Volume Of Coarse Pores Research Articles

Impact of heat curing regime on the compressive strength and drying shrinkage of alkali-activated slag mortar

Heat curing has been recognized as one of the strategies to mitigate the shrinkage of alkali-activated slag (AAS) mortar. However, the impacts of heat curing regime on the drying shrinkage and the compressive strength of AAS mortar remain unclear. Therefore, this paper investigated the performance of AAS mortars cured at three different temperatures and four different durations. The results show that the heat curing hinders the late-age strength development of AAS mortars, particularly for those with an insufficient curing duration. This is related to the retarded early alkaline reaction and the increased volume of coarse pores inside the mortars. Furthermore, increasing the curing temperature is more effective in mitigating the drying shrinkage of AAS mortars than extending the curing duration. The decrease of drying shrinkage is primarily attributed to the reduced viscous deformation during the drying process, although the heat curing tends to increase the effective capillary pore pressure.

Tensile bond strength of lime-based mortars: The role of the microstructure on their performance assessed by a new non-standard test method

In recent years the study of renderings within conservation practice has acquired major technical and methodological advances. Due to the need of compatibility, usually repair mortars must be based on lime, and standardized tests are sometimes ineffective for these compatible substitution materials, which are often low strength mortars. The influence of the aggregates' characteristics on several factors that affect the adhesive strength of lime-based mortars is assessed and a new non-standard test method to determine the tensile bond strength of low strength mortars to porous substrates is presented and validated. The outcome shows that the new methodology offers the advantages of precision of the test device, ease of application and mostly consistency of the results. Furthermore, the main data show close relationship between the tensile bond strength and the pore size distribution of the mortars, which is very sensitive to the aggregates’ characteristics: In general, increasing the mortars pore volume of coarse pores (above the critical pore diameter of the substrate) strengthens the effective bond between these elements. Moreover, the compositional similarity between the aggregates and the substrate could also favour the bond between these elements.

Soil Structure and Its Relationship to Shallow Soil Subsidence in Coastal Wetlands

Accelerating sea-level rise poses a threat to mangroves and salt marshes. Sediment accretion on the soil surface and belowground root production is proposed to increase soil elevation enabling these intertidal habitats to maintain their position relative to mean sea level. However, shallow soil subsidence is frequently observed, which may cancel out or even outweigh the positive effects of surface accretion and root production on soil elevation gains. The processes that lead to shallow soil subsidence have not often been investigated. Here, we used computed tomography (CT) imaging to determine the volume of coarse pores in the top 20 cm of 30-cm-deep soil cores collected from mangroves and salt marshes within Moreton Bay, eastern Australia. The four field sites have long-term observations of variation in soil surface elevation gain, surface accretion rate, and shallow subsidence rate using the rod surface elevation table-marker horizon (RSET-MH) method. Over our sites, we found that the rates of shallow soil subsidence were positively related to the volume of soil coarse pores and soil clay and silt content rather than to the volume of fine pores or total porosity or other soil properties. In turn, the volume of soil coarse pores was positively related to the volume of animal burrows and root mass. Fine-pore volume and total porosity of soils were negatively associated with soil bulk density, which was in turn negatively related to soil organic matter content. Our results indicate influences of differently sized soil pores in shallow soil subsidence and suggest that animal burrowing may play a role in shallow soil subsidence.

Effect of sensor installation on the accurate measurement of soil water content

SummaryWe evaluated the effects of different methods of installing a capacitance soil moisture sensor on the sensor's output with six soil types and three methods of sensor installation. For Method 1, the sensor was first placed in a container and then buried. For Method 2, the entire sensor (including prongs and circuitry) was inserted into a prepacked soil sample. For Method 3, the sensor prongs were installed directly into a prepacked soil sample, and then soil was placed around the circuitry. The sensor outputs of Method 1 were significantly smaller for the volumetric soil water content (θ) of most of the soil types compared with the sensor outputs of the other two methods. Large differences in sensor outputs were observed in relation to the installation method, which resulted in a large estimation error when using a soil moisture sensor. For example, the difference in θ values calculated by the calibration equation obtained by Methods 1 and 2 was 0.076 m3 m−3, a maximum for the Andisol sample. We observed a significant linear relation between the maximum differences in θ (which might result from the different sensor installation methods) and the coarse pore volume determined from soil water characteristic curves. Compaction around the sensor induced by sensor installation, which might be considerable for soil with many coarse pores, was considered the main reason for an increase in the soil moisture sensor's output value. For the sensor installed by Methods 2 or 3, a second‐order polynomial equation could be used to translate sensor output to θ accurately except for soils with > 40% clay content or very low bulk density.Highlights An appropriate calibration equation is important to monitor soil water content precisely. Effects of different sensor installation methods on calibration equations have not been determined. Method of installation considerably affected output values of a capacitance sensor. Soil compaction by sensor installation increases the sensor output: more so in coarse pore soil.

Soil physicochemical properties and moisture dynamics of a large soil profile in a tropical monsoon forest

Evergreen forests in tropical monsoon Asia experience a severe dry season lasting several months. Deep soil moisture is responsible for evergreen forest transpiration during this season. This study provides preliminary information on soil physicochemical properties in a large soil profile (800cm deep) and evaluated the influences of deep-soil moisture dynamics on the transpiration of evergreen forests in Cambodia using a water flow model. In general, changes in soil physicochemical properties with depth were small, excluding topsoil. The soil texture in the large soil profile was characterized by very little gravel and a large sand fraction. The soil carbon stock was 71.7 and 130.1Mg Cha−1 at depths of 0–150 and 0–800cm, respectively. The coarse pore volume (−100≤ψ<−0.2cm) and saturated hydraulic conductivity (Ks) clearly decreased with depth from 100 to 600cm and were extremely low at 600–700cm. In the water flow simulation, a rooting depth deeper than 400cm was necessary for the evergreen forest to maintain transpiration during the dry season. On the other hand, when the Ks of deep soil (550–750cm depth) was assumed to be higher than that estimated by the cylinder sample, a rooting depth of 800cm was necessary, since most of the soil water that was replenished during the rainy season was rapidly lost during the dry season. Also, it was necessary for evergreen forests to effectively use soil water within the deep root zone (400–800cm depth). The compacted deep soil horizons played an important role in maintaining the moist conditions in the root zone of an evergreen tropical monsoon forest in Asia that experienced a severe dry season.

Zur Wirkung von Kalium auf ausgewählte bodenphysikalische Eigenschaften und den Wurzeltiefgang landwirtschaftlicher Kulturpflanzen

Soil physical properties and root penetration (root depths, root growth rate) of various crops (sugar beet, corn, spring barley, winter barley) were studied in a long-term K-fertilization trial on loess chernozem in Bernburg, Germany. Over the last 14 years, annual K/Mg applications in the treatments were 0/0; 83.0/0; 41.5/4.5; 83.0/9.0; 124.5/13.5 kg ha−1, respectively. In comparison with the unfertilized treatment, continuous K supply led to an increase in soil water content within the whole range of water retention function up to the permanent wilting point (pF 4.2). Higher soil K concentrations increased coarse pore volume and water capacity at comparable dry bulk density. At the highest K level (winter wheat), the storage capacity for plant-available soil water (available water capacity) of the topsoil (0–30 cm soil depth) increased by 6 mm (relatively 9%) in comparison with the unfertilized treatment. A favourable soil structure at the higher K level enhanced plant emergence and development in the early growth stages. This advance in plant development improved the root penetration of plough pan as well as the complete exploitation of the effective root zone. Plants with different root systems (tap roots or fasciculated root systems, respectively) showed similar response to increased K supply. Root growth rate was affected by annual weather conditions. K fertilization increased root growth rate within the first weeks after emergence, particularly in sugar beet and corn, but also in winter barley. The difference in spring barley was only significant in 2010.

Soil pore characteristics of evergreen and deciduous forests of the tropical monsoon region in Cambodia

AbstractBoth evergreen and deciduous forests (Efs and Dfs) are widely distributed under similar climatic conditions in tropical monsoon regions. To clarify the hydraulic properties of the soil matrix in different forest types and their effects on soil water storage capacity, the soil pore characteristics (SPC) were investigated in Ef and Df stands in three provinces in Cambodia. Soils in the Ef group were characterized in common by large amounts of coarse pores with moderate pore size distribution and the absence of an extremely low Ks at shallow depths, compared to Df group soils. The mean available water capacity of the soil matrix (AWCsm) for all horizons of the Ef and Df group soils was 0·107 and 0·146 m3 m−3, respectively. The mean coarse pore volume of the soil matrix (CPVsm) in the Ef and Df groups was 0·231 and 0·115 m3 m−3, respectively. A water flow simulation using a lognormal distribution model for rain events in the early dry season indicated that variation in SPC resulted in a larger increase in available soil water in Ef soils than in Df soils. Further study on deeper soil layers in Ef and each soil type in Df is necessary for the deeper understanding of the environmental conditions and the hydrological modelling of each forest ecosystem. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Effect of compaction on pore functions of soils in a Saalean moraine landscape in North Germany

AbstractSoil compaction and related changes of soil physical parameters are of growing importance in agricultural production. Different stresses (70, 230, 500, and 1000 kPa) were applied to undisturbed soil core samples of eight typical soils of a Saalean moraine landscape in N Germany by means of a confined compression device to determine the effect on (1) total porosity/pore‐size distribution, (2) saturated hydraulic conductivity, and (3) air conductivity to assess the susceptibility towards compaction. Different deformation behaviors after exceeding the mechanical strength particularly resulted from a combination of soil characteristics like texture and initial bulk density. The saturated hydraulic conductivity, as an indicator for pore continuity, was largely affected by the volume of coarse pores (r² = 0.82), whereas there was no relationship between bulk density and saturated hydraulic conductivity. Since coarsely textured soils primarily possess a higher coarse‐pore fraction compared to more finely textured soils, which remains at a high level even after compaction, only minor decreases of saturated hydraulic conductivity were evident. The declines in air conductivity exceeded those in hydraulic conductivity, as gas exchange in soils is, besides the connectivity of coarse pores, a function of water content, which increases after loading in dependence of susceptibility to compaction. A soil‐protection strategy should be focused on more finely textured soils, as stresses of 70 kPa may already lead to a harmful compaction regarding critical values of pore functions such as saturated hydraulic conductivity or air capacity.

Drying Shrinkage of Cement-Based Materials Under Conditions of Constant Temperature and Varying Humidity

Currently, deformations along the central axis of specimens were usually measured under fixed environmental conditions. Seldom were the effects of environmental factors on the drying-shrinkage deformation of cement-based material considered. For this paper, the drying-shrinkage deformation at different w/b ratios and different additions to mortars was investigated under different environments at a temperature of 20 °C and humidity ranging from 100% to 50%. The specimens were cured in water for 28 days before measurement. The results illustrate that mortar shows much less shrinkage under various drying conditions when a lower w/b ratio is adopted. With a decrease in relative humidity the speed of drying-shrinkage becomes gradually lower. The addition of silica fume reduces the drying-shrinkage of mortar under higher relative humidity, because the pore structure of mortar with silica fume becomes more refined. The addition of fly ash increases the total porosity and the volume of coarse pores in the mortar. The drying-shrinkage of mortar under different conditions increases with the addition of more of fly ash.

Forest damages by the storm 'Lothar' in permanent observation plots in Switzerland: The significance of soil acidification and nitrogen deposition

In a network of permanent observation plots in Switzerland,the storm ‘Lothar’ uprooted 18.7% of Fagussylvaticaand 14.8% of Picea abies. The percentage of uprootingwas significantly inversely correlated with actual soil basesaturation (NH4Cl-extract). At a base saturation of≤40% (calculated as an average over 0–40cm depth) uprootingwas increased by a factor of 4.8 in beech and by a factor of3.6 in Norway spruce compared to less acidic soils. In beech,the percentage of uprooted trees was also significantlycorrelated with nitrogen concentration in the leaves(positively) and with coarse pore volume in the soil(negatively). There was neither a relation with seasonalozone dose nor a relation with crown transparency, stemdiameter, crown size, slenderness, social position andposition within the stand. The results suggest thatanthropogenic stress factors play an important role in theextent of the ‘Lothar’ damages in Switzerland.

Global weapons’ fallout 137Cs in soils and transfer to vegetation in south–central Chile

The contamination and depth distribution of 137Cs in soil due to the fallout from atmospheric weapons’ tests were measured at 29 sites in the 9th and 10th administrative regions in Chile located in the 40 ° latitude in the southern hemisphere. The depth distribution in most of the sites follows no systematic pattern in the upper few centimetres, but below this depth an exponential decline could be deduced. The calculated relaxation depth appears to be a good indicator for estimating the long-term 137Cs distribution in these soil profiles. It ranges from 4.4±1.9 cm in Palehumults to 8.4±4.4 and 9.7±5.1 cm in Hapludands and Psamments, respectively. For these soil types the value for the relaxation depth tends to increase with decreasing clay content and increasing volume of coarse pores. 137Cs activity densities at the selected sites ranged from 450 to 5410 Bq m −2 and correlate significantly ( r=0.791∗∗) with the mean annual rainfall rate of the sampling sites. 137Cs concentration ratios of prairie plants/soil were found to be in the range 0.008–2.3 and could be related to relaxation depths in undisturbed soils.

The effect of wollastonite micro-fibre aspect ratio on reinforcement of Portland cement-based binders

Reinforcement of Portland cement-based binders with natural wollastonite microfibres has been further investigated with emphasis on the effect of fibre geometry on property modification. Wollastonite micro-fibres were separated into five different size groups before addition to cement and cement-silica fume matrices. The aspect ratio (length/width) of the wollastorite micro-fibres was determined by scanning electron microscopy technique. Systematic experimentation including flexural tests, mercury intrusion porosimetry, helium gas pycnometry, and isopropyl alcohol saturation measurement showed that, at constant micro-fibre content, the flexural strength and total porosity of the composites remained essentially unchanged and independent of the aspect ratio of the wollastonite micro-fibres. However, the volume of coarse pores, the pore size distribution, the flexural toughness and overall ductility characteristics of the hydrated cement and cement-silica fume matrices were observed to change systematically as the aspect ratio of wollastonite micro-fibres was increased. A discussion of the differences in the observed properties is presented.

Physical properties of forest soils in northern kyoto with special reference to their pedogenetic processes

Abstract The physical properties and morphological characteristics of clayey podzolic soils and brown forest soils in the northern Kyoto region were studied. These podzolic soils were characterized by dense eluvial horizons with a higher bulk density and a lower volume of coarse pores and a lower water permeability than the underlying B horizons or the surface horizons of brown forest soils. These observations suggested the presence of a close relationship between the formation of the dense surface horizons and active eluviation of Fe under reduced conditions in these horizons. Based on the comparison of the physical properties with the chemical and mineralogical characteristics of the soils, it was assumed that the pedogenetic process of the podzolic soils in this region was as follows: 1. Al eluviation from the surface horizons due to strong acidification resulted in the decrease of the content of amorphous components of Al, followed by a weakening of the crumb structure. 2. As a result, the dense surfa...

硬化モルタル及びコンクリート中の遷移帯厚さの評価並びに遷移帯厚さと強度との関係の検討

A method for estimation of the thickness of transition zone is proposed by calculating the coarse pore volume in transition zone from discrepancy between pore size distribution of hardened mortar and concrete and hardened cement paste using specific surface area of aggregate. Thickness of layer of coarse pore in transition zone of mortar and concrete at the age of 28 days is calculated at 14.6μm and 12.3μm, respectively, and average thickness of transition zone in mortar and concrete is estimated at 30μm and 25μm, respectively by the method proposed. These values coincide well with those determined by SEM observation. Transition zone in mortar and concrete is generally formed at 3 days after placing mortar and concrete and increases in its thickness reaching the maximum value at 7 days and gradually decreases in its thickness with age although the change is not remarkable especially in concrete. Estimation of development strength and explanation of the difference of strength development between cement paste, mortar and concrete can be obtained from the time dependency of thickness and pore structure of transition zone.

An analysis of factors affecting coarse pore volume of forest soil with the quantification-I method (II)

An analysis of factors affecting coarse pore volume of forest soil with the quantification-I method (II)

An analysis of factors affecting coarse pore volume of forest soil with the quantification-I method (I)

An analysis of factors affecting coarse pore volume of forest soil with the quantification-I method (I)

Porosity In The Microstructure Of Blended Cements Containing Fly Ash

AbstractThe changes in porosity of OPC and an OPC-fly ash blended cement during hydration have been studied at water/solids ratios of 0.35, 0.47 and 0.59, cured for times of up to 1 year at 25°C. The porosity was measured indirectly by methanol exchange and methanol adsorption techniques and, directly, by quantitative image analysis using backscattered electron imaging in the scanning electron microscope. Measurements of porosity and of remaining anhydrous material by image analysis showed good correlation with indirect methods. Measurement of the diffusion of methanol and of the compressive strength were made in parallel with the determination of the porosity during hydration and attempts were made to relate the properties to the microstructure. For both binders the reduction of total porosity with increased reaction was small. The major change in pore structure was the subdivision of coarse pores by gel to form finer pores. Compressive strength and diffusion properties were dominated by the relative volume of coarse pores.

Porosity in the Microstructure of Blended Cements Containing Fly Ash

ABSTRACTThe changes in porosity of OPC and an OPC-fly ash blended cement during hydration have been studied at water/solids ratios of 0.35, 0.47 and 0.59, cured for times of up to 1 year at 25°C. The porosity was measured indirectly by methanol exchange and methanol adsorption techniques and, directly, by quantitative image analysis using backscattered electron imaging in the scanning electron microscope. Measurements of porosity and of remaining anhydrous material by image analysis showed good correlation with indirect methods. Measurement of the diffusion of methanol and of the compressive strength were made in parallel with the determination of the porosity during hydration and attempts were made to relate the properties to the microstructure. For both binders the reduction of total porosity with increased reaction was small. The major change in pore structure was the subdivision of coarse pores by gel to form finer pores. Compressive strength and diffusion properties were dominated by the relative volume of coarse pores.

Results of studies made from 1977 to 1984 to control erosion by cover crops and no-tillage techniques in Paraná, Brazil

From 1977 to 1984, the influence of tillage and cover crops on soil erosion and yield of main crops was studied on Oxisols in Paraná, Brazil. Tillage systems were no-tillage (NT), minimum tillage with a chisel plough (CP) and conventional tillage with a disc plough (CT). It was found that under NT, as compared to CT and CP, the total pore volume and coarse pore volume were lower, bulk density in the upper soil layer was higher, available moisture was higher, temperature was lower and infiltrability was higher. Percentage of soil cover was the main factor governing infiltration rate. Without soil cover the infiltration rate under NT was the same as under CP and CT. The use of cover crops and crop rotation had a marked positive effect on maize, soya bean and bean yields. Yields of wheat and soya beans were higher under NT and CP. It is concluded that in Paraná no-tillage in combination with adapted cover crops and crop rotations represents a production system which is efficient in reducing water runoff and consequently soil erosion, and in increasing crop yields.

Wirkungen meliorativer Gaben von Gesteinsmehlen und Gesteinssanden auf das Wachstum verschiedener landwirtschaftlicher Kulturpflanzen sowie auf physikalische Kennwerte eines Sandbodens und eines Tonbodens

Abstract Effect of amelioration doses of rock powder and rock sand on growth of agricultural plants and on physical characteristics of sandy and clay soil The effect of rock powder to increase the water holding capacity and adsorption degree of sandy soil and the influence of rock sand to augment the aeration and improve the workability of clay soil were tested in pot experiments.Additions of different rock powders (Basalt, Grauwacke, Kuselit, Muschelkalk and Porphyr) from 5 to 20 weight percent to sandy soil increased the field capacity; the increase in values ranged from 12 to 23% as compared to control. An 11% increase in coarse pore volume (&lt; pF 1.8) of clay soil was noticed when 10 weight percent rock sand was mixed in it. The shear strength of clay soil was hardly decreased. In short time tests five different plants reacted mostly positive to rock powders in sandy soil, the degree of reaction being different depending on rock type and amount used whereas in clay soil the reaction was slightly negative. Ten percent weight additions were better than 20 percent.Up to 67% increase in spring barley grain yield was registered in sandy soil with addition of 10 weight percent of different rock powders both at about 40 and 80% field capacity water levels. High N‐application i.e., 1600 mg N/7 kg soil caused a depression in yield at control whereas it increased the dry matter yield in treated pots. In clay soil at 80% field capacity an increase in grain yield was registered only in Grauwacke and Basalt treatments, which was off set at high N‐level. Porphyr and Kuselit treatments produced yield depressions.Addition of 10 weight percent of rock powders in sandy soil in the first year of experiment reduced the amount of leachate and nitrate leached between 8 to 29% in fallow treatments, but in planted treatments these were dependant on plant type and rock type even showing an increase in one case.