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Recycled concrete aggregate (RCA) is a promising substitute for natural aggregates and the reuse of this material can benefit construction projects both economically and environmentally. RCA has received great attention in recent years in the form of aggregate as well as a geotechnical material of sand size. Next to RCA, another recycled material, which reduces the waste volume and is a part of the present challenges in civil engineering, is tire waste. Despite the good engineering properties of recycled tire waste (RTW), its use is still limited, even after almost 30 years since they were first introduced. To broaden the applicability of reused concrete and rubber, a further understanding of their properties and engineering behavior is required. For this reason, the main subject of this paper is composite materials that consist of anthropogenic soil recycled concrete aggregate (RCA) and crushed pieces of recycled tire waste (RTW). In this study, a series of isotropic consolidated drained triaxial tests were undertaken to characterize the shear strength of eight mixtures of variable grain-size distribution, rubber inclusion (RC), and fine fraction (FF) content. The results show that the introduction of rubber waste leads to changes in the strength parameters of the tested mixtures. Improvements in RCA shear strength were observed, the largest for the mixture M7 with 10% of recycled tire waste. Similarly, the effect of fine fraction content on the angle of internal friction and cohesion was found. Dilation characteristics were observed in all analyzed composites. Based on the results of all tests performed, including physical, geometric, chemical, and mechanical properties of the created composites, it can be stated that the samples would meet local road authority requirements for sub-base applications.

The shear modulus of soils at small strain (G0) is one of the input parameters in a finite element analysis with the hardening soil model with small strain stiffness, required in the advanced numerical analyses of geotechnical engineering problems. The small strain stiffness can be determined based on the seismic wave velocities measured in the laboratory and field tests, but the interpretation of test results is still under discussion because of many different factors affecting the measurements of the wave travel time. The recommendations and proposed solutions found in the literature are helpful as a guide, but ought to be adopted with a certain measure of care and caution on a case-by-case basis. The equipment, procedures, tests results and interpretation analyses of bender elements (BE) tests performed on natural overconsolidated cohesive soils are presented.

One important aspect of soil dynamics is attenuation or energy loses. This inherent dynamic property is essential in the analysis of soil behavior subjected to a dynamic load. Energy absorption in soils leads to the definition of an equivalent viscous damping ratio (D). In resonant column testing there are commonly two different approaches in measuring material damping: during a steady-state vibration (SSV), when the specimen is vibrated at its first mode; and during free-vibration decay (FVD). The study reports results associated with the small to medium strain range material damping from FVD method, i.e. there is a cut off the constant vibration of the specimen at resonance and the specimen is allowed to free-vibration mode while the decay strain amplitude during free-vibration is calculated. The experiments were conducted on cohesive soils (sasiCl, Cl, clSa) from various test sites located in Warsaw, Poland. All the specimens were subjected to torsional mode of vibration at their first natural frequency, at different mean effective stress. The authors paid particular attention to the number of successive cycles after the free-vibration of the material is initiated. They examined various propositions from the literature and compare the received damping values using different number of cycles of vibration. The results showed that the most stable values of material damping ratio can be obtained by selecting each time a line of best fit on the authors’ choice of number of free-vibration cycles. However, the number of these cycles should not exceed 10.

In this paper the original results of uniaxial cyclic compression test on cohesive soil are presented. The shakedown phenomena in cohesive soil are described. Energy-based method highlights the change of soil material behaviour from plastic shakedown through plastic creep shakedown to incremental collapse. The samples were cyclically loaded under undrained conditions with the constant amplitude of stress in one-way test procedure. In this study the energy-based method was presented as a proper method to categorise response of cohesive soil to cyclic loading in uniaxial conditions. A shakedown criterion factor, S E, was introduced to help understand the shakedown phenomena in cohesive soil. In cohesive soils the absence of a limit between plastic shakedown and plastic creep shakedown was pointed out.

The recent significant development of technical infrastructures in Poland, along with the construction of tower blocks, roads, railways and underground rapid transit system, resulted in greater demands for investment projects as well as geotechnical data characterizing the variation of various soil parameters found in the subsoil. The most important parameter, which represents the stiffness of soil deposits, is the shear modulus G. Therefore, this study focused on determining the initial shear modulus of cohesive soils from the area of the capital of Poland. In this research, a set of the resonant column (RC) tests was performed and the influence of three selected factors, i.e. mean effective stress (p’), void ratio (e) and plasticity index (PI), on the low-amplitude shear modulus (G0) was presented and discussed. The results obtained from laboratory tests indicated that the stress state plays an important role for the small-strain shear modulus values of the Polish Quaternary cohesive soils. In contrast, there was no clear trend observed for the significant effect of e or PI on G0 for the studied soils. Based on the performed tests, the authors proposed the power-law relations for G0 versus p′ of the forms: G0=3.02p′0.68 and G0=0.82p′0.96.

In this work, the small-strain and nonlinear dynamic properties of silty clay samples were studied by means of the low- and high-amplitude resonant column (RC) tests at various mean effective stresses (p’). The tested specimens were collected from the centre of Warsaw, district Śródmieście. Initially, the low-amplitude tests (below 0.001%) were conducted. Subsequently, the nonlinear testing was performed, at shearing strains greater than 0.001%. These tests were carried out in order to receive the dynamic properties of silty clay specimens in the nonlinear shear strain range. The small-strain material damping ratios (Dmin) of silty clay samples were also measured during the low-amplitude resonant column testing. The results show that increasing shear strain (γ) above the elastic threshold (γte) causes a decrease of the shear modulus (G) and normalized shear modulus (G/Gmax) of analyzed soil samples. Simultaneously, it is observed a increase of its damping ratio (D) and normalized damping (D/Dmin) with increasing shear strain (γ). Predictive equations for estimating normalized shear modulus and material damping of silty clay soils were presented here as well. The equations are based on a modified hyperbolic model and a statistical analysis of the RC tests results. The influence of unloading process on dynamic properties of the tested material was also discussed in the paper.

Analysis of the multistage cyclic loading test on resilient modulus value. Upon cyclic excitation of soil mass, two types of strain can be recognized, namely elastic and plastic one. Proper analysis of these two types of deformations can help engineers in designing more reliable structures. In this study, a multistage uniaxial cyclic loading in unconfined conditions was performed. Tests were performed in order to characterize strain response to repeated excitation. Soil sample under cyclic loading was recognized as exhibiting the symptoms of a plastic strain growth during the cyclic loading process with exponential manner, when compared to number of cycles. Soil in this study was reconstituted and compacted by using the Proctor method to simulate conditions similar to those affecting the road subbase. The soil was recognized as sandy clay. Results were analysed and a proposition of empirical formula for plastic strain calculation with the use of characteristic stress values was presented. The resilient modulus values were also calculated. The Mr value was within range from 45 to 105 MPa. The conclusions concerning the cyclically loaded soil in uniaxial conditions were presented.

Slags are the final solid wastes from the steel industry. Their production from waste and associated materials is a proper implementation of the basic objectives and principles of the waste management. This study aims to investigate the chemical and selected significant geotechnical parameters of steel slag as the alternative materials used in road construction. These investigations are strongly desired for successful application in engineering. Young’s modules E, and resilient modules Mr showed that their values corresponding with requirements for subbase (principal or auxiliary) and riding surface as well. Tested mechanical properties were conducted in soaked and un-soaked (optimal moisture content) conditions. The designated high content of chromium and zinc are strongly associated with the internal crystal structure of steel slag. The results do not lead to threats when they are applied in roads’ structures. Mechanical characterization was obtained by performing California bearing ratio (CBR) tests for steel slag in fixed compaction and moisture content conditions. Moreover, cyclic loading of steel slag was conducted with the application of cyclic California bearing ratio (cCBR) apparatus to characterization of this material as a controlled low-strength material. Finally, field studies that consist of static load plate VSS tests were presented.

The paper concerns the evaluation of the initial stiffness of selected cohesive soils based on laboratory tests. The research materials used in this study were clayey soils taken from the area of the road embankment No. WD-18, on the 464th km of the S2 express-way, Konotopa-Airport route, Warsaw. The initial stiffness is represented here by the shear modulus (Gmax) determined during resonant column tests. In the article, a number of literature empirical formulas for defining initial value of the shear modulus of soils being examined were adopted from the literature in order to analyze the data set. However, a large discrepancy between laboratory test results and the values of Gmax calculated from empirical relationships resulted in the rejection of these proposals. They are inaccurate and do not allow for an exact evaluation of soil stiffness for selected cohesive soils. Hence, the authors proposed their own empirical formula that enables the evaluation of the test soils’ Gmax in an easy and uncomplicated way. This unique formula describes mathematically the effect of certain soil parameters, namely mean effective stress ( p′) and void ratio (e), on the initial soil stiffness.

Investigation of geosynthetics behaviour has been carried out for many years. Before using geosynthetics in practice, the standard laboratory tests had been carried out to determine basic mechanical parameters. In order to examine the tensile strength of the sample which extends at a constant strain rate, one should measure the value of the tensile force and strain. Note that geosynthetics work under different conditions of stretching and temperatures, which significantly reduce the strength of these materials. The paper presents results of the tensile test of geotextile at different strain rates and temperatures from 20 °C to 100 °C. The aim of this study was to determine the effect of temperature and strain rate on tensile strength and strain of the woven geotextile. The article presents the method of investigation and the results. The data obtained allowed us to assess the parameters of material which should be considered in the design of the load-bearing structures that work at temperatures up to 100 °C.

The depletion of natural resources is forcing researchers to explore the possibilities of new aggregates, such as recycled concrete aggregate (RCA). In this article, the mechanical properties and the influence of the size of the direct shear box on the obtained parameters were examined. The study was conducted in two apparatus: medium (120 × 120 mm) and large (250 × 250 mm). In each of these devices, a total of 6 tests were performed: 3 for dry sample and 3 at optimum moisture content. From the results, the conclusions described below have been drawn

The development of industry and application of new production techniques could bring about extraordinary problems that have been neglected. One of these challenges in terms of soil mechanics is high frequency cyclic loading. Well constructed foundation may reduce this troublesome phenomenon but excluding it is usually uneconomic. In this paper, shakedown theory assumptions were studied. Cyclically loaded soils behave in various ways depending on the applied stress rate. Common cohesive soils in Poland, i.e., sandy-silty clays are problematic and understanding of their behaviour in various conditions is desired. In order to study repeated loading of this material, cyclic triaxial test were carried out. Cyclic loading tests were conducted also in one way compression. These methods in small strain regime allow permanent strain increment analysis with resilient response after numerous cycles. This behaviour was subsequently exploited in the study of shakedown theory. This paper contains some conclusions concerning the above-mentioned theory.

Vertical and horizontal permeability measurement in organic soils. The paper is refer- ring to vertical and horizontal laboratory perme- ability measurements in soft organic soils. The estimation of anisotropic permeability in soft organic soils, as peats, requires to use a special apparatus and the knowledge of proper analysis of the test results. During loading the void ratio decreases substantially that causes the change- ability of the permeability. The change of perme- ability during the compression is very important because of the infl uence of the consolidation co- effi cient. Initial strain in soft organic soils appears very quickly, just after loading, and brings im- mediately the decrease of permeability. In most of the estimations, it is assumed that during the consolidation process the water fl ows just in the vertical direction. In soft organic soils, like peats, the consolidation theory should consider the changes of mechanical and physical properties in consolidation period, in both directions. The direct measurement of vertical and horizontal permeability of organic soil and the non-Darcian fl ow theory may be of considerable importance in estimating pore water pressure dissipation, and settlement rates in the consolidation model. In the paper, the method of investigation and the test re- sults of the vertical and horizontal permeability are presented. The Modifi ed Rowe Cell Set for obtaining consolidation and fl ow characteristics in different directions is used.

Several researches published comprehensive reports on dynamic soil properties of cohesive soils, in which many of them outlined, i.e., key factors affecting the dynamic shear modulus. For cohesive soils, the modulus at small strains (g 103%, e.g., 3 × 103%, 5 × 103%, 8 × 103%, 2 × 103%).

Soil investigations concerning cyclic loading focus on the evaluation, in particular, of design parameters, such as elastic modulus, Poisson’s ratio, or resilient modulus. Structures subjected to repeated loading are vulnerable to high deformations, especially when subgrade soils are composed of cohesive, fully-saturated soils. Such subgrade soils in the eastern part of Europe have a glacial genesis and are a mix of sand, silt, and clay fractions. The characteristic of, e.g., Young modulus variation and resilient modulus from repeated loading tests, is presented. Based on performed resonant column and cyclic triaxial tests, an analytical model is proposed. The model takes into consideration actual values of effective stress p′, as well as loading characteristics and the position of the effective stress path. This approach results in better characterization of pavement or industrial foundation systems based on the subgrade soil in undrained conditions. The recoverable strains characterized by the resilient modulus Mr value in the first cycle of loading was between 44 MPa and 59 MPa for confining pressure σ’3 equal to 45 kPa, and between 48 MPa and 78 MPa for σ’3 equal to 90 kPa. During cyclic loading, cohesive soil, at first, degrades. When pore pressure reaches equilibrium, the resilient modulus value starts to increase. The above-described phenomena indicate that, after the plastic deformation caused by excessive load and excess pore water pressure dissipation, the soil becomes resilient.

Wyprowadzenie równania różniczkowego cząstkowego konsolidacji z uwzględnieniem nieliniowości przepływu na przykładzie gruntów organicznych. W artykule zaproponowano wyprowadzenie równania różniczkowego cząstkowego konsolidacji z uwzględnieniem nieliniowości przepływu. Nieliniowe charakterystyki przepływu wyznaczono na podstawie badań flow-pump na gruntach organicznych. Zależność pomiędzy prędkością przepływu wskaźnikiem porowatości i gradientem została zapisana za pomocą równań empirycznych. Analiza wyników badań laboratoryjnych potwierdziła dużą zmienność przepływu wraz ze zmianą porowatości. Wiele budowli, takich jak: nasypy drogowe, obwałowania, zapory i wykopy budowlane, jest bardzo często posadowionych na ściśliwych gruntach organicznych, dlatego właściwe zamodelowanie przebiegu konsolidacji jest bardzo istotne. W tym celu należy wziąć pod uwagę czynniki, takie jak: fi zyczne i mechaniczne właściwości gruntu, nieliniową zależność naprężenia i odkształcenia, nieliniową charakterystykę przepływu i pełzanie. W artykule skupiono się na nieliniowych charakterystykach przepływu zmiennych z porowatością i gradientem hydraulicznym. Zaproponowano równanie różniczkowe cząstkowe konsolidacji uwzględniające nieliniowość przepływu w gruntach organicznych.

Impact of the stabilization of compacted cohesive soil - sandy clay on yield criterion improvement. Soft soils, exhibiting low strength properties in the case of external load, require improvement. Chemical stabilization is easy in preparing and presents very good results in improving mechanical properties. In this paper, results of CBR and unconfined compressive strength test are presented for cohesive soil - sandy clay. Stabilization medium was Reymix, which is a cement derivative. Conducted tests define the characteristics of mechanical properties improvement and estimate yield criterion for stabilized soil during the time of stabilization, which is different for non-stabilized soils

Small strain stiffness in overconsolidated Pliocene clays. A huge development of technical infrastructure, including the construction of many high-rise buildings, roads, railroads and extension of subway lines, took place over the recent years in Poland. Therefore, numerous planned investment projects require geotechnical data documenting the variation of soil parameters found in the subsoil. The shear wave velocity is one of the most important input parameters to represent the stiffness of the soil deposits. This paper focuses on the methods and devices using measurements of the shear wave velocity to estimate the initial shear modulus in cohesive soil. It is preferable to measure VS by in situ wave propagation tests, however it is often economically not feasible in all regions of Poland. Hence, a reliable correlation between shear wave velocity and parameters measured in triaxial cell or static penetration parameters would be a considerable advantage. This study shows results obtained from the bender elements tests and field techniques - seismic cone penetration test and seismic flat dilatometer, performed on overconsolidated cohesive soils in Warsaw. On the basis of the test results possible correlations between shear wave velocity (initial shear modulus), mean effective stress and void ratio are considered and four original empirical relationships are proposed. Moreover, the proposed formulas by two different techniques using triaxial apparatus and also RCPT cone were examined. The proposed formulas show a reasonable agreement with direct shear wave velocity profiles for clays and might be incorporated into routine laboratory and field practice

Soil investigations concerning cyclic and dynamic loading differ from static analysis. The Problem with the abovementioned loads becomes more important, when cohesive soils are taken into consideration. There are plenty of scientific reports containing the analyses of non-cohesive soil behaviour, yet there is still a lack of similar studies on cohesive soils. Repeated loading and dynamic excitations differ between themselves and parameters which are used to describe those phenomena are not congruent. Road constructors seek new approaches to design methods, which would take into account more types dynamic and cyclic excitations. For a successful utilisation of these occurrences in designing codes, mechanical parameters, such as resilient modulus Mr, shear modulus G and Poisson ratio υ or dumping ratio D, need to be determined. The laboratory tests were conducted on sandy clays, which are a common soil in Poland, using specialized laboratory equipment, such as a resonant column and cyclic triaxial apparatus. The aim of the work presented in this paper was to measureand analyse the abovementioned mechanical characteristics. The paper ends with conclusions regarding the application of cyclic and dynamic loading characteristics in road design.

Determination of the Resilient modulusMR for the lime stabilized clay obtained from therepeated loading CBR tests. The main aim of this paper is to prove that CBR repeated test is useful to give an adequate like unconfi ned cyclic triaxial test parameters for design the pavement and subgrade soils. That parameter is the Resilient modulus (MR) which is the elastic modulus based on the recoverable strain under repeated load. Resilient modulus (MR), is an important parameter which characterizes the subgrade’s ability to withstand repetitive stresses under traffic loadings. The 1993 AASHTO guide for design of flexible pavements recommends the use of MR. The additional aim is connected with the concept of sustainable development. For many countries, where resources are at premium, it is very important that stabilized local soil can be used for road construction. For ensuring that stabilized clay can be used for pavement material standard compaction, CBR and repeated CBR tests were performed. In that paper parameter MRof the subgrade lime stabilized clay soil by laboratory CBR repeated test were determined using for calculation formulas from triaxial cyclic test. Based on AASHTO empirical equation the static CBR values using back analysis was also calculated. Finally both values of CBR determined and calculated were compared.

The uncertainty of the water flow velocity data obtained in the laboratory test The uncertainty of the water flow velocity data obtained in the laboratory test. Some of the engineering constructions are significant for the environment and flood protection. There are dams for water retention as well as waste tailings dams and road embankments founded on organic soils. Constructions on soft organic soils make it necessary to calculate subsoil deformations with a special regard of the water flow. In this thesis, the approach of the water flow test in soft organic soils is presented. In the permeability test the modern flow-pump technique was applied. This technique takes into consideration organic fiber structure, large soil strain, short time of research and "real" hydraulic gradients appearing in situ. The specific behavior of soft subsoil demands to calculate the test reliability results. Therefore in the statistical analysis of the test results the suitable statistical method and the proper laboratory technique should be used. Several statistical models have been applied to the flow pump test results in order to find the correct description of water flow velocity in soft subsoil.

We represent the results of our investigations on size distribution of atmospheric aerosol particles by means of a multiwavelength lidar based on Nd : YAG and Ti : Sa lasers equipped with frequency multipliers. The measurements were performed in mountainous areas.

In this study, measurements of the vertical and temporal variations in ozone concentrations over the mountainous area during three observation periods in July 1997 and August 1998. The data used in this study were obtained from a differential measurement technique called Differential Absorption Lidar (DIAL) and from the ground-based stations at different altitudes. Many ozone profiles exhibited distinct local maxima up to 100 ppb and a large variation in mixing ratios existing in the height range between 1150–1650 m a.s.l. Ozone levels have more than doubled at about 1340 m a.s.l. as compared to higher altitudes.

We report the results of measurements of ozone concentrations during the solar eclipse of 11 August 1999. The experiment was performed in Warsaw (Poland) and its surroundings. The temporal evolution of ozone concentration was measured using the differential absorption lidar (DIAL) and it was compared with results obtained by several monitoring stations measuring with other methods. In almost all cases, a drop in the ozone concentration was observed during the eclipse. Experimental data was compared with calculations done using a simple model based on NO x –O 3 chemical kinetics.

In lidar measurements noise and fluctuations strongly affect the results. The reason is a rapid decrease of the signal-to-noise ratio with an increase of distance. The differential absorption lidar (DIAL) is particularly sensitive to the signal instabilities. In this paper we present a method of the signal acquisition that is suitable for registration of both large light fluxes and single photons. We also present new method of solution of the DIAL equations. Compared to the traditional algorithm used for signal elaboration our procedures are much more stable and they are able to increase the effective range of lidar measurements.

The results of field and laboratory investigations performed on two test sites located on organic soils in northwestern Poland are presented. Comprehensive investigations comprising observations at four test embankments and a laboratory investigation were carried out to study the influence of vertical drains on the consolidation process in organic subsoil and the behaviour of Geodrains-type strip drains in organic soils. It was shown that vertical strip drains may effectively improve the bearing capacity of amorphous peat and gyttja for stage-constructed embankments. However, it has been observed that there is a significant decrease in discharge capacity of Geodrains during embankment construction, depending on the type of drain filters (paper or polyester). Nevertheless, the vertical drain effectiveness was found to be quite satisfactory because the observed decrease of discharge capacity has practically no influence on consolidation rate. It was also detected that the buckling effect, probably owing to large horizontal displacements, does not significantly affect the discharge capacity of drains. Moreover, it is shown that there is a significant difference in pore-pressure distribution under embankments with and without vertical drains. As a result of the vertical drain installation under part of the slopes, a significant decrease in the horizontal displacements took place. Key words : consolidation, soil improvement, organic soils, vertical drains, field and laboratory tests.

The analysis of consolidation in organic soils. This paper is devoted to the specifi c diffi culties connected to construction on problematic soils. Different type of structures like: road embankments, fl ood control levees, dykes and dams are often located in soft subsoil areas, which consists mainly of peat, calcareous soil with a very high content of calcium carbonate and other high plasticity organic and no organic soils. These soils can be characterized as highly deformable with low initial shear strength and an insuffi cient bearing capacity. Soft soils show a large deformation, both vertically and horizontally, under load. The settlements often appear very quickly and can also continue for a long time. The consolidation process consists here of two main stages: primary settlement and secondary (and tertiary) settlement (creep). It is essential to have a good quality description of physical and mechanical properties of soil before the calculation and construction stage. For calculations of each stage of settlement the different physical and mechanical parameters of problematic soil are applied. In this paper the analysis of organic soils deformation process is presented. The deformation characteristics were defi ned on the basis of laboratory tests results. Soil investigations were performed on peat samples taken from test site located in Olsztyn region. Laboratory test of physical properties and consolidation tests in oedometer were carried out. Based on laboratory test results the empirical relationships between stress and deformation as well as stress and time were elaborated in order to describe the primary consolidation in organic soils.

Publisher Summary This chapter discusses the laboratory investigations. The common laboratory tests and equipments used for soft mineral soils can also be used for most organic soils. One condition for laboratory tests to be relevant to the field conditions for which the results are applied is that undisturbed and representative samples can be brought into the laboratory and mounted in the testing equipment. Particularly for peats, special samplers have to be used, as well as special trimming and mounting techniques. For fibrous and pseudo fibrous peats many of the common laboratory tests are not relevant. These soil types also often require larger specimens than usual to be tested and special apparatus, such as the compressiometer, to be used rather than ordinary oedometers. The initial ocular inspection and the very simple tests, with alkali extraction and lowering of samples into hydrochloric acid, required for preliminary soil classification, may be carried out in the field. In the laboratory, further quantitative analyses are carried out to enable a more precise classification and to give additional basic data.

In this paper, study on the use of reclaimed waste in Recycled Concrete Aggregate (RCA) was conducted. Reclaimed concrete problem has increased over the past decade, due to the replacement of the old concrete parts, such as rail substructures or pavement curb. The main idea of this article was the introduction of recycled materials to pavement engineering, which in Poland were usually deposited on waste landfills. Geotechnical study was undertaken to obtain physical and mechanical properties of RCA. For better understanding of its exceptional behavior under repeated loading, cyclic triaxial test was conducted in various stages of loading. For the purpose of bearing capacity analysis, uniaxial tests were made. Moreover, RCA improvement of mechanical properties was proposed. Chemical stabilization with lime and gypsum was undertaken in order to ameliorate mechanical characteristics. While the mechanical stabilization is a cause of aggregates crushing, created fine fraction could be a stabilizing medium. Stabilization process in this study demonstrates existence of free pozzolanic compound in crushed concrete. Determination of resilient modulus Mr from repeated loading test for non-stabilized and stabilized material was also presented for non-stabilized and stabilized RCA Mr value was 543.2MPa and 816.5MPa respectively. In this article, plastic strains occurrence was also analyzed. As a brittle material, RCA can response to cyclic loading by crushing. Repeated excitations can cause another mechanism of plastic strains development, not present in natural aggregates, where main causes of plastic strains are frictional forces occurring during contact between particles.

The following paper presents the results of tests performed on the reclaimed waste, namely the Recycled Concrete Aggregate (RCA). Geotechnical study was undertaken, in order to obtain physical and mechanical properties of RCA improved with rubber grains. Such a mix could exhibit increased elastic strain development during load cycles, which are typical for traffic. For better understanding of its exceptional behaviour under repeated loading, cyclic CBR tests were conducted in various stages of loading. For the purpose of bearing capacity analysis, uniaxial test was also conducted. While the cyclic loading and mechanical stabilization are a cause of aggregates crushing, another particle size distribution could occur and may not fulfil quality requirements. Determination of resilient modulus Mr on the basis of a repeated loading test and development of displacements during the tests have also been presented. The Mr value for pure RCA was equal to 495.6MPa. The addition of rubber chips in amount 0.5% and 1% results in rise of resilient modulus value, equal to 632.4MPa and 698.0MPa respectively. During the tests the plastic strain abate was recognised. The plastic displacement analysis shows increase of the permanent settlement due to cyclic loading in case of 0% and 1% rubber chips content. The 0.5% rubber chips addition results in smaller plastic displacement. The plastic and elastic displacement was later analysed in order to characterize the deformation behaviour of RCA. The paper proposes also a possible guideline for using the RCA mix as a material in pavement subbase construction.