Volumetric Moisture Research Articles

Effect of Balance and Imbalanced Fertilization on Soil Physical Properties, Growth and Yield of Rice in Chhattisgarh, India

Effect of balance and imbalanced fertilization on soil physical Properties, nutrient uptake, growth and yield of rice in Chhattisgarh was studied under long-term fertilizer experiment during kharif 2019-20 at research farm of Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.). The experiment comprised of different levels or doses of NPK fertilizers alone and in combination with zinc sulphate, farmyard manure (FYM), blue green algae (BGA) and green manuring (GM) was laid out in randomized block design with four replications and ten treatments viz. Control, 50% NPK, 100% NPK, 150% NPK, 100% NPK+ZnSO4@ 10kgha-1,100% NP, 100% N, 100% NPK + FYM @5t ha-1, 50% NPK+BGA@ 10kg ha-1 and 50% NPK + GM @40kg ha-1. The results showed that the physical properties like total porosity, gravimetric and volumetric moisture content, hydraulic conductivity, infiltration rate, water stable aggregates and mean weight diameter of the soil were increased, while the bulk density was reduced significantly with the 100% NPK FYM treatment over all other treatments. However, the use of imbalanced (100% N and 100% NP) fertilizer, super optimal (150% NPK) and sub optimal (50% NPK) rate of inorganic fertilizer as compared to the unfertilized control showed significant effect on the physical properties of soil. Integrated nutrient management practice including FYM and recommended dose of NPK showed as best treatment with respect to growth and yield parameters like plant height, no. of tillers and no. of grains as compare to other treatments. The grain (5065 kg ha-1) and straw (7075 kg ha-1) yield of rice was registered higher in 150% NPK treatment followed by 100% NPK FYM treatment (4855 kg ha-1 and 6565 kg ha-1) and lowest in control treatment (2350 kg ha-1 and 2680 kg ha-1).

Como utilizar o ponto de inflexão da curva de retenção de água e os atributos físicos do solo para previsão da capacidade de campo?

ABSTRACT Agricultural productivity is closely related to soil physical attributes, specifically those that affect the soil-water relationship, as the soil serves as the main water reservoir for plants. This research aimed to determine the field capacity for different soils, using equations based on the water retention curve. The database used included 150 soil profiles from studies published by other authors encompassing information related to textural classification, soil bulk density, particle density and soil water retention. The inflection point for each soil profile and the corresponding matrix potential were generated. Multiple correlations were established between volumetric moisture at field capacity and clay, silt and sand contents. The calculated inflection point can be an estimator of field capacity, what may facilitate and speed up the calculation of water availability.

Increasing cotton lint yield and water use efficiency for subsurface drip irrigation without mulching.

Planting without mulching can eliminate the residual film pollution caused by the long-term use of plastic film covers, but it will increase soil moisture evaporation and heat loss and severely reduce water use efficiency and cotton productivity in cotton (Gossypium hirsutum L.) fields in arid regions. It is unclear whether the advantages of subsurface drip irrigation and nighttime irrigation can be leveraged to reduce the amount of irrigation applied in fields, improve the soil and leaf hydrothermal environments, and increase the synchronicity of yield and water use efficiency (WUE). Therefore, in a two-year field experiment (2019-2020), cotton was grown under different irrigation treatments (I5, 3753 m3 ha-1; I4, 3477 m3 ha-1; I3, 3201 m3 ha-1; I2, 2925 m3 ha-1; and I1, 2649 m3 ha-1). The soil volumetric moisture content, soil temperature, leaf relative water content (RWC), daily changes in gas exchange parameters, lint yield, and WUE were evaluated. The results showed that reducing irrigation can reduce the soil volumetric moisture content (0-40cm soil layer), increase the soil temperature and soil temperature conductivity, and increase the leaf temperature, intercellular carbon dioxide concentration (Ci), and WUE; however, reducing irrigation is not conducive to increasing the leaf RWC, net photosynthetic rate (Pn), stomatal conductance (Gs), or transpiration rate (Tr). There was no significant difference in WUE between the I3 and I4 treatments from 8:00 to 20:00, but the lint yield in these treatments increased by 2.8-12.2% compared to that in the I5 treatment, with no significant difference between the I3 and I4 treatments. In addition, a related analysis revealed that the positive effects of the leaf hydrothermal environment on the Pn and soil temperature on the WUE occurs during the same period (10:00-16:00). Overall, an irrigation amount of 3201-3477 m3 ha-1 applied with a subsurface nighttime irrigation system without mulching can enhance the soil moisture content and soil temperature, maintain a high photosynthetic capacity, and increase the lint yield and WUE. These results revealed that the negative impacts of plastic film contamination in arid areas can be alleviated.

Cauchy problem for a non-Newtonian filtration equation with slowly decaying volumetric moisture content

Cauchy problem for a non-Newtonian filtration equation with slowly decaying volumetric moisture content

Spatial variability of edaphic attributes on Coleoptera (Insecta) in land use systems

The alteration of the natural landscape structure affects abiotic conditions and promotes a biological response in the local community. The diversity of edaphic organisms is related to the diversity of other taxa and abiotic characteristics, which represent potential bioindicators of the ecosystem. The objective of this study was to identify which soil attributes explain the beetle community and explore their effects through spatial modeling. The study was conducted in three landscapes in western Santa Catarina (Brazil), located in Chapecó, Pinhalzinho, and São Miguel do Oeste. The land use and cover systems identified were: no-till farming, native forest, pasture, eucalyptus planting, crop-livestock integration, and shrub vegetation. Soil, plant litter, and Coleoptera samples were collected. The variables were selected through the Threshold Indicator Taxa Analysis and spatial modeling by Geostatistics. Higher values of soil penetration resistance, associated with the no-till system, resulted in a lower abundance of Staphylinidae beetles, conditioned by total soil porosity. Lower volumetric moisture values, identified in the no-till system near native vegetation fragments, led to increased abundance of Nitidulidae family beetles, due to the family's adaptability to dry environments. The trend of higher microbial carbon concentration in native vegetation areas explained the greater abundance of Chrysomelidae family beetles in these areas, due to the phytophagous habits of the species in this family. Thus, the Coleoptera community has the potential to serve as bioindicators of soil quality, and their relationships with soil physics, chemical, and microbial attributes can be spatially modeled through Geostatistics.

Features of radiometric sensing of tundra soils moisture in the P-band

In this paper, in the P-band (409 MHz), the features of tundra soils microwave emission are theoretically studied during the thawing of active layer. The soils in vertical section of active layer were characterized by the profiles of volumetric moisture, weight content of organic matter, and time series of physical temperature. The brightness temperature of the active layer of tundra soils was calculated based on the phenomenological model of microwave emission for a stratified non-isothermal half-space. A dielectric model that allows to calculate the real and imaginary parts of the relative complex dielectric constant of tundra soils with a high organic matter content of 35%-80%, in the temperature range from -30C to +25C was used to modeling the brightness temperature. As a result, It was shown that as the active layer of tundra soils thaws, the interference of emissivity is observed, the amplitude of which is determined by the kind of vertical profile of the organic matter content. The interference of emissivity can be neglected when the active layer thaws more than 18.5 cm. If the volumetric moisture of the thawing part of the active layer is less than (or close to) the maximum content of bound water, then interference of emissivity is not observed. Modeling showed that the average sensing depth of tundra soil moisture does not exceed 4.5 cm.

Variation of Stem CO2 Efflux and Estimation of Its Contribution to the Ecosystem Respiration in an Even-Aged Pure Rubber Plantation of Hainan Island

The stem CO2 efflux (Es) plays an important role in the carbon balance in forest ecosystems. However, a majority of studies focus on ecosystem flux, and little is known about the contribution of stem respiration to ecosystem respiration (Reco) for rubber (Hevea brasiliensis) plantations. We used a portable CO2 analyzer to monitor the rate of Es in situ at different heights (1.5 m, 3.0 m and 4.5 m) in an even-aged rubber plantation from 2019 to 2020. Our results showed that Es exhibited a significant seasonal difference with a minimum value in April and a maximum in September. The mean annual rate of Es at 3.0 m in height (1.65 ± 0.52 μmol·m−2·s−1) was slightly higher than Es at 4.5 m in height (1.56 ± 0.59 μmol·m−2·s−1) and Es at 1.5 m in height (1.51 ± 0.48 μmol·m−2·s−1). No obvious differences in vertical variations were found. An area-based method (Ea) and a volume-based method (Ev) were used to estimate stem respiration at stand levels. One-way ANOVA showed that Ea had no obvious differences in vertical variation (p = 0.62), and Ev indicated differences in vertical variation (p < 0.05). Therefore, the Ea chamber-based measurements at breast height were reasonable and practical extrapolation proxies of stem respiration in an even-aged rubber plantation. With the use of the area-based method, the stem carbon values released from a mature rubber forest were estimated to be 1.214 t C·hm−2·a−1 in 2019 and 1.414 t C·hm−2·a−1 in 2020. Ea/Reco and Ev/Reco showed seasonal changes, with a minimum value in April and a maximum value in December. The leaf area index (LAI) and soil volumetric moisture content (VWC) were the major impact factors of Ea/Reco in an even-aged pure rubber plantation.

Comparing quasi-3D soil moisture derived from electromagnetic induction with 1D moisture sensors and correlation to barley yield in variable duplex soil

Farms in Western Australia (WA) are highly variable in soil texture and water retention capacity; therefore, information of soil moisture spatial variability in the field is important for effective crop management. In practice, farmers often rely on point sensors to determine soil moisture in their fields for crop planning. The limitation of point measurements to account for spatial variability highlights the need to develop methods that can assess soil moisture across variable broadacre fields. This information can enable more effective site-specific crop management practices. In this study, we used a mobile non-intrusive electromagnetic induction (EMI) sensor to map soil apparent electrical conductivity (ECa) to predict soil moisture levels at three different depths (0–0.5, 0.5–0.8 and 0.8–1.6 m) across the field and compared it with barley yield production. To convert the depth specific electrical conductivity (EC) from EMI surveys into soil moisture estimates, calibrations between electrical resistivity tomography (ERT) to volumetric moisture were used. These calibrations were developed for the different soil textural classes of the field, with R2 of 0.97–0.99. There was no significant difference between the estimated soil moisture from EMI surveys and the point moisture measurements obtained from soil moisture sensors and soil sample extracts, with Pearson R values of 0.64 for 0–0.5 m depth and 0.73 for 0.5–0.8 m depth. Additionally, correcting the temperature drift relative to the measured soil temperature on EMI surveys by 10% in dry season and 31% in wet season, improved the moisture estimation results. This study successfully demonstrated the effectiveness of spatial soil moisture estimation using EMI sensor in a field characterized by horizontal and vertical soil texture variability. However, no significant correlation was found between the mapped soil moisture or soil texture with barley yield. This may be due to relatively high initial moisture levels resulting from two years of fallow rotation.

Changes in crack width on the surface of heavy soils during drought, determined by precise measurement and calculation

Abstract In heavy soils, changes in humidity incur soil volume changes. In the horizontal plane, these are manifested by cracks formation and in the vertical plane by the movement of the soil surface. Cracks have a significant impact on hydrodynamics of the soil profile. The work is based on the hypothesis that soil volume changes depend on both the content of clay particles in soil and soil volumetric moisture. The aim of the work is to measure and analyze the changes in the width of the cracks and their reaction to the changes in volumetric soil moisture. One of the objectives of the work was to design a simple tool for accurate measurement and calculation of the crack width on the soil surface. For the study of crack width, a soil profile in an area on the East Slovakia Lowland was selected. The profile was examined under conditions of extreme drought, at the turn of July and August 2022. Crack width varied between 1.0 cm and 3.3 cm. The calculation procedure was evaluated as satisfactory for estimating the change in crack width on the soil surface.

Deciphering microbiomes dozens of meters under our feet and their edaphoclimatic and spatial drivers.

Microbes inhabiting deep soil layers are known to be different from their counterpart in topsoil yet remain under investigation in terms of their structure, function, and how their diversity is shaped. The microbiome of deep soils (>1 m) is expected to be relatively stable and highly independent from climatic conditions. Much less is known, however, on how these microbial communities vary along climate gradients. Here, we used amplicon sequencing to investigate bacteria, archaea, and fungi along fifteen 18-m depth profiles at 20-50-cm intervals across contrasting aridity conditions in semi-arid forest ecosystems of China's Loess Plateau. Our results showed that bacterial and fungal α diversity and bacterial and archaeal community similarity declined dramatically in topsoil and remained relatively stable in deep soil. Nevertheless, deep soil microbiome still showed the functional potential of N cycling, plant-derived organic matter degradation, resource exchange, and water coordination. The deep soil microbiome had closer taxa-taxa and bacteria-fungi associations and more influence of dispersal limitation than topsoil microbiome. Geographic distance was more influential in deep soil bacteria and archaea than in topsoil. We further showed that aridity was negatively correlated with deep-soil archaeal and fungal richness, archaeal community similarity, relative abundance of plant saprotroph, and bacteria-fungi associations, but increased the relative abundance of aerobic ammonia oxidation, manganese oxidation, and arbuscular mycorrhizal in the deep soils. Root depth, complexity, soil volumetric moisture, and clay play bridging roles in the indirect effects of aridity on microbes in deep soils. Our work indicates that, even microbial communities and nutrient cycling in deep soil are susceptible to changes in water availability, with consequences for understanding the sustainability of dryland ecosystems and the whole-soil in response to aridification. Moreover, we propose that neglecting soil depth may underestimate the role of soil moisture in dryland ecosystems under future climate scenarios.

Pre-treatment of steel slag and its applicability in asphalt mixtures for sustainable pavements

The secondary utilization of steel slag is significant for land occupation reduction, natural aggregate conservation, and environmental protection. This study aims to enhance the utilization of steel slag aggregate (SSA) in pavement engineering by providing guidance on selecting efficient and rapid pre-treatment methods. It compares the macroscopic morphological characteristics of basalt, SSA, and SSA prepared using various pre-treatment methods. The chemical composition and surface micromorphology of the samples were investigated by X-ray fluorescence spectrometry and scanning electron microscopy. The effects of the pre-treatment methods on the SSA and the performance of its asphalt mixture were comparatively evaluated based on laboratory tests. The carbon dioxide equivalent (CO2e) and cost associated with steel slag asphalt mixtures were quantified in this study. The findings revealed that the high angularity and roughness of the SSA make it an ideal candidate for use in pavement layer aggregates. Pre-treatment methods such as thermal water and acetic acid soaking expedited the hydration and oxidation reactions. Furthermore, applying a silane coupling agent resulted in the forming of a polymer membrane on the SSA surface, significantly enhancing its volume stability and adhesive properties. All these methods present compelling alternatives to natural aging. Compared with the original SSA, the performance of asphalt mixtures prepared using pretreated SSA was optimized, particularly concerning the volumetric stability and moisture damage resistance. In general, although the CO2e from using SSA for pavement construction increased compared to those using other substances, the CO2e was significantly lower than those from SSA lying idle, which positively impacts the alleviation of SSA accumulation and promotes sustainable development.

New procedure to estimate soil field capacity based on double ring infiltration data

Many models have been proposed to explain the water infiltration curve in soil, but according to the studies we have done so far, no model can simultaneously estimate the field capacity (FC) and soil hydraulic conductivity (K). The aim of this research is to present a new model that is defined based on the dynamic balance of water-soil-time and is able to estimate FC and soil hydraulic conductivity using cumulative field infiltration data. The studies were carried out in Varamin region with an area of 1370 square kilometers. For the penetration test, first, seven sides (A, B, C, D, E, F and G) were selected in 7 areas of agricultural land and with a double ring with an outer diameter (70 cm) and an inner diameter (30 cm) became. Also, to determine the soil texture, apparent specific gravity, PWP and FC, soil sampling was done at the depths of 0–10 and 20–30 cm. To determine FC moisture, pressure (−10 kPa) was used in a pressurized membrane device, and to determine volumetric moisture in PWP, sieved samples were placed on ceramic plates. Using a spray, the samples were wetted, so that they reached the saturation level, and the pressure was set to 1500 kPa. Examining the FC values showed that the maximum value of FC in site F (clay loam texture) is equal to 14.73 cm and the lowest value in site G (sandy clay loam texture) is equal to 6.8 cm by the model estimated by the results obtained in Laboratory confirmed. Meanwhile, the minimum saturated hydraulic conductivity of soil at site A was estimated to be 0.06 cm/min and the maximum at sites D and F was 0.28 cm/min. Time constant (Ksh) has shown completely different water infiltration rate in the first term of the model (Rfksh) compared to the second term of it (K), and no obvious relation has detected between them. But, their summation (k+Rfksh) was always equal to the maximum infiltration instantaneous rate (T→0). The research results showed that using the new model, the FC value varies between 6.8 and 14.73 cm. Also, the minimum and maximum instantaneous speed of water infiltration occurred in the site. An equal to 0.621 and in site D equal to 1.735 cm/min. The results of fitting the penetration model on cumulative penetration data showed that R2 varies between 0.994 and 0.999 and RMSE between 0.116 and 1.197. Therefore, the model is able to describe the penetration data well.

Cultivation of Crops in Strip-Till Technology and Microgranulated Fertilisers Containing a Gelling Agent as a Farming Response to Climate Change

Climatic and soil conditions are changing in response to the increasing human impact. This requires the introduction of low-cost, low-emission, but effective technologies in the field cultivation of crops, in turn requiring and justifying research in this area. In laboratory tests and field studies, the production and environmental effects of strip-till and the application of microgranular fertilisers with a gelling component were determined (and, in particular, their use in combination as a plant cultivation technology). These effects were measured in terms of soil properties, the biomass production, and the yields of maize (Zea mays L.), spring barley (Hordeum vulgare L.), and winter rape (Brassica napus L.). Fertiliser microgranules with a gelling agent absorbed water in the amount of 118.6–124.7% of fertiliser mass and increased the volumetric moisture content of the soil in the layer in which they were applied (0–7.5 cm) by 3.0–3.9 percentage points compared to the soil moisture without fertiliser. Strip tillage with the application of fertilisers with a gelling agent significantly increased the amount of water in the soil during the sowing period for winter and spring plants and reduced the CO2 emissions from the soil relative to the conventional tillage without microgranular fertiliser. The biomass of maize, spring barley, and winter rape before flowering, as well as the yields of these plants, were higher when cultivated using strip-till and fertilisers with gelling agents than when ploughed with a mouldboard plough without the use of microgranulated fertilisers. This technology also increased the number of microorganisms, including bacteria, actinobacteria, and filamentous fungi in the soil after harvesting compared to the unfertilised, ploughed soil. Strip tillage and microgranulated fertilisers containing a gelling agent can thus reduce the environmental pressure exerted by agriculture and reduce the risk of climate change, as well as being a way of adapting agriculture to climate change.

A Comparative Study of the Effect of Moisture Susceptibility on Polyethylene Terephthalate–Modified Asphalt Mixes under Different Regulatory Procedures

Water damage is one of the main causes of road deterioration during its lifespan, leading to a decrease in the structural and functional qualities of the road surface. Moreover, the management and disposal of polyethylene terephthalate (PET) bottles at the end of their lifecycle are becoming increasingly complex challenges. Hence, this study investigates the feasibility of incorporating crushed PET bottles into the production of asphalt mixtures, considering different PET quantities (6%, 10%, 14%, 18%, and 22%) and two incorporation processes in the mixture design (dry process and modified dry process). PET-modified mixtures‘ volumetric properties, Marshall parameters, and moisture susceptibility characteristics were evaluated and compared with PET-free asphalt mixtures. The results indicated that PET content significantly influences the properties being assessed, and the modified dry process yields a higher resistance to moisture susceptibility. Finally, the obtained TSR (tensile strength ratio) results based on European standards are compared with those obtained using American standards, in an aim to comprehend and assess the testing methods, result reliability, and applicability.

Determining Attribute—Response Relationships of Soils under Different Land Uses: A Case Study

Soil researchers are interested in a gaining better understanding of the soil system state by analyzing its properties and their dynamics in time as well as in relation to land use change. Tilled, abandoned, and forest soils were assessed regarding attribute–response relationships for the bulk density (BD), total porosity (TP), volumetric moisture (θv), and penetration resistance (PR) with the use of the interquartile ratio (IRI) integrated into a resilience formula and Shannon entropy indices. The IRI results differentiated soil properties according to agrotechnics (wheel track vs. between wheels) and the state of the system (tilled vs. abandoned vineyard). Entropy (En) indicated a high level of uncertainty for PR. The linear regression applied to the pairs of BD-TP, TP-θv, and PR-θv showed better results for the IRI weight (IRIweight) compared to the entropy weight (Enweight) for the soil between the wheels. The soil of the abandoned vineyard showed a faster tendency toward resilience that was more pronounced in the tilled wheel tracks than in the area between the wheels. The IRI can thus be an alternative to entropy in the evaluation of the response of some soil properties according to their use. When integrated into a resilience formula, the IRI can estimate the dynamics of soil properties for abandoned land compared to reference soil.

Spatial pattern consistency and repeatability of proximal soil sensor data for digital soil mapping

AbstractData from proximal soil sensors can facilitate digital soil mapping at high spatial resolutions. However, their use for predicting static soil properties, such as texture, is affected by spatio‐temporal changes in environmental and measurement conditions. In this research study, seasonal changes in spatial patterns and repeatability of data provided by a platform that simultaneously measures the red (Red) and near infrared (NIR) reflectance, apparent soil electrical conductivity (ECa), temperature, and volumetric moisture content of topsoil (at 3–6 cm depth) were assessed. Test fields are located in Southern Finland with textures dominated by clay and fine sandy till. During single scans, mean relative differences between the data from duplicated measurement points ranged from ~4% to 6% and were the highest for temperature and Red values. The consistency of spatial patterns across seasons (spring and autumn 2021 and 2022) was the highest for ECa values, and the lowest for NIR. ECa and moisture were significant for predicting the clay contents at a cereal grain crop site, whereas temperature was significant at grass ley sites. Errors were generally lower when using spring data compared with autumn data (RMSE ranging from 4.8% to 11.1% for the data from different fields and measurement dates). For the fields, where static soil properties change at small spatial scales, spatially detailed moisture and temperature data support the understanding of seasonal changes in the spatial patterns derived from multi‐sensor data, and the corresponding changes in the performance of calibration models.

Influence of Compaction on Electrical Resistivity Characteristics of Fine-grained Soil East of Baghdad City, Iraq

In geotechnical practice, there is a continuous demand for an efficient method for measuring the soil moisture content and dry unit weight of compacted soils used in a wide range of earthwork constructions. The Electrical Resistivity method has increasingly been used for rapid and non-invasive assessment of some geotechnical properties. This study aims to evaluate the influence of Moisture Content (MC), Dry Unit Weight (DUW), and Compaction Energy (E) on the Electrical Resistivity (ER) of soil collected from the east of Baghdad City, Iraq. To achieve this goal, soil specimens were compacted to various MC and DUW found in geotechnical practice using different E levels. The ER of prepared specimens was measured using the two electrodes method and compared with various geotechnical parameters related to the compaction process. The results showed that the employed MC, DUW, and E levels influenced the ER. The higher the MC, DUW, and E, the lower the ER. However, the ER was more sensitive to these variables for specimens compacted dry of the optimum. Furthermore, the ER was correlated very well with Volumetric Moisture Content ϴ and Degree of Saturation Sr of soil, with a high correlation coefficient (R2 >94%) and very low p-values, which indicated that these correlations were statistically significant. The current findings indicate the usefulness of the ER method for predicting these parameters. Therefore, using the ER method as a rapid and cost-effective technique for the preliminary evaluation of soil compaction variables in earthwork constructions is recommended. However, the current laboratory findings must be confirmed on different soil types.

Analytical and HYDRUS solutions for exfiltration through inclined seepage faces

Steady, phreatic flows in wedge-shaped aquifers subtended by a tilted bedrock and discharged through a hillslope seepage face are studied by 2-D and 1-D analytical models for fully saturated and a FEM numerical model for saturated-unsaturated flows. The curvilinear triangle in the hodograph domain is conformally mapped onto a reference half-plane where the Hilbert problem is solved for two holomorphic functions. Free boundaries and sizes of seepage face segments are found for given flow rates of the incident flows seeping downhills. The approximate (Dupuit-Forchheimer) water table is conjugated with a saturated triangle where the exact 1-D solution gives a constant Darcian velocity as a function of the angles of the soil wedge. HYDRUS-2D model gives the distributions of the pressure head, volumetric moisture content, isotachs, vector-fields of velocity and other characteristics of seepage described by the Richards-Richardson equation. Applications to stability of exfiltrating zones near tailwaters of earth dams are discussed.

Environmental and mechanical effects of rubberised open-graded asphalt mixtures incorporating with titanium dioxide: a laboratory investigation

ABSTRACT To reduce the impact of automobile exhaust on the urban environment and residents’ health, the rubberised open-graded (ROG) asphalt mixtures incorporating with TiO2 particles were developed in the present study. Five types of ROG asphalt mixtures were designed with varying Titanium dioxide (TiO2) content (0.2%, 0.3%, 0.4% and 0.5%, respectively). A comprehensive investigation of pavement performance was carried out for the potential evaluation of the designed mixtures, including the volumetric properties, Marshall stability, rutting resistance, moisture sensitivity and cracking resistance. The tail gas absorption test was to be carried out as well using the self-developed experimental equipment and evaluating method. The testing results showed that the designed mixtures can meet the requirements of the open-graded (OG) asphalt mixture in China's current specifications. The usage of TiO2 in the ROG asphalt mixture showed significant absorption effects on the three types of gases (CO, HC and NO). The increase of catalytic times will significantly reduce the catalytic degradation efficiency, thus affecting the durability of automobile exhaust degradation. Based on the consideration of the environmental and mechanical effects, the optimised TiO2 content incorporated into the ROG asphalt mixture was determined as 0.4%.

Stabilization of High Sulfate-Saline Soil with Lime, Ground Granulated Blast Furnace Slag (GGBFS), and Basic Oxygen Furnace Slag (BOFS)

Saline soil is an inferior and special material consisting of fine soil particles and possesses poor engineering properties. The swelling, salt heaving, and corrosive behaviors of this soil render it unsuitable for pavement construction due to its deteriorating effects. To use this soil as a subgrade material in the roadway, this soil needs to meet various engineering standard criteria such as deformation, sulfate reduction, strength, and durability for use as subgrade material. Hence, the soil underwent careful stabilization using designed proportions of chemical additives such as lime and slag-based materials. The paper studied the feasibility of using slag-based materials (by-products of the steelmaking process) such as ground granulated blast furnace slag (GGBFS) and basic oxygen furnace slag (BOFS) with lime in stabilizing sulfate-saline soil. On this premise, four designed mixtures, which include saline soil (control), [soil+6% lime], [soil+4% lime+2% (50% GGBFS+50% BOFS)], and [soil+4%lime+2% (70% GGBFS+30% BOFS)] for use to determine their various geotechnical and durability properties. The experimental program for determining these properties included proctor compaction, unconfined compressive strength, three-dimensional (3-D) swelling, and dielectric constant tests. As a result, the laboratory test findings have revealed that adding GGBFS and BOFS to the lime-treated saline soil decreased the maximum dry density, enhanced the strength parameter, and reduced the soil's volumetric swelling and moisture susceptibility.