**5. Sample preparation**

The results of tests must achieve the least acceptable amounts. As mentioned in **Table 1**, laboratory and field experiments are needed to investigate additive performance. The similarity of samples must be considered. In this regard, all the specimens have equal water content and compaction energy.

The specimens were made with different additive dosages according to ASTM D 698 standard. The compaction energy for all the specimens was same and determined from eq. (1):

$$E = \frac{N^\* L^\* W^\* h}{V} \tag{1}$$

where E is compaction energy (kJ/m<sup>3</sup> ), N is the number of blows, L is the number of layers, W is hammer weight (N), h is the height of falling (m), and V is the mold volume (m<sup>3</sup> ).

According to the manufacturer's guidance, additive usage amounts were classified into five dosages of 0, 0.09, 0.15, 0.21, and 0.27 lit/m<sup>3</sup> . The chemical process needs at least 8 hours for ion exchange.

**Figure 3.** *Particle size distribution of the soil.*

*Developing a Novel Superstructure System for the Ballasted Railways Using RRP235special... DOI: http://dx.doi.org/10.5772/intechopen.111470*
