Wall Moisture Research Articles

Leachability and Decay Resistance of Wood Polyesterified with Sorbitol and Citric Acid

Research Highlights: Polyesterification of wood with sorbitol and citric acid (SCA) increases decay resistance against brown-rot and white-rot fungi without reducing cell wall moisture content but the SCA polymer is susceptible to hydrolysis. Background and Objectives: SCA polyesterification is a low-cost, bio-based chemical wood modification system with potential for commercialisation. Materials and Methods: This study investigates moisture-related properties and decay resistance in SCA-modified wood. Scots pine sapwood was polyesterified at 140 °C with various SCA solution concentrations ranging from 14–56% w/w. Dimensional stability was assessed and leachates were analysed with high-performance liquid chromatography (HPLC). Chemical changes were characterized with attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and spectra were quantitatively compared with peak ratios. Low-field nuclear magnetic resonance (LFNMR) relaxometry was used to assess water saturated samples and decay resistance was determined with a modified EN113 test. Results: Anti-swelling efficiency (ASE) ranged from 23–43% and decreased at higher weight percentage gains (WPG). Reduced ASE at higher WPG resulted from increased water saturated volumes for higher treatment levels. HPLC analysis of leachates showed detectable citric acid levels even after an EN84 leaching procedure. ATR-FTIR analysis indicated increased ester content in the SCA-modified samples and decreased hydroxyl content compared to controls. Cell wall water assessed by non-freezing moisture content determined with LFNMR was found to increase because of the modification. SCA-modified samples resisted brown-rot and white-rot decay, with a potential decay threshold of 50% WPG. Sterile reference samples incubated without fungi revealed substantial mass loss due to leaching of the samples in a high humidity environment. The susceptibility of the SCA polymer to hydrolysis was confirmed by analysing the sorption behaviour of the pure polymer in a dynamic vapour sorption apparatus. Conclusions: SCA wood modification is an effective means for imparting decay resistance but, using the curing parameters in the current study, prolonged low-level leaching due to hydrolysis of the SCA polymer remains a problem.

Water accessibility to hydroxyls confined in solid wood cell walls

The hydrophilicity of wood cell walls derives from the presence of hydroxyls, but their accessibility is restricted by physical confinement from the stiff, solid cell walls. This study examines how this confinement affects water uptake of the accessible hydroxyls by tuning their amount through replacement with various non-hydrophilic functional groups. Results from gravimetrically determined hydroxyl accessibility by deuterium exchange are shown not to correlate with moisture uptake in cell walls under vapour conditions or at water-saturation. Instead, spatial availability for water inside solid cell walls is suggested as the dominant factor in controlling cell wall moisture uptake at given climatic conditions.

Climate data analysis to assess resilience of wall assemblies to moisture loads arising from the effects of wind-driven rain

In North America, and abroad, there currently exist standard test protocols for assessing the watertightness of wall assemblies and fenestration components although most of these methods are not directly related to expectations of in-field conditions as might be experienced by a wall assembly over its intended service life. How useful might such test protocols be to help determine the longevity of wall assemblies to future climate loads? Existing walls may, depending on their geographic location, be vulnerable to future climate loads and thus risk premature deterioration. For the design of new wall assemblies consideration ought to given to the non-stationarity of the climate and implications on the moisture loads on walls and the expected performance over the long-term. To permit assessing the resilience of wall assemblies to the effects of a changing climate as may occur in the future, and indeed, perhaps heightened moisture loads, one requires sufficient information on the watertightness of the assembly in relation to specified wind-driven rain loads and wall air-leakage conditions from which wall moisture retention functions could readily be developed. Such moisture functions are the basis of input of moisture loads to hygrothermal models and from which the expected long-term wall moisture performance can subsequently be derived. In this paper, a description is provided of the strategies used to analyze the WDR load for generating experimental input for a watertightness test protocol under development to assess resilience of wall assemblies to moisture loads arising from the effects of wind-driven rain in consideration of both historical climate loads and those as may arise from a changing climate.

IMPROVING WATERPROOFING PROPERTIES IN THE WALL BASEMENT AREA BY INJECTION METHOD

The article is focused on the natural experimental research of injection waterproofing impact on basement areas of existingbuildings brick walls. Two types of experimental installations for waterproofing material injection have been developed. Thesecond type turned out to be more efficient due to the fact that it could cover larger waterproofing wall area. It can possiblyspeed up the process of walls waterproofing and major repairs of buildings in general. According to the experimental data, after the injection waterproofing placement, the wall moisture content decreased by half due to the high quality waterproofingmaterial and performed installation work.

Effect of root canal wall moisture and filling techniques on the sealability of iRoot sp

To study the effect of root canal wall moisture and filling techniques on the sealability of iRoot sp. Sixty-two undamaged extracted human single-rooted teeth with fully developed apex were selected and prepared by crown-down technique. Two teeth were selected randomly to observe dentin tubules, opening, the residual teeth were randomly assigned to 3 groups: group A (wet), group B (slightly moist),group C(dry).The roots were further divided into 4 subgroups, group a: iRoot sp sealer without a core material (bulk-fill); group b: iRoot sp sealer with single cone obturation techniques; group c: iRoot sp sealer with heated gutta-purcha vertical pressure; group d: iRoot sp sealer with cold gutta-percha lateral compression technique. Glucose microleakage were measured in each group by glucose oxidase method. The differences in distribution of each group were analyzed with SPSS 19.0 software package. Group A and group B always showed the maximum and minimum amount of glucose penetration in the whole experimental process, and the difference was statistically significant at 28d (P<0.05). Under the same degree of moisture of root canal wall, glucose leakage of subgroup Aa was significantly higher than that of subgroup Ab and Ac at 15 d; and significantly higher than Ab, Ac, Ad at 21 d and 28 d(P<0.05). In group B and C, the subgroups a, b, c, d had no significant difference from each other during the experimental process(P>0.05). iRoot sp sealer has the best sealing effect when root canals were slightly moist. When the root canal wall is completely dry or slightly moist, the sealability of iRoot sp bulk-fill is similar to that of iRoot sp sealer with gutta-percha filling technique.

Moisture in modified wood and its relevance for fungal decay

Water plays an essential role in fungal decay of wood, and limiting the cell wall moisture content by chemical modification can effectively improve the durability of the material. Investigating the wood-water relations of modified material under climatic conditions relevant for fungal decay are, however, experimentally challenging. Most studies in literature therefore focus on moisture sorption under conditions outside those of importance for fungal decay. This review discusses the validity of such data for characterising the wood-water relations at very humid climatic conditions, relevant for fungal decay. Moreover, the review attempts to cover the basics of fungal decay, the important role of water, and how controlling water content by modification can improve durability.

Measured moisture in buildings and adverse health effects: A review.

It has not yet been possible to quantify dose-related health risks attributable to indoor dampness or mold (D/M), to support setting specific health-related limits for D/M. An overlooked target for assessing D/M is moisture in building materials, the critical factor allowing microbial growth. A search for studies of quantified building moisture and occupant health effects identified 3 eligible studies. Two studies assessed associations between measured wall moisture content and respiratory health in the UK. Both reported dose-related increases in asthma exacerbation with higher measured moisture, with 1 study reporting an adjusted odds ratio of 7.0 for night-time asthma symptoms with higher bedroom moisture. The third study assessed relationships between infrared camera-determined wall moisture and atopic dermatitis in South Korea, reporting an adjusted odds ratio of 14.5 for water-damaged homes and moderate or severe atopic dermatitis. Measuring building moisture has, despite extremely limited available findings, potential promise for detecting unhealthy D/M in homes and merits more research attention. Further research to validate these findings should include measured "water activity," which directly assesses moisture availability for microbial growth. Ultimately, evidence-based, health-related thresholds for building moisture, across specific materials and measurement devices, could better guide assessment and remediation of D/M in buildings.

Thermal and moisture monitoring of an internally insulated historic brick wall

Internally insulating walls is an effective method of energy retrofitting buildings. However insulation changes the hygric behaviour of a wall and can increase the risk of wall decay by moisture accumulation. This paper investigates thermal and moisture behaviour of internal insulations applied to a brick wall over a two and a half year period with probes positioned near the interface between the leveling plaster and brick wall.The in-situ performance of the insulations agrees with their laboratory measured thermal and moisture properties. It is consistently evidenced that the vapour permeability of the insulation has a large impact on the wall moisture. Walls with vapour permeable insulations closely reflect internal room relative humidity (RH) conditions and show the greatest response and the shortest lag time in reflecting changes in room RH. Conversely, the walls with low vapour permeable insulations display lower RH fluctuations and longer lag periods as moisture movement is impeded. There is a reduction in the wall's RH for all insulations when room heating is applied with the walls with vapour permeable insulations showing the largest reduction in RH due to wall moisture drying and raising wall temperatures while the less vapour permeable insulation lowered RH mostly on account of rising wall temperatures. The results suggest that vapour permeable insulations are suitable in moisture environments with periods of low RH that provide the wall with an opportunity to dry. The thermal performance of an insulation must be counterbalanced against moisture performance and the resultant longterm durability of the building.

Role of Moisture in the Failure of Coatings on Wood

Most wood coating tests are done either in a short term artificial weathering chamber or long term on an outdoor rack/fence. In both cases, the coatings are exposed to both ultraviolet radiation and water. This study is focused on the influence of moisture alone on wood opaque film forming coating failures. As moisture is sorbed into the wood structure, the wood swells in proportion to the volume of water sorbed. As moisture is lost, the wood shrinks in proportion to the volume of the water lost. Moisture in the wood end grain is responsible for coating failure in, for example, window corners and end to end siding. The wood cell wall moisture can be greatly reduced by a process known as acetylation which not only reduces the moisture sorbed in the cell wall but results in high levels of dimensional stability. The reduced moisture uptake along with the stability results in less stress created between the coating wood surface interface improving the performance of the coating and increasing its useful lifetime.

BOUNDARY ELEMENT METHOD MODYFICATIONS FOR USE IN SOME IMPEDANCE AND OPTICAL TOMOGRAPHY APPLICATIONS

The article presents two elements associated with the practice of application of the boundary element method. The first is associated with BEM ability to analyze an open boundary objects and application of infinite boundary elements in the area of mammography. The second element is associated with the damped wall investigations. Wall humidity and moisture represents heterogeneous environment (Functionally Graded Materials) which has to be treated in a special way.

The states of water in Norway spruce (Picea abies (L.) Karst.) studied by low-field nuclear magnetic resonance (LFNMR) relaxometry: assignment of free-water populations based on quantitative wood anatomy

Abstract Low-field nuclear magnetic resonance (LFNMR) relaxometry was applied to determine the spin-spin relaxation time (T 2) of water-saturated Norway spruce (Picea abies (L.) Karst.) specimens cut from mature sapwood (sW) and mature and juvenile heartwood (hW), where earlywood (EW) and latewood (LW) were separated. In combination with quantitative wood anatomy data focusing on the void volumes in various morphological regions, the NMR data served for a more reliable assignment of free-water populations found in water-saturated solid wood. Two free-water populations were identified within most sample types. One was assigned to water in the tracheid lumen and the other to water inside bordered pits. Whether water in the ray cell lumina was included in one or the other of these two populations depends on the curve-fit method applied (continuous or discrete). In addition, T 2 differences between the different tissue types were studied and, for comparison, sorption isotherms were measured by means of a sorption balance. There was a significant difference between EW and LW as well as between juvenile wood and mature wood in terms of T 2 related to the cell wall water. However, no differences were seen between the sorption isotherms, which indicates that the observed T 2 differences were not due to differences in cell wall moisture content (MC).

Coating Acetylated Wood

Wood exposed to the outdoor environment is susceptible to weathering due to a series of chemical, biological and physical processes. Acetylation of wood is known to reduce cell wall moisture content, improve dimensional stability and durability against fungal decay. As a result of these improvements, less stress is created between the coating and the wood surface improving the performance of the coating and increasing its useful lifetime. This paper is a review of research done on the chemistry of the acetylation process, the coating performance of acetylated wood and concentrates on the factors influencing coating performance.

Measurement of moisture content in solid brick walls using timber dowel

Moisture within walls can have a serious detrimental impact on buildings and undermine their long-term durability and integrity. This paper investigates the accuracy of the timber dowel method for measuring wall moisture content in a solid brick wall. The timber dowel is inserted in the wall and removed at intervals and moisture readings obtained using a resistance-based, moisture-meter. The moisture content of timber dowels and the surrounding brick and mortar in a laboratory wall is measured and compared to the moisture content in the timber dowel, brick and mortar in different relative humidity environments (saturated salt solutions). The paper finds that a linear relationship of increasing moisture content in the dowel and laboratory wall is observed. At medium dowel moisture content (dowel moisture content >15 %), the moisture content in the dowel, brick and mortar is similar in both the laboratory wall and the RH environments. At higher moisture content there is a divergence whereby at the same dowel moisture content, the laboratory brick and mortar show higher moisture contents than those achieved in the RH environments. It appears that liquid water present in the wall has difficulty transferring to the dowel and consequently the dowel underestimates at high moisture contents. It is concluded that the dowel gives a good indication of the moisture content in the wall when the dowel readings are not higher than 15 % and indicates changes in relative wetness above this. In-situ monitoring of the moisture content of a nineteenth century brick wall following the application of lime plaster showed expected changes in moisture content. An increase in wall moisture content following the application of the plaster and the wall returned to its original moisture state by 9 months.

Simulation of heat and moisture transfer in a multiplex structure

We present a 1D numerical model of heat, steam, and water diffusion across a wall, consisting of several layers of different material. The model is a system of coupled diffusion equations for material temperature, vapour pressure, and water concentration in material pores, accounting for vapour condensation and water evaporation. The system of nonlinear partial differential equations (PDEs) is solved numerically using the finite difference method. The primary objective of modelling is the simulation of the long-term behaviour of the building wall moisture distribution under the influence of seasonal variations in atmospheric air temperature and humidity.

The relationship between fungal diversity in house dust and childhood asthma development

Background: Childhood asthma prevalence has increased in recent decades. A relationship between early fungal diversity exposure and later asthma development, per the hygiene hypothesis, has not been established due to the absence of quantitative, unbiased techniques to measure fungal diversity. Aims: We used next-generation DNA sequencing to quantitatively evaluate fungal taxa and diversity in house dust samples without the biases of culturing. This research aims to characterize relationships among fungal taxa and diversity in house dust, measured wall moisture, and later asthma development in children. Methods: House dust and environmental measurements, including wall moisture, were collected in the CHAMACOS birth cohort study in Salinas, CA at child age 12 months. Current asthma status was evaluated at age 7 years in the available 292 children. A nested case-control analysis included 13 asthma cases and 28 controls. Dust was analyzed by 454 pyrosequencing to determine fungal identifications and diversity (number of different species per normalized sample). Results: Children from homes with low fungal diversity had an odds ratio of 4.8 (95% confidence limits 1.04-22.1) for developing asthma, not due to confounding. Homes with high measured moisture had increased fungal diversity. Negative confounding by moisture partially obscured the relationship between fungal diversity and asthma. No fungal taxa (species, genus, class) were significantly more common in asthma case homes but some taxa were significantly more common in control homes. Over 30 unique fungal taxa were significantly associated with moisture or mold indicators. Conclusions: This study avoided fungal culturing biases by using next-generation DNA sequencing to evaluate fungal diversity and taxa in house dust. Our findings suggest that low fungal diversity is associated with childhood asthma development.

Assessment of airborne exposures and health in flooded homes undergoing renovation.

In June 2008, the Cedar River crested flooding more than 5000 Cedar Rapids homes. Residents whose homes were flooded were invited to participate in this study. Household assessments and resident interviews were conducted between November 2008 and April 2009. We characterized exposures and symptoms experienced by individuals inhabiting 73 flood-damaged homes. Active air sampling and passive electrostatic dust collectors were used to assess exposures to culturable mold, culturable bacteria, fungal spores, inhalable particulate matter (iPM), endotoxin, glucans, allergens, lead, asbestos, radon, carbon dioxide, and carbon monoxide. Wall moisture levels and relative humidity were also measured. Exposures and questionnaire-based health assessments were compared at two levels of remediation, in-progress and completed. Homes with remediation in-progress (N = 24), as compared to the completed homes (N = 49), had significantly higher airborne concentrations of mold, bacteria, iPM, endotoxin, and glucan. Residents of in-progress homes had a significantly higher prevalence of doctor-diagnosed allergies (adjusted OR = 3.08; 95% CI: 1.05, 9.02) and all residents had elevated prevalence of self-reported wheeze (adjusted OR = 3.77; 95% CI: 2.06, 6.92) and prescription medication use for breathing problems (adjusted OR = 1.38; 95% CI: 1.01, 1.88) after the flood as compared to before. Proper post-flood remediation led to improved air quality and lower exposures among residents living in flooded homes. The number and severity of floods is on the rise, and health departments need evidence-based information to advise homeowners on recovery after such disasters. Our study suggests that proper remediation of flood-damaged homes can reduce bioaerosols to acceptable levels but exposures are significantly increased while remediation is in-progress leading to an increased burden of allergy and allergic rhinitis.

Numerical Analysis on the Slope Stability of the Multi-Step Waste Rocks Dump with Retaining Wall

In recent years, with the rapid development of highway, high-speed railway and other large cross-section tunnel engineering, a large number of waste rocks are piled up and induce various security issues which affect people's production and living environment seriously. The actual capacity of the LQS tunnel waste rocks dump has been far more than its design dimensions, and brings about a certain extent potential safety hazard to some expressway projects in Sichuan Province. Utilizing FLAC3D and its Mohr-Coulomb criterion establish 2D model, and analyzes displacements, and calculate its safety factor, estimate the slope stability and destructiveness of the waste rocks dump. The calculation results are coincide with the actual damage situation well. In order to improve the slope stability of LQS tunnel waste rocks dump, the influence degree of its wall height, moisture ratio, and slope ratio of safety factor will be analyzed, sequentially confirm the critical value of every factor, and find out the prominent factors. The numerical analysis on the slope stability of multi-step waste rocks dump with retaining wall will be the basis of similar sites.

Analysis of Starch Bubble Breakage during Extrusion Expansion by Finite Elements Method

Major factors that influenced the breakage of starch bubbles during extrusion expansion such as the initial bubble radium, the initial cell wall thickness, the initial cell wall temperature, the initial cell wall moisture content, the stress strength constant of starch and the changes of failure stress of bubble wall, stress of bubble wall, bubble radium, cell wall thickness, pressure different with time were investigated and the critical breaking points for each operation parameters under certain conditions were determined. The results showed that the smaller the initial bubble radium, the higher the initial cell wall thickness, and within certain range, the lower the initial temperature, the lower the initial moisture content, and the higher the stress strength constant of starch, the lower the tendency the bubble broke.

Effect of mechanically induced ventilation on the indoor air quality of building envelopes

Experiments were conducted to study the effect of mechanically induced fresh-air ventilation on the indoor air quality (IAQ) of the Tuskegee Healthy House (THH), selecting the outdoor weather conditions almost identical during the “fan OFF” and “fan ON” periods. Measurements of outdoor and indoor temperature and relative humidity (RH), in addition to the indoor dust particle concentration levels and interior wall moisture content, were systematically carried out during the summer month of August 2008. Results show that the effect of mechanically induced ventilation (“fan ON” period) is to raise the indoor RH, interior wall moisture content, and indoor dust particle concentration values significantly above those measured during the “fan OFF” period. The indoor temperature increases only slightly during the “fan ON” period.

Assessing the effects of soil grading on the moisture content-dependent thermal conductivity of stabilised rammed earth materials

New data for both the dry-state and the moisture content-dependent thermal conductivity of cement-stabilised rammed earth (SRE) materials is presented. For highly compacted SRE materials, no correlation was found between thermal conductivity and dry density or void ratio. The thermal conductivity of SRE materials increases linearly with the saturation ratio, S r of the material and can be expressed as λ ∗, the moisture content-dependent thermal conductivity. The sensitivity of λ ∗ to an increase in the saturation ratio of SRE materials varies according to soil grading. The influence of grading parameters on λ ∗ can cause material variations of approximately 0.8 m 2 K/W. The experimental data has been applied to standard SRE wall design configurations and the effect of wall moisture content on the total thermal resistance has been shown. The R-value of an SRE wall irrespective of cavity insulation can vary by as much as 0.13 m 2 K/W.