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Digital fabrication methods with concrete have been rapidly developing, with many problems related to component production and material control being solved in recent years. These processes produce inherently layered cementitious components that are anisotropic, and in many cases, produces a weak interface between layers, which are generally referred to as cold joints. While material strength at these interfaces has been well studied in recent years, durability has received less attention, even though cold joints can function as channels for aggressive agents, such as chlorides. This work presents a method using micro-X-ray fluorescence (μXRF) to image chloride ingress into layer interfaces of 3D printed fine-grained concrete specimens produced with varying layer deposition time intervals, and also compares it to neutron imaging of moisture uptake. The results show that cold joints formed after a 1 day time interval are highly susceptible to chloride ingress, and that curing conditions play a major role in how quickly interfacial transport can take place. The μXRF method is also shown to be useful for study of transport of chlorides in cold joints, due to its spatial resolution and direct analysis of an aggressive species of interest., Materials and Structures, 56 (3), ISSN:1359-5997, ISSN:0025-5432, ISSN:1871-6873

The recent interest in 3D printing with concrete has generated great interest on how inhomogeneities arise and affect performance parameters, in particular strength and durability. With respect to durability, of particular interest is how 3D-printed layer interfaces can impact transport of species of interest, such as moisture, chlorides or carbon dioxide in carbonation processes. This is of particular interest considering that the primary use case of 3D-printed concrete has been as a lost formwork for a cast structural concrete, and thus it is of interest to determine the carbonation resistance. This study consists of a preliminary look at the microstructure after accelerated carbonation of a 3D-printed concrete used as a lost formwork. Preferential carbonation is observed in the layer interfaces compared to the bulk of the printed filaments, possibly related to porosity from air voids or a locally high capillary porosity corresponding to the lubrication layer.The new technology of 3D printing with concrete has been making a lot of headlines recently due to its great potential to make construction safer, cheaper and faster. It also allows us to make buildings and infrastructure objects that are more materially efficient, meaning that they use much less concrete compared to a more standard construction, so they are less environmentally harmful. However, this is all assuming that the printed concrete will perform similar to normal concrete. A lot of attention has been paid to whether the printed concrete is as strong as normal concrete, however not so much attention has been paid to if the printed concrete is as durable as normal concrete. The aim of this study is to make a first look at this, using the microscope. When we speak of concrete durability, we typically mean the protection of the steel reinforcement in the concrete, which acts to take up tensile stresses that may arise. Concrete acts as a protective barrier to this steel from corrosion, but aggressive species can go through this barrier to attack the steel. One of these aggressive species is carbon dioxide, which acts to reduce the pH around the reinforcement and results in its corrosion. Printed concrete, made in a layer-by-layer process, has many interfaces between these layers where the connection is potentially not as dense as in normal concrete. This study shows that these layer interfaces essentially can serve as highways for carbon dioxide to enter the concrete and attack the reinforcement. This means that any new 3D-printed structures need to take this into account, if the printed concrete is expected to serve as any kind of a protective barrier. We caution the reader that this study is purely observational, however, and a more in-depth study where we can actually make predictions about the printed concrete should be carried out.

While digital fabrication technologies with concrete have focused primarily on process development and compressive strength in terms of performance, more recently studies evaluating the durability performance of 3D printed cementitious materials have started to appear. To date, however, no field performance assessments have been published regarding 3D printed cementitious materials. In this study, we present the condition of bespoke 3D printed columns that have been exposed to the high alpine environment of Riom-Parsonz, Switzerland, for a period of two years. Damage levels are variable from column to column, often appearing as vertically oriented cracks that can also track along weak layer interfaces. The damage is conjectured to be linked primarily to freeze-thaw damage and/or thermal or differential shrinkage strains. The link between column design and damage is discussed in depth, in particular as it relates to the current predominant use case of 3D printed cementitious materials as a lost formwork. ISSN:2211-0844

Digital fabrication with concrete has been touted as an avenue to more sustainable construction through more material efficient design, but notably has produced materials with higher carbon footprints and a strong likelihood of reduced durability compared to standard construction. In this short article, a relationship to give a sense of the environmental impact of a structure is introduced, and it is emphasized that shape efficiency is the only unique environmental benefit that digital concrete brings. However, efforts should still continue to bring digital concrete more in line with standard concrete, especially through incorporation of large aggregates and better characterizing the durability. Finally, it is shown that while most 3D printed concretes appear to be overdesigned due to processing requirements, the use of aluminum based accelerators in a 2K system can be beneficial in decoupling buildability from structural strength, allowing greater freedom to lower carbon footprints in mix design., Cement and Concrete Research, 158, ISSN:0008-8846

The issue of reinforcement remains a difficult one for digital fabrication in concrete construction, with many solutions offered on how to best incorporate it with the technology in a practical manner. While certain technologies, such as digital casting systems, allow more seamless introduction of traditional steel reinforcement bars, the dominant technology of extrusion-based 3D printing still shows great limitations, with the most typical application being that of a lost formwork for traditionally cast concrete, or as unreinforced masonry. The use of both conventional and unconventional reinforcement materials, and their incorporation into processes, is a large and active area of research with the digital concrete community. In this work, we present a 3D printing platform and manufacturing concept in which a 3D printed form serves as a vertical substrate for a reinforcement, either textile or conventional steel. The structural concrete is then either applied by hand or sprayed around the reinforcement. ISSN:2211-0844

Digital fabrication with concrete is considered to potentially revolutionize the construction sector and is often presented as a means to reduce its environmental footprint. However, at least in the case of concrete, it encounters significant challenges in terms of material design, since high paste volumes and Portland cement contents are normally used due to process requirements. In this article, the application to layered extrusion of a recently developed low clinker cement containing 50% Portland cement and 50% supplementary cementitious materials, such as limestone, burnt oil shale, and fly ash, is presented. It is found that an accelerator paste composed by Calcium Aluminate Cement (CAC) and anhydrite provides the required hydration and structural build-up for 3D printing, while not compromising the early and long-term compressive strength. Such a low clinker mortar can be successfully retarded, processed, pumped, and extruded just after mixing it in line with the accelerator paste. This accelerated mortar formulation contains only 303 kg/m(3) of Portland cement, which is roughly half the amount used in current accelerated formulations used for digital fabrication with concrete. ISSN:2329-7662 ISSN:2329-7670

Digital concrete processes are a series of unit operations, similar to a chemical engineering process, each subject to their own rheological and other performance requirements, such as homogeneity, etc. In this article we examine the concrete extrusion 3D-printing process from this standpoint, first decomposing it into individual unit operations. We examine the role that residence time distributions play in the overall process, and then analyze how large scale printing to structural heights could be performed continuously. We then focus on the critical step of secondary (inline) mixing just before extrusion from the standpoint of mixing processes in the chemical processing industries. This unit operation is then analyzed in the context of scaleup to larger print areas and larger flowrates, finding that increase in viscosity plays a major role in power requirements and printhead mass. Further research questions are then raised based on these analyses., Cement and Concrete Research, 155, ISSN:0008-8846

The pursuit for complex geometries in contemporary architecture is driving innovation towards an unconstrained fabrication freedom for building components. Concrete is a building material with excellent structural and architectural qualities, which has the theoretical capacity of being cast into any shape. However, in practice, concrete is generally limited by the formwork manufacturing industry to solid, planar shapes. The aim of this research is to overcome the fabrication limitations for formwork and, indirectly, for concrete. To achieve this aim, the objective of this research is twofold: a) enable the fabrication of building-scale concrete components through 3D-printed plastic formworks and b) develop computational design and optimisation methods suitable for this fabrication method. The resulting design and construction method takes advantage of the load-bearing capacity of concrete and relies on the fabrication freedom inherited from the 3D-printed formwork, thus making complex topologies and precise details possible for concrete structures. The research method for demonstrating this fabrication process focused on the design to fabrication steps of skelETHon a functional four-meter-long concrete canoe which was designed, built and raced in a regatta on the Rhine river (Figure 1). The main research achievement was the fabrication of the canoe, an optimised truss-like concrete component with members as thin as 15 mm in diameter. Such slender geometric features are difficult to produce in concrete with other known formwork systems., Gestão & Tecnologia de Projetos, 14 (1), ISSN:1981-1543

Digital Fabrication with Concrete (DFC) encompasses 3D Concrete Printing (3DCP) and many other methods of production. DFC is emerging from an era of invention and demonstration to one where the merits of one principle over another needs to be quantified systematically. DFC technologies vary in characteristics, complexity and maturity which hampers the synthesis of research and comparisons of performance. The interdependence of design geometry, material properties and process characteristics is well recognised. Materials research has made significant progress in recent years and there have been many applications with varying design geometries demonstrated. Far less has been done to guide the definition and description of the processes used. This work takes a step forward by presenting classification and process description guidance for DFC. The approach was developed by engaging a broad cross-section of the international community through the activities of the RILEM Technical Committee 276 between 2016 and 2020., Cement and Concrete Research, 134, ISSN:0008-8846

The characterization of swelling clays is important for diverse fields, including the field of conservation of built cultural heritage. Villarlod molasse, a building stone utilized frequently across Switzerland, is known to be damaged by swelling clays embedded in its matrix. In this study, the mechanism of how the clays lead to swelling in the stone itself is examined, and similar to previous studies, crystalline swelling is noted as the most likely source. A scaling factor linking X-ray diffraction (XRD) and dilatometric swelling experiments is calculated, and evidence for the existence of an initial monolayer of moisture in the embedded clays at ambient relative humidities is presented. A qualitative micromechanical model describing how the nonswelling stone matrix exerts a pressure on the clay layers, affecting their swelling behavior, is presented., Environmental Earth Sciences, 82 (11), ISSN:1866-6280, ISSN:1866-6299

Cement and Concrete Research, 132, ISSN:0008-8846

RILEM Bookseries, 28, ISSN:2211-0844, Second RILEM International Conference on Concrete and Digital Fabrication. Digital Concrete 2020, ISBN:978-3-030-49915-0, ISBN:978-3-030-49916-7

Digital concrete technologies aim to minimize or eliminate the need for formwork, produce less waste, and build material efficient designs at increased productivity. This paper discusses how Admixture Controlled Digital Casting (ACDC) could address these aims by producing thin folded structures. For the process, a set on demand concrete composition was used to achieve minimal deformations when robotically filling weakly supported formworks. The formworks were constructed from bendable materials such as foil, geotextile or paper tensed between a frame on top and bottom and could be reconfigured for different geometries. The prototypes were assembled and post-tensioned to achieve a one-to-one scale fully functional architectural roof element. With the demonstrator presented, ACDC challenges the way we think about casting and formworks in the construction industry at the age of the 4th industrial revolution.

The advent of digital fabrication for concrete calls for advancing our understanding of the entanglement of processing technology, rheology, admixture use and hydration control, in addition to developing novel measurement and control techniques. We provide an overview of recently proposed building processes, defining the type and range of yield stress evolution that they require for successful building. In doing so, we explain which mechanisms are at stake and how their consequences can be measured. Controlling the structural build-up of concrete with the precision required by digital processes will be at the heart of future progress. For this, chemically controlling cement hydration of concrete is essential and we provide an overview of admixtures, focusing on “set on demand” solutions, concluding that activators should be added as closely to the delivery point as possible. Advantages and limitations are discussed and showcased using recent successes in process scaling and material and process control.

One of the principal reasons for premature deterioration in reinforced concrete is chloride-induced corrosion. In materials such as stone, or earthen materials, salt crystallization plays a significant damaging role, and chloride distribution is an important factor. The reliable quantification of chlorides can therefore provide fundamental insights into their behaviour in such materials, particularly in concrete. One of the most widely used techniques for chloride quantification in concrete includes a destructive sample preparation for either titration (powder dissolved in nitric acid) or XRF (powder fused into pellets). However, in order to obtain a quantitative mapping of chlorides, a more effective approach with a higher spatial resolution is essential. We present here a new method with a (semi) non-destructive approach, whose limits of quantification are suitable for fundamental studies of the behaviour of chlorides in concrete. This work also emphasizes the standard and sample preparation, an aspect often overlooked by other authors. The achieved levels of trueness are comparable to those indicated by the international standard organization procedure for cement chemical analysis with XRF.

Salt-induced stone weathering is often erroneously listed among the physical causes of damage when it is in fact physicochemical. We introduce here a succinct version of the theory behind crystallization pressure along with a simple yet dramatic demonstration of the damage induced in sandstone by sodium sulfate. The contents here presented might be implemented in chemistry for cultural heritage, conservation science, geosciences, and materials science undergraduate courses.

Digital fabrication represents innovative, computer-controlled processes and technologies with the potential to expand the boundaries of conventional construction. Their use in construction is currently restricted to complex and iconic structures, but the growth potential is large. This paper aims to investigate the environmental opportunities of digital fabrication methods, particularly when applied to complex concrete geometries. A case study of a novel robotic additive process that is applied to a wall structure is evaluated with the Life Cycle Assessment (LCA) method. The results of the assessment demonstrate that digital fabrication provides environmental benefits when applied to complex structures. The results also confirm that additional complexity is achieved through digital fabrication without additional environmental costs. This study provides a quantitative argument to position digital fabrication at the beginning of a new era, which is often called the Digital Age in many other disciplines.

Digital fabrication techniques with concrete and cementitious materials have seen a large amount of research and industrial activity recently, with industrialization of techniques such as 3D printing becoming more of a reality. The potential to revolutionize construction is real, not only through reducing costs, but also bringing more sustainability and increased functionality. Material challenges are significant, chief among them understanding and controlling early age hydration and the link to rheology, incorporation of reinforcement, and overall, the link between processing, material, and performance, both from a structural and durability point of view. Interdisciplinarity is crucial, as the field brings together many disparate fields and has been driven by fields such as architecture so far. This article is a review of the state of the art in the newly forming field of digital fabrication with concrete, and aims to provide some direction in terms of the research challenges encountered thus far.

Digital fabrication with concrete introduces new challenges in terms of continuous processing of concrete. To enable increased vertical building rates, accelerators are dosed at a nozzle reactor unit directly before placement in many of these processes. The details of this mixing process have large implications for the behavior of the system and the success of the process. The measurement of residence time distribution (RTD) is a potentially useful tool in understanding these processes and diagnosing pathological behavior of reactors. In this study, the RTD of the Smart Dynamic Casting (SDC) reactor is measured, and implications for this process and other digital fabrication processes are considered.

Additive manufacturing (AM) has had an enormous impact in the manufacturing sector. Its role has evolved from printing prototypes to manufacturing functional parts for a variety of applications in the automotive, aerospace, and medical industries. Recently, AM processes have also been applied in the infrastructure construction industry. Applications of AM processes could bring in significant improvements in infrastructure construction, specifically in the areas of productivity and safety. It is desirable to have a review on the current state of emerging AM processes for infrastructure construction as well as existing gaps in this field. This paper reviews AM processes in infrastructure construction. It discusses the process principle, application examples, and gaps for each of the AM processes.

Recent developments in computational design and digital fabrication with concrete enable the realization of freeform geometries that optimize material use. 3D Concrete extrusion Printing (3DCP) is presently one of the most utilized digital fabrication methods with concrete. The expected advantages of 3DCP result from shaping concrete without formwork and from placing material only where functionally required. Although these advantages were pointed out more than 20 years ago, it is difficult to find competitive examples and their usage in real buildings. Consequently, the nonspecific character of the process acts as a shortcoming by opening up extensive possibilities without a clear direction. This paper proposes an automated 3DCP prefabrication platform for customized columns. The process-specific parameters are, therefore, fine-tuned for high-quality products with diverse forms and textures. Additionally, this paper proposes an evaluation method for geometric complexity and identifies the types of column typologies that may benefit from a 3DCP prefabrication platform., Automation in Construction, 122, ISSN:0926-5805

Over the past decade innovative techniques for shaping concrete have emerged, all aiming to use less material and reduce the need for traditional formwork. One very promising method is to shape concrete dynamically: referred to as Smart Dynamic Casting (SDC), this process was pioneered in 2012 as the first robotically-driven system for slipforming bespoke concrete structures. The process has successfully been adapted to produce structures using ultra-thin formworks that are cast using our digital set-on-demand procedure. More generally we frame this approach as Digital Casting Systems (DCS), which allows the user precisely to determine the hydration rate of the material, thus eliminating formwork pressure. This paper highlights the major findings from SDC that led us to continue developing DCS. It lays out the material concepts fundamental the family of DCS, which, by eliminating the need for bulky formworks, has a large potential impact on future construction methods.

Concrete is a highly versatile construction material, not only for the reason that it has excellent properties in terms of structural performance, building physics, availability and price, but also because it can be moulded into virtually any shape regardless of its geometric complexity. However, even though current digital design tools allow to effortlessly design and calculate structures, which are exploiting these properties, this potential remains all too often unrealized. This is due to the fact that geometrically complex concrete structures require expensive, one-of-a kind formwork, which can often not be reused or even recycled. Consequently, the current practice for producing non-standard curvilinear architecture in reinforced concrete is neither ecologically sustainable nor economically feasible for a broader range of architectural typologies. Additive Manufacturing (AM) processes, like 3D printing with concrete, on the other hand, currently struggle with the integration of structural reinforcement, limiting the technique to predominantly compression-loaded applications. This research addresses both issues and proposes Mesh Mould, a robotic fabrication process that unifies concrete formwork and structural reinforcement, and hence potentially reduces formwork waste and construction costs for non-standard reinforced concrete constructions. The development of a fully automated robotic fabrication process involved various research disciplines, including architecture, material science, mechanical engineering, robotics as well as civil engineering. This paper describes the technological developments of the Mesh Mould construction system that were necessary to meet the challenges of 1:1 construction. The results are demonstrated in a final loadbearing structure, the Mesh Mould wall of the DFAB HOUSE on NEST.

RILEM Bookseries, 19, ISSN:2211-0844, ISBN:978-3-319-99518-2, ISBN:978-3-319-99519-9

This study presents five different lithotypes of limestone containing stylolites and commonly used as dimension stones in Egypt, Hungary and Israel. All the studied limestones are generally hard, dense, with high degree of cementation and have high strength and low porosity. Stylolites are small tooth-like irregular surfaces most often developed on the carbonate-rich stones. Insoluble particles, i.e., organic matter, oxides and clays are usually incorporated within the stylolitic planes. The presence of stylolites and their filling materials generally has a large effect on the physical and mechanical properties of the host stones. The main aim of this study is to evaluate the damage mechanism of different stylolitic limestones and to understand the role of the clay in the deterioration of these stones. Hundred cube samples (2 cm) of all the studied limestones were subjected to 500 thermal cycles (10–70 °C) and 20 cube samples (3 cm) of a grey Israeli limestone with high open porosity were subjected to multiple wet/dry cycles. The changes in mass, strength, and ultrasound Vp velocity, were measured to follow any damage that happened due to cycling. The thermal cycling was proved to be an effective deterioration mechanism of both Egyptian and Hungarian lithotypes. The response of Israel grey lithotype to the wet/dry cycling was clearly shown by the splitting of the tested samples through the stylolite planes and the sharp decrease of their strength.

Blucher Design Proceedings, 3 (12), Proceedings of the 21st Congreso Internacional de la Sociedad Iberoamericana de Gráfica Digital

The buildings of the Malecon, the historical section of Havana along the coastline, suffer accelerated degradation due to the aggressive environment. The primary damage mechanism at play is the crystallization of sodium chloride at repair mortar interfaces, as shown in petrographic and SEM analysis. This preferential precipitation leads to crystallization pressures that reduce the adherence of the lime based mortars from the substrate. Environmental monitoring shows that the daily relative humidity fluctuates around the deliquescence point of sodium chloride, exacerbating the problem through continual cycles of dissolution and recrystallization. The potential for an alternative repair material such as limestone calcined clay cement based mortar is discussed.

Biocides are included in organic building façade coatings as protection against biological attack by algae and fungi but have the potential to enter the environment via leaching into runoff from wind driven rain. The following field study correlates wind driven rain to runoff and measured the release of several commonly used organic biocides (terbutryn, Irgarol 1051, diuron, isoproturon, OIT, DCOIT) in organic façade coatings from four coating systems. During one year of exposure of a west oriented model house façade in the Zurich, Switzerland area, an average of 62.7 L/m(2), or 6.3% of annual precipitation came off the four façade panels installed as runoff. The ISO method for calculating wind driven rain loads is adapted to predict runoff and can be used in the calculation of emissions in the field. Biocide concentrations tend to be higher in the early lifetime of the coatings and then reach fairly consistent levels later, generally ranging on the order of mg/L or hundreds of μg/L. On the basis of the amount remaining in the film after exposure, the occurrence of transformation products, and the calculated amounts in the leachate, degradation plays a significant role in the overall mass balance.

Many historically and culturally significant buildings have sandstones that contain swelling clay inclusions in the binding phase. Differential strains that evolve during wetting and drying cycles can generate stresses that are on the order of the strength of the stone, leading to degradation. Most damage observed in the field is surface delamination and buckling of the stone over a flaw, indicating that the damage is occurring during wetting. Classical buckling theory predicts buckling to occur at a particular aspect ratio, or flaw size. The results of this study confirm buckling theory experimentally. Through finite-element simulation and experiment, the study then explores a potential flaw propagation mechanism whereby nonuniform wetting patterns generate stress intensities capable of flaw propagation. As a result, small natural flaws can grow to the critical size necessary for buckling.

Many clay-bearing sedimentary stones such as Portland Brownstone will swell when exposed to water, and this can generate damaging stresses as differential strains evolve during a wetting cycle. Current swelling inhibitors, consisting of α,ω-diaminoalkanes, can reduce swelling in Portland Brownstone up to 50%. In this study, through x-ray diffraction and swelling strain experiments, we demonstrate that the α,ω-diaminoalkanes inhibit swelling by substituting for interlayer cations and partially hydrophobicizing the interlayer, then rehydrating on subsequent wetting cycles. We also introduce the copper (II) ethylenediamine complex as a potential treatment for swelling inhibition.

Swelling clays in stone can generate damaging stresses during a wetting or a drying cycle, which lead to deterioration of building stones such as Portland Brownstone. There are two primary types of swelling identified for clays: short-range, ordered intracrystalline swelling, and long-range, continuous osmotic swelling. Identification of the swelling mode is important for understanding and ultimately preventing swelling damage. Through comparison of XRD and swelling experiments with cationic pretreatments and organic solvents, we demonstrate that intracrystalline swelling is the primary mode of swelling present in three different stones, including Portland Brownstone. The results highlight the importance of the counterbalancing cation to the swelling process, and a method for characterizing the intracrystalline swelling in sandstones is developed. Finally, the implications of long-term swelling behavior for stones are discussed.

International audience; Clay minerals that swell when exposed to water play an important role in the deterioration of buildings and monuments, as well as in a number of civil engineering problems. A novel method for the in situ determination of the key properties governing these phenomena has been recently proposed by Scherer and Gonzalez [Geol. Soc. Am. Spec. Pap. 390 (2005) p.51]. A comprehensive relation between the experimental observations and the material properties could however not be established up to now. The present study develops an analytical model in which the interplay between geometrical factors and material properties, as well as initial and boundary conditions is accounted for. An extensive parametric study reveals that the discrepancies between the observations and the modelling approach by Scherer and Gonzalez is due to initial and boundary conditions on the one hand and the dispersion of the moisture front on the other hand. Based on the developed model, recommendations for performing in situ tests are formulated and conditions for the applicability of the more simplified modelling strategy by Scherer and Gonzalez are derived. A comparison with experimental data supports these conclusions.

Biocides are used in the building industry to prevent algal, bacterial and fungal growth on polymericrenders and thus to protect buildings. However, these biocides are leached into the environment. To better understand this leaching, the sorption/desorption of biocides in polymeric renders was assessed. In this study the desorption constants of cybutryn, carbendazim, iodocarb, isoproturon, diuron, dichloro-N-octylisothiazolinone and tebuconazole towards acrylate and silicone based renders were assessed at different pH values. At pH 9.5 (porewater) the constants for an acrylate based render varied between 8 (isoproturon) and 9634 (iodocarb) and 3750 (dichloro-N-octylisothiazolinone), respectively. The values changed drastically with pH value. The results for the silicone based renders were in a similar range and usually the compounds with high sorption constants for one polymer also had high values for the other polymer. Comparison of the octanol water partitioning constants (Kow) with the render/water partitioning constants (Kd) revealed similarities, but no strong correlation. Adding higher amounts of polymer to the render material changed the equilibria for dichloro-N-octylisothiazolinone, tebuconazole, cybutryn, carbendazim but not for isoproturon and diuron.

Organic architectural coatings require the use of biocides to prevent microbial defacement of building facades. The biocides are meant to slowly release to the surface, but they can still potentially enter the environment via runoff during rain events. Accurate source emissions estimates are necessary for risk assessments, and knowledge of the release mechanism can aid both regulators and producers alike. In this study, several biocides and several market and reference coating systems were subjected to regular irrigation and drying cycles with varying temperature conditions. The results were compared to other studies and models from the controlled release literature, demonstrating diffusion controlled release with dependence on the experimental conditions. The role of wetting and drying cycles in accelerating release is highlighted.

Many sedimentary rocks contain clays that swell on exposure to moisture, producing stresses from differential strain. Wendler and Snethlage showed that the swelling can be reduced by treatment with α−ω diamino alkanes. In this paper, we present results showing that mixtures of such molecules are more effective than any single molecule, and that better results are obtained by applying smaller molecules before the larger ones.

Many clay-bearing sedimentary stones such as Portland Brownstone will swell when exposed to water, and this can generate damaging stresses as differential strains evolve during a wetting cycle. Current swelling inhibitors, consisting of α,ω-diaminoalkanes, can reduce swelling in Portland Brownstone up to 50%. In this study, through X-ray diffraction and swelling strain experiments, we demonstrate that the α,ω-diaminoalkanes inhibit swelling by substituting for interlayer cations and partially hydrophobicizing the interlayer, then rehydrating on subsequent wetting cycles. We also introduce the copper (II) ethylenediamine complex as a potential treatment for swelling inhibition.