental Scanning-Electron Microscopy (ESEM) and Energy Dispersive Xray Spectrometry (EDS) analysis of the indented locations, it was found that Ecp is highly dependent on the presence of interfacial cracks and inversely proportional to the concentration of Si and Ca, representative for corrosion product mixed with the surrounding concrete. Furthermore, higher concentration of Fe leads to higher Ecp. Based on this study, an average range of values for Ecp between 80-100 GPa can be suggested for use in numerical models for corrosion induced cracking, regardless of cement type of the structure under investigation.

In the Netherlands, beside cement replacement with more green cement types, there is also an urgent need for alternative materials for natural sand in new concrete in order to make it circular. Furthermore, the recyclers have raised questions regarding upscaling and the potential of fine recycled concrete aggregates (fRCA) in structural concrete elements since the availability of recycled construction rubble is increasing. The variations in their chemical and physical properties and lack of standards for their quality evaluation is the main reason for not yet using fRCA in new concrete. In this paper, an in-depth characterization of different fRCA is performed in order to define their chemical properties. The properties can be eventually related to concrete mix design and performance (next step), so that fRCA can be classified as a material that can be used in more advanced applications. This is achieved with a multi-level chemical characterization of individual and total fractions (0-0.25 mm, 0.25-4 mm and 0-4 mm) for finding type and content of the original sand and cement phases and potential contamination of selected fractions. The tests include quantification of element composition with X-ray fluorescence (XRF), qualitative and quantitative phase analysis with X-ray diffraction (XRD) and Rietveld method. In addition, cement paste content, chlorides and sulfates of each type of fRCA was measured in order to evaluate contamination of studied material. It was shown that fRCA from different origins have similar chemical and mineralogical composition and contain comparative chloride content. The chemical composition testing can provide a first line control regarding composition and potential contamination of fRCA. After that, it can be decided which additional tests are necessary to be done in order to evaluate the suitability of fRCA for replacement of primary natural fine aggregates in new concrete.