Water Penetration Depth Research Articles

Numerical study of the closure flow within the chimney of a typical MTR reactor

Abstract In this work, the closure flow values effect on the penetration depth of radioactive water inside the core chimney of a typical MTR reactor is studied numerically using commercial CFD software ANSYS FLUENT. The closure flow values within the chimney are allowed to change from the reactor design value of 50 m3/h to no flow value. The flow stream function is presented for each value of the closure flow showing the penetration depth for each closure flow. The stream functions show the flow structure within the core chimney. The penetration depth of the radioactive water increases with decreasing the value of the closure flow. The stream function contours reveals that for a closure flow greater than 1 m3/h, no radioactive water penetrates from the chimney to the pool.

Experimental study on mechanical properties of concrete with marble dust

This study aims to investigate the extensive test data on the mix design and mechanical properties of concrete by replacing parts of fine aggregates with marble dust. A full factorial experiment with 180 cubic samples of 30 mixes was used. The effects of water/cement ratio: 0.4, 0.45 and 0.5, marble dust/sand ratio: 0, 0.05, 0.1, 0.15 and 0.2, superplasticizer/cement ratio: 0, 0.25, 0.5, 0.75 and 1, and fineness modulus of sand [FM = 2.4 and FM = 3] on slump, 28-day compressive strength and depth of water penetration were determined. The results indicate that the proposed ratios can be used to enable the design of a concrete mix that corresponds to its required performance

Water transport mechanisms in concretes bearing mixed recycled aggregates

Aggressive agents present in the environment that penetrate concrete through its pore structure induce deterioration, compromising the service life of concrete members. Determining the viability of using recycled materials in structural concrete calls for a prior understanding of their effect on water transport, the primary vehicle for external agent ingress. This article describes durability indicators such as electrical resistivity, water permeability (pressure testing), total water absorption, effective porosity and sorptivity that directly or indirectly measure water penetration and consequently performance across the service life of concrete bearing 20% to 100% mixed recycled aggregate (MRA). The 28 d concretes studied here with up to 75% MRA exhibited <7% weight gain due to water absorption, <15 vol% porosity and <30 mm maximum depth of water penetration under pressure, all indicative of high quality concrete. In 90 d materials, the values of the aforementioned parameters were 40% lower. Even in concrete with up to 100% MRA (with 28 d readings of 50 Ω m to 100 Ω m), electrical resistivity remained unaffected, The present findings reveal that high quality high durability structural concrete can be viably manufactured with up to 75% MRA.

Mechanical properties, durability characteristics and shrinkage of plain cement and fly ash concretes subjected to accelerated carbonation curing

The paper presents an experimental study on assessment of the effect of accelerated carbonation curing (ACC) on the performance of two concrete mixtures having the same mixture proportions but different cementitious materials (plain-cement and fly-ash-blended-cement). Different sets of specimens were cast utilising both concrete mixtures and were then subjected to ACC for ten hours at a constant pressure of 414 kPa (60 psi). After exposing the specimens to ACC, they were tested for weight gain, carbonation depth, compressive and tensile strengths, modulus of elasticity, water penetration depth, rapid chloride permeability, shrinkage, SEM and XRD. ACC of the concrete specimens for ten hours resulted in a significant weight gain with less than 2 mm of carbonation depth. Both mixtures gained compressive strength above 20 MPa after ten hours of ACC. The strength increased further when ACC-treated specimens were exposed to air, with a significant increase up to seven days for plain-cement concrete and up to 28 days for fly-ash-blended-cement concrete. Compared to reference moist-cured concretes, the ACC-treated concretes were found to exhibit a slightly lower long-term strength (15% for plain-cement and 5% for fly-ash-concrete). However, the overall performance of the ACC-treated concrete mixtures was comparable with the respective moist-cured concrete mixtures.

Freeze-thaw resistance and water permeability properties of roller compacted concrete produced with macro synthetic fibre

The increase in popularity of using Macro-Synthetic (MS) fibre reinforced Roller Compacted Concrete (RCC) as a wearing course material in road construction brought about a need to fully identify how this fibre utilisation affects the permeability and the resistance of RCC in the frequently cold exposure applications. This paper tackles the important aspect of this practical problem by investigating the effect of MS fibre utilisation on the freeze–thaw resistance and the water permeability properties of RCC. Initially, the optimum water content values for the RCC mixtures prepared with 0%, 0.2%, 0.4% and 0.6% fibre ratios by volume were identified using the soil compaction method. The concrete samples were then produced accordingly, water cured for 28 days and exposed to the freeze–thaw cycles by complying with the international standards. The weight change, ultrasonic pulse velocity, dynamic modulus of elasticity, skid resistance, flexural and compressive strength tests were undertaken to quantify the freeze–thaw resistance of RCC produced with various amount of MS fibre. Additionally, the water absorption, depth of water penetration under pressure and sorptivity tests were conducted to elucidate the effect of fibre amount on the permeability properties of RCC. The obtained results reveal that MS fibre utilisation in RCC production is clearly in favour of the freeze–thaw resistance. The water absorption capacity and the depth of water penetration under pressure values are indicated an increase in terms of the utilised MS fibre amount along with the reduction in the sorptivity results.

Influence of nanosilica on mechanical and durability properties of concrete

The results of an experimental study on the effect of the partial replacement of ordinary Portland cement with nanosilica (NS) on the mechanical and durability properties of concrete are presented. Concrete mixes were made with varying NS contents at a constant water/binder ratio of 0·40. The test results demonstrated that the inclusion of 3% NS as a partial replacement of cement enhanced the mechanical properties and reduced the water penetration depth and water absorption of the concrete, resulting in overall improved performance. Compared with normal concrete, the water penetration depth and water absorption of the NS concrete was reduced by 42·85% and 36·84%, respectively. The carbonation depth was also reduced as a result of cement replacement with NS, leading to enhanced concrete durability. These enhancements in the mechanical and durability properties were mainly due to the high fineness and increased pozzolanic activity of the added NS.

Comparación entre la normativa peruana y la normativa Extranjera relacionada a la durabilidad del concreto

En la presente investigación se realizó una comparación entre las normas peruana, estadounidense, argentina, boliviana y brasilera de concreto estructural, con el fin de analizar su contenido respecto a la durabilidad del concreto y encontrar posibles falencias de la normativa peruana vigente. La durabilidad del concreto es la capacidad que tiene este material de soportar la acción de diversos agentes que modifican sus propiedades. Este aspecto ha adquirido importancia en los últimos años debido a que su consideración en el diseño de estructuras podría prevenir problemas como agrietamiento, corrosión, carbonatación y otros, los cuales podrían poner en riesgo la funcionalidad de construcciones vitales en la sociedad, además de causar gastos por reparación y en los peores casos, reconstrucción. Para elaborar un concreto durable se hace un análisis del tipo de exposición en el que se encontrará la estructura proyectada, de modo que se puedan tomar medidas que atenúen efectos negativos sobre esta. Las normas consultadas consideran diversos parámetros para cada tipo de exposición, las cuales tienen diversa nomenclatura. Algunos de los parámetros encontrados son: resistencia a la compresión del concreto, relación agua/cemento, tipo de cemento, profundidad de penetración y velocidad de absorción. Los datos encontrados en las normas analizadas son congruentes entre sí, en algunos casos, son los mismos; esto se debe a que algunas normas han sido elaboradas en base a la norma estadounidense. Se hallaron también parámetros propios de cada país, siendo uno de los casos el ensayo de profundidad de penetración al agua, reglamentado únicamente en Argentina.

Air permeability, water penetration and water absorption to specify durability of eco-efficient concrete

The durability of eco-efficient, clinker reduced concrete is a key factor of its performance. In the presented study, different durability indicators of a newly developed eco-concrete composition (ECO) are tested versus standard normal concrete as reference (REF). The tested durability indicators are open porosity, water penetration depth, rate of water absorption by capillarity and two different methods of measuring air permeability (PermeaTORR AC device versus Testing bubble counter). The ECO mix and in particular its cementitious matrix is designed by a combined filler concept substituting Portland cement partially by properly selected limestone fillers of different grain sizes. The approach is based on a combination of particle packing optimization techniques and the reduction of water demand for certain flowability of the paste. Cement content is below the limits of traditional standards while w/c-ratio exceed such limits. While the performance of the eco-concrete in terms of workability and strength is at least equivalent to the standard mix, ecological impact indicators as global warming potential and embodied energy are substantially improved. Durability indicators overall show nearly equivalent performance of ECO and REF. In detail, the resulting air permeability coefficient tested with a bubble counter differs significantly from the coefficient tested by PermeaTORR.

Study on the optimum nano-natural pozzolan content in the concrete binder

The objective of this study is to investigate the optimum nano-natural pozzolan (NNP) content in the NNP-based binder concrete. NNP was obtained by grinding a local volcanic scoria for six hours. Twenty-four concrete mixes with four w/b ratios (0.4, 0.5, 0.6 and 0.7) and six-replacement levels of NNP (0%, 1%, 2%, 3%, 4%, and 5%) have been produced. The investigated concrete properties were the compressive strength, the water penetration depth, the concrete porosity and the chloride ion permeability. The efficiency factor (k) of NNP in terms of compressive strength was calculated using the Bolomey equation. Durability indicators have been used to globally evaluate the behavior of NNP-based binder concrete versus control concrete. The results revealed that the efficiency factor (k) decreased to some extent when the NNP content was more than 4%. The calculated durability indicators showed that NNP contents of 3-4% had approximately the highest indicators values. These indicators would be helpful for concrete mix designers. Some correlations between the investigated properties were derived from the analyzed data. The modification of the microstructure of NNP-based cement paste has been observed, as well.

Bacillus subtilis bacteria used in fiber reinforced concrete and their effects on concrete penetrability

Fiber-reinforced concrete has found wide applications in recent years as a remedy for compensating for the weak concrete tensile and flexural strengths. The use of fibers in concrete, however, increases its porosity. This drawback calls for remediation techniques to reduce concrete porosity and permeability in order to enhance its durability. Calcite sediments are capable of filling part of concrete pores to reduce its porosity. In the present study, use was made of bacteria as sediment producing agents in concrete specimens strengthened with different types of fiber. For this purpose, a strain of Bacillus subtilis was employed in its culture medium at a concentration of 107 cell/ml both as a replacement for the water in the concrete mixture and in a surface treatment gel. Moreover, polypropylene, steel, and barchip fibers were used at volume percentages of 0.3, 1, and 0.75%. The concrete specimens thus obtained were subsequently cured for 28, 56, and 90 days (depending on the type of experiment) in either plain water or the calcium lactate-urea solution. Measurements of water, CO2 and chloride ion penetration depths revealed that the use of bacteria in both curing environments led to reduced water, CO2, and chloride ion penetration depths in the bacteria-incorporated specimens, with the highest reductions of 64.75%, 39.77%, and 27.4% recorded for water, chloride ion, and carbonation depths, respectively. This is while the specimens subjected to surface treatment exhibited reductions of 57.75%, 24.94%, and 23.3% in their water, chloride ion, and carbon dioxide penetration depths, respectively, relative to those of the control specimens. Thus, the use of bacteria in the concrete mixture and its curing in the calcium lactate-urea solution were found capable of filling concrete pores to reduce porosity in fiber-reinforced specimens.

Long-term mechanical properties of cellulose fibre-reinforced cement mortar with diatomite

This paper presents a study investigating the long-term mechanical properties of cellulose fibre-reinforced cement mortars incorporating diatomite as a replacement material for quartz sand. Important properties including mass, compressive and flexural strength, sorptivity, water penetration depth and porosity have been rigorously investigated. Significant findings demonstrated that increasing the replacement level of diatomite resulted in a systematic decrease in the final mass of cellulose fibre-reinforced cement mortars and a dramatic increase in both flexural and compressive strength. In the short term, sorptivity, water penetration depth and porosity were enhanced, whereas the pozzolanicity of diatomite provided long-term strength gain over the 6 month period of study. Microstructural development of mortars, confirmed using scanning electron microscopy, revealed a denser, more compact structure in the diatomite specimens, which was consistent with the physical property measurements. This research supports the development of environmentally friendly diatomite-based mortars for construction.

Moisture movement within concrete exposed to simulated hot arid/semi-arid conditions

The ambient environment has a considerable influence on the permeation properties of the near-surface zone of exposed concrete (i.e. the cover zone). Monitoring the mass transport and flow processes and properties within this region is crucial in evaluating the long-term performance of concrete for a particular exposure condition. This paper presents an experimental study on both the spatial and temporal moisture movement within the surface region of concrete with and without supplementary cementitious materials. Prior to exposure, the samples were conditioned under two regimes representing poor and good curing; the samples were then exposed to a simulated hot environment with a diurnal temperature fluctuation of ∼20–40°C and ∼60% ambient relative humidity. Moisture movement within the surface region was monitored using discretised electrical conductivity measurements which, together with gravimetric measurements, allowed evaluation of the volumetric uptake and sorptivity of the concrete and the rate and depth of water penetration into the concrete cover zone; it is shown that when these are combined, the degree of saturation, effective porosity and total porosity of the surface region could be estimated. By evaluating the conductivity prior to and after water absorption, the zone of influence of wetting/drying action (i.e. the convective zone) could be evaluated.

Water diffusion simulation in photovoltaic module based on the characterization of encapsulant material using in-situ gravimetric technique

Durability of photovoltaic (PV) module under outdoor exposure is predominantly controlled by the ambient humidity, temperature, and ultraviolet (UV) irradiation as well as the mechanical and thermal stresses. Outdoor exposure with multiple cycles of water absorption and desorption degrades the PV module materials as well as their interfaces. This water diffusion behavior, when characterized through reliable and realistic methods, can be used to accurately predict the water concentration within the PV module and thereby help to predict the water-induced degradation in PV module. An in-situ gravimetric method was used in this study to characterize the effects of temperature on the water diffusion behavior of ethylene vinyl acetate (EVA). Both water absorption and desorption in the EVA showed a simple Fickian behavior. The water diffusion and solubility coefficients determined from in-situ gravimetric experiments in the test range of 24°–50 °C reasonably fitted the Arrhenius rate equations with an activation energy of 30.64 kJ/mol and heat of solution −16.86 kJ/mol, respectively. Finally, the data from the in-situ gravimetric technique was used to simulate and compare the water diffusion within a glass-glass PV module laminate where exposed to accelerated and Delhi outdoor environments. Water penetration depth is limited to about 50 mm for the ten cycles of the humidity freeze test, while it extends to about 110 mm for both 1000 h of damp heat test and one-year outdoor environment.

Efficiency of nano-volcanic scoria in the concrete binder

The objective of this study is to investigate the efficiency of volcanic scoria when added to the concrete binder at a nano-scale. Nano volcanic scoria (nano-VS) was obtained by grinding a local volcanic scoria for 6 h. Twenty-four concrete mixes with four w/b ratios (0.4, 0.5, 0.6 and 0.7) and six-replacement levels of nano-VS (0%, 1%, 2%, 3%, 4%, and 5%) have been produced. The investigated concrete properties were the compressive strength, the water penetration depth, the concrete porosity and the chloride ion permeability. Workability of fresh concrete mixes has been also determined. The efficiency factor (k) of nano-VS in terms of compressive strength was calculated using the Bolomey equation. Durability indicators have been used to globally evaluate the behavior of nano-VS-based binder concrete versus control concrete. The results revealed that the efficiency factor (k) decreased to some extent when the nano-VS content was bigger than 4%. The calculated durability indicators showed that the nano-VS contents of 3% and 4% had approximately the highest indicators values. These indicators would be helpful for concrete mix designers. Some correlations between the investigated properties were derived from the analyzed data. The modification of the microstructure of nano-VS-based cement paste has been observed, as well.

Reusing gold-mine tailings in cement mortars: Mechanical properties and socio-economic developments for the Lefke-Xeros area of Cyprus

Abstract Unexpected closure of the operations at an abandoned mine in the Lefke-Xeros area of Cyprus has resulted in an enormous environmental degradation and health hazards in the locality. In order to explore the possible ways for the rehabilitation of the abandoned mine site as well as to suggest alternative waste management approaches, gold mine tailings of Lefke-Xeros area are incorporated in cement mortars in this paper. Experimental measures such as compressive strength, water penetration depth, porosity, resistance to freeze/thaw cycling and carbonation depth of cement mortars incorporating gold tailings, carried out over the period of 9 months, have shown to be improved significantly. The release of heavy metals of cement mixtures incorporating gold tailings were substantially lower than the limits of US Code of Regulations. Cost effectiveness analysis also validated the efficient use of gold tailings both as cement and sand replacement in these mortars. Particularly, it is shown in the paper that the use of 30% gold tailings as a binder replacement resulted in a 22% decrease in the CO2 emissions arises from cement manufacturing. It must be emphasized that the use of gold tailings does not only result in a considerable reduction in CO2 emissions originates from cement production but also plays a crucial role in sustaining a healthy ecosystem of the immediate environment after the closure of mine sites and helps maintaining the economic growth of the locality.

Experimental investigation on the effect of silica fume and zeolite on mechanical and durability properties of concrete at high temperatures

Fire assessment of structures is an important area of concern. When the knowledge of concrete structures behavior at high temperatures is insufficient, there will be irreparable damage and financial losses. In this study, the mechanical and durability properties of concrete, aiming to overcome the adverse effects of high temperature by substituting a portion of cement with pozzolans is presented. The mechanical properties at the hot condition and the durability characteristics were tested when they reach the ambient temperature. The mechanical properties including compressive, tensile and shear strength, and the durability were evaluated based on the surface water absorption, water penetration depth, electrical resistance, and weight loss tests. Tests were conducted at different temperatures ranging from 28 to 800 °C. The results show that by increasing the temperature, the mechanical properties of the concrete decreased, with further increase in temperature they recovered and then started to decrease. Application of silica fume improved the compressive and tensile strength in a range of 1.35–26.74%, and 0.37–234.58% at the tested temperatures. However, pozzolans have not a significant impact on the shear strength. The study of the durability of concrete has shown that the heat reduced the durability of concrete while the addition of zeolite and silica fume compensated this reduction. In tests based on capillary properties and in the electrical resistivity test, samples containing zeolite had better durability properties. Meanwhile, in samples containing zeolite, those with a higher content of zeolite were better in terms of durability properties.

Durability of concrete with electric arc furnace slag aggregate

The durability of concrete mixes with EAF slag as aggregate (HS) is studied; mixes with limestone (HC) and barite (HAB) aggregates were used as reference for structural and heavy-weight applications, respectively. Compressive strength, elastic modulus, water penetration under pressure, wet-dry cycles, freeze-thaw cycles, influence of environmental condition and leaching tests were conducted. The results indicate that HS tends to present higher depth of water penetration under pressure, a slightly higher expansion, higher carbonation depth and similar compressive strength than reference HC. Should be payed attention to the formation of stain points on HS concrete surface subjected to wet-drying cycles.

Artificial Neural Network Estimation of the Effect of Varying Curing Conditions and Cement Type on Hardened Concrete Properties

The use of mineral admixtures and industrial waste as a replacement for Portland cement is recognized widely for its energy efficiency along with reduced CO2 emissions. The use of materials such as fly ash, blast-furnace slag or limestone powder in concrete production makes this process a sustainable one. This study explored a number of hardened concrete properties, such as compressive strength, ultrasonic pulse velocity, dynamic elasticity modulus, water absorption and depth of penetration under varying curing conditions having produced concrete samples using Portland cement (PC), slag cement (SC) and limestone cement (LC). The samples were produced at 0.63 and 0.70 w/c (water/cement) ratios. Hardened concrete samples were then cured under three conditions, namely standard (W), open air (A) and sealed plastic bag (B). Although it was found that the early-age strength of slag cement was lower, it was improved significantly on 90th day. In terms of the effect of curing conditions on compressive strength, cure W offered the highest compressive strength, as expected, while cure A offered slightly lower compressive strength levels. An increase in the w/c ratio was found to have a negative impact on pozzolanic reactions, which resulted in poor hardened concrete properties. Furthermore, carbonation effect was found to have positive effects on some of the concrete properties, and it was observed to have improved the depth of water penetration. Moreover, it was possible to estimate the compressive strength with high precision using artificial neural networks (ANN). The values of the slopes of the regression lines for training, validating and testing datasets were 0.9881, 0.9885 and 0.9776, respectively. This indicates the high accuracy of the developed model as well as a good correlation between the predicted compressive strength values and the experimental (measured) ones.

Investigating the effect of Nano‐silica on the depth of water penetration in concrete used in seawater: Case study of Caspian Sea

AbstractOne of the requirements of concrete structures is functional continuity whatever for it is required to be resistance in a particular period. Water during cementing process leads to hydration causing concrete hardness, whereas after hardening of concrete in most cases damages it's structure and properties. Dams, waveguides, docks and oil platforms in the seawater are subject to gradual erosion, which is very slow but measurable. Seawater due to the properties of sulfate, acid and alkali is a significant threat to concrete durability. Reducing the water absorption into the concrete body is the primary step to address the concrete erosion. Changing the concrete characteristics is an approach to increase concrete density and decrease its porosity leading to erosion reduction. Adding fine‐grained such as Nano derivatives can fill the void space within the concrete and reducing seawater absorption. In this research, we study the effect of Nano‐silica with 1% and 5% replacement ratios instead of cement on compressive strength and water penetration depth for concrete in environments of the Caspian Sea.

Penetration depth of meteoric water in orogenic geothermal systems

Warm springs emanating from deep-reaching faults in orogenic belts with high topography and orographic precipitation attest to circulation of meteoric water through crystalline bedrock. The depth to which this circulation occurs is unclear, yet it is important for the cooling history of exhuming orogens, for the exploitation potential of orogenic geothermal systems, and for the seismicity of regional faults. The orogenic geothermal system at Grimsel Pass, Swiss Alps, is manifested by warm springs with a clear isotopic fingerprint of high-altitude meteoric recharge. Their water composition and their occurrence within a 3 Ma fossil upflow zone render them particularly favorable for estimating the temperature along the deep flow path via geochemical modeling. Because the background geotherm has remained stable at 25 °C/km and other heat sources are unavailable, the penetration depth can be derived from the deep-water temperature. We thus estimated the base of the Grimsel system to be at 230–250 °C and 9–10 km depth. We propose that deep temperatures in such systems, particularly those with normal background geotherms (<30 °C/km), have been systematically underestimated. Consequently, far more enthalpy may be accessible for geothermal energy exploitation around the upflow zones than previously thought. Further, the prevalence of recent earthquake foci at ≤10 km beneath Grimsel suggests that meteoric water is involved in the seismicity of the host faults. Our results therefore call for reappraisal of the heat budget and the role of meteoric water in seismogenesis in uplifting orogens.