Watertightness Tests Research Articles

Experimental analysis of biocementation technique for sealing cracks in concrete water storage tanks

Water supply systems are vital infrastructures that provide an indispensable public service to society. An important percentage of water losses is caused by the development of cracks in water storage tanks, so efficient crack sealing repair works must be investigated. Biocementation has been used with good results for sealing cracks in many construction concrete infrastructures (e.g., buildings), as an alternative to standard materials, such as polymeric resins and cement mortars. This research aims at the experimental evaluation of biocimentation effectiveness in terms of watertightness for sealing cracks structures in contact with pressurized water, to be further applied to repair cracks in water storage tanks. Biocementation treatment is applied in cracks artificially created in small rectangular concrete plates 4 cm thick, with three crack widths (i.e., 0.1, 1 and 10 mm) to cover different real cases in which the repair with this technique is viable. The 10 mm width cracks were filled with sand before the treatment. Different rounds of bacteria Sporosarcina pasteurii are applied, being the efficiency of the treatment investigated by performing watertightness tests through variable water head tests starting at 10 kPa (1 m of water). Dissolution is discarded through measurements of ultrasonic pulse velocities before and after the watertightness tests and the results are explained by images of thermographic camera. The presence of biocement is confirmed by mineralogical analysis of the precipitate extracted from the cracks after breaking the plates through bending tests. Obtained results are very promising since the biocement precipitated can completely stop water flow in the 0.1 mm cracks and, for the cracks with 1 mm and 10 mm widths, the treatment can reduce the initial flow rate, on average, by 95% and 98%, respectively. The performance of the 10 mm width cracks previously filled with sand was similar to that of the 1 mm cracks, where no sand was used. The material strength recovered after the treatment is not as good as desirable: although a maximum recovery of 95.5% of the initial strength (average values) is found for the smallest crack width and it was almost null for the other two crack widths. These results demonstrate that the technique is effective when watertightness is required, but not when material strength must also be recovered. Further research is required to investigate the maximum water pressures that can be applied to each case, eventual effects of biocimentation on water quality and the durability of the treatment.

Closing the gap between traditional wind-driven rain studies and the performance-based design of building façades: Case study of the Netherlands

Over the last few decades, analyses of wind-driven rain exposure on building façades have been conducted in multiple regions. Sometimes, these studies also included the driving rain wind pressure, thereby characterising both critical factors contributing to rainwater penetration into façade materials. However, practitioners typically rely on performance results obtained from standardised watertightness tests to make façade design decisions, even though these tests do not recreate the specific exposure combinations that can occur on each façade. Consequently, there is no quantitative correlation between the traditionally identified exposures and actual façade designs, resulting in pure qualitative choices and poorly optimised designs. This study addresses this issue by correcting the existing methodological deficiencies in a prior calculation procedure, which aims to relate the exposure parameters that the façade configuration withstood during any watertightness test to the expected climate exposures at its design operating conditions. New contributions are presented to enhance the method reliability as well as to reduce calculation effort and reliance on exhaustive weather data. The various climate parameters required to establish this relationship were analysed and tabulated for the Netherlands, enabling a truly performance-based design of façades to resist rainwater penetration throughout the country. Different methods of implementing this procedure, according to the availability of weather data, were also compared for façade case studies located in Amsterdam and Maastricht.

Reliability performance in tension governed reinforced concrete reservoirs as a function of target crack width

AbstractThe limit state that typically governs the design of circular reinforced concrete water retaining structures is the limitation of leakage through cracks. Current design codes prescribe target crack widths in the range of 0.05–0.2 mm, depending on the design situation, to limit leakage to acceptable levels. Fairly high model uncertainty exists in the prediction of load‐induced crack widths and the beneficial effect of autogenous self‐sealing has not effectively been quantified, so that the achieved levels of reliability using current codified procedures are unknown. This research uses a reliability analysis previously developed by the authors to assess the level of SLS reliability achieved in tension‐governed reinforced concrete reservoirs covering much of the scope of practice. The SLS reliability performance is evaluated using a limit state of allowable versus predicted leakage, including a probabilistic quantification of the effect of autogenous self‐sealing, and the uncertainty present in the prediction of load‐induced crack widths. Many permutations of practical reservoir geometries are considered for four combinations of stabilization period and water tightness test time (leakage regimes) typically used in water tightness tests. The target crack width recommendations of EN 1992‐3 and Model Code 2010 are evaluated across the range of geometries and leakage regimes. The commonly used target crack width of , recommended by Model Code 2010 and many other codes, was found to be inadequate to achieve a target SLS reliability index of . The values from EN 1992‐3 showed better performance but were found to result in reliability indices frequently in excess of , indicating that the values are perhaps too stringent. Results confirm that smaller target crack widths and longer water tightness test times increase the achieved reliability. However, even for a given target crack width and leakage regime, a substantial range of achieved reliabilities is observed depending on reservoir configuration. This shows that design to meet current target crack widths is not effective at meeting target reliability across the range of practical application. A suggestion is made to refine reservoir specific crack width targets to achieve target reliability more consistently.

An analysis of historical wind-driven rain loads for selected Canadian cities

The performance and durability of wall assemblies are greatly affected by the moisture load to which they may be subjected, in particular those arising from Wind-Driven Rain (WDR). Standard approaches for estimating such moisture loads assume 1% of the WDR load, whereas these loads have also been assessed from watertightness tests, although these assumed loads have been determined based on limited climate information. To more accurately estimate the moisture loads to which wall assemblies may be subjected over their service life, an analysis of historical WDR loads was completed for 11 cities across Canada. The magnitude, probability of occurrence of WDR loads in different cities and correlations between WDR related climate parameters, are discussed in this paper. Also, a novel WDR severity index is introduced, referred to as the Wind-Driven Rain Pressure Index, to permit quantifying the real-time and simultaneously occurring effects of WDR intensity and Driving Rain Wind Pressure (DRWP). To estimate the WDR intensity and DRWP with a specific probability of occurrence, an Extreme Value Analysis (EVA) was completed for a climate dataset of 31 years (1986–2016) using the Generalized Extreme Value and Gumbel distributions. • There is no correlation between the Wind-Driven Rain (WDR) load and concurrent Driving Rain Wind Pressure (DRWP). • A novel Wind-Driven Rain Pressure Index (WDRPI) is proposed. • Current watertightness test protocols are not reflecting most of the WDR conditions. • Gumbel distribution is a better option to generate the Intensity-Duration-Frequency curve for the WDR and WDRPI. • WDR conditions in different cities varies greatly.

Assessing the Moisture Load in a Vinyl-Clad Wall Assembly through Watertightness Tests

The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR) load that is deposited on the surface of wall assemblies as specified in the ASHRAE-160 standard whereas this ratio has been shown to be inaccurate as compared to results derived from several watertightness tests. Accurate assessment of moisture loads arising from WDR can be obtained through the watertightness test during which different levels of WDR intensities and Driving Rain Wind Pressures (DRWPs) are applied to a test specimen and water that penetrates wall assembly can thus be quantified. Although many previous studies have included watertightness tests, only a few of these have attempted to correlate the moisture loads to WDR conditions as may occur in specific locations within a country. To improve the assessment of moisture loads for a vinyl-clad wall assembly, a wall test specimen was tested following a test protocol based on local climate data using National Research Council of Canada’s Dynamic Wind and Wall Testing Facility (DWTF). The use of this test protocol permitted quantifying the moisture load in the vinyl wall assembly when subjected to several different simulated WDR conditions. The moisture load was formulated as a function of the WDR intensity and DRWP which thereafter allowed evaluating the moisture load based on a given climate’s hourly rainfall intensity and wind velocity. Such work is particularly relevant considering that the intensity, duration and frequency of WDR events across Canada will in some regions increase due to the effects of climate change.

Healing fine cracks in concrete with bacterial cement for an advanced non-destructive monitoring

Cracks in concrete are inevitable and they can adversely affect the service life of structures. An efficient method to heal the cracks coupled with a reliable monitoring technique is of paramount importance. Standard crack healing materials are unable to penetrate thin cracks [1]. This paper presents an experimental demonstration of healing of fine cracks of around 0.6 mm using the bacterial based healing technique. Simultaneously, the evidence and efficiency of bacterial healing is investigated using advanced monitoring techniques. Ultrasonic signals passing through the healing area have been recorded and the waveform has been studied to interpret the condition of the crack. It has been validated through a series of water-tightness tests. The bacterial technique was able to heal the crack to the extent that no water was seen to permeate through the crack. The evidence of bacterial healing was confirmed through scanning electron microscopy and X-ray dispersion spectrum. It was found that the ultrasonic technique is able to monitor the progression of healing.

Pressure-equalised façade systems: Evaluation of current watertightness test standards used to assess the performance of enclosure components

Watertightness test standards are used to evaluate enclosure components in terms of water penetration resistance. Currently, there is a wide variety of watertightness tests in use for façades elements and wall systems; however, none of them specifically addresses and evaluates the drainage capacity in pressure-equalised façade systems. In addition, recent research has revealed many inconsistencies in the possibility of these test standards to represent all possible conditions that can occur under different operating conditions, varying building configurations and at different locations. As such, the three main variables for water penetration testing (water spray rate, pressure differential and duration of the pressure application) have been called into question. Nonetheless, these studies do not bring up the protocols and other technical specifications incorporated in the test standard procedures. Furthermore, neither are concerns raised about the influence that these other parameters might have on the outcomes of the watertightness test, which is the aim of this research. To this end, the article provides a critical review of current watertightness tests standards from around the world in the first section. Thereafter, a thorough comparison of the information incorporated in the protocols of the test standards has been carried out. The evaluation and discussion of the test parameters and technical specifications incorporated in the tests standards is undertaken based on the state of the art and laboratory experiments of three mock-ups with pressure-equalised façade systems, where the water management capacity of the system is assessed. As a result of this research work, a guideline was prepared for the establishment of test procedures when developing new watertightness standards for pressure-equalised façade systems.

Low-cost drifting buoys for surface water observations in wetlands

Low-cost technologies are needed in developing and least-developed countries to improve monitoring capabilities to determine the dispersion characteristics of inland and coastal waters. Thus, the objective of the paper is to describe the design and construction of a low-cost saucer-shaped drifter, including its internal electronics, remote-control unit, and software. The system can operate over short timescales and distances and is thus suitable for estimating dispersion coefficients and differential kinematic properties of the fluid. The drifter was constructed primarily from readily available plastic products. The main electronic components were a global positioning receiver, microcontroller, lithium-polymer battery, wireless communication module, and activation and battery status indicators. The electronic design simplifies operation because the stored positions can be transferred to a computer via a mini-universal serial bus port without having to open the buoy. In addition, communication between the control unit and saucer-shaped drifter and its memory enhances its operational capability in the field. Water tightness tests were successful, and the operation of electronics was tested at a wetland known as Estero Topila, Mexico, to infer dispersion characteristics using a trio of drifters. Agreement with the Richardson’s 4/3 power law provides reliability of the electronics system performance and measured data.

Performance of Lightweight Wet-Room Floor with Two Waterproof Membranes

The purpose of this paper is to present and evaluate the performance of a lightweight wet-room floor structure with two waterproof membranes with a water-resistant cast compound between the membranes (twin floor). The twin floor was developed for use in existing buildings with a reduced load-bearing capacity of foundation or floor division. A watertightness test in the laboratory clearly indicated that wet-room materials for structures with one membrane were workable in the twin floor. Hereafter, two twin floors were constructed in an existing building including sensors for measuring temperature and moisture content in the cast compound. Multiple moisture measurements and watertightness tests near one floor gully showed potential water ingress in the cast compound through either the primary membrane, floor gully, or their assembly. Neither in the laboratory tests nor in the full-scale twin-floor tests was water penetration through the secondary membrane observed. In conclusion, the twin-floor showed promising results for working in practice. However, a redundancy layer is crucial to implement in the twin floor, because of the difficulties in testing and constructing the twin-floor structure.

Reliability and adequacy of current watertightness test standards used to evaluate the performance of façades

Watertightness test standards are used to evaluate enclosure components in terms of water penetration resistance. Currently, there is a wide variety of watertightness tests in use for façades elements and wall systems. However, recent research has revealed many inconsistencies in the possibility of current test standards to reproduce real exposure conditions. As such, the main test parameters specified in watertightness test standards have been called into question. Nonetheless, these studies do not pay attention to the protocols and the technical specifications incorporated in the test standards. Neither to the influence that these aspects could have on the watertightness results. The present paper provides a general overview of current watertightness tests standards from around the world. Thereafter, a thorough comparison of the technical specifications incorporated in the protocols of the test standards has been carried out. Finally, an evaluation and discussion of some parameters suggested in the tests standards is undertaken based on the state of the art and laboratory experiments over diverse mock-ups.

Improvement alternatives for determining the watertightness performance of building facades

The accurate determination of a facade's watertightness performance is important for optimizing design. Different micro-climatic conditions can affect water penetration. The recently developed Bayesian method allows this performance to be estimated for any operating condition and location, based on the results of standardized watertightness tests. This performance-based method uses semi-empirical calculations for wind-driven rain, estimates of wind velocity based on the wind profile power law and analyses of the annual maximum climatic data. This method determines the return period of climatic conditions that each facade system can withstand. Alternative approximations are studied that may be implemented using the Bayesian method to obtain more precise or functional estimations: improved friction coefficients, peaks-over-threshold analyses or catch ratios from computational fluid dynamics (CFD), among others. The effects of these alternatives on the results of the Bayesian method were evaluated by analysing different case studies in two cities in Spain. This analysis suggests that the original formulation of the method underestimates watertightness performance and highlights the fundamental importance of wind velocity to estimate the performance of any facade accurately. This will provide greater precision for estimating facade performance and provides potential for introducing performance-based codes for watertightness.

A comparison of methods for determining watertightness test parameters of building façades

Watertightness tests allow evaluating the performance of building façades using standardised parameters that simulate real weather conditions, i.e., a combination of wind-driven rain and driving rain wind pressure. It has been a challenge for researchers to experimentally test simultaneous wind and rain conditions in a rigorous manner. However, two new methods have minimised this problem, creating a precise relationship between the experimental result and the expected performance of the façade under real conditions and vice-versa. This article reviews both alternative methods and analyses their theoretical foundations and comparative advantages. In addition, the two methods are applied in the same case study, analysing the exposure conditions for a generic façade located in Bilbao (Spain). Ten-minute climatic records gathered over 14 years at the city airport have been used for this analysis. The comparative results show an adequate convergence between both procedures. However, their methodological differences would suggest using each one for different specific applications.

An extended method for comparing watertightness tests for facades

Watertightness tests for building facades attempt to simulate the most relevant climatic exposures for water penetration by reproducing standard conditions. Such conditions do not represent all possible climatic exposures, hence a new method was recently presented that relates test severity to watertightness performance of a facade under any operating conditions. In addition, test conditions vary for each regulatory framework (i.e. the results generated for one test cannot necessarily be extrapolated to other tests). A process is presented for considering the influence of exposure time. This allows a comparison of the severity of the conditions imposed by different watertightness tests independently of the exposure parameters. This comparison, which is based on a performance criterion, can enable a global certification of watertightness of any facade design under any operating conditions using results from only one watertightness test. The method developed herein was applied to facades under various operational conditions at a reference location, comparatively evaluating the conditions recreated by different international watertightness tests. The results suggest that American tests are more appropriate for recreating high climatic exposures, while European tests are more suitable for evaluating moderate and protected conditions of wind-driven rain and wind pressure.

A new method for determining the water tightness of building facades

Wind-driven rain and wind pressure are two fundamental climatic parameters affecting the penetration of water through building facades. Water tightness tests attempt to reproduce exposure extremes in order to evaluate the resistance to the passage of water through a facade. However, the exposure conditions for a given return period in a real situation can vary with each location and operating condition. Therefore, standardized test conditions may not be representative of all actual exposure conditions, which prevent a precise evaluation of the facade's performance under operating conditions that differ from test settings. A key challenge for water tightness tests is creating a correlation between standard exposure parameters used in testing and any actual exposure conditions. To address this concern, a new method is proposed that determines the return period associated with the tested exposure for the operating conditions of each facade. The new method is used to assess the adequacy of standardized test exposures (specified by EN 12865:2001 for European localities) on a specific facade at a site in Spain. The method estimates more rigorously the design return period related to water tightness performance of any facade and allows for an improvement of its design using the standardized test results. La pluie battante et la pression du vent sont deux paramètres climatiques fondamentaux affectant la pénétration de l'eau à travers les façades des bâtiments. Les tests d'étanchéité à l'eau tentent de reproduire les conditions extrêmes d'exposition afin d'évaluer la résistance au passage de l'eau à travers une façade. Cependant, les conditions d'exposition pour une période de retour donnée dans une situation réelle peuvent varier avec chaque lieu et chaque condition d'exploitation. Par conséquent, les conditions de test normalisées peuvent ne pas être représentatives de toutes les conditions d'exposition réelles, ce qui empêche une évaluation précise des performances de la façade dans des conditions d'exploitation qui diffèrent des paramètres de test. L'une des principales difficultés pour les tests d'étanchéité à l'eau est d'établir une corrélation entre les paramètres d'exposition standard utilisés pour effectuer les tests et n'importe quelles conditions d'exposition réelles. Pour faire face à cette préoccupation, il est proposé une nouvelle méthode qui détermine la période de retour associée à l'exposition testée pour les conditions d'exploitation de chaque façade. Cette nouvelle méthode est utilisée pour évaluer l'adéquation des expositions des tests normalisés (spécifiées par la norme EN 12865 : 2001 pour les localités européennes) par rapport à une façade spécifique d'un site situé en Espagne. La méthode estime de manière plus rigoureuse la période de retour de conception en lien avec les performances d'étanchéité à l'eau de n'importe quelle façade et permet d'en améliorer la conception en utilisant les résultats des tests normalisés. Mots clés: enveloppe des bâtiments, charges climatiques, conception des façades, paramètres de test, étanchéité à l'eau

Physical and mechanical properties of durable sisal fiber–cement composites

Sisal fiber–cement composites reinforced with long unidirectional aligned fibers were developed and their physical–mechanical behavior was characterized in the present study. Flat and corrugated sheets were cast by a manual lay-out of the fibers in a self-compacted cement matrix and compressed with a pressure of 3 MPa. Direct tensile and bending tests were performed to determine the first crack, post-peak strength and toughness of the composites. Drying shrinkage, capillary water absorption and water tightness tests were performed to characterize the physical properties of the composites. To ensure the composite durability, the ordinary Portland cement matrix was modified by adding metakaolin and calcined waste crushed clay brick to consume the calcium hydroxide generated during Portland cement hydration. The durability of the newly developed composite was determined through accelerated aging conditions using the hot-water immersion test. The developed material presented a multiple cracking behavior under bending, even when subjected to 6 months of hot-water immersion under 60 °C. Scanning Electron Microscopy was used to investigate the micro-structure of the composites before and after aging.

Water Penetration of Cladding Components—Results from Laboratory Tests on Simulated Sealed Vertical and Horizontal Joints of Wall Cladding

Abstract Considerable work has focused on the deterioration of jointing compounds used to seal building joints; less emphasis has been placed on understanding the consequences of seal failure, particularly in respect to watertightness. Jointing products are subjected to different climate effects; some induce aging in the sealant that in time leads to deficiencies. Deficiencies may also come about from design faults or improper installation. Water entry at deficiencies may lead to a number of different deteriorating effects on the building fabric that may induce failure of other envelope components or premature failure of the joint sealant. Joints are also subjected to substantial wind driven rain loads, in particular atop multi-story buildings. The approach taken in this study focuses on determining the fault tolerance of joint systems of a simulated wall panel when subjected to watertightness tests that emulate heightened wind-driven rain loads. Vertical and horizontal joints of 20 mm width and sealed with a one-component polyurethane product were subjected to water spray rates ranging between 1.6 and 6 L/(min-m2) and pressures of up to 2 kPa. Faults introduced to the sealed joint and representative of deficiencies through which water could penetrate consisted of cracks of 2 to 16 mm long introduced along the sealant to substrate interface. For specific crack lengths, the crack size related to the degree of joint extension, the extension reaching a maximum of 10 % of joint width. Rates of water entry across the joint were determined for cracks of different lengths and size and the nature of water entry at deficient joints in which cracks were introduced was also examined. Results on vertical joints indicated that water readily enters open cracks in relation to the crack size, quantity of water present at the crack, and pressure across the opening. Water may also penetrate cracks of nonextended “closed” joints.

수밀성 재료에 의한 숏크리트의 수밀성에 관한 연구

The use of shotcrete-sprayed concrete for the support of underground excavations was pioneered by the civil engineering. Now, for the nuclear wastes disposal plant in our country, watertightness of shotcrete is one of the very important properties This study evaluated the watertightness of shotcrete using cement mineral accelerator with watertightness materials for the long-term watertightness. In this study, for improvement of watertightness of shotcrete, it used two types of obtainable at a store. Watertightness tests of shotcrete were performed the water absorption coefficient, permeability, porosity and hydrates variation. In a shotcrete containing watertightness materials, watertightness of shotcrete was improved about 15%~65% rather than plain shotcrete.

Effects of steel fibers and mineral filler on the water-tightness of concrete pipes

Abstract Water-tightness of concrete and reinforced concrete pipes used to convey sewage flow of any kind is extremely important from the aspects of (1) groundwater contamination and (2) durability of the pipes. In this study, water-tightness tests were applied on plain concrete, reinforced concrete, and steel fiber concrete pipes of 500 mm diameter. Standard seepage tests were applied on many pipes of various materials and combinations with the objective of determining the pipes with the best water-tightness. Tests on plain concrete pipes whose concrete included finely ground limestone passing the no. 100 sieve (d

A modified on-site water chamber tester for masonry walls

The paper begins with a review of the currently available on-site water-tightness tests for masonry walls. The development of a modified on-site water chamber tester is reported. Results derived from experiments using this new tester are discussed. The results show that the leakage rate is not significantly affected by the flow rates but is significantly affected by the pressure difference of the applied water. Careful selection of a differential pressure seems to be more crucial than the water intensity rate for modelling realistic extreme wind driven rain situation in field-testing.