Lime Dosage Research Articles

Reliability-Based Design Optimization of Chemically Stabilized Coal Gangue

Abstract The coal gangue (CG) is a noncombustible waste mechanically separated from coal during the sorting or coal washing phase of mining. Because of the negative implications of unscientific disposal of CG, there is a need to utilize it in bulk civil engineering works. More precisely, the application of CG in earthworks facilitates its bulk application. The present study aims to evaluate the unconfined compressive strength (UCS) characteristics of lime- and gypsum-treated CG. The lime and gypsum dosages were varied from 2 to 6 % and 0.5 to 1.5 %, respectively. The influence of lime and gypsum addition on the UCS was evaluated for varying curing periods (CPs) of 7, 14, and 28 days. An exponential model is developed to evaluate UCS based on the experimental data using lime content, gypsum content, and CP. Further, attempts were made to estimate the optimum amounts of lime and gypsum content for satisfactory UCS performance of stabilized CG using target reliability-based design optimization (TRBDO). Furthermore, carbon footprint analysis (CFA) was performed to quantify the environmental benefits attainable by applying CG as subbase material in the pavement. The results showed that the maximum dry density increased from 1.74 to 1.84 g/cc for 4 % lime addition. The UCS of CG linearly increased with an increase in lime dosage, gypsum dosage, and CP. The highest increment of 1,050 % was attained for 1.5 % gypsum and 6 % lime addition. The CFA results indicate that CG’s procurement (embodied) emissions are substantially higher, with an 88 % share in overall emissions. From the reliability studies, it is noted that the TRBDO is helpful in predicting the optimum dosages of lime and gypsum for the satisfactory performance of pavements.

Land use change and its effect on ecosystem services in an Oxisol of the eastern High Plains of meta department in Colombia

Increasing cultivation on acid soils of Colombia’s Eastern High Plains in the Orinoquia region require crop management strategies that balance commercial and environmental interests. Previous research showed the effects of land preparation and management on certain aspects of ecosystem services of these acid soils. This research aimed to comprehensively evaluate the impact of use and soil management in a native savanna Oxisol converted to five production systems gaining traction among local farmers: Annual crops rotation–sugarcane (ACR-S); Annual crops rotation-maize-soybean (ACR-MS); Sugarcane monocrop (SM); Rubber associated with Desmodium ovalifollium (R-Do) as a cover crop; Pasture Brachiaria decumbens - Annual crops rotation (PBd-ACR) and native savanna (NS) as a control. The experimental design consisted of conditioning the soil with two doses of dolomitic lime and incorporating three tillage methods over 5 years. A Principal Components Analysis (PCA) constructed indicators of ecosystem services (ES), such as fertility, water regulation, macroinvertebrate diversity, climate control related to greenhouse gas emissions (GHG) and carbon stock. The indicator values were adjusted between 0.10 and 1.0. Physicochemical variables with the greatest statistical weight were identified for components 1 and 2 each year. The fertility indicator of the native savanna for year one had a low range with a value of 0.11 compared to the other systems (p ≤ 0.05). During the years two, three, and four, soil fertility increased in the PBd-ACR (0.51) production system compared to the other systems. PBd-ACR generally improved water supply, although with lower indicator values than ACR-MS and R-Do. PBd-ACR show high biodiversity for edaphic macroinvertebrates compared to other systems. Field measurements detected methane emissions only in the SM system. Oxisols changed with the introduction of crops. The positive and negative tradeoffs of production systems and their agronomic practices should be considered in agricultural development of these acid soils.

Investigation of the strength evolution of lime-treated London clay soil

The paper investigates the effect of hydrated lime on shear strength properties and behaviour of London clay, triaxial. Unconsolidated undrained tests were performed to identify the effect of lime dosage, compaction water content and curing time on the shear strength and stress–strain behaviour of the treated soil. The mineralogical and physicochemical transformations occurring during the curing of the soil were also monitored. The results showed that strength gain was strongly influenced by lime content and the curing period, whereas compaction water content was less influential. It was found that the strength evolution is likely to continue over long periods of time and result in very considerable strength gains on the hardening of pozzolanic reaction products. It was also shown that adequate early strength gains can be obtained with reduced material consumption, thus further increasing the sustainability of the treatment processes. The paper also highlighted the importance for engineering design of considering the brittle stress–strain response of the lime-treated soil, and the benefit of using lower amounts of lime to alleviate this undesirable effect. The implications of various aspects of soil brittleness in different situations merit further attention and should be explored by way of modelling in future work.

Removal of Model Aromatic Hydrocarbons from Aqueous Media with a Ferric Sulfate–Lime Softening Coagulant System

The removal of model hydrocarbon oil systems (4-nitrophenol (PNP) and naphthalene) from laboratory water was evaluated using a ferric sulfate and a lime-softening coagulant system. This study addresses the availability of a methodology that documents the removal of BTEX related compounds and optimizes the ferric-based coagulant system in alkaline media. The Box–Behnken design with Response Surface Methodology enabled the optimization of the conditions for the removal (%) of the model compounds for the coagulation process. Three independent variables were considered: coagulant dosage (10–100 mg/L PNP and 30–100 mg/L naphthalene), lime dosage (50–200%), and initial pollutant concentration (1–35 mg/L PNP and 1–25 mg/L naphthalene). The response optimization showed a 28% removal of PNP at optimal conditions: 74.5 mg/L ferric sulfate, 136% lime dosage, and initial PNP concentration of 2 mg/L. The optimal conditions for naphthalene removal were 42 mg/L ferric sulfate, 50% lime dosage, and an initial concentration of naphthalene (16.3 mg/L) to obtain a 90% removal efficiency. The coagulation process was modeled by adsorption isotherms (Langmuir for PNP; Freundlich for Naphthalene). The surface properties of flocs were investigated with pHpzc, solid-state UV absorbance spectra, and optical microscopy to gain insight into the role of adsorption in the ferric coagulation process.

Последействие извести и минеральных удобрений на плодородие почвы и потребление элементов питания растениями при сенокосном использовании

The results of a long-term experience on the aftereffect of lime and mineral fertilizers on the agrochemical properties of soddy-podzolic hayfield soil, forage quality and yield are presented. In a long-term expe-riment on hayfields (85 years), lime in doses from 6 to 24 t/ha lost the ability to maintain the optimal soil regime in the variants with the annual alienation of the herbage. The use of lime in the hayfield contri-buted to the preservation of the humus content and an increase in its reserves in the soil only with a suffi-cient amount of organic matter. In this case, a lower C : N ratio is observed. With the annual mowing of the herbage, this trend was absent; mineral fertilizers, both against the background of lime and without lime, did not show a positive effect on the humus content in the soil. In the experiment, the effect of lime doses on the content of mobile forms of mineral elements was not noted. Their concentration in the soil was determined by the use of mineral fertilizers. The positive effect of the use of mineral fertilizers on the background of the aftereffect of lime was reflected in the use of mineral elements by the herbage of the hayfield. Plants did not increase nitrogen intake, but used more phosphorus –– by 25%, potassium –– by 50–60%, calcium –– by 55–60%, copper –– from 5.9 to 6.7 mg/kg, zinc –– from 32.6 to 36.2 mg/kg. Ob-servations over the past 10 years have established a gradual decrease in the effectiveness of high doses of lime on the yield of herbage: in options without fertilizers –– from 16.5 to 13.0 centners/ha, in options with mineral fertilizers –– from 17.0 to 13.5 centners/ha of dry matter.

ВПЛИВ ВАПНУВАННЯ ТА МІНЕРАЛЬНИХ ДОБРИВ НА ВРОЖАЙНІСТЬ ПШЕНИЦІ ОЗИМОЇ НА ЧОРНОЗЕМІ ОПІДЗОЛЕНОМУ

One of the factors of soil degradation is acidification, which is manifested even in chernozems that have a close to neutral or neutral in nature reaction of the soil solution. In terms of acidity, wheat belongs to the group of crops that prefer slightly acidic and close to neutral reaction of the soil environment and responds well to liming not only strong and medium acid, but also weakly acidic soils. Therefore, obtaining objective data on its response to different doses of lime and fertilizer systems in a long stationary experiment is relevant. The aim of the research was to establish the effect of liming in combination with the application of different types and doses of mineral fertilizers on the dynamics of winter wheat yield on chernozem podzolic in field crop rotation. The study was conducted in a stationary experiment (certificate NAAS №86), laid on the research field of Uman NUS, with geographical coordinates of 48 ° 46 '56,47' 'N. w. and 30 ° 14 '48.51' 'east. e. The experiment was based on a 4-field field crop rotation (winter wheat, sugar beet, corn, peas) in three fields. Growing a variety of winter wheat Mission Odesa and Lazurna. The total dose of lime was calculated by the level of metabolic acidity. A single dose of defect containing 60% CaCO3 was 9.0 t/ha. Defect, in doses of 4.5 t/ha 9.0 and 13.5 t/ha was introduced under the first three crops of crop rotation - winter wheat, sugar beet and corn. Against the background of liming mineral fertilizers were applied in the form of ammonium nitrate, granular superphosphate and potassium chloride. The issue of complex influence of different doses of defects and mineral fertilizers on the productivity of winter wheat on chernozem podzolic heavy loam of the Right-Bank Forest-Steppe of Ukraine is considered. Carrying out liming with a defect dose of 9.0 t/ha in the first rotation - increased the yield of winter wheat with the application of mineral fertilizers at a dose of N90P60K60 by 0.83 t/ha, or 12%, and in the second rotation - by 0.41 t/ha, or 7%. With the introduction of 0.5 and 1.5 doses of lime, the increase in yield for two rotations of crop rotation, respectively, was 4% and 10%. Applying 1.5 doses of lime, calculated on the basis of metabolic acidity, has a lower starting effect compared to a single dose, but has a longer aftereffect. The application of defect at a dose of 4.5–13.5 t/ha contributed to an increase in yield on average for two rotations of crop rotation by 0.17–0.35 t/ha. Improving the potassium nutrition of plants increases the efficiency of liming - the increase in grain yield is 0.28-0.63 t/ha.

Application and depression mechanism of sodium sulfite on galena-pyrite mixed concentrate flotation separation: Huize Lead-Zinc Mine, China, as an example

Galena, sphalerite, and pyrite are important metallic sulfide minerals and are often associated with one another. In the flotation separation of galena-pyrite mixed concentrate, large amounts of lime (CaO) are used for the depression of pyrite. In this study, the negative effects of lime were reduced by using an efficient depressant Na2SO3 + CaO reagent in the flotation separation of galena from pyrite. Real ore sample flotation separation tests showed that the mixed depressant can efficiently depress pyrite from galena-pyrite mixed concentrate. The obtained galena concentrate had a Pb recovery and grade of 58.36% and 83.45%, respectively. Micro-flotation experiments showed that Na2SO3 depressed the floatability of pyrite more strongly than that of galena. Moreover, the depression mechanism of Na2SO3 was observed through contact angle measurements, ultraviolet–visible spectrophotometry (UV–Vis) analysis, and time of flight secondary ion mass spectrometry (TOF-SIMS). This study provides an important reference for the depression of pyrite from a galena-pyrite mixed concentrate with low lime dosage.

Changes in agrochemical indicators of light gray forest soil and productivity of meadow clover depending on the level of mineral nutrition against the background of the aftereffect of liming in the conditions of the South-East of the Volga-Vyatka region

The research was carried out in a long-term stationary experiment, launched in 1978 on light gray forest soil in the conditions of the Nizhny Novgorod region. In 2020-2021, the effectiveness of various doses of mineral fertilizers (N0P0K0, N15P40K60, N30P80K120, N45P120K180) was studied against the background of liming when laying the experiment (in doses 0; 0.5;1.0;1.5; 2.0; 2.5 of hydrolytic acidity) on the yield of meadow clover Martum of the 1st and 2nd years of use. It has been established that the studied lime doses introduced in 1978, by August 2021 had not affected the change in agrochemical parameters of light gray forest soil (acidity, content of mobile forms of phosphorus and potassium, humus) and the yield of meadow clover of the 1st and 2nd year of use. A long-term use (1978-2021) of single and double doses of mineral fertilizers did not provide the accumulation of humus, mobile forms of phosphorus and potassium as compared to their initial content in arable layer of light gray forest soil. Increased content of mobile forms of phosphorus and potassium (Р2О5 per 34.1 mg/kg, К2О per 22.3 mg/kg) was observed by long-term application of three-fold doses of mineral fertilizers. Application of mineral fertilizers in a dose of N45P120K180 enabled to obtain 36.5 and 37.9 t/ha of green mass during the 1st and the 2nd year of use and the highest total yield of 74.4 t/ha that is 12.0-22.2 t/ha higher than the control and all the rest variants of mineral fertilizers application.

Soil Stabilization using Crumb Rubber Powder and Lime

Karewa soils are widely spread in the stateof Jammu and Kashmir and they have been used assubgrade of pavement layers. Karewa soils are usuallyclayey soils and are characterized as low bearing capacity materials for flexible pavement layers.When such soils cannot be replaced, its performance should be increased by several modification techniques. The purpose of this research is to evaluate the use of low contents of lime and crumb rubber powder in the modification of Karewa soil properties. In this study an effort is made to obtain the optimum dosage of lime and crumb rubber powder for stabilization of locally available Karewa soil. Crumb rubber powder addition was made in the soil in the proportion of 5% initially to 10%, and then 15% by weight and unconfined Compressive Strength Tests and California bearing ratio tests are conducted for cohesive soil with 3%, 4% and 5% lime with the varying rubber percentage 0%, 5%, 10% and 15% and the results were noted and compared. The experimental investigations reveal that there is a tremendous increase in the CBR value of the soil treated with lime, thus leading to decreased thickness requirements of the sub-base and base courses. With addition of crumb rubber powder in soil, there is specific increase in the shear parameters of soil as well as will increase the permeability of soil.

A novel approach for treating acid mine drainage by forming schwertmannite driven by a combination of biooxidation and electroreduction before lime neutralization

Acid mine drainage (AMD) contains abundant iron, sulfates, and various metal ions, and it causes environmental pollution. The traditional AMD lime neutralization forms a layer of iron hydroxide and gypsum on the surface of the lime particles, preventing continuous reaction and leading to excessive lime addition and neutralized sludge production. In this study, an approach for treating AMD using a cyclic process of biooxidation and electroreduction before lime neutralization was proposed, in which the Fe2+ in AMD was oxidized to Fe3+ and induced to form schwertmannite through Acidithiobacillus ferrooxidans. The remaining Fe3+ was reduced to Fe2+ using an electric field. After three biooxidation and two electroreduction cycles, 98.2% of Fe and 62.4% of SO42− in AMD precipitated as schwertmannite (Fe8O8(OH)5.16(SO4)1.37). The yield of schwertmannite reached 33.98 g/LAMD, with a high specific surface area of 112.59 m2/g. The lime dosage and sludge yield of the treated AMD in the subsequent neutralization stage (pH = 7.00) decreased by 85.0% and 74.5%, respectively, than those of raw AMD. The pilot test results showed that the integrated treatment of biooxidation–electroreduction cyclic mineralization and lime neutralization has practical applications.

Determine the Effect of Lime and Boron Interaction on Nutrient Availability and Acidity Parameters in Soil

Field experiment was conducted to examine the determine the effect of lime and boron interaction on nutrient availability and acidity parameters in soil. The experiment was carried out in Randomized Block Design (RBD) in field with four levels of lime (L0 – No lime, L0.3 – Furrow application @ 300 kg ha-1, L2.0 – Broadcasting @ 2 t ha-1, L5.0 – Broadcasting @ 5 t ha-1) and four levels of boron (B0 – No Boron, B0.5 – Broadcasting @ 0.5 kg ha-1, B1.0– Broadcasting @ 1 kg ha-1, B1.5 – Broadcasting @ 1.5 kg ha-1), respectively. B fertilization is therefore important to improve soil B availability and crop growth in the region. Availability of applied B in soil may be affected due to its possible interaction with lime which is usually recommended as an ameliorative measure in acidic soils. In this view, a field experiment was undertaken to evaluate the effect of lime and B application on growth, yield and quality of soybean, as well as their effect on nutrient availability and acidity parameters in soil. The crop was grown with four doses of lime (0, 0.3, 2.0 and 5.0 t ha-1) and as many doses of B application (0, 0.5, 1.0, and 1.5 kg ha-1). The experiment was taken in RBD design with factorial arrangements of the treatments. Seed yield of soybean increased with increasing doses of lime and Boron application with the highest yield being observed at 5tha-1 lime and 1 kg ha-1 B application; lime and B interaction was not significant Application of B @ 1 kg ha-1 increased seed yield by 18.6%, while lime application @ 5 t ha-1. Increased yield by 36%.The positive effect of lime and B application on soybean yield was mediated through improved growth and pod formation in the crop.

Experimental Study on Engineering Characteristics of Cement-Lime-Improving Silt in Eastern Henan Province

With the construction of expressways in eastern Henan, silt has been widely used as a filling material. However, the silt in this area is lacking clay, the content of active oxides in the soil is low, and the soil particles are bonded together. The property is poor, the erosion resistance is not strong, and the direct filling of the roadbed is prone to engineering problems. Due to the obvious regionality of silt in eastern Henan, this paper firstly analyzes the basic physical properties of silt in eastern Henan using compaction, compression, direct shear and particle gradation tests. The research displays that with the increase of the dosage of cement or lime, the optimal water content increases, while the maximum dry density decreases. The compressibility decreases linearly with the increase of the content. The improved soil has a significant increase in large particles. When the dosage of lime is 2%–6%, the improved soil has a good gradation, and the improved soil has a significant increase in large particles. When the dosage is 2%–6%, the improved soil has a good gradation, and the improvement effect on the cohesion is much greater than that on the internal friction angle. The comprehensive analysis of cement lime shows that the dosage of cement should be 4%–6%. In the early stage, the improvement effect of cement on silt is better than that of lime.

Data-driven prediction of neutralizer pH and valve position towards precise control of chemical dosage in a wastewater treatment plant

Proper pH control is important to the neutralization of industrial wastewater that will facilitate downstream biological treatment and can strongly affect the utilization of chemical reagent/resource. This study aimed to apply machine learning (ML) models for both pH prediction and lime dosage control towards enhanced automated control of neutralization processes. To achieve this goal, eight ML models were employed and compared in modeling performance, and optimized by using correlation analysis, cross-validation, and grid search techniques. In the neutralizer pH prediction, the highest coefficients of determination (R2) results were obtained at 0.765 (k-nearest neighbors - KNN), 0.918 (eXtreme Gradient Boosting - XGBoost), and 0.900 (random forest - RF) for three neutralizer tanks, accompanied with the lowest root-mean-square error (RMSE) values of 0.289, 0.100, and 0.093, respectively. The impacts of input features were quantified by sensitivity analysis using SHAP values, which demonstrated the importance of temperature, valve position, and upstream pH as high as 0.214, 0.156, and 0.118 (the mean of absolute SHAP value). For lime dosage control, the best model performance came from XGBoost (R2 values of 0.605) for valve 1, RF (0.788) for valve 2, and RF (0.436) for valve 3 with the corresponding RMSE values of 8.056, 6.125, and 4.466, respectively. The recommended valve position was based on the target pH and some examples were illustrated at different upstream pH values. The results of this study has demonstrated that ML approach can be an effective tool to help conserve chemical resources via enhanced chemical dosage control in wastewater treatment.

Microelements Changes in Leaves and Fruits of Raspberry (Rubus idaeus L.) Under the Influence of Ameliorative Measures

ABSTRACT The study evaluated the effects of lime and dolomite application (2 and 4 t ha−1) in combination with NPK fertilizer (1 t ha−1) or borax (50 kg ha−1) on micronutrient concentrations in the raspberry leaves and fruits grown in the soil with a strongly acid reaction. Changes in the content of micronutrients (Fe, Mn, Cu, Zn, and B) and Al in the soil and raspberry leaves and fruits were monitored during a two-year period. Calcification reduced the content of micronutrients and Al in the soil, as well as their content in the plant. Applied doses of lime or dolomite of 4 t ha−1 almost completely neutralized the high to toxic content of mobile Al in the soil, but the values in the leaves although reduced were still high. In all applied treatments, high and very high concentrations of available forms of Fe and Mn in the soil and/or leaves and fruits were significantly reduced. However, the Mn concentrations in the soil, leaves, and raspberry fruits were very high. Calcification did not reduce the available Cu in the soil, while this effect was observed in raspberry leaves and fruits where the Cu concentrations were within optimal values. After calcification, the Zn and B concentrations decreased in the soil and plant, but they mostly remained within the optimal values. The results indicate that due to the very high concentrations of Al and Mn in the soil and plant after lime application, additional doses of lime materials in more than one season are required.

Liming and Phosphate Application Influence Soil Carbon and Nitrogen Mineralization Differently in Response to Temperature Regimes in Allophanic Andosols

Andosols are characterized by high organic matter content and play a significant role in carbon storage. However, they have low phosphorus fertility because of the high phosphate-fixing capacity of active aluminum. For agricultural use of Andosols, it is necessary to ameliorate its poor phosphorus fertility by applying lime and high doses of phosphate fertilizers. The objective of the present study was to clarify how such soil amendments affect the mineralization of soil organic carbon (C) and nitrogen (N) in allophanic Andosols under different temperature regimes. The soil was treated using combinations of liming and heavy phosphate application, followed by incubation under different temperature conditions. The N mineralization and the soil CO2 evolution rate were measured periodically. The patterns of N mineralization were analyzed by fitting them to first-order kinetics. Liming increased C and N mineralization irrespective of temperature, and the increase was further enhanced by phosphate application. Kinetic analysis of the N mineralization curve indicated lowering of the activation energy of N mineralization reactions with phosphate application, suggesting that P application may accelerate N mineralization at lower temperatures. These findings provide a basis for developing soil management strategies to reduce the loss of soil organic matter.

Advanced Pneumatic Mechanical System for Water Treatment Application: Dosing Rate Assessment for Lime Dosage

This paper presents a new developed pneumatic mechanism for lime dosing system in water treatment application. Technically, a choke formation due to scaling problem in such existing water treatment system utilising pump as the transferring medium has caused the high cost of operation due to scheduling maintenance and replacement of pump tubing. In that sense, the pneumatic system will be a new advancement in replacing the transferring medium. In this work, the air regulator is used to control air pressure at several levels. At the same time, there is one valve that is installed to control the airflow the regulator (air compressor) to the pneumatic cylinder cartridge. The assessment is conducted for water with 10% of lime concentration on water sample 25 PPM as the standard lime concentration for water treatment plant as the domestic usage in Malaysia. The trend of dosing rate for the present novel lime dosage utilising a pneumatic system shows consistency of increment with the increment of applied air pressure during the dosing process.

Production potential, quality and soil health of newly introduced baby corn as influenced by best management practices in eastern Himalayas

Management of the newly introduced short duration and high economic value crops like baby corn in acidic soil is poorly understood and related information is scarce in particular to eastern India. Keeping these things in view, a field study was conducted during the two consecutive winter seasons (2013–2014 and 2014–2015) to assess the effect of best management practices (application of straw mulch, doses of lime and integrated nutrition) on production potential, quality and soil health in baby corn under the acidic soil of eastern Himalaya. Yields, economics and quality of baby corn were increased significantly with application of straw mulch @ 5 t ha−1 as compared to without mulch. Yield of baby corn increases with increasing levels of liming up to 1.0 t ha−1. Also, higher quality parameters were noted in same treatment. Application of 1.0 t lime ha−1 also improved the soil fertility status after crop harvest. Baby cob, baby corn, green fodder and dry fodder yields was significantly higher with 100% RDF + 25% RDF (through farm yard manures as organic nitrogen ON). This treatment also improved nitrogen content, their uptake and protein content in baby corn, cob husk and green fodder compared to control. Economic parameters were significantly higher with applications of 100% RDF + 25% RDF (ON). Higher doses of integrated nutrition [100% RDF + 25% RDF (ON)] also enhanced the soil health. Thus, it may be concluded that baby corn should be grown with straw mulching and integrated nutrition of 100% RDF + 25% RDF (ON) along with liming of 1.0 t ha−1 to achieve the higher productivity, quality and soil health under acidic soil of eastern Himalaya.

The effect of different doses of lime on the potash state in sod-medium podzolic medium loamy soil

To study the transformation of soil potassium under the action of lime doses, long-term microfield experience was used. The one-factor experiment is laid in sixfold repetition. The location of plots is systematic with an offset. During three years of research, the following cultures of the crop rotation link were cultivated: annual grasses (vetch-oat mixture), winter triticale (variety - Izhevsk 2), spring wheat (variety - Yoldyz). In a long-term experiment on sod-medium podzolic medium loamy soil, it was found that the use of various doses of lime did not reduce the content of water-soluble and easily exchangeable potassium, but significantly increased the amount of mobile potassium to 8 mg/kg and non-exchangeable potassium to 13 mg/kg in the soil. In addition, liming affected the productivity of agricultural crops. Depending on the lime dose, it increased by 4 - 20%.

Analysis of Mechanical Properties of Loess with Lime Incorporation Ratio

Taking loess as the research object, the effect of lime content on mechanical properties of loess was studied. Firstly, the basic physical parameters of loess were obtained by laboratory physical index test and improved by lime. Secondly, the mechanical parameters of lime-modified loess were obtained by heavy compaction test and liquid-plastic limit test under different incorporation ratios (3%, 5%, 7%, 9%). Finally, the shear strength parameters and compressive strength of improved soil samples were obtained by unconsolidated and undrained triaxial shear test and unconfined compressive strength test respectively. The results showed that the liquid limit, plastic limit and plastic index of the loess improved by adding lime increased compared with the original soil sample, indicating that the binding force between soil particles was improved and the plasticity was enhanced. The variation range of dry density and water content had no obvious relationship with the dosage of lime. At the same time, the compressibility of soil is reduced and the collapsibility of soil is eliminated. With the increase of age, the strength of lime-modified soil also increases. Through unconsolidated and undrained triaxial shear tests and unconfined compressive strength tests, the strength of the loess improved by adding lime is significantly improved, and the strength of soil-cement increases with the increase of the dosage, and the water stability is obviously improved.

Performance Evaluation of Stabilized Reclaimed Asphalt Pavement as Base Layer in Flexible Pavement

The increased scarcity of natural quarry material has resulted in increases in the cost and burden on the environment. Pavement materials comprising asphalt coated aggregates that can be reused are called reclaimed asphalt pavement (RAP). RAP is crushed and screened, and then blended with one or more stabilization agents to produce a stabilized base or subbase aggregate. In the present study, the influences of fly ash dosage, lime dosage, and curing period on the strength, stiffness, and durability characteristics of RAP fly ash–lime (RFL) mixes were studied for utilization as a base layer material in flexible pavements. The dry density and moisture content relationship were determined by conducting a modified proctor test on all RFL mixes. Unconfined compression tests were conducted on specimens with different dry weight percentages of fly ash (10%–25%) and lime (5%–10%) content for different curing periods (0, 7, and 28 days). The optimum mix obtained as RFL2 had the proportions 70% RAP:22.5% fly ash:7.5% lime. A resilient modulus of 540 MPa at 28 days was observed for RFL2. The durability of RFL2 tested using the resistance index and a wet–dry cycle (weight loss) was observed to be 0.88% and 7.3%, respectively. Pavement analyses were performed for a pavement system with three layers using the KENLAYER program. The RFL2 mix as the base layer material was found to be superior to conventional wet mix macadam, hence the service life of an RFL2 pavement would be higher. Trial sections of the stabilized base and conventional pavement were constructed on a major district road. The falling weight deflectometer showed a better modulus (286 MPa) in RFL2. An RFL mix could therefore be used in a stabilized base layer to replace a conventional base layer.