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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Road salt retention and transport through vadose zone soils to shallow groundwater</title>
      <link>https://trid.trb.org/View/1739647</link>
      <description><![CDATA[Increasing background salinity in watersheds has largely been attributed to road salt retention in groundwaters due to their long residence times. However, laboratory studies demonstrate that soils temporarily store salts, either in porewater or adsorbed onto particles. Field studies of road salt retention in soils are nevertheless rare, and mechanisms of salt transport across multiple hydrological reservoirs (e.g., from soil to groundwater) are unknown. Thus, the authors collected roadside soil porewater and karst spring water weekly for ~1.5 yr to determine salt transport through the vadose zone into the phreatic zone. They observed dual retention mechanisms of sodium (Na⁺) and chloride (Cl⁻) in soils due to slow porewater movement, causing ion movement through the soil as slow as 1.3 cm/day, and cation exchange processes, leading to initial Na⁺ retention followed by later release months after application. Cation exchange processes also caused base cation loss from exchange sites into mobile porewater. Rapid Na⁺ and Cl⁻ delivery to groundwater occurred through karst conduits during the winter. However, elevated background levels of salt ions in groundwater during the non-salting months indicated accumulation in the catchment due to slower porewater flow in the soil and rock matrix and delayed Na⁺ release from soil exchange sites.]]></description>
      <pubDate>Tue, 27 Oct 2020 12:24:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/1739647</guid>
    </item>
    <item>
      <title>Impact of wetting—drying cycles on the mechanical properties of lime-stabilized soils</title>
      <link>https://trid.trb.org/View/1672840</link>
      <description><![CDATA[This article addresses the results of an experimental study on the behavior of soil; this soil was exposed to long-term treatment with lime and numerous wetting-drying cycles. This research investigated the effect of a wide range of lime contents on the soil volume, soil water content evolution and durability (unconfined compressive strength (UCS), plasticity index (PI) and cation exchange capacity (CEC)) for stabilized soil in contact with water. This experimental study was performed on soil treated with lime (varying from no lime to 8%) corresponding to three levels of improvement: soil improvement only, stabilization and insensitivity to water, and long-term stabilization during wetting-drying cycles. The results indicated that the UCS increases, PI and CEC decreases with the lime level. For lime levels above 4%, the behavior of the treated soil under wetting-drying was satisfactory. Mineralogical analyses indicated that the formation of calcium silicate hydrate C-S-H, ettringite C-S-A-H is responsible for the increased or decreased strength of the treated soil. CaO, SiO₂ and Al₂O₃ were three important minerals responsible for the increase or decrease in soil sample stabilization. Simple model executed in JMP statistical software was proposed and validated. The authors note that CaO and SiO₂ have the most influential effects by very low values of probability for the responses studied, which confirms the hypothesis that these models can be used to model UCS and PI in curing time and wetting-drying cycles.]]></description>
      <pubDate>Sat, 21 Dec 2019 12:03:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/1672840</guid>
    </item>
    <item>
      <title>Modification of CA-Montmorillonite by Low-Temperature Heat Treatment</title>
      <link>https://trid.trb.org/View/1366848</link>
      <description><![CDATA[Objectives of this investigation were to measure the effects of moderate heat treatments (below the dehydroxylation temperature) on physical and chemical properties of a calcium (Ca)-montmorillonite clay. Previous workers have noted the reduction in cation exchange capacity and swelling property after heating in the range 200 to 400°C, and have suggested several possible explanations, such as hysteresis effect, increased inter-layer attractions due to removal of inter-layer water, or changes in the disposition of inter-layer or layer surface ions. The liquid limits of Ca-montmorillonite were steadily decreased with increased temperature of treatment, levelling at about 450°C. The plastic limit decreased slightly up to 350°C, above which samples could no longer be rolled into threads. The gradual change is in contrast with sudden major changes noted for weight loss (maximum rates of change at l00°C and 500°C), glycol retention surface area (520°C), and d001 diffraction peak intensity (17.7 A spacing) and breadth after glycolation (530°C). Other properties showing more gradual reductions with heat treatment were amount of exchangeable calcium (without water soaking), cation exchange capacity by NH4AC method, and d001 intensity (21 A spacing) after storing at 100% r.h. one month and re-wetting with water. Previous water soaking allowed much greater release of fixed Ca++ up to 450°C. Similar results were obtained with cation exchange capacities when samples were treated with N CaCl2 solution. The 21.0 A peak intensity curve showed close similarity to the liquid limit and plastic index curves in the low temperature range, and an explanation is suggested.]]></description>
      <pubDate>Fri, 25 Sep 2015 16:17:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/1366848</guid>
    </item>
    <item>
      <title>SWELLING MODEL OF MONTMORILLONITE IN CONSIDERATION OF INTERMOLECULAR FORCE</title>
      <link>https://trid.trb.org/View/1351787</link>
      <description><![CDATA[Due to the high cation exchange capacity and large potential of swelling when wet, bentonite is the promising material for use in the disposal of the high-level radioactive waste. However, its swelling ability is affected by cations leached from both concrete barrier container and groundwater. This paper describes the phenominetic model of bentonite swelling in electrolyte solution, forcing on that for montmorillonite that is the main component in bentonite, to elucidate the effect of kind of cation on its swelling ability. It was assumed that swelling of montmorillonite caused according to two different steps：First step was the swelling of tactoids that were the assembles of basic layered element, so-called clay lamella, of montmorillonite and then second step, which was the rearrangement of structure in solution, was occurred. Swelling tactoids can be calculated from slit like pore model between two parallel plates considering the intermolecular forces between plates. As for rearrangement of aggregate structure of tactoid, it was assumed the actoides were aggregated and formed diamond-shaped structure, and to chemical potential in bulk solution that was equilibriumed to the solution in the slit pore. The later assumption required the when the slit distance was small, the chemical potential of bulk solution was influenced by the intermolecular forces between plates. The deformation due to rearrangement of structure could be calculated from difference between the experimental volume and the swelling volume of tactoids. It could be found that there was a good relationship between chemical potential and deformation due to rearrangement of structure despite the kind of cation. This enable the authors to estimate the effect of kind of cation on swelling of montmorillonite in electrolyte solutions.本研究では陽イオンによるモンモリロナイト（Mo）の膨潤モデルの構築を行った。Moの体積変化は（1）Moの基本構造の単位層の集合体であるTactoid（Ta）の膨潤による体積変化と、（2）Taが形成する粗大構造の膨潤による体積変化の総和と考えた。前者は2平板の分子間力を考慮したモデルより算出し、後者の粗大構造の変化は実測した体積変化とTaの膨張による体積変化の差から算出した。粗大構造中の溶液とTa中の単位層間の溶液は一様であると考え、その化学ポテンシャルを2平板間の分子間力により決定した。その結果、粗大構造と化学ポテンシャルにはイオン種によらず関係性が見られ、化学ポテンシャルに基づくMoの膨潤予測モデルの構築ができた。]]></description>
      <pubDate>Tue, 26 May 2015 16:12:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/1351787</guid>
    </item>
    <item>
      <title>Effects of Chemical and Mineralogical Properties on the Engineering Characteristics of Arkansas Soil</title>
      <link>https://trid.trb.org/View/1333150</link>
      <description><![CDATA[Soil samples were collected from 82 soil series in 15 Arkansas counties and analyzed for engineering, chemical, and mineralogical properties. The objectives were (1) determine if soil chemical and physical properties can be related to soil engineering properties, and (2) determine if clay mineralogical composition is related to the chemical and physical properties that are related to soil engineering properties. All data were subjected to linear regression analysis. First, the data from all 15 counties were combined and results for liquid limit (LL), plasticity index (PI), group index (GI), maximum density (MD), and optimum moisture (OM) were treated as dependent variables. The independent variable was either cation exchange capacity (CEC), % clay (C), % expandable clay (PE), exchangeable potassium (K) or exchangeable calcium (Ca). Then the data were subdivided according to texture, horizons, plastic or non-plastic, parent material, and families to determine if R² values could be improved. The mineralogical and chemical data were also analyzed by the two groupings. The variables, illite (I), amorphous material (A), quartz (Q), vermiculite (V), montmorillonite (M), kaolinite (Ka), exchangeable potassium (K), and CEC were each treated under separate analysis as the independent variable and all others functioned as the dependent variables. The results revealed: (1) Data for CEC or C from all 15 counties can be combined and used to predict LL, PI, GI, MD, and OM; (2) Mineralogical data can be used to predict CEC of these respective soils; and (3) There was no advantage in dividing the data into soil subgroupings.]]></description>
      <pubDate>Thu, 04 Dec 2014 12:16:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/1333150</guid>
    </item>
    <item>
      <title>Performance of GCL after 10 Years in Service in the Arctic</title>
      <link>https://trid.trb.org/View/1314256</link>
      <description><![CDATA[The performance of a geosynthetic clay liner (GCL) installed as part of a geocomposite barrier (geomembrane/GCL) to contain a hydrocarbon spill adjacent to the Arctic Ocean was evaluated by examining sacrificial samples exhumed after 1, 4, 6, 7, and 10 years in service. The hydraulic and chemical characteristics of the GCL were most affected by the location within the soil profile relative to the water table (typically about 1.3 m below ground level). The bentonite in the GCL samples exhumed from a depth of 0.0-0.8 m was well hydrated with a dispersed structure. Despite the significant cation exchange that took place between these GCL samples and the surrounding soil (the percentage of the exchangeable sodium decreased from 68% to 10-15%), there was no change in the hydraulic conductivity (k) of GCL for tap water or jet fuel. A similar bentonite structure was observed for GCL samples exhumed from 0.8 to 1.3 m below ground level; however, an observed network of horizontal and vertical microcracks (200-400 μm wide) in the bentonite layer was attributed to the formation of ice lenses. As a result, the k of these GCL samples increased by one to two orders of magnitude when permeated by both tap water and jet fuel. The bentonite in GCL samples exhumed from below the water table after 6 and 10 years was flocculated with relatively high free pore space. The k values of these samples increased by one to four orders of magnitude for tap water and jet fuel. Despite this increase in k at some depths, there was no evidence of migration of hydrocarbons through the barrier over the last 10 years, indirectly suggesting that the subsurface geocomposite barrier system is still performing well.]]></description>
      <pubDate>Thu, 24 Jul 2014 15:21:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1314256</guid>
    </item>
    <item>
      <title>Studies on Tobermorite-Like Calcium Silicate Hydrates : Technical Paper</title>
      <link>https://trid.trb.org/View/1219282</link>
      <description><![CDATA[Parallel studies were carried out on certain characteristics of CSH(l) synthesized at room temperature and on CSH(gel) produced by paste or bottle hydration. Instrumental methods employed included x-ray diffraction, DTA, infrared spectroscopy, and electron microscopy. Surface areas of the CSH(l) samples were measured by water vapor adsorption and heats of adsorption were calculated. Both CSH(l) and CSH(gel) were shown to have a negative surface charge in the absence of Ca(OH)2. A method was devised to measure the cation exchange capacities of these materials, and the exchange capacities measured were the order of 5-20 meq/100g. The evidence suggests that CSH(gel) is a single, well-defined phase regardless of starting material or mode of hydration, and that CSH(l) has well-defined properties regardless of variations in composition. The two phases are difficult to distinguish by x-ray methods, but can be differentiated by the intensity of the high-temperature exotherm on DTA, by particle shape as revealed by electron-microscopic observation, and by the appearance of the main Si-0 vibration band region in infrared spectroscopy.]]></description>
      <pubDate>Tue, 11 Dec 2012 11:56:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/1219282</guid>
    </item>
    <item>
      <title>Detection of Aggregate Clay Coatings and Impacts on Concrete</title>
      <link>https://trid.trb.org/View/926020</link>
      <description><![CDATA[This article will discuss how deleterious clay minerals often enter concrete as coatings on aggregates. The impacts of the certain clays introduced by this mechanism is the subject of this study. The effects of different clay properties, including cation exchange capacity (CEC) and the nature of the exchangeable cations on concrete, were measured. The material selected for this research was an igneous clean coarse aggregate which, for purposes of repeatability and experimental control, was lab-coated with four different clay suspensions (kaolin, illite, sodium montmorillonite, and calcium montmorillonite). The coated aggregate was then used to make concrete test specimens. The results clearly show that the impact of the clays is not only a function of the CEC of the clay but also of the nature of the exchangeable cation.]]></description>
      <pubDate>Thu, 19 Aug 2010 11:18:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/926020</guid>
    </item>
    <item>
      <title>Chemical Alteration of Calcium Silicate Hydrate (C-S-H) in Sodium Chloride Solution</title>
      <link>https://trid.trb.org/View/876626</link>
      <description><![CDATA[The effect of sodium chloride on the chemical alteration of calcium silicate hydrate (C-S-H) was measured and discussed. The release of calcium from C-S-H was increased as the concentration of sodium chloride in the solution increased. It was observed that sodium sorbed onto the C-S-H phases and some sodium replaced calcium in C-S-H so that the release of calcium was enhanced. An integrated modeling approach employing an ion-exchange model and an incongruent dissolution model of C-S-H is developed. It reasonably and accurately predicted the release of calcium from C-S-H in sodium chloride solution by considering cation exchange and the effect of the ionic strength on the solubility of C-S-H.]]></description>
      <pubDate>Tue, 30 Dec 2008 12:32:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/876626</guid>
    </item>
    <item>
      <title>CATIONIC SUBSTITUTION IN TRICALCIUM ALUMINATE</title>
      <link>https://trid.trb.org/View/746863</link>
      <description><![CDATA[Tricalcium aluminate in normal Portland cement clinkers is generally modified in chemical composition by cationic substitutions.  In this study, cubic and orthorhombic crystals of tricalcium aluminate doped with sodium oxide, iron oxide and silicon dioxide were prepared and examined using an electron probe microanalyzer.  The cationic ratios based on six oxygen atoms were derived from the oxide compositions. These data, together with those in previous studies for clinker aluminates containing Mg2+ and K+, provided excellent correlations between Al+Fe and Si (Al+Fe=2.001-1.03Si) and Ca+Mg and Na+K+Si [Ca+Mg=3.006-0.51(Na+K+Si)]. The chemical variation that is constrained by these equations is accounted for by the general formula (Na,K)sub2x(Ca,Mg)sub3-x-y[(Al,Fe)sub1-Siy]sub2O6, where x is the amount of Ca substituted by Na and, and y is the amount of Al substituted by Si.  The crystal system changed from cubic to orthorhombic with increasing x value.  The substitution of Si and Fe for Al extended the solid solution range of the orthorhombic phase to lower values of x, while its effect on the solid solution range of the cubic phase was reversed.  The modified general formula proposed here may be applicable to a wide range of chemical variations in solid solutions.]]></description>
      <pubDate>Mon, 27 Dec 2004 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/746863</guid>
    </item>
    <item>
      <title>EFFECT OF PETROGRAPHIC VARIATIONS OF SOUTHWESTERN IOWA LOESS ON STABILIZATION WITH PORTLAND CEMENT</title>
      <link>https://trid.trb.org/View/122443</link>
      <description><![CDATA[PROPERTIES OF LOESS SOILS ARE STUDIED FOR AN UNDERSTANDING OF STABILIZATION INVOLVING CEMENTING REACTIONS. MECHANICAL ANALYSES WERE PERFORMED ON FOUR LOESS SAMPLES BY HYDROMETER AND PIPETTE METHODS. SODIUM METAPHOSPHATE WAS USED AS THE DISPERSING AGENT. MINERALOGICAL COMPOSITION WAS DETERMINED BY SILT AND CLAY FRACTIONS. EXTENSIVE CHEMICAL TESTS WERE PERFORMED AS FOLLOWS: (1) CATION EXCHANGE CAPACITY USING AN AMMONIUM ACETATE METHOD, (2) EXCHANGEABLE CATIONS DETERMINED WITH A FLAME PHOTOMETER, (3) PH, BY AN ELECTROMETRIC METHOD, (4) CARBONATE CONTENT EXPRESSED AS PERCENT CALCIUM CARBONATE BY A VERSENATE METHOD, (5) SULFATE CONTENT DETERMINED BY WATER-SOLUBLE SULFATE METHOD, (6) CHLORIDE CONTENT DETERMINED BY MOHR'S METHOD, (7) FREE IRON OXIDE CONTENT, BY JEFFRIES' METHOD (8) TOTAL IRON CONTENT, AND (9) ORGANIC MATTER CONTENT DETERMINED BY A DICHROMATE OXIDATION METHOD. PARTICLE-SIZE ACCUMULATION CURVES FOR THE LOESS SAMPLES WERE DETERMINED BY PETROGRAPHIC ANALYSIS. MICROSCOPIC EXAMINATION OF THE LOESS REVEALED THAT CLAY OCCURRED MAINLY AS COATINGS ON LARGER GRAINS, WHICH TENDS TO INCREASE THE EFFECTIVENESS OF THE CLAY. DATA ARE PRESENTED ON THE SPHERICITY AND ROUNDNESS OF SILT GRAINS. SOIL-MECHANICS TESTS WERE PERFORMED TO GIVE INFORMATION OF SOME OF THE BEHAVIOR CHARACTERISTICS OF LOESS. SOIL CEMENT STABILIZATION IS DISCUSSED FROM THE BASIS OF CEMENT REQUIREMENTS, WEATHERING, AND MINERAL SURFACE AREAS. STABILIZATION OF SOIL CEMENT WITH TREATMENTS OR ADMIXTURES WERE ALSO INVESTIGATED. POSSIBLE EXPLANATIONS FOR VARIOUS QUESTIONS INVOLVING STABILIZATION OF LOESS WITH PORTLAND CEMENT ALONE AND WITH ADMIXTURES HAVE BEEN SUGGESTED. PETROGRAPHIC INFORMATION IS CONCLUDED TO BE ESSENTIAL ON A SOIL MATERIAL FOR AN UNDERSTANDING OF STABILIZATION INVOLVING CEMENTING REACTIONS.]]></description>
      <pubDate>Sun, 15 Aug 2004 02:43:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/122443</guid>
    </item>
    <item>
      <title>EXCHANGE ADSORPTION BY CLAYS OF LARGE ORGANIC CATIONS &amp; DISCUSSION</title>
      <link>https://trid.trb.org/View/121976</link>
      <description><![CDATA[CLAYS AND CLAYEY SOILS HAVING HIGH CATION-EXCHANGE CAPACITIES ALSO HAVE HIGH WATER-ADSORBING CAPACITIES. REACTIONS OBSERVED AND DEVELOPED ON AUTHORIZATION OF THE PROPERTIES OF CLAYS BY ORGANIC CATION ADSORPTION ARE TRACED. SATURATION OF CLAYS WITH LARGE ORGANIC CATIONS DESTROYS THE FORCES THAT ATTRACT WATER MOLECULES AND MAY POSSIBLY BE A MEANS OF AMELIORATING CLAYS FOR CERTAIN TYPES OF ENGINEERING USED. RESULTS OF THESE STUDIES ARE PRESENTLY EMPLOYED WITH GREAT SUCCESS IN THE MANUFACTURE OF PAINTS, LACQUERS STRAINS AND LUBRICANTS TO GIVE SUPERIOR CONSISTENCY PROPERTIES OF THESE MATERIALS AND IMPROVE RESISTANCE OF THE PROTECTIVE FILM FORMED BY THEM. IT IS EVIDENT FROM THE RESULTS REPORTED BY JORDAN AND ASSOCIATES, AND BY WINTERKORN & GIESEKING THAT ORGANIC-AMMONIUM-SATURATED CLAYS ARE MORE HYDROPHOBIC THAN NATURAL CLAYS. JORDAN HAS SHOWN THAT THESE COMPLEXES ARE MORE ORGANOPHILIC THAN THE NATURAL CLAYS, WINTERKORN HAS SHOWN THAT ANILINE-TREATED SOILS ARE MORE STABLE TOWARD ALTERNATE WETTING AND DRYING AND ALTERNATE FREEZING AND THAWING THAN THE CORRESPONDING UNTREATED SOILS. SATURATION OF NATURAL CLAYS WITH ORGANIC CATIONS IS AN EXPENSIVE OPERATION. IT APPEAR THAT THE PRESENCE OF ONLY SMALL AMOUNTS OF ORGANIC CATIONS ON THE CLAY SURFACES MIGHT PROVE TO BE BENEFICIAL IN CERTAIN SOIL-STABILIZING OPERATIONS. THE ORGANIC AMMONIUM CLAY COMPLEXES ARE ALREADY IN WIDESPREAD USAGE IN HIGH UNIT COST MATERIAL SUCH AS PAINT, LUBRICANTS, AND ASPHALTIC MATERIALS.]]></description>
      <pubDate>Sun, 15 Aug 2004 02:41:34 GMT</pubDate>
      <guid>https://trid.trb.org/View/121976</guid>
    </item>
    <item>
      <title>CHARACTERISTICS OF LIME RETENTION BY MONTMORILLONITIC CLAYS</title>
      <link>https://trid.trb.org/View/121669</link>
      <description><![CDATA[PREVIOUS WORK HAS SHOWN THAT HYDRATED LIME ADDED TO CLAYEY SOILS REDUCES THEIR PLASTICITY. ABOVE A CERTAIN PERCENT LIME THERE IS A LEVELING OFF AND NO FURTHER REDUCTION. THE POINT AT WHICH THIS LEVELING OFF BEGINS MAY BE REFERRED TO AS THE LIME RETENTION OR LIME FIXATION POINT. THE AMOUNT OF LIME NEEDED TO SATISFY THE LIME RETENTION REQUIREMENT OF CLAYS MUST BE EXCEEDED IF LATER POZZOLANIC CEMENTITIOUS REACTIONS ARE TO PROCEED. LIME RETENTION OCCURS IN CLAYS ALREADY CALCIUM SATURATED, ALTHOUGH SODIUM CLAYS TAKE MORE LIME. THE TOTAL CALCIUM RETAINED EXCEEDS THE CATION EXCHANGE CAPACITY AS MEASURED BY THE AMMONIUM ACETATE METHOD. LIME RETENTION BY CLAYS WERE STUDIED BY MEASUREMENTS OF PLASTIC LIMIT, PH, VISCOSITY, EXCHANGEABLE CALCIUM, AND X-RAY DIFFRACTION. THE LIME RETENTION POINT WAS MOST PRONOUNCED IN MONTMORILLONITIC CLAYS, AND COINCIDES WITH A GRADUAL INCREASE IN PH AND A SHARP RISE IN VISCOSITY OF SUSPENSIONS AS MEASURED BY A STORMER PADDLE- ROTATION TYPE OF VISCOSIMETER. THE RISE IN VISCOSITY WAS OBSERVED WITH NATURAL SODIUM- AND CALCIUM-SATURATED BENTONITES AND WITH IOWA GUMBOTIL AND PLASTIC LOESS SOILS. VISCOSITY DEPENDS ON PH AS WELL AS ON CALCIUM ION CONCENTRATION, AND REACHES A MAXIMUM AT AROUND PH 11.8. HYPOTHESES OF LIME RETENTION ARE PRESENTED. /AUTHOR/]]></description>
      <pubDate>Sun, 15 Aug 2004 02:40:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/121669</guid>
    </item>
    <item>
      <title>DETERMINATION OF SOIL CATION EXCHANGE CAPACITY BY A SIMPLE SEMIMICRO TECHNIQUE</title>
      <link>https://trid.trb.org/View/121396</link>
      <description><![CDATA[METHODS OF ESTIMATING THE CATION EXCHANGE CAPACITY (CEC) OF SOILS USING VARIOUS INDEX CATIONS AND DIFFERENT SATURATION ARE DESCRIBED. A CEC TEST METHOD IS DESCRIBED WHICH DOES NOT INVOLVE REMOVAL OF THE EXCESS SATURATING CATION BY EXHAUSTIVE WASHING PROCEDURES, THUS ELIMINATING SOURCES OF ERROR IN THIS DETERMINATION DUE TO SALT RETENTION, LOSS OF THE INDEX CATION BY HYDROLYSIS, OR SAMPLE DISPERSION. IN THIS METHOD, THE SOIL SAMPLE IS TREATED WITH ONE NORMAL AMMONIUM ACETATE, THE AMMONIUM ACETATE IS REMOVED BY LEACHING WITH AN AMMONIUM NITRATE SOLUTION, AND THE TREATED SAMPLE ANALYZED DIRECTLY FOR AMMONIUM-NITROGEN BY STEAM DISTILLATION WITH 2 MOLAR SODIUM CHLORIDE AND MAGNESIUM OXIDE AFTER PARTIAL REMOVAL OF AMMONIUM NITRATE BY WASHING WITH A SMALL AMOUNT OF ISOPROPANOL. THE AMOUNT OF NITRATE NITROGEN IN THE SAMPLE IS SUBSEQUENTLY DETERMINED BY STEAM DISTILLATION OF THE SAMPLE WITH DEVARDA ALLOY, AND THE AMOUNT OF SALT RETAINED IN THE SAMPLE CORRECTED BY USE OF THE NITRATE-NITROGEN VALUE. THE METHOD IS SIMPLE AND PRECISE, IF NOT SUBJECT TO OBVIOUS ERRORS OF MANY OTHER CEC PROCEDURES, AND GIVES RESULTS SIMILAR TO ACCEPTED CEC METHODS INVOLVING USE OF AMMONIUM AS THE INDEX CATION.]]></description>
      <pubDate>Sun, 15 Aug 2004 02:39:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/121396</guid>
    </item>
    <item>
      <title>RECENT DEVELOPMENTS IN THE CLASSIFICATION OF THE SOILS OF THE TROPICS</title>
      <link>https://trid.trb.org/View/121121</link>
      <description><![CDATA[PROBLEMS WHICH THE CLASSIFICATION OF THE SOILS OF THE TROPICS FACE ARE DISCUSSED.  THESE PROBLEMS DEAL WITH THE CORRELATION OF SOIL PROPERTIES WITH THE GEOGRAPHIC DISTRIBUTION OF SOIL-FORMING FACTORS, IN THE CASE OF THE CATION-EXCHANGE CAPACITY OF THE CLAY AS RELATED TO AGE. THE POSITION OF TROPICAL HYDROMORPHIC SOILS, HAVING PLINTHITE, IS VIEWED FROM THE STANDPOINT OF SIMILARITIES AMONG PROFILES AS A BASIS FOR DECIDING WHICH SOILS BELONG TOGETHER. SIMULTANEOUS OCCURRENCE OF OXIC AND ARGILLIC HORIZONS IN ONE PEDON IS DISCUSSED. GENETIC SEQUENCES OF PROFILES OF TROPICAL CLIMATES FROM YOUNG TO MATURE SOILS WILL PASS THROUGH DIFFERENT ORDERS, EVENTUALLY INCLUDING ENTISOLS, INCEPTISOLS, ULTISOLS, AND OXISOLS. THIS SEQUENCE REFLECTS MORE ADVANCING WEATHERING THAN CLIMATIC INFLUENCES. SMALL- SCALE MAPS WILL HAVE TO TAKE INTO ACCOUNT GEOMORPHIC AND GEOLOGICAL DATA, MORE THAN PRESENTLY PREVAILING CLIMATE.]]></description>
      <pubDate>Sun, 15 Aug 2004 02:38:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/121121</guid>
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