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【Objective】 Heavy-textured soils tend to swell or shrink following rewetting or drying, while most soil water characteristic curves measured from such soils do not consider such effects. The purpose of this paper is to investigate these and proposes an improved model to account for soil swelling and shrink. 【Method】 Changes in soil moisture and matric potential during three wetting-drying cycles in three soils were measured using thermo-TDR probe and soil water potential probe, respectively, and the results obtained from each cycle for each soil were fitted to the van Genuchten formula. We introduced a shrinking percentage parameter to improve the fitting of the van Genuchten formula. 【Result】 The heat pulse probe improved soil volume measurement, with the relative error reduced from 10%~40% to less than 10% and the associated root mean square errors reduced from 0.3~0.4 g/cm3 to less than 0.1 g/cm3. Increasing dry-wet cycles reduced the values of the parameters α and n in the van Genuchten formula. The influence of soil water on soil volume waned as soil water content decreased. The values of the parameters α and n in the van Genuchten formula both decreased as clay content increased. Accounting for the shrinkage in the modified model improved the fitting compared to the original van Genuchten formula that does not consider soil deformation. 【Conclusion】 The heat pulse probe can accurately measure change in soil volume induced by wetting and drying, and the proposed model considering volumetric change of soils following wetting or drying improves the fitting of the van Genuchten formula to the measured data.

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The aim of this paper is the collection, processing and statistical analysis of data from the results of testing concrete cube samples which are tested in the Laboratory for materials of the Faculty of Civil Engineering, University of Belgrade, in the period from 2012. to 2017. year. For the needs of the analysis, the data from the Report on testing of control concrete cubes were taken, the basic characteristics of hardened concrete are also classified. Statistical analysis of the date of concreting, age of samples, composition of concrete, volume mass, pressure strength, required concrete marks etc have been carried out. The statistics showed that the most commonly used cements were the following markings: CEM II A-M (V-L), CEM II A-M (S-L), CEM II A-S, with the highest share of concrete mark MB 30 with 66,8% and MB 40 with 14,3 % stake.

In the field stationary experiment, the dynamics of the general biological activity of chernozem, depending on the biomass of plant residues, methods of the basic soil tillage under different hydrothermal conditions was studied. It was established, that the release of carbon dioxide by microorganisms from the soil more intensively occurred on the background of deep tillage, where the best conditions for aeration and distribution of plant residues in the profile of the arable layer were found. Minimization of soil tillage, in consequence of the compaction of the arable layer by more than 1.3 g / cm³ limited the volume of active zone of biotic activity and growth processes of field crops in crop rotation while inhibiting the overall biological activity and reducing the amount of carbon dioxide released. However, small soil tillage contributed to the enhancement of the anti-erosion resistance of the chernozem surface from the shock energy of rain drops, and also provided more favorable conditions for the humification of organic residues instead of undesirable intensive mineralization, especially humus. [ABSTRACT FROM AUTHOR]