Diffusive and Convective Salt Transport in Building Materials Depending on Pore Solution Concentration and Moisture Content

2008 ◽  
Vol 31 (3) ◽  
pp. 199-211 ◽  
Author(s):  
K. Terheiden
Keyword(s):  
Moisture Content ◽  
Building Materials ◽  
Pore Solution ◽  
Solution Concentration ◽  
Salt Transport

scholarly journals Molecular Crystallization Inhibitors for Salt Damage Control in Porous Materials: An Overview

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1873
Author(s):  
Maria Paola Bracciale ◽  
Svetlana Sammut ◽  
JoAnn Cassar ◽  
Maria Laura Santarelli ◽  
Assunta Marrocchi
Keyword(s):  
Porous Materials ◽  
Building Materials ◽  
Damage Control ◽  
Solution Concentration ◽  
Salt Transport ◽  
Salt Crystallization ◽  
Environmental Aspects ◽  
Historical Building ◽  
Crystallization Inhibition ◽  
Microclimatic Conditions

The use of inhibition chemicals holds the prospect of an efficient strategy to control crystallization in porous materials, thereby potentially contributing to the prevention or mitigation of the salt decay phenomenon in modern as well as historical building materials in a more sustainable manner. In this review, we first provide an essential background on the mechanism of salt crystallization and on the factors influencing this phenomenon; next, we illustrate the mechanism at the basis of the action of crystal growth inhibitors, and critically discuss the major advances in the development of different families of inhibitors, particularly focusing on their influence on salt transport and crystallization within the structure of porous media. Specifically, correlations between the crystallization inhibition processes in porous materials and variables, such as porous substrate composition and properties, contaminant salt type and concentrations, microclimatic conditions, inhibiting solution concentration and properties, and application methods, will be highlighted. Environmental aspects, limitations, and problems associated with some inhibition chemicals are also taken into account. Finally, a survey and a discussion on the most representative experimental techniques and instrumentation available to assess qualitatively and quantitatively the inhibitor effectiveness, as well as recently developed modelling tools are given out.

scholarly journals Change of the cadmium, lead and uranium content in the soil pore water depending on the temperature in conditions of low soil moisture

2019 ◽  
Vol 55 (2) ◽  
pp. 212-222
Author(s):  
G. A. Sokolik ◽  
S. V. Ovsiannikova ◽  
M. V. Papenia
Keyword(s):  
Heavy Metal ◽  
Moisture Content ◽  
Pore Water ◽  
Chemical Nature ◽  
Pore Solution ◽  
Uranium Content ◽  
Iron Hydroxides ◽  
Water Capacity ◽  
Cadmium Lead ◽  
Definite Temperature

Effect of the soil temperature on concentration and total reserve of cadmium, lead and uranium in the interstitial (pore) water of (0–20)-cm samples of sod-podzolic soil with moisture content of 60 % of the water capacity (WC) after their keeping at the definite temperature (in the range of 14–40 °С) was established. It was found that character and extent to which temperature effects on concentration and total reserve of every heavy metal (Cd, Pb, U) in the soil pore solution depended on the chemical nature of heavy metal and peculiarities of soil. In the temperature range of 14–40 °С and moisture content in the soil samples 60 % of the WC, portions of the cadmium, lead and uranium in the soil pore solution decreased in the following way: aCd (0.2–0.4 %) > aPb (0.06–0.07 %) > aU (0.03–0.04 %). The concentrations and total reserves of cadmium, lead and uranium in the soil pore solution increased with lowering the temperature and it was especially true in regard to cadmium. The 5 °С temperature decrease in the range of 14–40 °С caused the content of cadmium in the soil pore solution to increase an average of 25 %, lead – 5.2 and U – 4.6 %. The iron content in the soil solution also increased with decreasing temperature, which indicated a decrease in the sorption capacity of iron hydroxides present in the soil, which probably played a prominent role in fixing cadmium, lead and uranium in the soil studied.

Solute Transport in the Soil near Root Surfaces

2000 ◽  
Author(s):  
Peter B. Tinker ◽  
Peter Nye
Keyword(s):  
Soil Solution ◽  
Dynamic Equilibrium ◽  
Pore Solution ◽  
Plant Root ◽  
Unit Length ◽  
Solution Concentration ◽  
Root Surface ◽  
Transport Processes ◽  
Soil Pores ◽  
Intact Root

We discussed in chapter 4 the movement of solute between small volumes of soil, and in chapter 5 some properties of plant roots and associated hairs, particularly the relation between the rate of uptake at the root surface and the concentration of solute in the ambient solution. In the chapters to follow, we consider the plant root in contact with the soil, and deal with their association in increasingly complex situations; first, when the root acts merely as a sink and, second, when it modifies its relations with the surrounding soil by changing its pH, excreting ions, stimulating microorganisms, or developing mycorrhizas. In this chapter, we take the simplest situation that can be studied in detail, namely, a single intact root alone in a volume of soil so large that it can be considered infinite. The essential transport processes occurring near the root surface are illustrated in figure 6.1. We have examined in chapter 3 the rapid dynamic equilibrium between solutes in the soil pore solution and those sorbed on the immediately adjacent solid surfaces. These sorbed solutes tend to buffer the soil solution against changes in concentration induced by root uptake. At the root surface, solutes are absorbed at a rate related to their concentration in the soil solution at the boundary (section 5.3.2); and the root demand coefficient, αa, is defined by the equation . . . I = 2παaCLa (6.1) . . . where I = inflow (rate of uptake per unit length), a = root radius, CLa = concentration in solution at the root surface. To calculate the inflow, we have to know CLa, and the main topic of this chapter is the relation between CLa, and the soil pore solution concentration CL. The root also absorbs water at its surface due to transpiration (chapter 2) so that the soil solution flows through the soil pores, thus carrying solutes to the root surface by mass flow (convection). Barber et al. (1962) calculated whether the nutrients in maize could be acquired solely by this process, by multiplying the composition of the soil solution by the amount of water the maize had transpired.

Einfluss der elektrochemischen Doppelschicht auf die Sorption und den Transport von Chlorionen im Zementstein / Influence of the electrochemical double layer on sorption and transport of chlorides in hardened cement paste

2000 ◽  
Vol 6 (4) ◽  
pp. 415-428
Author(s):  
O. Wowra ◽  
M.J. Setzer
Keyword(s):  
Double Layer ◽  
Cement Paste ◽  
Building Materials ◽  
Pore Solution ◽  
Chloride Ions ◽  
Transport Processes ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Electrochemical Double Layer

Abstract Besides the formation of Friedel salt the transport and binding of chlorides in concrete is mainly defined by the electrochemical double layer at the interface between cement matrix and pore solution. Due to the alkaline pore solution the surface of hardened cement paste is negatively charged which may change to positive values by the potential regulating calcium ions. Inverting of the surface charge leads to an attraction of anions and therefore, to an adsorption of chloride ions in the diffuse part of the electrochemical double layer. Influence from outside like sulphates and carbon dioxide may lead to a decomposition of Friedel salt. Apart from these effect temperature, pH-value and certain environmental conditions affects the electrochemical double layer as well. The chloride equilibrium is mainly controlled by adsorbed ions in the electrochemical double layer. The model presented here is relevant for the assessment of ion transport processes in mineral building materials. Continuing investigations may lead to optimize transport models and a better evaluation of the critical chloride threshold value in reinforced concrete.

scholarly journals Time Domain Reflectometry (TDR) technique – A solution to monitor moisture content in construction materials

2020 ◽  
Vol 172 ◽  
pp. 17001
Author(s):  
Teresa Stingl Freitas ◽  
Ana Sofia Guimarães ◽  
Staf Roels ◽  
Vasco Peixoto de Freitas ◽  
Andrea Cataldo
Keyword(s):  
Moisture Content ◽  
Time Domain ◽  
Building Materials ◽  
Correct Diagnosis ◽  
Construction Materials ◽  
Gravimetric Method ◽  
Reference Method ◽  
Time Domain Reflectometry ◽  
Relative Dielectric Permittivity ◽  
Porous Building Materials

Measuring moisture content in building materials is crucial for the correct diagnosis of buildings’ pathologies and for the efficiency evaluation of the treatment solution applied. There are several different techniques available to measure the moisture content in construction materials. However, perform long-term minor-destructive measurements is still a great challenge. The TDR – Time Domain Reflectometry – technique is commonly used for moisture content measurements in soils, but is considered a relatively new method with regard to its application in construction materials. In the present state of research, the current use of the TDR technique for monitoring moisture content in all types of consolidated porous building materials is not possible yet. Indeed, the empirical conversion functions proposed for soils are mostly not suitable for building materials. Furthermore, to successfully use the TDR technique, a good contact between the TDR probe and the material under study is required, which may be difficult to achieve in hard materials. In this paper, the TDR technique was implemented in two limestone walls constructed in the lab to test experimentally the efficiency of a wall-base ventilation channel to speed up drying after a flood. Each wall was equipped with four two-rod TDR probes for continuous monitoring the moisture content in both situations: with and without the ventilation channel. All the equipment used, procedures followed during the drilling until the probes’ final installation, as well as the individual calibration required for each probe are explained in detail. Instead of using unsuitable functions proposed for soils, the evaluation of the moisture content from the apparent relative dielectric permittivity measured was established using as reference method the gravimetric method. The results obtained suggest that the TDR technique is suitable for moisture content monitoring in consolidated porous building materials.

Application of a LTCC sensor for measuring moisture content of building materials

2012 ◽  
Vol 26 (1) ◽  
pp. 327-333 ◽  
Author(s):  
Mirjana Maksimović ◽  
Goran M. Stojanović ◽  
Milan Radovanović ◽  
Mirjana Malešev ◽  
Vlastimir Radonjanin ◽  
...  
Keyword(s):  
Moisture Content ◽  
Building Materials

scholarly journals Role of Time Relaxation in a One-Dimensional Diffusion-Advection Model of Water and Salt Transport

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Igor Medved’ ◽  
Robert Černý
Keyword(s):  
Diffusion Coefficient ◽  
Structural Damage ◽  
Building Materials ◽  
Chloride Transport ◽  
Salt Transport ◽  
One Dimensional ◽  
Advection Diffusion ◽  
Dimensional Diffusion ◽  
Lime Plaster

The transport of salt, necessarily coupled with the transport of water, through porous building materials may heavily limit their durability due to possible deterioration and structural damage. Usually, the binding of salt to the pore walls is assumed to occur instantly, as soon as the salt is transported by water to a given position. We consider the advection-diffusion model of the transport and generalize it to include possible delays in the binding. Applying the Boltzmann-Matano method, we calculate the diffusion coefficient of the salt in dependence on the salt concentration and show that it increases with the rate of binding. We apply our results to an example of the chloride transport in a lime plaster.

Sign in / Sign up

Export Citation Format

Share Document