This article presents the test results for the physical and mechanical properties and fracture toughness of polymer-modified hydraulically-bound mixtures (HBM) produced with Portland cement for road base layers. The modifier used was a redispersible polymer powder (RPP) based on a vinyl ethylene acetate (EVA) copolymer obtained by spray drying. A three-level full factorial design with two factors was applied to determine the contents of Portland cement and polymer powder in the cement-bound mixture (CBM). Both Portland cement and polymer powder were added at three levels: 0%, 2%, and 4%. The assessment included basic physical properties (water absorption, density, and bulk density) and mechanical properties (stiffness modulus, axial compressive strength, and indirect tensile strength) of the CBM. Particular attention was paid to the assessment of fracture toughness in the semi-circular bending test. The results of the research show that polymer powder positively influenced the mechanical properties of CBM by improving its cohesion while maintaining its stiffness. Another benefit coming from the use of polymer powder was the CBM’s increased resistance to cracking, which is the desired characteristic from the perspective of pavement durability.

The paper presents the results of tests of the impact of hydraulic and bituminous binders on the properties of the cold-recycled mixture (CRM). The composition of the cold-recycled mixture includes two types of different binders, i.e., bituminous binder in the form of foamed bitumen and bitumen emulsion, as well as Portland cement (CEM I 32.5R) and hydraulic binder. The hydraulic binder was produced by mixing three base ingredients in the following ratio: 40% CEM I 32.5R; 20% Ca(OH)₂ and 40% CBD (cement bypass dust). The cold-recycled mixtures were produced under industrial conditions on a test section. The prepared CRM with bitumen emulsion (MCE) and foamed bitumen (MCAS) was collected from the test section and compacted under laboratory conditions. The impact of the type and kind of the binder was assessed in terms of physical properties, mechanical properties and deformation modulus (bearing capacity of subbase) of the recycled base course after 1, 7 and 28 days. It was found that the use of hydraulic binder in the recycled base course, regardless of the type of bituminous binder, reduced cohesion without reducing the remaining parameters.

This research focuses on a mineral–cement mixture containing bitumen emulsion, designed for cold recycling procedures, the formulation of which includes 80% (m/m) of waste material. Deep cold recycling technology from the MCE mixture guarantees the implementation of a sustainable development policy in the field of road construction. The utilised waste materials include 50% (m/m) reclaimed asphalt pavement (RAP) from damaged asphalt layers and 30% (m/m) recycled aggregate (RA) sourced from the substructure. In order to assess the possibility of using a significant amount of waste materials in the composition of the mineral–cement–emulsion (MCE) mixture, it is necessary to optimise the MCE mix. Optimisation was carried out with respect to the quantity and type of binding agents, such as Portland cement (CEM), bitumen emulsion (EMU), and redispersible polymer powder (RPP). The examination of the impact of the binding agents on the physico-mechanical characteristics of the MCE blend was performed using a Box–Behnken trivalent fractional design. This method has not been used before to optimise MCE mixture composition. This is a novelty in predicting MCE mixture properties. Examinations of the physical properties, mechanical properties, resistance to the effects of climatic factors, and stiffness modulus were conducted on Marshall samples prepared in laboratory settings. Mathematical models determining the variability of the attributes under analysis in correlation with the quantity of the binding agents were determined for the properties under investigation. The MCE mixture composition was optimised through the acquired mathematical models describing the physico-mechanical characteristics, resistance to climatic factors, and rigidity modulus. The optimisation was carried out through the generalised utility function U^III. The optimisation resulted in indicating the proportional percentages of the binders, enabling the assurance of the required properties of the cold recycled mix while utilising the maximum quantity of waste materials.

The research was aimed at assessing the effect of the redispersible polymer powder on the fracture resistance of a subbase made of a mineral–cement mixture with a bitumen emulsion. The test was performed at two temperatures, i.e., 0 °C and 20 °C. The prepared mixtures differed in the content of cement, asphalt emulsion, and polymer modifier. Cement and redispersible polymer powder were dosed in 1.5% steps from 0.5% to 3.5% while the amount of bitumen emulsion ranged from 0.0% to 5.0%. The SCB (semi-circular bending) tests carried out in the laboratory showed the dependence of the influence of the amount of binder and polymer modifier on the fracture resistance of the recycled subbase. Mixes containing a polymer modifier in their composition are characterized by a much higher resistance to cracking than traditional mineral–cement–emulsion mixtures. An example is the doubling of the framework’s fracture toughness (KIC) when the amount of the polymer modifier is increased from 0.5% to 2.0% with a constant cement content of 0.5%. The obtained results (KIC) in this case were 2.90 and 5.81. The key is the right ratio of polymer powder and cement in the base composition.

The article presents the impact of a polymer modifier (P) on the properties of mineral-cement-emulsion (MCE) mixes. The theoretical part of the article discusses the ways of producing mixes using deep cold recycling. The “in-place – on site” and “in-plant – delivered” production methods are described. The paper also presents a description of a redispersible polymer powder (RPP) used as the polymer modifier. The part dedicated to the conducted research presents the experiment design and discusses the research methodology used to evaluate the effect of the polymer modifier on the properties of the MCE mix. The project involved the production of MCE mixes varying in terms of the type and amount of polymer powder, cement and bitumen emulsion. Mixes were designed with a variable share of cement range from 0.5% to 3.5%, a share of bitumen emulsion ranging from 0% to 5% and a fraction of redispersible polymer powder from 0.5% to 3.5%. A total of 15 mixes were made as part of the experiment, designed according to the Box-Behnken experiment design. The following physical and mechanical properties were assessed in the plan of the research: air void content Vm, water absorption nw, indirect tensile strength ITS, water damage resistance TSR, IT-CY stiffness modulus and SCB fracture toughness. The test results were analysed to assess the impact of the redispersible polymer powder on the properties of the recycled MCE mix. Following the analyses, the composition of mix was optimised regarding the requirements set out in the Polish design guidelines.

The subject of the research is to evaluate the influence of the composition and quantity of the hydraulic binder on the stiffness modulus of the recycled subbase, made of a mineral-cement-emulsion mixture (BE-RCM). Road subbases made in the technology of deep cold recycling are a proven method for the construction of the construction layer of the road surface. Among the many advantages, it is necessary to indicate the reuse of materials obtained during the demolition of a degraded pavement. There is also a real possibility of reducing the costs and time of reconstructing the road infrastructure. It is extremely important to choose the right hydraulic binder for the recycled mixture. The subbase must be a durable and load-bearing layer. It should be noted that the use of too much binder, in the form of Portland cement, may lead to the stiffening of the layer and the appearance of uncontrolled reflected cracks. Cracks of this type are initiated precisely in the hydraulically bound base layer. Currently, attempts are being made to modify the binder composition to avoid the occurrence of undesirable effects. The paper presents the results of research on the stiffness modulus of the recycled BE-RCM subbase depending on the measurement temperature and the composition of the hydraulic binder. Portland cement I class and a modifier in the form of a redispersible polymer powder with a polymer base (polyethylene-co-vinyl acetate) EVA were used as a binder. The impact analysis was performed using the assumptions of the Box-Behnken experiment plan in which three variables are controlled. The variables in the experiment were the content of: polymer, cement and asphalt emulsion in the mixture. The mentioned ingredients were dosed with a step of 1.5% of the percentage share in the mixture composition. EVA redispersible polymer powder and Portland cement were dosed from 0.5% to 3.5%. In contrast, the pure asphalt that came from the asphalt emulsion added to the mix was 0.0%, 1.5% and 3.0%, respectively. The obtained test results may be an impulse to optimize the binder composition of recycled cold mixes with asphalt emulsion. There is a chance to reduce the Portland cement content in BE-RCM mixes thanks to the use of a polymer modifier. The subbase made in this way has the appropriate parameters and values of the stiffness modules. The introduced polymer allows to reduce the occurrence of uncontrolled cracks in the foundation.