In the theoretical part of the thesis, different methods of testing frost susceptibility in the Czech Republic and other countries of the European Union are compared. The practical part of the thesis deals with laboratory testing of frost susceptibility of concrete and mixed recycled materials using the direct method of frost heave tests as well as determining the California Bearing Ratio (CBR) and design module of elasticity using the cyclic triaxial test. Suitability of materials for construction of road infrastructure is then assessed on the basis of the results of these tests.

The Portland Cement Association commissioned a research project at Brigham Young University to compare selected laboratory durability tests available for assessing stabilized subgrade materials. Improved understanding of these tests is needed to enable more objective selection of durability tests by design engineers and to facilitate more meaningful comparisons of data obtained for different stabilizer treatments using different evaluation procedures. The laboratory research associated with this project involved two subgrade materials, four stabilizers at three concentrations each, and three durability tests in a full-factorial experimental design. The two subgrade soils used were a silty sand and a lean clay, while the four stabilizer types included Class C fly ash, lime-fly ash, lime, and Type I/II portland cement. The three tests used in this comparative study were the freeze-thaw test, the vacuum saturation test, and the tube suction test. On average, to achieve the same 7-day unconfined compressive strength (UCS) values, the sand required 4.4 times more Class C fly ash than cement, 3.6 times more lime-fly ash than cement, and 6.0 times more lime than cement. Likewise, the clay required 10 times more Class C fly ash than cement, 7.5 times more lime-fly ash than cement, and 1.8 times more lime than cement. Analyses of the test results indicated that the UCS and retained UCS were higher for specimens tested by vacuum saturation than the corresponding values associated with freeze-thaw cycling. This observation suggests that the freeze-thaw test is more severe than the vacuum saturation test for these particular fine-grained materials. Testing also suggested that specimens with 7-day UCS values below 200 psi will generally not survive freeze-thaw cycling. After both freeze-thaw and vacuum saturation testing, the sand specimens treated with lime-fly ash had significantly higher UCS and retained UCS than specimens treated with Class C fly ash, lime, or cement. Similarly, the clay specimens treated with Class C fly ash or lime-fly ash had significantly higher UCS values than specimens treated with cement or lime; however, clay specimens treated with Class C fly ash and lime-fly ash were not significantly different. None of the four stabilizer types were significantly different from each other with respect to retained UCS after vacuum saturation testing. Dielectric values measured in tube suction testing were lowest for specimens treated with lime-fly ash and cement with respect to the sand and for specimens treated with Class C fly ash and cement with respect to the clay. The lime-fly ash and cement successfully reduced the dielectric value of sand specimens to a "marginal" rating, while no stabilizer reduced the moisture susceptibility of the clay to a satisfactory level. A strong correlation was identified between UCS after the freeze-thaw test and UCS after the vacuum saturation test, while very weak correlations were observed between the final dielectric value after tube suction testing and all other response variables. Differences in variability between test results were determined to be statistically insignificant in an analysis of the CVs associated with data collected in this research. Although the freeze-thaw test utilized in this research was determined to be more severe than the vacuum saturation test for materials similar to those tested in this study, the vacuum saturation test is recommended over both the freeze-thaw and tube suction tests because of the shorter test duration, usability for specimens with 7-day UCS values even below 200 psi, and lack of a need for daily specimen monitoring.

This diploma thesis deals with the issue of the determination of the frost susceptibility of soils in the subgrades of road structures. The theoretical part compares the ways of testing the frost susceptibility in the Czech Republic and other selected countries of the European Union. Furthermore, it also deals with the development of the frost susceptibility index in the Czech Republic. The empirical part focuses on the laboratory testing of the frost susceptibility of the given sample of soil by the direct frost heave method. Moreover, it also deals with the simulation of penetration of frost by the subgrade and the possibility of shortening the length of the freezing during the direct testing the frost susceptibility.

The work deals with the use of mixed construction recycled material for earth bodies of roads. The theoretical part describes the production, usability and economic evaluation of recycled building materials against common natural materials. It then describes the necessary laboratory tests that examine its properties for the use of these materials in roads. In the last chapter, the work deals with foreign experience with the use of mixed construction recyclates for transport construction. The practical part examines the properties of the given recyclates for their use in the core using tests of soil freezing rate, California bearing ratio and immediate bearing index.

The theoretical part of the diploma thesis searches the production of Construction and demolition waste and their subsequent transformation into the final recyclate and its possible use in roads. Attention is focused on the use of mixed recycled material into subgrade of the pavement and the characteristics of tests that must be performed before its used to the road. The next chapters pai attention to the problematic properties of recyclates, foreign experience with the use of mixed recyclate in Construction and the possibilities of its development. The practical part verifies the suitability of mixed recycled material into subgrade of the pavement using laboratory tests. The tests are performer on individual mixtures of mixed recycled material with cement, blast furnace slag or cement dust in various percentages. The results are then compared and it is evaluated which mixtures show the best properties. Part of the practical part is also the economic evaluation of these mixtures against commonly used materials.