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Department of defense (DoD) hand grenade training ranges have implemented alkaline hydrolysis, which is the practice of applying hydrated lime [Ca(OH)2] to range soil, to manage the deposition of Composition B components, such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT). This paper will analyze hydrated lime effects on soil pH and the degradation of munitions constituents with time. At one DoD hand grenade training range, lime treatment produced higher soil pH values and RDX concentration reductions by eight orders of magnitude, some achieved concentrations in the low parts per trillion (ppt). The presence of calcite (CaO), a reaction product of Ca(OH)2, in field samples confirmed that alkaline hydrolysis reactions occurred in the soil matrix. In total, 5 months after the addition of lime to range soils, RDX was detected in collected field samples in small quantities. Column and lysimeter studies that use spiked native soils will be conducted to understand the effects of lime loading on RDX leachate and surface water runoff for site soils. The simulation efforts that used the training range environmental evaluation and characterization system (TREECS) modeling software predicted the reduction in aquifer RDX concentrations from the application of lime to the hand grenade range surface soil layer. The simulations verified the alkaline hydrolysis application parameters identified ex situ. [ABSTRACT FROM AUTHOR]

Fine-grained soils that expand when in contact with water can be a major issue in some geotechnical situations, but the soil can be stabilized through chemical means by hydrated lime incorporation. However, there is not yet any rational dosage methodology that combines the effects of both lime content and porosity of the treated soil specimen to predict its behavior regarding swelling. Thus, the present research intends to assess the one-dimensional swelling response of an expansive fine-grained soil stabilized with lime. For this purpose, compacted soil–lime blends were molded with three distinct amounts of lime (2%, 4%, and 6%), compacted to three different dry unit weights (14, 15, and 16 kN/m3) and tested after 3 h of curing. The results show that lime content, porosity, and their interaction are statistically significant in altering the swelling behavior of the compacted blends. Moreover, both can be combined through the adjusted porosity/lime index and related to the one-dimensional swelling. As a result, a single unique relationship could be established between the swelling and the proposed index with a coefficient of correlation (R2) of 96%. This approach was also successfully employed in other fine-grained soils treated with lime as validation. [ABSTRACT FROM AUTHOR]

Given the schedule pressure of lime-stabilized soil construction, many agencies specify the use of elevated temperature (e.g., 41°C), shorter duration (e.g., 5-7 days) accelerated specimen curing for unconfined compressive strength () testing and acceptance as a proxy for of specimens normally cured under 28-day 23°C conditions. Moreover, lime and highway transportation industry associations prescribe a unique accelerated curing regime for all lime-stabilized soils (7-day, 41°C). This paper presents the results from a laboratory investigation of stress-strain-strength development of four lime-stabilized soils under 2-8 day 41°C accelerated curing and the 0-28 day 23°C normal curing regime. Specimens cured at 41°C reached values equivalent to 28-day 23°C after 1.8-5.9 days. Accordingly, 7-day 41°C curing overestimates 28-day normal cure by 13-260%. When combined with a detailed analysis of data available in the literature, the results illustrate that the prescription of a unique equivalent accelerated curing regime is oversimplified and can lead to significant overestimation of design . [ABSTRACT FROM AUTHOR]

Lime generally improves the performance of soils. However, some cases reported an adverse effect. To develop an understanding of the underlying mechanisms, a systematic study covering a wide range of plasticity and mineralogy of soils was carried out. Six different soil samples were reconstituted using two extreme types of soils, in other words, a montmorillonite rich expansive soil and a silica-rich non-expansive soil. The influence of lime stabilization on these soils was evaluated through determination of geotechnical properties such as liquid limit, plastic limit, swell, compressive strength, mineralogy, and microstructure. An optimum lime content beyond which the strength improvement decreased was found. This phenomenon is more prominently observed with silica-rich soils that form silica gel. As the silica gel is highly porous, when formed in large scale the strength gain from cementation is substantially countered by the strength loss from gel pores, giving rise to a visible reduction in overall strength. Additionally, the gel materials hold a large amount of water, leading to increased plasticity and swelling. Therefore, excessive lime treatment should be avoided for silica-rich soils. [ABSTRACT FROM AUTHOR]

Lime treatment is an attractive technique for soil improvement in the construction of rail tracks and pavement layers, in slope protection of earth dams, and as a support layer for shallow foundations. However, there are no dosage methodologies based on rational criteria as in the case of soil-cement technology, where the voids/cement ratio is shown to be a key parameter for the estimation of both strength and stiffness. The present study, therefore, was aimed at quantifying the influence of the amount of lime, porosity, and voids/lime ratio on the initial shear modulus (G0) and unconfined compressive strength (qu) of a lime-treated clayey sandy soil. From the results of unconfined compression tests and bender elements measurements, it was shown, for the soil-lime mixtures investigated, that the voids/lime ratio is an appropriate parameter to assess both initial stiffness and unconfined compressive strength. Also, a unique G0/qu versus voids/lime ratio relationship was established linking the soil-lime mixture initial stiffness and compressive strength. [ABSTRACT FROM AUTHOR]

Laboratory tests have been carried out in order to evaluate the improvement in engineering properties relevant to highway design and construction obtained when clayey subgrade soils are stabilized with lime or fly ash. The experimental program included California bearing ratio (CBR) tests to evaluate the bearing strength of stabilized soils used as working platforms during highway construction. The admixture of lime or fly ash caused an increase in the plasticity limit, while both the liquid limit and the plasticity index of the soils have been reduced. Substantial increases in the California bearing ratio value, higher than those of the soil-fly ash mixtures, have been obtained when the soil samples were mixed with lime. The swelling after a 4-day soaking period has been reduced with the addition of both additive materials. The increase in optimum moisture content acts subsidiarily to the increased CBR value, particularly at high lime or fly ash percentages. An analogous effect has been found for the maximum dry density reduction. [ABSTRACT FROM AUTHOR]

Seasonal conditions (e.g., rise in the water table, precipitation, freeze–thaw cycles, and wet–dry cycles) affect stabilized subgrade moisture conditions which, in turn, have a significant impact on in-service pavement performance. Studies have shown the effect of seasonal conditions on stabilized subgrade soils' mechanical properties, including unconfined compression strength (UCS), modulus of elasticity (E), and resilient modulus (MR). There have been a limited number of studies addressing the hysteretic behavior of UCS, E, and MR in stabilized subgrade soils with moisture conditions. This study investigated the impact of moisture hysteresis on the UCS, E, and MR values of stabilized fine-grained soils following wetting, drying, and wetting–drying cycles. The results of this study can help predict changes in the bearing capacity of pavements subjected to seasonal conditions. Cylindrical specimens were first prepared with optimum moisture content and maximum dry unit weight. After each specimen's moisture content was altered to attain the target moisture content, the specimens were tested for UCS, E, and MR values. The tests showed hysteretic behavior comparable to the soil–water characteristic curve; specimens subjected to wetting had lower MR values than those subjected to drying. The hysteretic behavior of the mechanical properties in stabilized specimens can be explained by the following: (1) wetting and drying accelerates chemical reactions, (2) soil suction changes within the pores, and (3) hydration and Born repulsion create repelling/attracting. Scanning electron microscope (SEM) micrographs show increased cementation products within specimens subject to drying and wetting–drying cycles. Findings also showed that pavement distresses, namely rutting and AC bottom-up fatigue cracking, changed as moisture content varied. However, the impact of moisture variations was more evident in a thin-HMA pavement section compared to a thick-HMA pavement section. [ABSTRACT FROM AUTHOR]

The article presents a study on dealing with sulfate-induced heave in lime-stabilized soils. It mentions the use of X-ray diffraction (XRD) analysis on treated soil samples to examine the mineralogical developments at different curing periods, as well as the identification of the cured specimens' microstructural changes using a scanning electron microscope (SEM). Furthermore, the assessment of thaumasite formation during treatment of sulfate-bearing soil is presented.

The article presents a study on sulfate-induced heave in lime-stabilized soils in Great Britain. It mentions water absorption in the ettringite and its effect on the expansion process. It also mentions the drop in the thaumasite's strength behavior as a result of the pozzalonic reactions during curing periods. Furthermore, the authors recommend using water during lime stabilization to reduce heave.