This paper aims to assess the influence of clogging on paving material (pervious concrete) drainage characteristics as well as the influence of the properties of an unbound base layer on drainage characteristics of the whole paving system. The clogging influence has been studied measuring the drainage characteristics on pervious concrete flags before and after their clogging, according to ASTM C1701-09. Additionally, the drainage characteristics of uncontaminated pervious concrete as a paving material was assessed using the falling head method. To assess the influence of properties of an unbound base course (UBC) on drainage characteristics of the whole paving system, the unbound base layer was compacted in two different levels of compaction and the drainage characteristics were measured (according to ASTM C1701-09). It is concluded that pervious concrete prepared with a smaller aggregate fraction is more prone to clogging. Regarding the influence of UBC, it is important to find a balance between pervious concrete infiltration and UBC exfiltration rate, particularly in a case of pervious concrete flags made of coarse aggregate.

During road construction, granular materials for the unbound base course (UBC) and cement-bound base course (CBC) are mostly compacted by vibratory rollers. A widespread laboratory test for determining the optimal moisture content (OMC) and maximum dry density (MDD) of the mixture for installation in UBC and CBC is the Proctor test. Considering that the Proctor test does not produce any vibrations during compaction, this paper compares the Proctor test and the vibrating hammer test. The examination was conducted on UBC and CBC with varying cement content and aggregate types. All mixtures were compacted by both methods with the aim of determining the compaction and strength characteristics. The results indicated the high comparability of the two test methods for mixtures with natural aggregate in terms of MDD, OMC, density and strength characteristics (California bearing ratio (CBR) for UBC and 28-day compressive strength for CBC). For mixtures with higher cement content, the OMC difference depending on the laboratory compaction method used can be significant, so the laboratory compaction method should be chosen carefully, particularly for moisture-susceptible materials. This paper also reveals that by increasing the proportion of rubber in the mixture, the compaction and strength characteristics differ significantly due to the compaction method. Therefore, when using alternative and insufficiently researched materials, the compaction method should also be chosen carefully.

Besides all the positive characteristics of cement bound courses (CBC), it has some detrimental effects on the pavement wearing courses. Due to cement hydration, this mixture is affected by shrinkage. Shrinkage induces cracks in the whole layer which along with weather conditions propagate through asphalt layers in a short period. Also, it’s stiffness negatively affects cracks propagation without providing elastic support for upper layers. As a result, roads are covered with various damages which reduces driving comfort and safety and demand new financial investments. The focus is on reducing the detrimental effect of CBC on the pavement. Nowadays, large quantities of recycled rubber can be found on the market. Wasted rubber is a large ecological problem due to its long decomposition period. On the other hand, by mechanical grinding and separation process, suitable fractions of rubber can be obtained for use in construction. Consequently, the replacement of conventional material by crumb rubber reduces the consumption of natural material and energy for its exploitation. Appropriate amounts and fractions of recycled rubber have the potential to reduce shrinkage and increase the elasticity of CBC. Within this paper, preliminary research results will be presented on the possibilities of crumb rubber implementation in CBC and its effects on mechanical characteristics. By using recycled materials in construction processes we undertake a major step in the sustainable management of natural resources.

Digital image correlation (DIC) is a method of point displacement measurement by an optical system. If two cameras are used for capturing the same point displacement, three-dimensional data are obtained using the 3D-DIC method. The areas of application of this method in pavement construction are diverse, but it is mainly used for displacement monitoring during standard tests of the failure of specimens due to load application. Furthermore, DIC technology was used only for testing particular material characteristics and assuming their influence on the overall pavement system. Within this research, DIC was applied in two areas: defining material mechanical characteristics and analyses of pavement structure behaviour under cyclic loading. The scope of this research was to gain more insights into DIC’s potential application within pavement behaviour analyses, specifically on cement-bound granular material (CBGM) characterisation. Results from this study confirm the suitability of 3D-DIC technology for pavement material characterisation. Furthermore, it is shown that certain trends of material behaviour defined on the simple material level of each independent pavement layer will significantly differ when it is placed in the system, and this kind of complex analysis is possible by using 3D-DIC technology.

Different types of natural aggregates (gravel, crushed stone, sand) are used in the construction of load-bearing layers of pavement structures, the granulometric composition of which has a great influence on the compaction and load-bearing capacity of the layer. Special care should be taken when compacting single-grain materials, such as sand, as difficulties can be expected with these. For this reason, it is useful to modify the granulometric composition of the sand by adding new material of finer fractions. The bearing capacity of mixtures for the production of unbound load-bearing layers of a pavement structure is tested by determining the California Bearing Ratio (CBR), the value of which depends on the dry bulk density achieved and the granulometric composition of the mixture. The bearing capacity of the mixture is influenced by the grain shape and grain surface characteristics of the stone material. This paper describes the testing of mixtures intended for the performance of load-bearing layers of pavement structures, consisting of Drava sand and wood ash (WA) of different fractions (bottom wood ash (WBA) and fly (cyclonic) wood ash (WFA)) and different proportions. The CBR index was determined after immersion of the samples for 4 days under water, during which time swelling was monitored. The results showed that wood fly ash (WFA) has a greater impact on the bearing capacity of the sand mixture and, using it, lower linear swelling results are achieved as well as higher CBR results. Different types of natural aggregates (gravel, crushed stone, sand) are used in the construction of load-bearing layers of pavement structures, the granulometric composition of which has a great influence on the compaction and load-bearing capacity of the layer. Special care should be taken when compacting single-grain materials, such as sand, as difficulties can be expected with these. For this reason, it is useful to modify the granulometric composition of the sand by adding new material of finer fractions. The bearing capacity of mixtures for the production of unbound load-bearing layers of a pavement structure is tested by determining the California Bearing Ratio (CBR), the value of which depends on the dry bulk density achieved and the granulometric composition of the mixture. The bearing capacity of the mixture is influenced by the grain shape and grain surface characteristics of the stone material. This paper describes the testing of mixtures intended for the performance of load-bearing layers of pavement structures, consisting of Drava sand and wood ash (WA) of different fractions (bottom wood ash (WBA) and fly (cyclonic) wood ash (WFA)) and different proportions. The CBR index was determined after immersion of the samples for 4 days under water, during which time swelling was monitored. The results showed that wood fly ash (WFA) has a greater impact on the bearing capacity of the sand mixture and, using it, lower linear swelling results are achieved as well as higher CBR results.

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Cement bound base courses increase pavement bearing capacity and resistance to detrimental effects of frost along with being a good base for surface courses. Due to its stiffness, cement bound base courses reduce vertical deflections and tensile stress in asphalt layers thus reducing fatigue and appearance of alligator cracks in asphalt. But, in order to generate required layer strength and stiffness of cement bound base, appropriate amount of cement is necessary. This in turn can cause shrinkage induced cracks which spread towards surface courses and cause accelerated deterioration of pavements. To prevent rapid deterioration of pavement surface layers and occurrence of reflective cracking, incorporation of recycled rubber from waste tire in mixtures for cement bound base courses is currently being considered. In this paper a short review of waste tire application and its behaviour in pavement structures will be shown. In addition, planned methodology and activities that are going to be conducted with in a research project are going to be discussed.