Capillary Water Absorption Test Research Articles

Enhancing Water Resistance and Mechanical Properties of Cemented Soil with Graphene Oxide.

Although cemented soil as a subgrade fill material can meet certain performance requirements, it is susceptible to capillary erosion caused by groundwater. In order to eliminate the hazards caused by capillary water rise and to summarize the relevant laws of water transport properties, graphene oxide (GO) was used to improve cemented soil. This paper conducted capillary water absorption tests, unconfined compressive strength (UCS) tests, softening coefficient tests, and scanning electron microscope (SEM) tests on cemented soil using various contents of GO. The results showed that the capillary water absorption capacity and capillary water absorption rate exhibited a decreasing and then increasing trend with increasing GO content, while the UCS demonstrated an increasing and then decreasing trend. The improvement effect is most obvious when the content is 0.09%. At this content, the capillary absorption and capillary water absorption rate were reduced by 25.8% and 33.9%, respectively, and the UCS at 7d, 14d, and 28d was increased by 70.32%, 57.94%, and 61.97%, respectively. SEM testing results demonstrated that GO reduces the apparent void ratio of cemented soil by stimulating cement hydration and promoting ion exchange, thereby optimizing the microstructure and improving water resistance and mechanical properties. This research serves as a foundation for further investigating water migration and the appropriate treatment of GO-modified cemented soil subgrade.

Effects of seawater and sea sand on early creep of concrete under different stress levels

Early-age creep of seawater sea sand concrete has a profound effect on construction engineering. This study investigates the ramifications of seawater and sea sand on the early-age creep behavior of concrete subjected to different compressive stresses. To discern the impact of seawater and sea sand on deformation, creep tests were conducted. In parallel, mechanical tests, shrinkage deformation tests, and capillary water absorption tests were conducted to elucidate the influence of seawater and sea sand on macroscopic performance. Moreover, mercury intrusion porosimetry and scanning electron microscopy were deployed to scrutinize the concrete's pore structure and microstructure. The findings reveal that seawater and sea sand precipitate augmented shrinkage and creep deformations in concrete, with seawater exerting a more pronounced effect. Furthermore, seawater and sea sand diminish the porosity of concrete, optimizing its pore structure by curtailing the count of large pores and augmenting the number of gel pores and capillary pores, thereby bolstering its durability. Seawater also reduces the critical stress threshold for the manifestation of nonlinear creep in early-age concrete, while sea sand exerts a minimal influence. These insights hold substantial implications for comprehending the influence of seawater and sea sand on the early-age creep of concrete and offer valuable guidance for their practical deployment in engineering projects.

Study on the evolution of concrete pore structure and moisture transfer mechanism after high temperature based on different sequence NMR technology

This study investigates the influence of elevated temperatures on concrete's pore structure and moisture transfer mechanisms. Concrete samples exposed to temperatures of 200℃, 400℃, 600℃, and 800℃ were subjected to capillary water absorption (CWA) tests, and their properties were analyzed using Scanning Electron Microscopy (SEM) and Nuclear Magnetic Resonance (NMR) techniques employing different sequences (CPMG and SE-SPI). The results reveal after high temperature four distinct categories of pores within the concrete: micropores, mesopores, capillary pores, and macropores. Mesopores are in the highest abundance, followed by capillary pores, macropores, and micropores. As temperature increases, hydration reactions lead to an upsurge in micropores and a decline in the proportion of other pores. With further temperature escalation, the cement slurry's volume alteration causes pore expansion, resulting in a rise in capillary pores and macropores and a decrease in micropores. Furthermore, NMR technology, employing CPMG sequences, identifies three stages in the concrete's CWA process: rapid moisture transfer, moisture transfer rate descent, and moisture transition stage. SE-SPI sequence-based NMR results show that, following high-temperature exposure, moisture transfer within concrete progresses as follows: initially, water rapidly permeates mesopores and capillary pores from the exterior. As CWA time increases, these pores tend to saturate, and water gradually infiltrates micropores and macropores. High temperatures significantly impact the CWA process, enlarging pore sizes and altering the type of pore filling during capillary water absorption in concrete.

Research on Capillary Water Absorption Characteristics of Modified Recycled Concrete under Different Freeze–Thaw Environments

Recycled coarse aggregate is processed through the second crushing, which causes some internal damage, resulting in its physical indicators being far worse than natural coarse aggregate; its durability is relatively poor, and in the northern region, the soil contains a large number of acidic salt ions from the erosion of concrete, resulting in a decline in its durability. In this test, concrete was made from the single and composite immersion of recycled coarse aggregate using 5% water glass and 8% silane solution and subjected to a rapid freeze–thaw test in water, 3.5% NaCl solution, and 5% Na2SO4 solution, followed by a capillary water absorption test. The study was conducted to test the durability of recycled concrete, establish the initial capillary water absorption prediction model under freeze–thaw in different media, and analyze the internal structure of the RAC group after freeze–thaw using SEM. The test results showed that the composite-modified water absorption decreased the most, which can effectively improve the durability of recycled concrete, and the chloride salt caused the greatest erosion of recycled concrete and had the least clear water. The predictive model has high accuracy and can be used as a reference for capillary water absorption experiments on recycled concrete.

Effects of elevated temperatures’ exposure on the properties of concrete incorporating recycled concrete aggregates

The concrete and its thermal gradient response must be considered when it is subjected to high temperatures. This study examines the impact of exposure to elevated temperatures (500 °C, 700 °C, and 1000 °C) on concrete's physical and mechanical properties incorporating recycled concrete aggregates (RCA). It emphasizes substituting RCAs for natural coarse aggregate (NCA) at 20%, 40%, 60%, 80%, and 100%. The intended behavior is post-heating; a cold sample serves as a control. The evolution of graduating temperature in the muffle furnace is similar to the ISO curve in a fire. The data analyzed indicate that a temperature rise affects the characteristics of recycled aggregate concrete (RAC). A heating level of 500 °C does not significantly affect the initial resistance, which is not the situation at temperatures of 700 °C and 1000 °C. Regarding residual strength, the concrete with 40% RCAs concrete performs quite well. At 700 °C, its strength loss in compressive strength is 24.4%, whereas the control concrete is 29.8%. Mass loss, capillary water absorption, water-accessible porosity and non-destructive tests reveal that elevated temperature damages RAC. Lastly, XRD, TGA, and SEM microstructural analyses are employed to interpret the fundamental mechanisms of heated RAC due to temperature changes.

Suitability of Vetiver straw fibers in improving the engineering characteristics of compressed earth blocks

Although conventional earth construction has been replaced by modern materials in industrialized nations over the last century, interest in earthen materials has surged in industrialized countries due to their economic, social, and environmental sustainability benefits. Compressed earth blocks (CEBs) have gained popularity for their energy efficiency and lower greenhouse gas (GHG) emissions compared to fired clay bricks or cement concrete (CC) blocks. This research explores the potential of Chrysopogon zizanioides, commonly known as Vetiver, a perennial grass found in tropical and subtropical regions, to enhance the engineering properties of CEBs. While the use of Vetiver roots for soil erosion prevention and slope stabilization is well documented, the impact of Vetiver straw fibers on CEBs has not been sufficiently researched. Here, CEBs were manufactured with varying Vetiver straw fiber contents (0%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% by dry soil mass). The physical properties of the Vetiver straw fiber-reinforced CEBs revealed a reduction in bulk density and volumetric shrinkage. As for the strength-ductility behavior, the Vetiver straw fibers noticeably increased the ductility of the CEBs. However, the rise in strength was not significant, and it showed little change over time. Durability characteristics were assessed through capillary water absorption and wear resistance tests, indicating reduced water absorption and enhanced wear resistance in CEBs with Vetiver straw fibers. Microstructural analysis through scanning electron microscopy reveals a more uniform and isotropic soil matrix with fewer voids, indicating stronger bonding between the fibers and the soil. Overall, Vetiver straw fiber has demonstrated its potential as a valuable reinforcement material for CEBs, making them more sustainable and resilient.

Discussion on the water absorption depth of gangue-based concrete and its relationship with the damage layer thickness

Capillary water absorption is one of the key factors in evaluating the durability of concrete structures. In this paper, solid waste-coal gangue was used as raw material, and activated gangue powder (ACGP) was used to prepare gangue-based concrete (GBC) by partially replacing cement. The capillary water absorption performance of GBC under the action of freeze-thaw cycles was investigated by freeze-thaw cycle test as well as capillary water absorption test. The relationship between water absorption depth and water content was established. The interrelationship between the water absorption depth and the damage layer thickness was analyzed. The test results indicated that the frost resistance of concrete was enhanced after incorporating ACGP. The capillary water absorption performance of GBC was weaker than that of ordinary concrete, with less water content and lower sorptivity, and the effect was most apparent when the dosage of ACGP was 20%. The water absorption depth gradually grew with the number of freeze-thaw cycles and the water absorption time. There was a significant linear correlation between the water content and the water absorption depth, which provided a new insight into the prediction of the hardly measurable water absorption depth from the easily accessible water content. The water absorption depth was significantly higher than the damage layer thickness, and the difference between them was broadened after the incorporation of ACGP. Besides, an approximate linear relationship between the water absorption depth and the damage layer thickness was pointed out.

Inhibiting effect of styrene-butadiene copolymer on the whitening of calcium aluminate cement mortar

This paper was based on the results of the research group's previous research on early whitening of mortars. The inhibition of whitening and changes of white deposit on the surface of calcium aluminate cement (CAC) mortar with styrene-butadiene copolymer (SB) were studied using a long-term accelerated whitening method under conditions of (20 ± 2) ℃ and (60 ± 5)% RH. The whitening phenomenon and white deposits of CAC mortars were studied using digital processing of images, optical microscopy (OM) and scanning electron microscopy (SEM). The results indicate that the white deposit on the surface of CAC mortar primarily consists of newly formed carbonation products, calcium carboaluminate hydrate (C4AC¯H11) and calcium carbonate (CaCO3), and with the extension of this exposure time, C4AC¯H11 will be carbonized to generate CaCO3 and Al(OH)3 (AH3). It is interesting to note that SB reduces the production of C4AC¯H11 and CaCO3 and that at SB dosing levels above 12% the C4AC¯H11 disappears and there is hardly whitening of mortar at this time. The inhibition mechanism of SB on the whitening of CAC mortar was investigated using X-ray diffraction (XRD), capillary water absorption and water contact angle tests. The analysis reveals that hydration product of CAC is mainly CAH10 after curing at 20 ℃ for 1 d, and the addition of SB did not change the type of CAC hydration products. Furthermore, incorporating SB enhances the hydrophobicity and reduces the capillary water absorption in CAC mortar, and forms a polymer film in CAC mortar. They prevent the transfer of ions from the interior of CAC mortar to the exterior and the contact of CO2 from the air with the cement hydrate on the surface of CAC mortar, thus reduces the production of white deposit on the mortar surface and inhibits the whitening of CAC mortar.

Microstructural and mechanical properties of photocatalytic cement mortar with g-C3N4/CoAl-LDH nanoflowers

The g-C3N4/CoAl-LDH nanoflowers with a strong photocatalytic activity under UV–visible light irradiation was synthesized and applied with different dosages to prepare photocatalytic cement mortars (PCM). Besides the photocatalytic assessment by NOx degradation, the effect of g-C3N4/CoAl-LDH on the microstructural and mechanical properties of cement mortars were investigated by means of X-ray diffraction (XRD), X-ray computed tomography (X-CT), mercury intrusion porosimetry (MIP), capillary water absorption and strength tests. The results show that in addition to the unique air self-purification characteristics, g-C3N4/CoAl-LDH can promote cement hydration with filling effect and further improve the microstructural and mechanical properties of mortar. Moreover, the ability of g-C3N4/CoAl-LDH to capture CO32− can alleviate the influence of carbonation on photocatalytic performance. Therefore, g-C3N4/CoAl-LDH exhibits lasting photocatalytic performance in cement-based materials. This work is expected to contribute to the effort of searching for new multifunctional nano-additives for improved sustainability of building materials.

Durability properties of basalt fiber-reinforced mortars with different mineral admixtures exposed to high temperatures

This study investigated the durability properties of mortars containing basalt fiber and various mineral admixtures against high temperatures. Different types of mortar samples were produced with basalt fiber, metakaolin, silica fume and fly ash. The samples were exposed to temperatures of 400 °C, 600 °C and 800 °C. Residual compressive strength, flexural strength, ultrasonic pulse velocity, mass loss, water absorption, capillary water absorption and microscope analysis tests were carried out. Test results revealed that basalt fiber improved the residual durability properties of the mortars exposed to high temperatures. Basalt fibers exhibited bridging behavior and prevented high temperature-induced cracks. Basalt fibers showed excellent consistency with all three mineral admixtures, and the mineral admixtures increased the contribution of basalt fiber to durability properties. Because of this harmony, basalt fiber-reinforced and mineral admixture-added samples had 86.42% greater residual compressive strength and 144.42% greater flexural strength than the control samples. The void-free internal structure provided by mineral admixtures increased the effect of BF and significantly reduced water absorption, capillary water absorption and mass loss values. UPV tests and microscopic analysis revealed that basalt fiber and mineral admixtures reduced high temperature-induced cracks.

GEOTECHNICAL STUDY AND PHYSICO-CHEMICAL CHARACTERIZATION OF SOILS OF THREE QUARRIES IN THE CITY OF ABECHE IN CHAD

This article focus on the geotechnical and physicochemical studies of soils from three sites in the city of Abéché. The article presents the locations of the sampling sites, experimental devices, and some physical parameters. Prior to the geotechnical study, a physicochemical characterization of soil from different quarries was conducted, including wetting-drying tests, capillary water absorption tests, and desorption isotherms of bricks. Finally, geotechnical characterizations of three soils were performed, including analyses of grain size by sieving and sedimentometry, Atterberg limits, methylene blue tests, and the bulk density of solid particles. The results showed that the different soils were very similar, being of a low-plasticity loam and clay type. The results also showed that the organic matter content in the different soils was very low and that the average pH value of the three sites was around 7.1, which is neutral with a slightly basic tendency.

Effects of Curing Methods on the Permeability and Mechanism of Cover Concrete

Curing methods are one of the most important factors in determining the quality and compactness of cover concrete. The effect of curing methods on the water absorption and sorptivity coefficient of cover concrete with the substitution ratio of fly ash (FA) and ground granulated blast slag (GGBS) for cement between 30 and 40 wt % was studied by capillary water absorption test. The vacuum saturation test and mercury intrusion test were employed to characterize these differences in the pore structure of cover concrete under different curing methods. With further analysis of the compactness of microstructure by SEM, the mechanism of the impact of curing methods on the permeability of cover concrete was revealed. The results obtained indicate that the effect of curing methods on the water absorption, sorptivity coefficient and porosity of cover concrete shows the trend of natural curing > cover curing > water curing > standard curing. It is also shown that reasonable curing is advantageous to reduce the porosity and permeability of cover concrete. In natural curing conditions, the appearance of porosity increasing and pore structure coarsening is more critical for cover concrete with mineral admixtures than for pure cement concrete. Therefore, the permeability of cover concrete with mineral admixtures is more sensitive to the early-age curing methods.

Influence of Aeolian Sand on Capillary Water Absorption of Concrete Under Freeze–Thaw Conditions

Aeolian sand (AS) can become a green resource for concrete after the reasonable utilization. Study the evolution of AS concrete (ASC) capillary water absorption (CWA) under freeze–thaw (FT) conditions is of great significance for its popularization and application. One-dimensional (1D) CWA test was performed to analyze the effects of AS and freeze–thaw cycling (FTC) on concrete water absorption characteristics. Pore relative saturation (PRS) and pore saturation were defined to reveal the influence mechanism of AS content on concrete water absorption under FT conditions and predict the moisture distribution in damaged ASC combining with the capillary mechanics theory. The results showed that concrete frost resistance increased with increased AS content and the optimal frost resistance achieved with 100% AS replacement despite its low strength. The initial water absorption rate (WAR), pore saturation, and saturation speed of the ASC decreased with increased AS, while the PRS increased with low AS content but decreased with excessive AS. The water absorption depth increased with increased mass and dynamic elastic modulus loss rates. The mechanism regarding why excessive AS improved concrete frost resistance lay in its internal pore structure and large pore ratio, which reduced pore content that can easily absorb water, enclosed a higher volume of air bubbles, and easily formed "air locking," thereby increasing water transmission resistance and forming long transmission paths during the process of CWA.

An Investigation of Cement Mortars Containing Glass Powder as A Partial Cement Replacement

Lately, because of the pollution caused by cement production waste materials that can be used instead of cement aroused interest by researchers. Glass is one of these waste materials. Glasses due to their nonbiodegradable properties, cause serious environmental risks and recycling this waste material would minimize these environmental concerns. Therefore, finely granulated glass powders, due to their high silicious content are being used as pozzolanic admixture. In this study, glass powders are replaced with cement (by weight) at 0%, 5%, 10% and 15%. And mechanical and durability performances are investigated. Compressive and flexural strength, flow test, abrasion resistance, sulfate resistance and capillary water absorption test were conducted. Results indicated that an increase in glass powder dosage in cement mortars leads to decrease in mechanical properties.

Residual Durability Performance of Glass Fiber Reinforced Concrete Damaged by Compressive Stress Loads

Concrete is exposed to a variety of stresses throughout its service life, which can result in cracks and damage. The use of fibers in concrete mixtures is known to improve the mechanical and durability properties of the concrete. In this study, glass fiber-reinforced concrete cube specimens were produced and stressed at 70 and 90 percent of their maximum compressive strength. The effects of stress loading-induced cracks and glass fiber reinforcements on mechanical and durability properties of concrete specimens were investigated using UPV, capillary water absorption, acid effect, and high-temperature effect tests. Glass fibers increased compressive strength and reduced water absorption in specimens that were not stressed. On the other hand, glass fibers increased the durability of stressed specimens at both degrees of compressive load stress. The bridging effects of glass fibers reduced crack creation, resulting in improved UPV test results. Glass fibers did not dissolve in acid solution due to their chemical resistance, resulting in less weight loss and higher compressive strength in concrete specimens. In the high-temperature effect tests, decreasing compressive strength values were observed as the stress load and temperature levels increased. However, such reductions were lower for glass fiber reinforced concrete than for control concrete without glass fiber. As a result of the present findings, glass fiber reinforcements prevent stress-induced cracks, making the concrete more durable and stronger against external forces.

Influencing factors to the capillary water uptake of (un)cracked cementitious materials

Capillary water absorption tests are widely used in uncracked cementitious materials to assess the quality and durability. Due to the easy execution of the test, it is also frequently used to assess the self-healing efficiency of self-healing concrete and mortar. It is established that the presence of a crack significantly increases the water uptake by a specimen. However, it is not known how the crack width, healing agents and mix composition influence the capillary water absorption. In this research, for cylindrical mortar specimens with four different crack widths, both a capillary water absorption test and water permeability were test were executed in order to investigate the relation between these two test methods. After the first round of testing, cracked specimens were healed manually with polyurethane and methyl methacrylate and the capillary absorption test was performed again to investigate the sensitivity of the test method to different degrees of crack healing. Furthermore, prismatic specimens were cast to investigate the influence of crack creation and geometry. It was found that the crack width does not have an influence on the capillary absorption rate. However, the crack width has a significant influence on the water flow through the crack. As expected, manual healing with polyurethane is better in comparison to the sealing of the crack mouth with methyl methacrylate.

The fracture energy and mechanical properties of high-strength concrete containing polyolefin macro-fibres

In this study, the mechanical properties and fracture energy of high strength fibre reinforced concrete (HSFRC) have been investigated. For this purpose, eight mix compositions have been made in two water-to-binder (W/B) ratios of 0.32 and 0.37. The quantity of coarse and fine aggregates in the two W/B ratios were not the same. The polyolefin macro-fibres were used at three different fibre volume fractions of 0.2, 0.4 and 0.6%. The compressive strength, flexural strength, fracture energy, capillary water absorption, electrical resistivity and ultrasonic pulse velocity tests of concrete mixes were studied. The results showed that polyolefin macro-fibres had negligible effect on the compressive strength. However, the use of polyolefin macro-fibres improved the flexural strength of high-strength concrete. The highest improvement of flexural strength was obtained in the volume fraction of 0.4% at the W/B ratio of 0.32, which improved by 22.1% in comparison to the control mix. Moreover, the fracture energy of high-strength concrete highly depended on the amount of macro-fibres. For instance, the use of 0.2, 0.4 and 0.6% macro-fibres has led to the improvement of fracture energy by 133, 228 and 190% for mixes with W/B ratio of 0.32, respectively. Furthermore, by increasing the amount of fibres, the capillary water absorption coefficient of concrete enhanced; therefore, its water penetration increased.

Mechanical, thermal and durability investigation of compressed earth bricks stabilized with wood biomass ash

There is a growing interest in raw earth as an eco-material of building for its local character and the low energy consumption that characterizes its overall life cycle. This work evaluates the effect of the recovery of two biomass ashes (WBAa, WBAb), resulting from domestic wood heating on the mechanical, thermal and durability properties of compressed earth bricks (BWBAa, BWBAb). These specimens were obtained in a partial substitution of a silty-clay soil by WBA, in various proportions (0, 5, 10, 15 and 20 wt%). The specimens manufactured were compacted with a compaction stress of 10 MPa, exposed to the open air and kept in the laboratory at a 20 ± 2 °C temperature, then allowed to harden for 7 and 28 days. The mechanical level strength increases with wood ash content and with curing time. BWBAb has the best flexural and compressive levels strength caused by formation of compounds with binding properties, but BWBAa shows good thermal insulation. Capillary water absorption test was performed to prevent the durability of the elaborated specimens under water action. These bricks showed different behaviors in contact with water based on the different microstructure present in the two ashes. The experimental study conducted highlighted the benefits of the high periclase (MgO) content on the mechanical properties and durability of compressed earthen bricks.

Investigation on the effects of polyaniline/lignin composites on the performance of waterborne polyurethane coating for protecting cement-based materials

Waterborne polyurethane (WPU) coatings are widely used for the protection of cement-based materials by reducing surface permeability. However, poor mechanical property and moisture permeability caused by good hydrophilicity of WPU coatings limit the protecting application for building engineering. This work has investigated the effect of reinforcing WPU coating with polyaniline/lignin (PL) in protecting cement-based materials. Through the XRD, FT-IR and SEM characterizations, the successful preparation of PL complex has been proved. After the reinforcing of WPU coating by PL, the mechanical property and water contact angle has increased from 1.63 MPa to 2.07 MPa (by 26.99%), and from 72.1° to 116.5° (by 61.58%), respectively. Besides, as shown by capillary water absorption test, the impermeability of mortar with PL-modified WPU (LWPU) coatings has improved, and the capillary water absorption of mortar samples with LWPU coatings at 8 days decreased from 0.3074 mm3/mm2 to 0.1763 mm3/mm2 (by 42.65%). As a result of barrier effect and increased hydrophobicity, the rapid chloride migration (RCM) coefficient of mortar samples with LWPU coatings decreased from 8.52*10−12 m2/s to 6.34*10−12 m2/s by 25.59%. This study demonstrates that PL composites could be used as an effective additive to enhance WPU coating performance in protecting cement-based materials. Such green and effective waterborne coating shows great promises in civil engineering applications.

A Comparative Study on Hygric Properties and Compressive Strength of Ceramic Bricks.

This article analyzes the results of capillary rise, compressive strength and water absorption tests on solid ceramic bricks from existing structures and demolition materials taken from 11 different structures. In addition (for more extensive interpretation and evaluation of porosity), tests were performed for the selected series of bricks using a mercury porosimeter (MIP) and a micro computed tomography (micro-CT). Contemporary bricks (2 series) were also evaluated for comparison purposes. The conducted tests indicate that bricks obtained from different sources are characterized by "individual" relation of compressive strength and porosity, and "individual" relation of water absorption coefficient and porosity. In addition, on the basis of the results obtained in the study, compared with the literature data, it can be deduced that ceramic bricks with a water absorption coefficient of less than 50 g/m2s0.5 are characterized by a compressive strength of more than 80 MPa. As the research shows, the properties of bricks even from a single building can differ one from another, which can result in varying durability even within a single building. When choosing a material during the renovation or restoration of facilities, it is important to perform tests on the physical and mechanical properties of the original material, which will be reused.