Research on the Creep Characteristics of Thermal Insulation Shotcrete under the Action of Temperature and Humidity Circulation

In order to explore the creep characteristics of thermal insulation shotcrete under the action of temperature and humidity circulation, a series of uniaxial compression creep tests were carried out with different cycles of temperature and humidity and hierarchical loading conditions. The test results show that the axial creep deformation and creep strain of the thermal insulation shotcrete specimens increase with the increase of the number of drying and wetting cycles under normal temperature water bath condition. After 28 cycles, the deformation value becomes larger obviously, and the creep strain increases greatly in the precycle period. The thermal insulation shotcrete axial steady-state creep rate increases nonlinearly with the increase of the number of drying and wetting cycles under different stress levels. When the number of adjacent cycles is 0–3, the average increase is larger, and the axial steady-state creep rate of thermal insulation shotcrete for 28 cycles increases with the increase of water bath temperature. The instantaneous deformation modulus of thermal insulation shotcrete decreases logarithmically with the increase of the number of drying and wetting cycles, and the total deterioration degree of the average instantaneous deformation modulus increases gradually, but the deterioration degree between adjacent cycles decreases successively. The thermal insulation shotcrete specimens with 3 cycles of fracture were mainly stretched, and with the increase of the water bath temperature, the specimen was damaged by shear failure. When the water bath temperature is 40°C, the fracture degree of the specimen increases first and then decreases with the increase of the number of cycles.

Effects of Post-Harvest Conditions on Sorption Isotherms of Soybeans

This study focuses on the modeling of sorption characteristics of three varieties of soybeans (Akras R2, Lono R2, and Podaga R2). Three pretreatments related to post-harvest conditions were tested on the soybean varieties: (1) freshly harvested soybeans, (2) soybeans subjected to three drying and wetting cycles, and (3) soybeans subjected to three freezing and thawing cycles. The adsorption and desorption experiments were conducted at 5°C, 10°C, 15°C, 20°C, 25°C, and 30°C using a dynamic equilibrium relative humidity (ERH) apparatus. Equilibrium moisture content (EMC) and the corresponding ERH were measured. The parameters calculated for the modified Halsey equation are applicable for storage temperatures above 10°C in the relative humidity (RH) ranges of 10% to 80% for desorption and 30% to 80% for adsorption. No significant differences were found in sorption isotherms among the soybean varieties. However, the soybean varieties responded differently to the different pretreatments (i.e., drying/wetting and freezing/thawing cycles). The adsorption isotherms of Akras and Lono soybeans showed significant differences at 10°C to 30°C when subjected to drying and wetting cycles, while Akras and Podaga soybeans showed significant differences in the same temperature range when subjected to freezing and thawing cycles. The effect of drying and wetting cycles on the desorption isotherms was found only for Akras soybeans at 10°C and 15°C below 63% and 71% RH, respectively, and for Lono soybeans at 25°C and 30°C above 69% RH for both temperatures. In general, the effect of both pretreatments on the sorption isotherms of soybeans was a reduction in EMC of up to 20%, when compared to fresh samples at selected storage temperatures. The findings of this study serve as a primary tool for developing a lookup table for safe storage guidelines for soybeans. Keywords: Equilibrium moisture content, Equilibrium relative humidity, Halsey equation, Oswin equation, Soybeans.

Implications of root exudates on the formation of rhizosheaths

<p>Root exudates stimulate microbial activity and functions as a binding and adhesive agent that increases aggregate stability in the rhizosphere. The exudates produced from plant roots and microorganisms in the rhizosphere play a significant role in the formation of rhizosheath. Rhizosheaths comprises the soil that adheres to the roots with the help of root hair and mucilage even when it is removed from the surrounding soil. Low surface tension and great viscosity stabilize soil aggregates in surrounding root and develop rhizosheath formation. To our knowledge, no investigations are made on the influence of root exudates in soil rhizosheath formation, although it is well documented the formation and stabilization of rhizosheath of maize plants under various soil water contents but the influence of root exudates on the rhizosheath formation associated with other rheological properties is still missing. Such knowledge will greatly enhance the understanding of how rhizosheath is formed under different root and seed exudates and the effect of their physiochemical properties on the adhesion properties of mucilage will be studied in this project.</p><p>The aim of this study is to provide the first combined quantitative data on how root and seed exudates of different plants affect rhizosheath formation. We hypothesized that mucilage will contribute to the formation of rhizosheaths.  For this, we will use the mucilage of chia seeds which acts as a modelled plant root mucilage and mix it with soil in five different concentrations. After preparing the soil with mucilage, artificial roots (flax cords) will be incorporated in this soil and after drying and wetting cycles roots will be removed and the mucilage adhesion, simulation and rheological properties will be investigated under various soil water contents, soil texture, soil type, and soil compaction.</p><p><strong>Key words:</strong></p><p>                   Rhizosheath, mucilage, drying and wetting cycles and soil structure</p><p> </p>