Capillary Absorption Coefficient Research Articles

Hygric properties of porous building materials (VI): A round robin campaign

Hygric properties of porous building materials are important for hygrothermal analysis. Their experimental determination is however not always reliable, shown by the discrepant results from different laboratories on the same materials. In this study, a recent round robin campaign initiated by KU Leuven (Belgium) and participated in by eight institutes from different countries is reported. Ceramic brick was selected as the target material. The bulk density and open porosity from vacuum saturation tests, the capillary absorption coefficient and capillary moisture content from capillary absorption tests, and the vapor permeability from cup tests were measured. Results were analyzed statistically and compared with a previous round robin project, EC HAMSTAD. The reproducibility errors for determining the capillary absorption coefficient were noticeably reduced when compared with the EC HAMSTAD project, and the different laboratories in the present study obtained similar results from vacuum saturation tests and capillary absorption tests without a common protocol. For cup tests, large inter-laboratory discrepancies still exist. However, with a stringent common protocol different laboratories achieved consistent results. For all properties a common protocol did not change the average results of all laboratories.

Mechanical properties and water absorption of cement composites with various fineness and contents of waste brick powder from C&D waste

The use of waste brick powder (WBP) as supplementary cementitious material (SCM) provides an effective approach to reclaiming construction and demolition (C&D) waste. This research shows the evolution of preparing eco-friendly mortar with various fineness levels and replacement ratios of WBP from waste brick in C&D waste. Due to the pozzolanic activity and filler effect of WBP, incorporating an appropriate content and fineness of WBP refines the pore network of cementitious materials, while the number of hydration products decreases with WBP addition. With WBP incorporation, the water demand increases and mixture slump decreases, while the use of WBP improves the drying shrinkage resistance. The pozzolanic activity increases with increasing WBP fineness; when the WBP fineness is higher than the cement fineness, the compression strength with WBP contents up to 15% is superior to that without WBP, while the compression strength decreases with WBP incorporation when the WBP fineness is close to or lower than the cement fineness. Incorporating an appropriate WBP content decreases the water absorption of mortar, and the water absorption further decreases with increasing WBP fineness; for example, when the median diameter of WBP is 6 μm and 42 μm, the capillary absorption coefficient of mortar with 30% WBP is 34.1% lower and 10.3% higher than that of plain mortar, respectively. In addition, a similar conclusion is observed for the water distribution in WBP mortar.

Effect of SiO2 Sol/Silane Emulsion in Reducing Water and Chloride Ion Penetration in Concrete

Here, a new concrete hydrophobic treatment method is developed using SiO2 sol and silane emulsion. The effectiveness of the modification for concrete protection is evaluated through testing water absorption and chloride diffusion. Two types of concrete with different strength grades (C40, C50) are used as the research object. The results show that the water capillary absorption coefficient and chloride ion diffusion coefficient of concrete decrease greatly under the protection of SiO2 sol and silane emulsion. Additionally, the protection effect is better with the increase of SiO2 consumption. Contact angle test results reveal that when the coating amount of SiO2 sol and silane emulsion is 300 g/m2, respectively, the contact angle reaches 150.2°, indicating the concrete (C40) surface reaches the superhydrophobic state. Through scanning electron microscope (SEM) observation, it is found that the hydrophobic effect of the SiO2 sol/silane emulsion is mainly due to the change in the surface morphology of concrete (C40).

Impact of nanotechnology on high performance cement and concrete

The nanoparticles are promising materials for the construction components in terms of compressive strength, density, porosity and novel applications. High performance concrete (HPC), functionalized concretes and coating materials can be prepared using various nanostructured Carbon cement additives, polymeric additives, ionic cement additives. CNT and graphene functionalization are the most promising routes to create cement nanocomposites. The strength of the cement for construction buildings can be improved with nanoparticle additives. The nanoparticles or nanoparticle mixture exhibit the best performance in terms of compressive strength, capillary absorption coefficient, and pore radius of cement mortars. It is evaluated that nanotechnology has a very important impact on high performance cement and concrete.

INFLUENCE OF LIGHTWEIGHT FILLERS ON THE PERFORMANCE OF CEMENT-BASED SKIM COAT

Lightweight fillers are used in dry-mixed building mortars in order to improve thermal insulation properties, yield, and workability. In the case of thin layer products, used as a finishing layer, reduced thermal conductivity coefficient enables to restrain of water vapor condensation on walls – which inhibits mold growth. The aim of the study was to determine the influence of 4 types of lightweight fillers on the performance of cement-based skim coat – with emphasis on the economic aspect. Formulas reflecting typical commercial products were used. The dosage of different components -such as expanded perlite, glass and polymeric bubbles or expanded glass – was optimized for sufficient yield and workability, keeping the constant price of 1 kg of the final product. Mechanical parameters, capillary absorption coefficient, and thermal conductivity coefficient were determined. Observations by Scanning Electron Microscope revealed poor incorporation of polymer microspheres in the cement matrix, leading to loss of mechanical strength. With the addition of expanded glass, an increase of flexural and compressive strength thanks to the pozzolanic reaction was observed. Glass bubbles were found the most effective additive.

Evaluation of effectiveness of silicoorganic treatments using hydric properties

In this work, the effectiveness of silicoorganic treatments for the consolidation, with or without waterproofing, of silicified stones (one conglomerate and four sandstones) from Zamora is analyzed, provided that these treatments are applied in the same way. Changes in the following properties have been monitored: total and free porosity, real and apparent density, absorption coefficient, imbibition coefficient, and capillary absorption coefficient. These intrinsic stone properties and the treatments employed have a significant effect on changes in these variables and lead to differences in the transport of fluid in the stone. This is the first time that the Canonical Biplot has been applied to this type of data to determine the control of the effectiveness of silicoorganic treatments applied to rocks. It was observed that the double action treatment RC80, which includes both waterproofing and consolidating, is more effective than the consolidating treatment RC70.

Coupled effects of sustained compressive loading and freeze–thaw cycles on water penetration into concrete

AbstractThe combined action of sustained loading and freeze–thaw cycles (FTCs) plays an important role in the durability and service life of concrete exposed to the cold coastal area. Water transport is a primary factor closely pertaining to freeze–thaw damage in concrete, and the microcracks induced by sustained loading could provide a flow path to facilitate water penetration into concrete. This paper presents the results of an experimental investigation on water penetration behavior of ordinary and air‐entrained concrete (OC and AC) subjected to sustained compressive loading and FTCs. Aiming at the combined effects of low compressive stress ratio and FTCs on water transport, a series of water absorption and permeability experiments with the stress ratio of 0, 0.3, and 0.5 after various FTCs were conducted. The relative dynamic elastic modulus and mass loss were afterwards measured to characterize the frost damage within concrete. The experimental results indicated that the sustained compressive loading and frost action have significant influences on capillary water absorption and permeability for the OC and AC specimens. Both the initial coefficient of capillary absorption and water permeability coefficient increase with the increase of FTCs, while they initially decrease and later increase with the increase of compressive stress ratio.

Modifying Mechanical Strength and Capillary Porosity of Portland Cement‐Based Mortar Using a Biosurfactant from Pseudomonas fluorescens

We characterized the effects of a biosurfactant derived from Pseudomonas fluorescens on slump loss, mechanical strength, capillary porosity, and bacterial colonization inside Portland cement‐based mortar samples. Standard tests were used to evaluate the utility of this biosurfactant as an admixture. The addition of 1.5% biosurfactant increased the plasticity and improved the workability of fresh samples. Although compressive and flexural strengths of mortars with biosurfactant were lower than those of mortars without biosurfactant after a short curing period (28 days), the addition of biosurfactant increased the compressive strength of mortar after a long curing period (180 days), with 1% biosurfactant having the highest value. After 180 days, mortar with biosurfactant had significantly lower capillary absorption coefficient A values (P < 0.05) than mortar without biosurfactant. Furthermore, the addition of biosurfactant reduced the relative abundance of the mortar‐deteriorating bacterial genus Pseudomonas (phylum Proteobacteria).

Influence of the incorporation of recycled coarse aggregate on water absorption and chloride penetration into concrete

Knowledge of the transport properties for recycled aggregate concrete (RAC) exposed to chloride environment plays a critical role in assessing its durability and predicting the service life. In this study, the effect of the incorporation of coarse recycled concrete aggregates (RCAs) on the durability of cement-based cementitious materials was experimentally investigated. Two types of RCAs were obtained to produce the RAC with water-to-binder ratio of 0.33 and 0.39, and different substitutions of RCAs ranging from 0%, 30%, 50% and 100% by weight were selected. A series of experiments including compressive strength, water and salt absorption test, and rapid chloride migration (RCM) test for RAC with various replacement ratios of RCAs were conducted. The results indicate that the incorporation of RCAs generally decreases the compressive strength, and inversely increases water and chloride transport coefficient compared to those of the control concrete. An increasing trend can be found in the influence of RCAs replacement ratio on the initial coefficient of capillary water absorption, but it inversely decreases as the quality of RCAs is improved. The chloride content and penetration depth in RAC were remarkably increased as RCA content increases and its quality decreases. The linear changing behavior for the penetration depth between water and chloride ion in RAC with different replacement ratios was well exhibited. This finding reveals the retardation effect that the chloride transport process lags behind water migration for the absorption tests of RAC.

Hygrothermal properties of light-earth building materials

This experimental study provides complete datasets of hygrothermal properties of numerous hemp-clay with density ranging from 200 to 350 kg m-3 for building thermal insulation. In addition, attention is also paid on protocols and methods, on the measurements repeatability and on the influence of conditioning temperature and relative humidity: mean uncertainties do not exceed 10% for all measurements, while initial conditioning influences at most the results, particularly for the sorption isotherm. Heat and moisture storage properties depend obviously of the constituent (hemp or clay). Furthermore, they can be estimated with a good accuracy with a mixing law. Thermal conductivity of the composites ranges between 0.06 and 0.12 W m-1 K-1 and clearly depends on the density. Water vapor diffusion resistance factor ranges between 2.24 and 4.14, while capillary absorption coefficient ranges between 0.027 and 0.135 kg m-2 s-0.5.

Application of Natural Plant Fibers in Cement-Based Composites and the Influence on Mechanical Properties and Mass Transport.

Recently, there is ongoing interest in the use of natural plant fibers as alternatives for conventional reinforcements in cementitious composites. The use of natural plant fibers makes engineering work more sustainable, since they are renewable, biodegradable, energy-efficient, and non-toxic raw materials. In this contribution, a comprehensive experimental program was undertaken to determine the influence of pineapple leaf fiber and ramie fiber on the mechanical properties and mass transport of cement-based composites. The compressive strength, tensile strength, modulus of elasticity, modulus of rupture, fracture energy, flexural toughness, coefficient of capillary water absorption, and chloride diffusion were measured. Natural plant fiber-reinforced cement-based composites (NPFRCCs) containing pineapple leaf fiber and ramie fiber, as compared to the plain control, exhibited a slight reduction in compressive strength and a considerable improvement in tensile strength, modulus of elasticity, modulus of rupture, and flexural toughness; the enhancement was remarkable with a higher fiber content. The coefficient of capillary absorption and chloride diffusion of NPFRCCs were significantly larger than the plain control, and the difference was evident with the increase in fiber content. The present study suggests that the specimen with 2% pineapple leaf fiber content can be used in normal environments due to its superior mechanical properties. However, one should be careful when using the material in marine environments.

Towards Resilience and Sustainability for Historic Buildings: A Review of Envelope Retrofit Possibilities and a Discussion on Hygric Compatibility of Thermal Insulations

ABSTRACT Our historic heritage needs to be prepared to face the new challenges imposed by climate change. A possible way to meet this urgent need consists in improving buildings resilience and energy efficiency through envelope refurbishment interventions. Consequently, an overview of the existing solutions for envelope retrofits in historic buildings is provided and their suitability for preserving valuable constructions is discussed. Thermal insulation solutions appear as the most discussed interventions and, therefore, their compatibility is considered in detail, accounting the hygric point of view. First, a general, rough criterium is introduced for ranking their hygric behaviour, according to their vapour permeability and capillary absorption coefficient, through a comparison with the average hygric characteristics of some historic building materials. Then, a method for performing fast, preliminary compatibility assessment is proposed, based on the definition of target interventions (qualitative hygric requirements) for specific clusters of situations (type of intervention, component, boundary conditions).

Experimental analysis on the relationship between pore structure and capillary water absorption characteristics of cement‐based materials

AbstractCapillary absorption capacity has an important influence on the durability of concrete and is closely related to pore structure. In this study, the pore structure and capillary water absorption of samples were determined by low‐field nuclear magnetic resonance spectroscopy and the gravimetric method, respectively. The test results show that the most probable pore diameter and equivalent pore diameter of cement‐based materials increase with increasing water to cement ratio (w/c) and fly ash (FA) content and decrease with increasing curing age and cement to sand ratio (c/s). The porosity of cement‐based materials increases with increasing w/c and c/s, decreases with increasing curing age, and first decreases and then increases with increasing FA content. The curves for the amount of capillary water absorption per unit area in specimens with the square root of time for cement‐based material under different influence factors are similar and show obvious linear and stable stages. The capillary absorption coefficient is nearly linearly related to w/c or c/s, and nonlinearly related to curing age or FA content, observation that are well correlated with the porosity and square root of the equivalent pore radius. A modified model is proposed for the capillary absorption coefficient with consideration of the pore structure, and the theoretical results of the model are in good agreement with the test results.

Concrete containing recycled aggregates: Estimated lifetime using chloride migration test

This paper presents a study regarding the durability of concrete containing Recycled Coarse Aggregate (RCA) from the largest civil construction waste plant in Latin America, CTR Grajau, located in São Paulo, Brazil. Conventional reference concretes were produced with natural aggregates and water/cement ratios of 0.35, 0.45, and 0.55. The recycled concretes were produced by replacing the Natural Coarse Aggregate (NCA) of the reference concretes with RCA in percentages of 50% and 100% by volume. Specimens were submitted to tests to determine the apparent porosity, capillary absorption coefficient andcompressivestrength. To verify durability aspects, the diffusion coefficients of chlorides (obtained by a procedure adapted from ASTM C 1202:2017) and electricalresistivity (obtained using a Wenner probe)were determined. Results demonstrated that NCA substitution with RCA increased porosity, with a consequent increase in the capillary absorption coefficient and a reduction in compressive strength. Total replacement of NCA with RCA reduces the concrete service life, calculated using Fick’s Second Law of Diffusion, by at least 40% for concretes with water/cement (w/c) ratio equal to 0.35, while a partial replacement (50%) reduces the service life by approximately 22%, considering a marine environment and 40 mm of cover thickness. The use of w/c minimum ratios, detailed RCA characterization and pre-wetting are some of the methods proposed for the application of the material for structural purposes. The lifetimes of the different concretes were determined.

Use of Waste Glass as A Replacement for Raw Materials in Mortars with a Lower Environmental Impact

Glass waste used in mortars or concretes behaves similar to cement, with resulting environmental benefits. In this light, the behavior of glass powder of various particle sizes has been analyzed as a cement replacement in mortars, in an attempt to minimize the loss of strength and durability, and maximize the amount of materials replaced. The dry density, water accessible porosity, water absorption by immersion, capillary absorption coefficient, ultrasonic pulse velocity and both compressive and flexural strengths were studied in the mortars. Furthermore, a statistical analysis of the obtained results and a greenhouse gases assessment were also performed. In view of the results obtained, glass powder of 38 microns allows up to 30% of the cement to be replaced, due to the filler effect combined with its pozzolanic activity. Moreover, it has been observed that glass powder size is one of the factors with the greatest influence among the properties of porosity, absorption and capillarity. On the other hand, in the mechanical properties, this factor does not contribute significantly more than the amount of glass powder. Finally, the greenhouse gasses analysis shows that the incorporation of glass powder reduces the CO2 emissions associated with mortar up to 29.47%.

Alkali-activated binary mortar based on natural volcanic pozzolan for repair applications

The goal of this investigation was evaluate the potential of an alkali-activated binary mortar (AABM), based on a natural volcanic pozzolan (70%) and granulated blast furnace slag (30%), as a repair material. This evaluation focused on its physico-mechanical characterisation (compressive, flexural and splitting tensile strengths; modulus of elasticity; capillary water absorption; and shrinkage) and the measurement of its adherence to three class of OPC concretes (substrates) using pull-off tests. A mixture of NaOH and Na2SiO3 was used as alkaline activator. The compressive and splitting tensile strength of AABM were 34.8 MPa and 2.13 MPa at 28 days of curing, respectively. Its capillary absorption coefficient and modulus of elasticity were 0.5088 kg/m2h0.5 and 8.66 GPa respectively. The results of the pull-off test demonstrate the adherent nature of the AABM, which was promoted by the strength (quality) of the OPC substrate, with pull-off adherences of 0.75 MPa, 1.14 MPa and 1.24 MPa for class C25/30, C35/45 and C50/60, respectively. According to the results obtained and standard specifications (EN 1504-3), this material can be classified as a class R2-repair mortar.

Design of alkali-activated materials for a modular green wall and green roof system

This study presents the work developed with alkali activated mixtures to be used as component of a new modular green wall and green roof system (GEOGREEN). The aim is to find the most appropriate composition of alkali-activated mixture to maximize water absorption and porosity and also find a good mechanical strength with reduced density. Alkali-activated mixtures were produced using two precursors, mine waste mud from Panasqueira mine (W) and ground waste glass (G) and two alkaline activators, sodium silicate (SS) and sodium hydroxide (SH). A ventilated oven was used to speed up the curing process. Variables as percentage substitution of W per G, molar concentration of SH, cure length and temperature, were tested to identify the reference mixture. After these tests different percentages of aggregates as sand (S), expanded cork granules (C) and expanded clay (A) were added to reference mixture (REF). Results indicate that S25 obtained the maximum compressive strength of 35 MPa after 7 curing days. However, about 30% compressive strength loss is observed after immersion of this mixture in water for 24h. Capillary absorption coefficient can reach to 4,77 kg/m2.h0,5 with C25 and to 4,11 kg/m2.h0,5 with S25. Also C50 enables a 20% density reduction compared to REF.

Hygric properties of hydrophobized building materials

Moisture loads due to wind-driven rain can lead to accelerated decay of exposed building facades. Hydrophobic impregnation reduces water absorption of facade materials and is thus presumed to decrease moisture related damages. Hydrophobic impregnation however also lowers the drying speed of the exposed facade, leaving mainly water vapour transfer to take place. This study examines the open porosity and capillary absorption coefficient of impregnated brick samples as well as the effect of hydrophobic impregnation on the vapour permeability of brick and mortar samples. The open porosity was measured with vacuum saturation test, the absorption coefficient was determined by water uptake tests, both done after one month of curing of the impregnated brick samples. The vapour permeability was `derived from cup tests and from drying tests. The resulting open porosity from brick samples indicates that the changes in the overall pore structure are minimal after impregnation. In addition, the absorption coefficient of brick was found to be fairly close to zero, even with low concentrations of active ingredient, and regardless the percentage of silane/siloxane. Our findings support the claim that the hydrophobic impregnation does not influence significantly the water vapour permeability of brick and mortar.

Bloques de Tierra Comprimida (BTC) con aditivos bituminosos

Los muros en tierra, presentan lesiones patológicas debido a su exposición al agua lluvia, y al agua proveniente del suelo. Además, por sus características de higroscopicidad los Bloques de Tierra Comprimida (BTC) presentan bajas resistencias a la penetración del agua y altos coeficientes de absorción capilar. Como alternativa para la reducción del coeficiente de absorción capilar e incremento de la resistencia a la penetración de agua se analizaron experimentalmente bloques de tierra comprimida adicionados con emulsión asfáltica en frío en proporciones del 0 %, 25 %, 50 %, 75 % y 100 %, respecto al peso del agua. Se estudió para cada una de las muestras la absorción capilar, resistencias a la compresión y penetración de humedad con el fin de evaluar la proporción optima de adición. Como resultado de la experimentación se determinó que los BTC adicionados con un 50 % de emulsión asfáltica presentan las mejores características de protección contra la humedad garantizando la resistencia a compresión necesaria para su uso en la construcción.

Characterization of a precast hemp concrete block. Part II: Hygric properties

The hygroscopic, insulating and agronomic properties of hemp concrete make it a promising building material for addressing the sustainable building challenge. Part I of this series of two papers described a characterization of the thermal properties of a prefabricated hemp concrete block, confronting the impact of different methods of measurement. Part II focuses on the hygric properties, which describe moisture transfer and storage. The sorption isotherm was measured at 23 °C and 45 °C, considering distinct experimental procedures (saturation salt solution (SSS) methods with single relative humidity step or stepwise equilibrium, and Dynamic Vapour Sorption (DVS)). Differences were observed in the results and hypotheses are formulated considering the distinct drying procedures between SSS and DVS methods or the specific water vapour sorption process on cellulose-based materials. With the measurements at two temperatures, the isosteric heat of sorption is evaluated which allows an evaluation of the sorption at any temperature. The water vapour permeability was measured with dry and wet cups. Different parameters were tested: thickness (5 and 8 cm), air velocity (0.5 and 2 m s−1) and calculation method (standard calculations, consideration of the water vapour interface resistances). Each parameter, with the chosen values, had an impact of around 10% on the final water vapour permeability calculated. The capillary absorption coefficient was evaluated through capillary uptake measurements, leading to an estimation of the liquid transfer coefficient, albeit 12 times lower than the one evaluated thanks to the dry and wet water vapour permeabilities. All these observations underline the significant impact of experimental parameters and methods on the determination of hemp concrete hygric properties and support the necessity to develop more specific measurement methods for such permeable and hygroscopic bio-based building materials.