# Prediction Models for Mechanical Properties of Cement-Bound Aggregate with Waste Rubber
## 1 Introduction
Furthermore, in [10], the authors emphasize that to develop prediction models, it is necessary to increase the number of UPV measurements in each direction (x, y, z) to four to increase the precision of the results. In addition, the importance of not carrying out measurements at the same point on the sample is emphasized. A prediction model for shear modulus estimation was developed in [11] by applying this method to cement-stabilized clays. The UPV proved helpful in multifunctional analysis, which predicts the compressive strength and rebound value [11]. Furthermore, this non-destructive method achieved reliable results in evaluating cement-bound aggregate. [PERSON] et al. [12] observed a strong relationship between the UPV and the compressive- and indirect-tensile-strength values and emphasized polynomial and exponential laws as the most appropriate to describe the relationship between strength and UPV. They also defined a range of UPVs in which CBA achieves satisfactory characteristics, which is helpful when making decisions during an examination. This paper develops models for steel-slag-stabilized mixtures for three different curing ages: 7, 28 and 90 days. [PERSON] et al. observed a difference between compression and tension modulus and developed a power function decay model for these two parameters [13]. According to [PERSON] et al. [14], the UPV can be used to estimate the mechanical properties of most cement-stabilized materials, except cement-stabilized clay, which behaves differently from other stabilized materials. This paper presents strong correlations in the developed models between the flexural strength and the constrained modulus and the flexural modulus and the constrained modulus based on 7-day-old specimens. These parameters are commonly tested for the evaluation of soil behavior. In addition to CBA, roller-compacted concrete (RCC) is also used in pavement construction. Regarding its mechanical properties, this material occupies a place between CBA and concrete. Prediction models have also been developed for such materials, which predict the compressive strength based on the rebound number and the UPV [15]. The relationship between the rebound number and the compressive strength is established by the power law, while the relationship between the UPV and compressive strength is established by the exponential law. Additionally, the authors developed a logarithmic relationship between the dynamic modulus of the elasticity and the compressive strength. Furthermore, [PERSON] et al. [16] developed an equation for estimating the \(\mathrm{E_{dyn}}\) of the RCC based on the fly ash content, UPV and curing period, which agrees with experimental tests. The RCC in these research works is combined with crumb rubber, nano-silica and fly ash, making UPV a universal tool for model development in different materials. The UPV mainly served as a compressive-strength-prediction tool in the research on stabilized granular materials and no research deals with the issue of the static modulus of elasticity. Furthermore, all the models of CBA developed are nonlinear. There is a consensus on the utility of using the UPV technique when evaluating the mechanical characteristics of coherent [9; 10; 11; 17] and incoherent materials [18]. The reliability of all the developed models is based on the coefficient of determination, which is not a reliable parameter for evaluating nonlinear models in the sphere of statistical inference. Therefore, the need for a more detailed statistical data analysis in this area is emphasized. The non-destructive nature of UPV measurement also applies to asphalt mixtures. [PERSON] et al. [19] state that the dynamic modulus measured by the UPV can replace the low-frequency standard dynamic test. They also emphasize this method as cheaper, faster and easier to implement. In determining the \(\mathrm{E_{dyn}}\) of asphalt mixtures by UPV, [PERSON] et al. [20] concluded that more reliable modulus values are obtained by considering the bulk density rather than the geometric density of asphalt specimens.