Karsten Tube Research Articles

Karsten tube analysis for joint mortar identification in masonry

The present work examines the Karsten tube penetration test to identify mortar types in existing masonry, for mortars containing air-lime or hydraulic binders. Mortar type identification is e.g. of relevance for the reusability of the fired clay bricks in the masonry, where a hydraulic binder content makes the mortar removal process significantly more difficult. The Karsten tube test makes it possible to make a simple and non-destructive mortar analysis on-site assessing the water absorption of the mortar, via the surface of the mortar joint alone. The present approach considers both the effect of the surrounding bricks and the surface finish of the pointing. Furthermore, the setup masks the brick surface exposed under the Karsten tube to focus the exposure on the mortar. Three different mortar types in existing masonry were tested: air-lime mortar, air-lime/hydraulic lime mortar and air-lime/cement mortar. The results showed linear water absorptions, which were clearly distinguishable for the hydraulic and non-hydraulic binders during the 15-minute tests. The measurement results in the present work document how the Karsten tube penetration test can be used for simple and non-destructive identification of joint mortar types determining whether the masonry was constructed with air-lime mortar or mortar containing hydraulic binders.

Study of the hygroscopic properties of environmentally friendly lightened composites through waste recovery

Gypsum-plaster is becoming an ideal binder in the valorisation and recovery of waste for designing more sustainable composites. Nevetheless, the main limitation of plaster lies in its susceptibility to the action of water. In this research, a complete study of the hygroscopic properties of a new material has been carried out, in which plaster material has been partially substituted in mass by dissolved expanded polystyrene waste in percentages of 8.8% to 26.5%. Additionally, fibres from end-of-life tyres have been incorporated at 1.2% by mass to improve the strength and durability of the compounds, achieving a total reduction of up to 28% of the original raw materials. The experimental campaign delves into the water performance of this new plaster composites through mercury porosimetry tests, water absorption by capillarity, total water absorption, water vapour permeability, Karsten Tube penetration, water-stove cycles, as well as the analysis of images obtained by scanning electron microscopy. The main results obtained show a reduction of 97.8% in surface water absorption, as well as a decrease of up to 17.44% in water vapour permeability compared to traditional plaster. Moreover, the developed materials exhibit good mechanical behaviour after undergoing several accelerated ageing cycles. This work highlights the potential of the new plaster composites designed to produce a more sustainable alternative to commercial prefabricated boards and panels, especially suitable for use in interior rooms where high resistance to the action of water is required.

Innovative approach for the protection of recycled concrete by biogenic silica biodeposition

Over the past few years, the construction industry has sought to be more sustainable through use of more economically responsible materials and the use of environmentally friendly techniques such as bio-remediation. One promising area in this regard is that of surface treatments, particularly bio-repair techniques, to reduce the deterioration suffered by cement-based materials as a result of environmental conditions. This study presents original work on the use of silicaceous biodeposition by diatoms as a waterproofing surface treatment for recycled concrete. A recycled concrete mix containing a 50% substitution of recycled aggregates (RA) was used as a test substrate and the effectiveness of the bio-treatment was assessed using four different tests: capillary absorption, high-pressure water penetration, low-pressure water absorption and also characterised the biodeposited layer using SEM. Results demonstrate reductions of up to 33% in the capillary absorption test, while high-pressure water penetration decreased by 54.7%, compared to controls. In addition, Karsten tube tests showed low-pressure water absorption was delayed by up to 436 times relative to control samples. In combination these tests confirm the efficacy of diatom biodeposition as a protective surface treatment for cement-based construction materials.

Influence of brick and concrete substrates on the performance of renders using in-situ testing techniques

The real performance of renders is influenced by several in-service factors. To analyze this influence two types of mortars - a traditional mortar (1:4 cement:sand in volume) and an industrial one-coat mortar - were applied on ceramic and concrete substrates, whose surface has been previously treated in three different ways: i) without moisture; ii) with double spraying of water, iii) with water immersion for 4 h. Through in-situ testing techniques (ultrasound, pendulum sclerometer and Karsten tube) at 28 and 90 days of age it was possible to discuss how the substrate and its suction influence the experimental results. When evaluating the performance over this period, it was possible to conclude that the applied mortars improved, in general, their mechanical behavior. In terms of preparation of the substrate, a double spray of water on the substrate surface achieved the best performance for both substrates. With the testing techniques it was found that the substrate and its suction had a significant influence on the performance of the applied mortars.

Durability of the hydrophobic treatment on brick and mortar

Hydrophobization lessens the water absorption by facade materials and is thus presumed to reduce moisture problems in internally insulated facades. However, to do this it should retain the water repellency performance throughout aging. The aim of this study is to evaluate the impact of aging on the durability of the hydrophobic treatment on bricks and mortars. The resulting absorption coefficient, after 635 repeating artificial aging cycles of alternating UV radiation (102 min) and water exposure (18 min) reveals that the hydrophobic layer maintains its water repellency performance both in brick and mortar. The samples were treated with two different water repellent agents in different concentrations and tested for capillary water uptake. Additionally, the findings show that cycles of weathering could contribute positively to further reduction of the absorption coefficient of hydrophobized brick and mortar samples. Subsequently, Karsten tube tests on samples from artificial aging illustrate the same water repellency performance as mock-up walls exposed to ambient conditions, six years after being hydrophobized. Contact angle measurements before and after artificial aging reveal that the beading effect declines through aging. However, the beading effect seems to be just a surface effect affected by UV-light. Moreover, after aging, hydrophobized brick and mortar samples, tested by visual inspection, maintain their appearance while untreated samples show signs of efflorescence. In total, these findings indicate that the water uptake of hydrophobized brick or mortar remains very low after aging including water spraying and UV light.

Use of Bioproducts Derived from Mixed Microbial Cultures Grown with Crude Glycerol to Protect Recycled Concrete Surfaces.

The large increase in the world population has resulted in a very large amount of construction waste, as well as a large amount of waste glycerol from transesterification reactions of acyl glycerides from oils and fats, in particular from the production of biodiesel. Only a limited percentage of these two residues are recycled, which generates a large management problem worldwide. For that reason, in this study, we used crude glycerol as a carbon source to cultivate polyhydroxyalkanoates (PHA)-producing mixed microbial cultures (MMC). Two bioproducts derived from these cultures were applied on the surface of concrete with recycled aggregate to create a protective layer. To evaluate the effect of the treatments, tests of water absorption by capillarity and under low pressure with Karsten tubes were performed. Furthermore, SEM-EDS analysis showed the physical barrier caused by biotreatments that produced a reduction on capillarity water absorption of up to 20% and improved the impermeability of recycled concrete against the penetration of water under pressure up to 2.7 times relative to the reference. Therefore, this bioproduct shown to be a promising treatment to protect against penetration of water to concrete surfaces increasing its durability and useful life.

Architectural ruins: geoculture of the anatomy of buildings as illustrated by Casa Ippolito, Malta

Ruins are a statement on the building materials used and the construction method employed. Casa Ippolito, now in ruins, is typical of 17th-century Maltese aristocratic country residences. It represents an illustration of secondary or anthropogenic geodiversity. This paper scrutinises these ruins as a primary source in reconstructing the building’s architecture. The methodology involved on-site geographical surveying, including visual inspection and non-invasive tests, a geological survey of the local lithostratigraphy, and examination of notarial deeds and secondary sources to support findings about the building’s history as read from its ruins. An unmanned aerial vehicle was used to digitally record the parlous state of the architectural structure and karsten tubes were used to quantify the surface porosity of the limestone. The results are expressed from four perspectives. The anatomy of Casa Ippolito, as revealed in its ruins, provides a cross-section of its building history and shows two distinct phases in its construction. The tissue of Casa Ippolito—the building elements and materials—speaks of the knowledge of raw materials and their properties among the builders who worked on both phases. The architectural history of Casa Ippolito reveals how it supported its inhabitants’ wellbeing in terms of shelter, water and food. Finally, the ruins in their present state bring to the fore the site’s potential for cultural tourism. This case study aims to show that such ruins are not just geocultural remains of historical built fabric. They are open wounds in the built structure; they underpin the anatomy of the building and support insights into its former dynamics. Ruins offer an essay in material culture and building physics. Architectural ruins of masonry structures are anthropogenic discourse rendered in stone which facilitate not only the reconstruction of spaces but also places for human users; they are a statement on the wellbeing of humanity throughout history.

Evaluation of in-service performance factors of renders based on in-situ testing techniques

In order to contribute to the knowledge about the influence of several factors on the in-service performance of renders, as well as about the applicability of in-situ testing techniques in the evaluation of their performance, an experimental work was carried. In this work, the influence of some factors (type of substrate, number and thickness of mortar layers) on the mechanical and physical performance of two mortars (site-made and industrial) was evaluated, using the following in-situ testing techniques: pendulum rebound hammer test (with two types of rebound hammer), ultrasonic pulse velocity test (with two types of device) and water absorption under low pressure test (with Karsten tubes). It was possible to verify that the above-mentioned factors influence the performance of the mortars. The in-situ testing techniques were, in general, able to identify differences in the behaviour of renders due to these factors. However, for the same technique, different devices sometimes led to distinct results. Nevertheless, the combination of the results of different techniques helped to reduce the uncertainty of the analysis.

Effectiveness of the anti-erosion of an MICP coating on the surfaces of ancient clay roof tiles

Rain erosion is one of the most important factors causing the weathering of ancient clay roof tiles. Weathering damage generally proceeds from the surface to the interior; thus, protecting tile surfaces is an effective method to resist weathering. In this study, the microbially induced carbonate precipitation (MICP) technique is used to form an anti-erosion layer on the surfaces of tiles. Next, the applicability of MICP for tile surface erosion control is examined in the laboratory by the static contact angle test, capillary water absorption test, Karsten tube test, durability test, acid resistance test, water vapour permeability (WVP) test and colour change test. Moreover, the effect of the concentration of bacteria and cementation reagent on the surface erosion control is analysed. The test results show that MICP can significantly improve the water resistance of tiles by changing the microstructure of the surface. Higher concentrations of bacteria and cementation reagent allow the sediment layer to provide better protection; however, this effect is not linear. The concentration threshold reduces the positive effect of the bacterial concentration on the water resistance of the sample surface. The MICP protection layer offers favourable durability with little negative impact on the air permeability and colour of the sample. The use of an MICP protection layer can effectively relieve the weathering of ancient clay roof tiles.

A new formulation of the protective coating for historical monuments

Historic buildings are more closely tied to the ground than modern buildings. They are more porous, take water from the ground, transport it through their structure and evacuate it, generating side effects such as oxidation and crumbling. Walls and floors are the point of exchange for these reactions. An increase in the soil moisture could lead to a greater circulation of dissolved salts, and therefore to a harmful crystallization on the decorated surfaces but also to a greater instability of the soil. Our objective in this work is the choice of a plaster coating to limit damage due to climatic factors and mainly humidity. We are characterized the coating compositions firstly, and then proposed plaster based formulations. The choice of the best plank may be made by carrying out Karsten tube penetration and capillary absorption tests.

Variability of in-situ testing in wall coating systems - Karsten tube and moisture meter techniques

To meet customers' demand and adequate levels of satisfaction, there are various reasons for the need of proactive maintenance and knowledge about in-service performance of building façades. From this perspective, performing inspections depends on the in-service appraisal's reliability and the presence of monitored and measured parameters along the life cycle under real exposure conditions. Water, the major in-service deterioration agent, has different origins and transport mechanisms through façades, including wind-driven rain, ground moisture, and wetting/drying of surfaces, resulting in various chemical and/or physical-pathological phenomena. Thus, water resistance is considered highly relevant due to its significant influence on the durability of coating systems. This study presents results of an investigation concerning the water resistance of in-service wall coating systems, focusing on conventional and industrial renders and adapting appropriate techniques for field analyses, namely Karsten tube and moisture meter. In-service parameters (water absorption under low pressure and surface moisture) are assessed, and the techniques' sensitivity is analysed considering exposure and inspection conditions, roughness, coating and finishing types, and existing anomalies. The capacity of these techniques to monitor in-service performance is also discussed, and in-service performance criteria are proposed.

Non-destructive mechanical and physical in-situ testing of rendered walls under natural exposure

Building façades are significantly influenced by the wall renders’ performance, since they are the first protection layer against degradation agents. During their service life, façades undergo a continuous performance reduction until they are unable to meet their demanded functions, such as protecting and waterproofing the façade. Therefore, the application of in-situ testing has great importance to evaluate in-service performance of wall renders under natural conditions. This study focuses on testing the physical and mechanical behaviour of rendered façades, taking into account different render colourings and roughness and natural exposure conditions according to the wall orientation. Physical (Karsten tube and moisture meter) and mechanical in-situ tests (pendulum rebound hammer and ultrasound pulse velocity) were performed on eight walls at a natural ageing station. The in-situ tests were used to detect the factors affecting the results of these techniques, and the evolution of the rendered walls’ performance over time was investigated. The relationships between the testing techniques were also assessed.

Alkali activated clay mortars with different activators

Abstract The purpose of this study was to develop alkali activated earthen materials with enhanced physical and mechanical properties. Specifically, clay mortars were produced, by using various alkaline activators of different pH (values 11–14). The specimens were cured in certain conditions. The physical and mechanical properties of the mortars manufactured were measured at the age of 28 days. Specifically, capillary absorption, shrinkage, Karsten tube penetration, porosity, as well as compressive and flexural strength tests were performed. Additionally, microscopic analysis was also conducted. The results of the experiments indicated the positive effect of potassium metasilicate and the combination of sodium metasilicate with sodium hydroxide solution on mechanical characteristics. The influence of sodium carbonate as an alkali activator was also proven beneficial on the physical properties of the specimens. In conclusion, the alkaline activators with pH > 12, lacked in enhancing physical properties, yet allowed the development of mechanical strength, while the alkaline activators with lower pH values showed reversed results.

Use of Oils for the Protection of Clay Mortars

In this study an effort has been made to find innovative and sustainable ways of increasing the hydrophobicity of clay-based mortars used in restoration by applying natural oils on the surface of selected samples. The concept was to find a new way of protecting the surface of these materials, but also to promote the idea of sustainability by using natural and recycled cooking oils. Thus, the oils applied for the surface protec­tion of the mortars were hemp oil, borage oil (natural) and recycled spent cooking oil. The tests conducted on the treated specimens were, a capillary absorption test, drying test, porosity, Karsten tube test, stereoscopic observation, color alteration using Mun­sell charts, water vapor test and absorption of water droplet test. The results indicate the protective role of all the oils, since they reduce porosity and water uptake. Borage and hemp oil tend to alter the color of the specimens, but offer increased hydropho­bicity, while the latter allowed the faster drying of the samples. The water vapor test indicates again the low level of water loss from the surface of the treated specimens, while for the specific test a sample with an admixture of recycled cooking oil inside the clay mass was created.

Avaliação da eficácia de hidrofugantes e antigraffiti no Arenito Itararé

No patrimônio pétreo, a rocha está exposta aos efeitos do intemperismo. Para postergar esse processo, existem produtos de tratamento e proteção, os quais devem ser testados e aprovados, pois podem danificar mais o patrimônio do que o próprio intemperismo se os produtos não forem compatíveis com a rocha. O Theatro Municipal de São Paulo, uma importante edificação do Centro Velho da cidade de São Paulo, possui o Arenito Itararé em sua fachada frontal. Essa é uma rocha muito frágil devido à presença de esmectita em sua composição. Esse mineral se degrada muito facilmente em presença de água. Visando estudar um meio de proteger essa rocha contra a ação da água, dois hidrofugantes (siloxano — H1 — e propil siliconato oligomérico — H2) foram testados. Outro problema que atinge os centros urbanos é o vandalismo por graffiti/pichação. Como essa é uma rocha porosa, a limpeza desse tipo de ação não é totalmente efetiva e os produtos utilizados deixam resíduos que prejudicam a durabilidade da pedra. Para proteger a rocha da pichação, também foi testado um antigraffiti (AG). Para avaliar a eficiência desses produtos, foram realizados ensaios de capilaridade, tubo de Karsten, medida do ângulo de contato, microscopia eletrônica de varredura, porosimetria de mercúrio, ciclos de saturação e secagem, velocidade de ondas ultrassônicas, espectrofotometria e profundidade de penetração. Os hidrofugantes mostraram comportamentos similares, entretanto o H1 diminuiu a porosidade da rocha e não polimerizou completamente. O antigrafitti escureceu a rocha e mudou a distribuição do tamanho dos poros.

Studying the efect of nano­liquids on the operational properties of brick building structures

The study reported here has established that the ceramic facing brick is characterized by capillary porosity that increases indicators of water absorption and capillary pull, as well as efflorescence formation at its surface. In order to protect the surface of such a brick and to provide it with the improved performance properties, we have used hydrophobizing substances. We have determined experimentally that the application of the PMPhS- and AP-based hydrophobizing agents leads to a decrease in porosity by 1.2-1.3 times, in water absorption ‒ by 1.2‒2.3 times, in water absorption at capillary pull ‒ by 1.1‒3.2 times. Research into frost resistance has found that for the ceramic brick, covered with PMPhS, it increases by 15 cycles, and when treating a brick surface with AP ‒ by 20 cycles, compared to the untreated brick (F50). By employing an electron microscopy, it was determined that the alternating freeze-thawing leads to that the brick's surface, treated with PMPhS and AP, demonstrates the formation of microcracks (in this case, water absorption increased by 42 and 28 %). By applying a method of mathematical planning of the experiment, it was found that the most effective hydrophobizing substance is the modifier that contains the nano-Al 2 O 3 powder (a nano-liquid). It was determined that when treating the surface with a nano-liquid (the amount of nanо-Al 2 O 3 is 0.8 %), its water absorption decreases to 1.2‒1.6 %, its water absorption indicator at capillary pull ‒ to 0.08‒0.12 kg/m 2 ∙h 0.5 . Using a method of defectoscopy, applying the Karsten tube, it was found that water absorption for the brick whose surface was coated with a nano-liquid reduced from 0.15 to 0.002 ml/cm 2 , indicating a high level of hydrophobization. The electron microscopy method confirmed that the modification of the ceramic brick surface by the hydrophobizing nano-fluids makes it possible to compact the structure through the colmatation of pores and microcracks, which reduces the capillary pull of the brickwork. That also leads to the improved atmospheric and frost resistance of brick building structures. Thus, there is a reason to argue about the possibility of improving the physical and technical indicators of the brick building structure by modifying the surface of the ceramic facing brick by a nano-fluid

NDT as a monitoring tool of the works progress and the assessment of materials and rehabilitation interventions at the Holy Aedicule of the Holy Sepulchre

This work aims to point out the key role that Non-Destructive Techniques (NDTs) like Infra-Red Thermography, Ground Penetrating Radar, Ultrasonic Testing, Digital Microscopy, Colorimetry and Karsten Tubes, can play, not only on the diagnostic level and for the assessment of conservation interventions at the end of a project, but also during rehabilitation works. The above-mentioned NDTs, were applied for the preservation state assessment and during different stages of rehabilitation works at the Holy Aedicule of the Holy Sepulchre. Their importance for scientific support to decision making throughout diagnosis and rehabilitation works of complex historical structures is demonstrated in practice in cases such as: revealing structural layers, defect areas and voids; detecting rising damp, and thermo-hygric anisotropy of different building materials; in real time compatibility assessment of interventions as repointing, building restoration masonries, grouting, consolidating wall-paintings and protection of stone facades.

Single-sided NMR as a non-destructive method for quality evaluation of hydrophobic treatments on natural stones

Moisture is a main cause for weathering effects in historical façades made of natural stones. If applied correctly, hydrophobic agents can successfully protect these façades without altering the appearance. The major challenge is to ensure the required surface penetration. In-situ measurements for quality assurance on historical façades are still mainly done destructively through the extraction of core samples or superficially through the measurement of water ingress. An alternative approach has been found in nuclear magnetic resonance, which is able to visualize pore water. Applying this, single-sided NMR sensors provide a non-destructive tool for use at the building site. For this paper, four sandstones of different porosity and one limestone have been treated with two hydrophobic agents of different composition. The ingress of water in the treated samples has been measured by the single-sided sensor using three criteria for quality assessment, namely the hydrophobic depth, the hydrophobic efficiency, and the water absorption coefficient. The results are compared to those of common quality assurance measurements: the visual assessment and the gravimetrical water ingress on core samples as well as the superficial Karsten tube penetration test. It is shown that the single-sided NMR sensor provides a tool for the non-destructive quality evaluation of hydrophobic treatments, which is generally applicable to the building site using the quality criteria now found.

Innovative carboxylic acid waterproofing admixture for self-sealing watertight concretes

The present paper evaluates the performances of an innovative carboxylic acid-based admixture to improve concrete watertightness and self-sealing ability of the cement matrix. Results indicate that fumaric acid-based waterproofing admixture improves concrete watertightness. In particular, addition of 1% by cement mass of the carboxylic polymer causes a reduction in the water penetration under pressure of 7-day wet cured concrete by 50% compared to that of the corresponding reference concrete. The ability to seal cracks (400 μm width) due to plastic shrinkage was also confirmed by Karsten tubes tests, optical microscopy and SEM observations on cracked and sound concrete slabs.

Non-invasive analytical technique to address water uptake on stone surfaces: The implemented Contact Sponge Method (i-CSM)

Abstract The assessment of capillary rise rate is a recommended test in Cultural Heritage diagnostics to evaluate the evolution of stone textural properties and decay, and performances of conservation treatments. Beside laboratory tests, diverse non-invasive and non-destructive, in-situ methods were developed in order to establish the monitoring for monumental structures and decorative apparatus: Karsten tube, Mirowsky pipe and contact sponge methods (CSM). The comparison between the diverse techniques demonstrated high comparability between the datasets obtained with the CSM (UNI 11432:2011) and those recast with capillary absorption. However, the dataset collected with the conventional method is affected by high standard deviation due to several variables, mainly operator-dependent. The adoption of a pocket penetrometer, coupled with the use of a thicker sponge, aimed at parameterizing the load upon the surface. The implementations allowed a higher reproducibility of the measures, as well as the possibility of applying increasing pressures. In this study the i(mplemented)-CSM was adopted to test the adsorption behaviour of a set of ornamental stones (Macigno Sandstone, Breccia Aurora, Rosso Verona and Vicenza Stone) both un-weathered and weathered by freeze-thaw ageing and salt weathering. A correlation between the maximum open pore radius and an increase in water absorbance at higher loads was established. The preliminary promising results wait to be further validated on larger datasets.