Adaptive reuse (AR) of heritage buildings is a complex process involving many stakeholders with different ambitions. Recently, a theoretical model has been proposed to facilitate this process. However, the validation of this model and investigation of the nexus between process steps, methods/tools used by architects, and the effectiveness of projects are still lacking. This paper aims to validate the model by examining four AR projects in the Netherlands, considered effective as winners of a prestigious architectural prize. The research methods included literature reviews, case visits, and interviews with architects and other stakeholders. The model was refined, and methods/tools used by architects in the process steps were identified, highlighting their link with the effectiveness of results.

@en

Crystallisation inhibitors, such as sodium ferrocyanide (NaFeCN), are highly effective in mitigating NaCl-induced weathering in lime-based mortars; however, direct addition of NaFeCN in lime-mortars increases its susceptibility to leaching and rapid depletion, thus compromising long-term performance. Here, we present hydrogel-capsules for the controlled-release of NaFeCN within hydraulic mortars for the prolonged prevention of salt weathering. Capsules were prepared by complexing chitosan and calcium-alginate in different ratios containing different concentrations of NaFeCN. The release of NaFeCN from these capsules was measured in (1) simulated lime-mortar solution (2) from mortar specimens incorporated with calcium alginate (CA) and chitosan-calcium-alginate (Cs-CA) capsules using ultraviolet–visible light spectrophotometry and Inductive Coupled Plasma-Optical Emission Spectroscopy. Mortars containing Cs-CA capsules exhibited controlled-release of NaFeCN with four times lower effective diffusion coefficient, compared to incorporating NaFeCN directly in mortar. Conversely, mortar containing CA capsules (without chitosan) released NaFeCN rapidly. Thus, chitosan’s presence in CA is necessary for tuning NaFeCN release and the reason may be attributed to chitosan’s role in reducing CA’s permeability and chitosan’s electrostatic-attraction to ferrocyanide anions, slowing diffusion of the latter. In conclusion, using Cs-CA capsules can control the release of NaFeCN within mortar, providing a steady NaFeCN supply to prolong mortar’s resistance against salt damage.@en

Salt (NaCl) weathering in mortar, can be mitigated by incorporating a crystallisation inhibitor (sodium ferrocyanide) during mortar preparation. However, the service-life of the inhibitor is limited, due to its susceptibility to leaching out of mortar. Encapsulating the inhibitor in chitosan-calcium alginate capsules has demonstrated controlled-release of the inhibitor and therefore, reduction in its leaching. Nevertheless, the addition of capsules may have a negative effect on mortar's properties and/or its salt-weathering resistance. In this research, natural hydraulic lime (NHL) and commercial cement-based mortars were prepared, with encapsulated inhibitor and with directly mixed-in inhibitor. Mechanical and physical properties of mortars were assessed experimentally. An accelerated NaCl-weathering test was performed to assess the durability of mortar to salt damage. The damage evolution was assessed visually and by quantifying material loss, efflorescence and leaching of the inhibitor. At the end of the test, crystal morphology inside the pores was examined using SEM. The results show that adding inhibitor, both in encapsulated and mixed-in form, had a negligible effect on the properties of NHL and cement-based mortars. Compared to the reference mortar without inhibitor, NHL-mortars with mixed-in inhibitor and encapsulated inhibitor had a better durability to salt damage, showing negligible material loss. The capsules facilitated controlled-release and reduced leaching of the inhibitor. In cement-based mortars including the reference, no damage was observed; still, the inhibitor was shown to be effective in modifying the salt crystal habit. The results show that encapsulation of the inhibitor can improve the service-life of the mortar without compromising its performance.@en

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.

@en

Plasters and renders used in historic monuments are vulnerable to degradation caused by salt weathering. Crystallisation inhibitors (molecules/ions that alter salt crystallisation) mixed into mortars have shown promising results in mitigating salt damage by inhibiting salt crystallisation, promoting salt transport to the evaporating surface, and modifying crystal habit. However, past research suggests that inhibitors easily leach out from mortars, meaning their long-term positive effect is lost. Encapsulation of an inhibitor within a mortar is a potential solution to minimise leaching. Herein, capsules composed of a polyelectrolyte complex of calcium alginate coated in chitosan are investigated for the controlled diffusive release of sodium ferrocyanide, a known NaCl crystallisation inhibitor. Capsules with varying chitosan-calcium alginate ratios are prepared using the extrusion dripping technique. The release of the inhibitor from capsules in solutions of various pH values ranging from 7–13 is investigated. Results show that increasing the capsule’s chitosan to calcium alginate ratio reduces the inhibitor release for all studied solution pH values compared to pure calcium-alginate capsules. Therefore, a controlled inhibitor release can be obtained by tuning the chitosan-alginate ratio. In future, additional tests will be performed to find suitable capsule compositions for optimising their performance when mixed in mortars.@en

Purpose: Housing interventions carried out in accordance with current regulations in the Old City of Aleppo, both before and after the Syrian war, are minor in comparison to those carried out without a license and illegally. This suggests current policies are inadequate and needs upgrading. Design/methodology/approach: This article critically reviews current Syrian policies and their implementation on residential heritage in the Old City of Aleppo with the aim to identify gaps and propose directions for modifications. Next to a review of the text of official policies and implementation documents, the archive of the Directorate of the Old City has been consulted and license applications, presented in the period 2018–2022, have been examined. Moreover, interviews with decision-makers from academics and practice were conducted. Findings: Major limitations of these policies and relative application procedures have been identified: these involve: legal/administrative, economic and social aspects. Originality/value: The specific needs have been highlighted and some proposals for improvement made.

@en

Reconstruction and recovery of historic cities after destruction due to conflict or natural disasters have gained increasing relevance in the last decades. The investigation of international examples of recovery after war or natural catastrophic events can provide knowledge for improving guidance and strategies for sustainable reconstruction/ intervention in similar cases in the future. This paper aims to identify and analyze the legal, administrative, social, and economic factors that can favor the reconstruction and recovery processes of the historic city and its residential neighborhoods. An extensive review of international examples and literature on guidance has been conducted to provide insight into best practices and potential solutions. As a result, a set of lessons learned that can be used to address post-conflict and post-disaster recovery and reconstruction in similar situations is given.@en

This recommendation is devoted to testing the resistance of natural stone and fired-clay brick units against salt crystallization. The procedure was developed by the RILEM TC 271-ASC to evaluate the durability of porous building materials against salt crystallization through a laboratory method that allows for accelerated testing without compromising the reliability of the results. The new procedure is designed to replicate salt damage caused by crystallization near the surface of materials as a result of capillary transport and evaporation. A new approach is proposed that considers the presence of two stages in the salt crystallization test. In the first, the accumulation stage, salts gradually accumulate on or near the surface of the material due to evaporation. In the second, the propagation stage, damage initiates and develops due to changes in moisture content and relative humidity that trigger salt dissolution and crystallization cycles. To achieve this, two types of salt were tested, namely sodium chloride and sodium sulphate, with each salt tested separately. A methodology for assessing the salt-induced damage is proposed, which includes visual and photographical observations and measurement of material loss. The procedure has been preliminarily validated in round robin tests.

@en

Sodium chloride (NaCl) is one of the most commonly occurring weathering agents, responsible for a progressive damage in mortar. Current solutions to mitigate salt damage in mortar, such as the use of mixed-in water repellent additives, have often exhibited low compatibility with the existing building fabric. In the last years, research has shown promising results in mitigating salt decay by making use of crystallisation inhibitors. Sodium ferrocyanide is one of the inhibitors that has proven to be particularly effective to reduce damage due to sodium chloride crystallisation. In this research the possibility of developing hydraulic mortars with mixed-in inhibitor (sodium ferrocyanide) for an improved resistance to sodium chloride crystallisation damage is investigated. As a first step, the interaction between the inhibitor and the hydraulic binder: natural hydraulic lime (NHL), was studied; the results are presented in this paper. Various concentrations of sodium ferrocyanide were tested (0%, 0.1% and 1% by binder weight). The effect of the inhibitor on several physical (hydration, water absorption, pore size distribution) and mechanical (compressive and flexural strength) properties was experimentally assessed, using several complementary methods and techniques. The results show that the addition of the sodium ferrocyanide does not affect the fresh and hardened properties of mortar. These results are promising and open new possibilities for the application of inhibitors to improve the durability of hydraulic mortars.

@en

Salt weathering is one of the most recurrent damage processes affecting both the natural and the built environment. Due to the complexity of the process, numerical models are rarely applied in practice; accelerated weathering tests in laboratory are still the most common way to assess and forecast durability of (conservation and renovation) building materials.....@en

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.@en

This paper investigates the leaching behaviour of sodium ferrocyanide, a known crystallisation inhibitor of sodium chloride, which is added to mortars for mitigation of salt decay. Leaching and depletion of the inhibitor is a practical performance related issue that might over time, make the inhibitor less effective against salt decay. In this research, the inhibitor was added to natural hydraulic lime (NHL) mortars during the mixing stage. Leaching of the inhibitor from the hardened mortar was assessed experimentally in laboratory. Both diffusion- and advection-driven transport mechanisms were considered. Diffusion experiments were carried out in a tank leaching test setup. Capillary absorption and drying cycles were used as a driving force to study advection-driven transport. Quantification of the leached species was carried out using various analytical techniques, including UV-VIS spectroscopy, ICP-OES and ion chromatography. The results from the tank leaching test show a high effective diffusion coefficient of ferrocyanide ions, in the same order of magnitude as sodium chloride transport. The advection test shows accumulation of the inhibitor at the evaporative surface and depletion of the inhibitor in the inner layers with successive wet-dry cycles. Based on these results it can be inferred that the degree of inhibitor leaching is significant and needs to be minimised to prolong the positive effect of the inhibitor on mortar durability. Potential solutions to reduce inhibitor leaching are discussed.

@en

Walls overgrown with plants can have a positive impact on urban comfort and contribute to biodiversity in the city. In particular, quay walls, thanks to their close contact with water, have the potential to be ecologically engineered to encourage the growth of herbaceous plants. Different factors can affect growth of vegetation on walls. This research aims at experimentally investigating the effect of several variables, including quay wall design, building materials and environmental conditions, on receptivity of brick masonry quay walls for herbaceous plants. To this scope, ten quay walls (size 2 m × 2 m x 0.43 m), have been built and placed in a canal in the city of Breda (the Netherlands). The survival and growth of vegetation and the moisture content in the wall were monitored during a period of about 2 years. The results show that the presence of a layer of soil substrate with high capillary suction, positioned in between the masonry cladding and the concrete structure of the wall, has the most relevant positive effect on vegetation growth on the masonry. Mortar composition and irregularities of the wall surface influence bio-receptivity too, but to a less extent; orientation had only a limited effect. Moreover, the strategy of using a mechanically strong bedding mortar in combination with a weaker but more bio-receptive pointing mortar has proven successful at favouring growth of herbaceous plants, while providing sufficient strength to the masonry.@en

Crystallisation due to commonly occurring salts like sodium chloride (NaCl) is a known cause of damage in the built environment. Use of crystallisation inhibitors is a potential solution to reduce salt decay in building materials. Researchers have reported lower damage when sodium ferrocyanide (NaFeCN), a known NaCl crystallisation inhibitor, is mixed in fresh mortar. However, the high solubility of NaFeCN in water could make it susceptible to leaching and thus diminish its effect over time.@en

Adaptive reuse (AR) of heritage buildings is common practice in The Netherlands and is becoming more and more common at the International level. While AR projects are generally considered positive actions towards preserving the qualities of heritage buildings, not all projects have similar (positive) impact. To propose a methodology for dealing with the AR of heritage buildings aiming for positive impact, the AR process has been studied. After a comprehensive systematic literature review, a theoretical model representing the steps of the AR process has been sketched (fig.1). This model depicts the ideal steps of architects in dealing with heritage buildings. To check whether these steps are actually followed, two effective AR projects, winners of the NRP golden phoenix prize, were studied namely ‘LocHal’ in Tilburg (fig.2) and ‘Energiehuis’ in Dordrecht (fig.3). During the research, the cases were visited, the published literature on the cases was reviewed, and architects and other stakeholders involved were interviewed. The interviews were based on the steps of the theoretical model but the model was not shown to the architects till the end of the interview. Finally feedback was asked from the architects if the model represented their actual steps and where they diverged. The analysis of the collected data confirmed that architects followed the steps reported in figure 1. However, the process was reported to be not linear, as suggested in the model, but to include several loops between some of the steps, mainly between steps 1, 2 , 3, 4, 5, and 6 (fig.4). Next to refining of the AR model, investigation of the case studies led to the identification of tools and methods used by architects, which have possibly positively influenced the effectiveness (positive impact) of the final result. Both case studies distinguished themselves, according to the NRP jury reports, because of their high ‘social value creation’. Involving end-users, other producers, and original users in different steps of the AR process has been identified as the main method used by the architects contributing to this positive impact.@en

Porous building materials are often subjected to damage due to salt crystallization. In recent years, the addition of crystallization inhibitors in lime-based mortar, has shown promising results in improving durability of this material against salt decay. Lime-based mortars have low mechanical properties and slow setting. They are often replaced with hydraulic binders to overcome these limitations. However, the effect of crystallization inhibitors in mortars with hydraulic binders is still unknown. Incorporation of crystallization inhibitors in hydraulic mortars would widen the application field of this new technology. In this research, the possibility to develop hydraulic mortars with mixed-in sodium ferrocyanide, an inhibitor of sodium chloride crystallization, is explored. As an essential first step, the influence of this inhibitor addition on the properties of hydraulic mortars is investigated. Two common types of hydraulic binders, natural hydraulic lime (NHL) and ordinary Portland cement (CEM I), were studied; the inhibitor was added in different amounts (0%, 0.1% and 1% by binder weight) during mortar (and binder paste) preparation. Relevant mortar and binder paste properties, in fresh (hydration, workability, setting time) and hardened (mechanical strength, elastic modulus, pore size distribution, water absorption) state, were assessed using several complementary methods and techniques. The results indicate that the addition of ferrocyanide does not alter the studied properties of both NHL and CEMI-based mortar and binder pastes. These results are promising for the further development of hydraulic mortars with an improved durability with respect to salt decay.@en

Adaptive reuse (AR) of modern buildings, including industrial buildings from the late 19th and 20th centuries, is a complex process as it involves many actions and actors, which influence the result of projects. Effective AR can provide many advantages for societies. This paper aims to provide an overview of the three most highlighted criteria, mentioned by previous researchers, for assessing effectiveness of AR of modern buildings.
This research followed seven steps: 1.Reviewing the criteria of “effectiveness” in AR projects in the literature 2.Collecting the data (jury reports of NRP and Europa-Nostra awards) 3.Distilling the reports related to modern heritage buildings 4.Translation of Dutch reports in English 5.Analysing and coding the texts following the criteria mentioned in the literature 6.Analysing the role of effective AR of modern heritage buildings in providing sublimation and social value 7.Formulating some conclusions/recommendations.
This review indicates despite the attribution of the effectiveness of AR of non-modern heritage buildings to the attraction of tourists, the effectiveness of AR in modern buildings is often attributed to positive effects on the surroundings and local community. Moreover, in modern buildings, compared to non-modern buildings, qualities provided by new interventions are highlighted more. This can be related to open space plans, stronger materials, wider spans, and spacious urban settings providing a higher tolerance for acceptable change.
By revealing the aspects of effectiveness within these two criteria, this study contributes to the broader understanding of the AR potential of modern buildings. Though this review is useful for encouraging the reuse of modern buildings, the methods/tools to be used to achieve effective results need more investigation in future research.
@en

Salt crystallization is a major cause of damage in porous building materials. Accelerated salt weathering tests carried out in the laboratory are among the most common methods to assess the durability of material to salt decay. However, existing standards and recommendations for salt weathering tests have limitations in terms of effectiveness and/or reliability. In the framework of the RILEM Technical Committee 271-ASC, a procedure has been developed which proposes a new approach to salt crystallization tests. It starts from the consideration that salt damage can be seen as a process developing in two phases: accumulation of the salt in the material and propagation of the decay. In the first phase, salts are introduced in the material and accumulate close to the evaporation surface, while in the second phase damage propagates because of repeated dissolution and crystallization cycles, induced by re-wetting with liquid water and by relative humidity changes. In this paper, the procedure is described and the results of a first round robin validation of the test, carried out on 7 materials and involving 10 laboratories, are presented. The results show that the procedure is effective to cause decay within the time period of the test (about 3 months) and that the decay increases with subsequent cycles. The decay observed differs in type and severity depending on the salt type and concentration and on the type of substrate. The decay types detected in the laboratories are generally representative of those observed in the field for the selected substrates. The differences in durability between the various substrates, as assessed at the end of the test, are in line with the durability expected based on field observation. The reproducibility of the results in terms of decay type is good; some differences have been observed in terms of material loss. These are more significant in the case of NaCl contaminated specimens. Based on the results, proposals for fine-tuning of the procedure are given.

@en

Adaptive reuse (AR) of heritage buildings is a complex process due to the involvement of many actions and actors, which influence the results of the projects. The effectiveness of AR projects can be described by various criteria. This paper aims to provide a comprehensive overview of the criteria of effectiveness in AR projects with the final scope to guide and improve the AR process. A review of the jury reports of two highly prestigious awards in the Netherlands (NRP Golden Phoenix award) and Europe (Europa Nostra) has been conducted. In total, the reports of 48 cases have been reviewed. The five criteria mentioned in the regulations of the NRP award have been used to categorize the aspects mentioned in the jury reports of both awards. These criteria are: “social value creation”, “sublimation (both architectural and cultural aspects)”, “environmental sustainability”, “economic value creation”, and “innovation”. This review reveals that “social value creation” and “sublimation” are among the most highlighted criteria that the juries considered for the effectiveness of AR projects. Often aspects mentioned for these criteria overlap partially with those aspects mentioned in the criterion of “economic value creation”. This indicates that enhancement of the qualities of heritage buildings and their surroundings and improvement of the social values and the resulting positive economic effects are strictly interrelated. The overview of the criteria of effectiveness, as defined in this work, will serve as a basis for the investigation of the tools and methods which can be used in the AR process to achieve these criteria@en

The Adaptive Reuse (AR) of heritage buildings is a complex process, which aims to preserve the values of heritage buildings while adapting them for use in the present and transferring them to the future. This paper aims to identify steps in this process and develop a structured model. The model is an ‘ideal’, it needs validation in practice; however, it is expected that following this model can help to preserve and conserve the values of heritage buildings. To come to an overview of the process and to identify its main steps, a literature review at an international level has been conducted. The analysis of the literature revealed that the AR process as a whole in relation to heritage buildings has not been widely studied. Based on the results of this review, a conceptual model representing the AR process of heritage buildings has been defined. This model consists of 10 steps: ‘initiative’, ‘analysis of heritage buildings’, ‘value assessment, ‘mapping level of significance’, ‘definition of adaptive reuse potential’, ‘definition of design strategy’, ‘final decision-making’, ‘execution’, ‘maintenance’, and ‘evaluation after years’. This model can act as a comprehensive theoretical basis for further studies on the AR process of heritage buildings.@en