Capillarity Coefficient Research Articles

AN EXPERIMENTAL STUDY CONDUCTED TO DETERMINE THE EFFECTIVENESS AND DURABILITY OF PRESERVATION TREATMENTS ON VOLCANIC TUFF STONES

In this study, two treatments were performed on deteriorated volcanic tuff stone samples taken from a 16th-century historical structure: (i)solventless mixtures of ethyl silicates (TEOS) tetraethoxysilane consolidation product followed by application of two different silane-siloxane-based water-repellent commercial products (TEOS+WR1 and TEOS+WR2), (ii) two different silane-siloxane based water repellent commercial products (one emulsion (WR2) and the other solution (WR1) based). This study aims to determine the effectiveness, compatibility, durability and service life of the studied conservation treatments on tuff stones. Therefore, colorimetric measurements, chemical and petrographic analyses (XRF, XRD, SEM-EDS) and physical and mechanical characterization tests were performed on the treated and untreated samples.Additionally, accelerated weathering tests were performed in the laboratory on all treated stones to determine the long-term performance of the chemical treatments.After these weathering tests,physical (water absorption under atmospheric pressure, water capillarity coefficient, water vapour permeability) and mechanical (ultrasonic pulse velocity, flexural and compressive strength) property tests were performed again and according to the results, the performance change in the efficiency indexes (TEI,%) was calculated. All results were compared and discussed. The results showed the best performance of TEOS+WR1 treatment in improving the consolidating and water-repellency abilities of tuff stone samples.However, the least colour change in the colour measurements after the treatments was in the treatments using emulsion-type water-repellent products.

The Effect of Incorporating Juncus Fibers on the Properties of Compressed Earth Blocks Stabilized with Portland Cement

This study investigates the impact of incorporating Juncus fibers (JF) into compressed earth blocks (CEBs) stabilized with varying Portland cement contents, aiming to enhance local construction materials’ performance and reduce housing costs. CEB composites were produced with soil stabilized using different cement contents (4%, 8%, and 12% by weight) and JF reinforcement (0 to 0.2% by weight), compressed at 10 MPa with a hydraulic press. After 28 days of drying, the CEBs underwent diverse experimental characterizations to assess their physical, mechanical, thermal, and durability properties. The results revealed that incorporating JF led to a reduction in unit weight, ultrasonic pulse velocity (up to 36%), and dry compressive strength (approximately 17%). Higher fiber content correlated with increased water absorption and an increased capillarity coefficient. Thermal conductivity analysis indicated improved thermal performance, decreasing from 0.4350 W/m·K (12% cement without fibers) to 0.2465 W/m·K (4% cement with 0.2% JF). Despite the decrease in mechanical strength, CEBs with lower cement (4%) and higher fiber content (0.2%) demonstrated satisfactory durability (abrasion and erosion) and thermal insulation properties. This research suggests the potential of this material as a promising composite for the building materials industry. The findings contribute valuable insights into sustainable construction materials and have implications for cost-effective housing solutions.

Examination of the permeability of rubberized concrete with different water/cement ratios and their resistance against acid and sulfate attack

This study aims to examine the permeability and acid and sulfate attack of waste rubber-substituted concrete containing recycled rubber in three different grain size classes (chips, crumb and powder) with two different water/cement (w/c) ratios (0.4 and 0.5). Waste rubber at different ratios (0%, 4%, 8%, 12%, 16%, 20%, and 24%) was used in concrete by replacing fine and coarse aggregates. Sorptivity, electrical resistivity, and acid and sulfate attack tests were conducted on concrete cured for 90 days. Although the capillarity coefficient values increased with the waste rubber replacement ratio increase, a decrease occurred after the 20% waste rubber replacement ratio. In 12% waste rubber-substituted concrete (0.4WR12) with a water/cement ratio of 0.4, the electrical resistivity value (8.3 kΩ.cm) was the highest, and concretes with low permeability could be produced. As a result of the use of 16% waste rubber in the concrete, 75% less compressive strength loss was observed after the acid attack compared to the control concrete. In concrete with a water/cement ratio of 0.5, when the waste rubber ratio increased by up to 16%, the compressive strength losses caused by the sulfate attack decreased dramatically (95.76% less) compared to the control concrete. The rubberized concrete with a water/cement ratio of 0.5 showed high resistance to acid and sulfate attacks. The experiment results showed that 12% to 16% waste rubbers are ideal ratios. In this study, the water/cement ratio was a valuable parameter for the waste rubber ratio in rubberized concrete.

Rayleigh-Taylor instability for incompressible viscous quantum flows

Consider the linear and nonlinear Rayleigh-Taylor instability of the three-dimensional incompressible viscous Navier-Stokes-Quantum equations. For linearized problem, we determine the critical number κc precisely. Then, we construct a linear growth solution by a modified variational method for κ<κc. In addition, we show that κc is infinite for a special steady state ρ¯, which implies that quantum potential inhibit the instability instead of cutting it off. Based on this unstable linear solution and the priori estimates of the smooth solution to the perturbed problem, we establish the nonlinear instability of the density and the velocities in the sense of Hadamard. Compared with the related study on Navier-Stokes-Korteweg equations (Zhang (2022) [41]), we do not ask the capillarity coefficient to be small.

Influence of silicon-dioxide nanoparticles in cementitious mortars: verification using x-ray diffraction, thermal analysis, physical, and mechanical tests

In recent years, nanotechnology has been applied to building materials, such as cementitious composites (e.g., mortar and concrete), to improve their properties. The aim of this study was to analyze the thermal, physical, and mechanical properties of mortars with and without silicon-dioxide (SiO2) nanoparticles. Experiments such as thermogravimetry and differential thermal analysis (TG-DTA), x-ray diffraction (XRD), fresh density, incorporated-air content, bulk density, capillary absorption, capillarity coefficient, flexural tensile strength, and compressive strength on prismatic specimens were performed on mortars and analyzed for different levels of nanosilica (nS). These levels were 1% and 3%, in addition to the reference mortar (0% nS). The TG-DTA curves showed an elevated content of chemically combined water and a lower content of calcium hydroxide (Ca(OH)2) in the 3% nS compositions, while the XRD curves presented a lower content of calcite and portlandite in the same mortar. These results indicate the fixation capacity of lime for the formation of calcium silicate hydrate (C-S-H), which is the primary cause of resistance in cementitious mortars. In addition, it was found that the use of nanosilica contributed to a fresh density increase of approximately 15%, which caused a minimum air-incorporated content decrease of 37% and a minimum bulk density increase of 10%. Higher densities resulted in a minimum water absorption reduction of 36%, owing to fewer pores in the mortars. Therefore, the capillarity coefficient decreased by a minimum of 41%. These nanoparticles also improved the minimum flexural tensile and compressive strengths by 88% and 158%, respectively, when using a 3% nS composition. These results can enable the use of lightweight aggregates in cementitious composites, improving their physical and mechanical characteristics and allowing greater reuse of these materials, including construction waste.

Investigation on properties of cement mortar with bottom ash and perlite

AbstractPerlite and some recycled materials are preferably used to provide thermal insulation and lightness in mortar. Cement is often used as a binder in such a composite, although it makes the composite heavier and impairs its insulation properties. In this study, recycled bottom ash (BA) and expanded perlite (EP) as the aggregate, and cement as the binder and the optimum solution were investigated by using Taguchi Method. Depending on the specimens prepared using orthogonal array L9, the values of compressive strength, flexural strength, flowability, dry unit weight, water absorption, capillarity coefficient, and thermal conductivity coefficient were calculated. In general, it was found that the cement dosage was the most effective parameter and the thermal conductivity coefficient increased in parallel with the increase in unit weight and strength.

Vanishing Capillarity Limit of the Navier--Stokes--Korteweg System in One Dimension with Degenerate Viscosity Coefficient and Discontinuous Initial Density

In the first main result of this paper we prove that one can approximate discontinious solutions of the 1d Navier Stokes system with solutions of the 1d Navier-Stokes-Korteweg system as the capilarity parameter tends to 0. Moreover, we allow the viscosity coefficients µ = µ (ρ) to degenerate near vaccum. In order to obtain this result, we propose two main technical novelties. First of all, we provide an upper bound for the density verifing NSK that does not degenerate when the capillarity coefficient tends to 0. Second of all, we are able to show that the positive part of the effective velocity is bounded uniformly w.r.t. the capillary coefficient. This turns out to be crucial in providing a lower bound for the density. The second main result states the existene of unique finite-energy global strong solutions for the 1d Navier-Stokes system assuming only that ρ0, 1/ρ0 ∈ L ∞. This last result finds itself a natural application in the context of the mathematical modeling of multiphase flows.

Activation of slag through a combination of NaOH/NaS alkali for transforming it into geopolymer slag binder mortar – assessment the effects of two different Blaine fines and three different curing conditions

This study investigates the effects of two different Blaine fineness and three distinct curing conditions on the physico-mechanical properties of a geopolymer-ground granulated blast furnace slag (GGBFS) binder mortar activated through a combination of NaOH/NaS alkalis. By ensuring constant curing and mixing conditions, geopolymer mortar (GPM) specimens were prepared and evaluated to determine their capillary water sorption, capillarity coefficient, and change in unit weight, alongside their compressive strength and flexural strength 3, 7, 28, and 56 d after production. It was found that the capillary water sorption decreased by approximately 50% as the curing temperature of the water increased from ambient temperature to 22 °C. The coefficient of capillarity remained constant across the geopolymer materials, irrespective of the Blaine fineness of the GGBFS. Furthermore, the increase in the unit weight, owing to the variation in the Blaine fineness of GGBFS, results in a reduction in the water sorption properties of GPMs. The GGBFS and alkali-based binders imparted a continuous increase in the compressive and flexural strengths. The results revealed that a Blaine fineness of 6000 cm2/g in the GGBFS under water-curing conditions imparted the most significant advantageous effect on the physico-mechanical properties of a GGBFS binder mortar activated through a combination of NaOH/NaS alkalis.

A new parameter influencing the reaction kinetics and properties of fly ash based geopolymers: A pre-rest period before heat curing

In this study, the influence of a pre-rest period before heat curing (as a new parameter), on the physical properties, flexural and compressive strength, and microstructure of geopolymer mortars and pastes produced with alkali activation of fly ash were investigated. In this context, geopolymer mortar and paste samples were prepared and pre-rested under laboratory conditions for 0, 1, 2, 3, 7, 14, and 28 days before heat curing. After the pre-rest period, the samples were subjected to heat curing at 75 °C in an oven, for 2 days. Mortar and paste samples exposed to a pre-rest period while in the fresh state before heat curing were compared with control samples without pre-resting. Water absorption, porosity, specific gravity, capillarity, flexural strength, compressive strength, and abrasion resistance tests were conducted on the geopolymer mortar samples. A reaction kinetics study using an isothermal calorimeter, XRD, and SEM analyses were performed on the geopolymer paste samples for microstructural investigations. Based on the results obtained, it was observed that the mechanical strength of the samples subjected to the pre-rest period before heat curing increased considerably compared to the reference (without pre-resting) samples. In addition, because of pre-resting, the capillarity coefficient, water permeability, and porosity of the samples decreased compared to the reference samples, and it was concluded that pre-resting improves durability-related properties. Moreover, the reaction kinetics and SEM analysis results, supporting the above findings, showed that a pre-resting period increases the geopolymeric reaction products and causes a denser microstructure.

Assessment of compatibility between historic mortars and lime-METAKAOLIN restoration mortars made from amazon industrial waste

In the field of conservation and restoration, incompatibility between historic materials and restoration materials should be avoided, and, therefore, a lot of studies are aimed at assessing compatibility in restoration projects. Thus, this work aims to evaluate the mineralogical, physical, and mechanical compatibility between historic mortars and lime-metakaolin (MK) restoration mortars, using MK derived from the industrial waste from the Amazon region. It is worth mentioning that this is the first attempt to use this kind of residue for the restoration of cultural heritage. Historical samples used in this work are from the 18th and 19th centuries, from Belém do Pará (northern Brazil). The composition of the restoration mortars was determined using a complete factorial duplicated in 22 with three central points. The evaluation of mineralogical compatibility was performed by XRD and DSC-TG, and the evaluation of physical and mechanical compatibility occurred by determining the compressive strength, open porosity, capillarity coefficient, and drying rate. As expected, lime mortars were the most compatible with historic mortars in terms of mineralogical composition. The mineralogy of lime-MK mortars resulted in the immediate formation of hydraulic products in the first days of curing, indicating rapid hardening and high initial mechanical strength. In general, the physical and mechanical properties of restoration mortars were compatible with historic mortars, which was influenced by the adopted features and mineralogy. The results indicate restoration mortars with lower mechanical resistance and greater open porosity, capillarity coefficient, and drying rate. This indicates that some of the restoration materials would not cause excessive stress on the old structure, favor gas exchange, and reduce the prolonged presence of moisture. The results also indicate that restoration mortars with MK are probably more resistant to weathering than restoration mortars without this additive, especially the prolonged presence of water, a common situation in the humid tropics. Thus, the conclusions of this work can be useful both for the field of conservation and restoration and for the field of applied clay science, as it directs towards the sustainable use of clays from industrial wastes as an additive in restoration mortars.

Investigation on sorptivity and capillarity coefficient of mortar and their relationship based on microstructure

Durability is one of the key properties of the cement-based materials (CBMs) and is affected significantly by water migration in CBMs. Sorptivity S and capillarity coefficient k are two of the vital parameters to evaluate the water migration behavior of CBMs and are related closely to its microstructure. In this study, the low-field nuclear magnetic resonance (LF-NMR) was used to measure the pore size distribution and porosity of mortars. Additionally, according to the authors’ previous experimental results using the LF-NMR imaging and gravimetric method, the S and k were calculated, respectively. The results showed that the equivalent pore radius rm of mortar, determined by the pore size distribution, increased with water to binder (w/b) ratio and sand to binder (s/b) ratio, and decreased with silica fume (SF) and super-absorbent polymer (SAP) content. However, the porosity of mortar increased with w/b ratio and SF content, decreased with s/b ratio, while first increased and then decreased with SAP content. Meanwhile, the S was improved with the increasing w/b ratio and SF content, deteriorated with the increase in s/b ratio, while first improved and deteriorated with SAP content. The trend of the k of mortar was similar to that of S. The analytical models for predicting S and k of mortars were proposed, which were based on their microstructure and considered the effects of tortuosity and roundness, and were successfully verified by the test results with the present investigation and the existing literatures. Besides, the relationship between S and k was given and the ratio k/S was approximately between 5.0 and 10.0.

Kinetic derivation of diffuse-interface fluid models.

We present a full derivation of capillary fluid equations from the kinetic theory of dense gases. These equations involve van der Waals' gradient energy, Korteweg's tensor, and Dunn and Serrin's heat flux as well as viscous and heat dissipative fluxes. Starting from macroscopic equations obtained from the kinetic theory of dense gases, we use a second-order expansion of the pair distribution function in order to derive the diffuse interface model. The capillary extra terms and the capillarity coefficient are then associated with intermolecular forces and the pair interaction potential.

Nonlinear dispersive regularization of inviscid gas dynamics

Ideal gas dynamics can develop shock-like singularities with discontinuous density. Viscosity typically regularizes such singularities and leads to a shock structure. On the other hand, in one dimension, singularities in the Hopf equation can be non-dissipatively smoothed via Korteweg–de Vries (KdV) dispersion. In this paper, we develop a minimal conservative regularization of 3D ideal adiabatic flow of a gas with polytropic exponent γ. It is achieved by augmenting the Hamiltonian by a capillarity energy β(ρ)(∇ρ)2. The simplest capillarity coefficient leading to local conservation laws for mass, momentum, energy, and entropy using the standard Poisson brackets is β(ρ) = β*/ρ for constant β*. This leads to a Korteweg-like stress and nonlinear terms in the momentum equation with third derivatives of ρ, which are related to the Bohm potential and Gross quantum pressure. Just like KdV, our equations admit sound waves with a leading cubic dispersion relation, solitary waves, and periodic traveling waves. As with KdV, there are no steady continuous shock-like solutions satisfying the Rankine–Hugoniot conditions. Nevertheless, in one-dimension, for γ = 2, numerical solutions show that the gradient catastrophe is averted through the formation of pairs of solitary waves, which can display approximate phase-shift scattering. Numerics also indicate recurrent behavior in periodic domains. These observations are related to an equivalence between our regularized equations (in the special case of constant specific entropy potential flow in any dimension) and the defocusing nonlinear Schrödinger equation (cubically nonlinear for γ = 2), with β* playing the role of ℏ2. Thus, our regularization of gas dynamics may be viewed as a generalization of both the single field KdV and nonlinear Schrödinger equations to include the adiabatic dynamics of density, velocity, pressure, and entropy in any dimension.

Investigation of the dynamic capillary pressure during displacement process in fractured tight rocks

AbstractThis work investigates the dynamic capillary pressure during the displacement process in fractured tight rocks, through specially designed experiments on fractured and intact core samples. The dynamic capillarity coefficient of matrix and the multiphase flow behaviors are also obtained. Results have shown that the dynamic capillary pressure of the matrix becomes around 5–20% higher after the fracturing treatment. The lower and less variable values of dynamic capillarity coefficient of matrix illustrate a weakened dynamic effect and a more uniform displacement front. Moreover, time derivative of water saturation is increased significantly with fractures. Finally, oil relative permeability after fracturing is lower than its value of the intact core at high water saturations. A dynamic capillarity coefficient model for matrix, which includes the influence of fractures, is derived and verified with the average R2 more than 0.95. This wok helps to understand and predict multiphase flow in fractured tight porous media.

Effects of Silica Fume on the Performance of Cemented Paste Backfill Mixed with Brine

Brine water as a filling affected the strength of the filling body in Sanshandao Gold Mine, because it introduced higher concentrations of Cl−, SO42−, Mg2+ and other ions. In this paper, the effect of brine on the strength of cemented paste backfill and the mechanisms of micro-corrosion were studied. The effect of silica fume on the corrosion resistance of brine ions in cemented paste backfill was also studied. The influence of bittern ions on cemented paste backfill was analyzed using scanning electron microscopy and X-ray diffraction. Chloride permeability, capillarity coefficient, shear stress and viscosity and shear rate are obtained through the capillary water absorption test, rapid chloride permeability test, compressive strength test, direct shear test, and rheological test of cemented paste backfill. Then the mechanism for improving the brine corrosion resistance of the filling body with silica fume was analyzed. The results show that there was an improvement in the bittern corrosion resistance and other properties of the cemented paste backfill when the content of silica fume was 8% by weight.

Global stability of combination of a viscous contact wave with rarefaction waves for the compressible fluid models of Korteweg type

This paper is concerned with the large-time behavior of solutions to the Cauchy problem of the one-dimensional compressible fluid models of Korteweg type with density- and temperature-dependent viscosity, capillarity, and heat conductivity coefficients, which models the motions of compressible viscous fluids with internal capillarity. We show that the combination of a viscous contact wave with two rarefaction waves is asymptotically stable with a large initial perturbation if the strength of the composite wave and the capillarity coefficient satisfy some smallness conditions. The proof is based on some refined L2-energy estimates to control the possible growth of the solutions caused by the high nonlinearity of the system, the interactions of waves from different families and large data, and the key ingredient is to derive the uniform positive lower and upper bounds on the specific volume and the temperature.

The Effect of Dynamic Capillarity in Modeling Saturation Overshoot during Infiltration

Core Ideas We provide detailed analysis of various forms of the dynamic capillarity coefficient. We focus on the region of saturation overshoot at larger saturation. The results are evaluated with the aid of experimental observations. Gravity‐driven fingering has been observed during downward infiltration of water into dry sand. Moreover, the water saturation profile within each finger is non‐monotonic, with a saturation overshoot at the finger tip. As reported in the literature, these effects can be simulated by an extended form of the Richards equation, where a dynamic capillarity term is included. The coefficient of proportionality is called the dynamic capillarity coefficient. The dynamic capillarity coefficient may depend on saturation. However, there is no consensus on the form of this dependence. We provide a detailed traveling wave analysis of four distinctly different functional forms of the dynamic capillarity coefficient. In some forms, the coefficient increases with increasing saturation, and in some forms, it decreases. For each form, we have found an explicit expression for the maximum value of saturation in the overshoot region. In current formulations of dynamic capillarity, if the value of the capillarity coefficient is large, the value of saturation in the overshoot region may exceed unity, which is obviously nonphysical. So, we have been able to ensure boundedness of saturation regardless of the value of the dynamic capillarity coefficient by extending the capillary pressure–saturation relationship. Finally, we provide a qualitative comparison of the results of traveling wave analysis with experimental observations.

Experimental and Numerical Studies of Saturation Overshoot during Infiltration into a Dry Soil

Core Ideas Experiments measured saturation overshoot during infiltration of water into dry soil. Two models based on Richards' equation with a dynamic capillarity term simulated the data. The IFA model is an alternative approach to simulate saturation overshoot. The IFA model and dynamic capillarity equation were combined to simulate experiments. Downward infiltration of water into almost dry soil, when there is no ponding at the soil surface, often occurs in the form of fingers, with saturation overshoot at the finger tips. While this is well known, there is still uncertainty about the exact saturation pattern within fingers. We performed a series of one‐dimensional water infiltration experiments into a dry soil to study the non‐monotonicity of the saturation. We observed that saturation showed a non‐monotonic behavior as a function of time. The overshoot was somewhat plateau shaped at relatively low flow rates but was quite sharp at higher flow rates. Two mathematical models, referred to as the extended standard (ESD) model and the interfacial area (IFA) model, were used to simulate the experimental results. Both models were based on extended forms of the Richards equation by including a dynamic capillary term. In the ESD model, standard equations for hysteresis were used. In the IFA model, the specific interfacial area was introduced to simulate hysteresis. Parameter values for both models were obtained from preliminary experiments or using empirical formulas. Only one parameter, the dynamic capillarity coefficient τ, was optimized to model saturation overshoot. While the ESD model did not reproduce the form of saturation overshoot for any combination of parameter values, the IFA model could provide good agreement with the data. To our knowledge, this is the first time where a combination of the IFA model and the dynamic capillarity equation has been used to simulate a set of experiments.

Recycling paper industry effluent sludge for use in mortars: A sustainability perspective

Abstract The paper and cellulose manufacturing industry generates significant quantities of waste, including an extremely humid sludge, which is considered to be an effluent with high environmental liability for the manufacturer. Studies have shown that this waste sludge may be utilized in construction material, such as mortar for fixing blocks, as well as for ceiling and wall coatings that use ceramic masonry as a sealant. The recycling of pulp and paper industry waste sludge has important environmental benefits, by preventing soil and water pollution caused by inadequate disposal and by reducing the depletion of natural resources, such as lime, used in cementitious materials. This study analyzed the sustainability of incorporating such waste into cement-based mortars. Tests were conducted replacing lime, one of the most expensive mortar components with high environmental impact, with waste sludge in contents of 5%, 10%, 15%, and 20%. Analysis was then performed on the samples to assess the primary technical characteristics of these incorporated mortars, such as the consistency index, heat of hydration, content of incorporated air, water retention, mechanical strength and the capillarity coefficient. The results were compared with the results of the characterization tests that were performed on the waste material. The results showed that for use in wall and ceiling mortar coatings, the level of incorporation should not exceed 10%, because higher levels yield lower values of mechanical strength resistance, incompatible with market requirements. This result is probably due to the low heat of hydration of the waste material which generates slower reactions. On the other hand, higher levels of waste material content, above 10%, are appropriate convenient for mortar used to fill small repairs in masonry that do not require control of properties.

Influence of production systems on the properties of fresh and hardened shotcrete

Abstract In modern shotcrete operations, the mixing and pumping steps are carried out using different production systems and equipment. This adds an element of uncertainty to the process because of variables such as mixer type, rotation speed, mixing time, etc. As a result, this may result in changes to the characteristics and properties of both fresh and hardened sprayed mortar and may ultimately impair the performance of the rendering material. This study assesses the influence of production systems, particularly the mixing process, on the properties of fresh and hardened sprayed mortar. The methods used comprehend the collection and testing of mortar samples produced in wet-mix and dry-mix shotcrete systems, as well as a pre-packaged mortar batched and mixed in a laboratory mixer under controlled conditions according to the manufacturer’s instructions. Results were processed using analysis of variance (ANOVA) and multiple comparison of means using Fisher’s method. A statistically significant difference was observed in the flow table index, water retention, flexural strength and capillarity coefficient of the mortars produced using wet- and dry-mix systems.