PSI - Issue 63

Stanisław Majer et al. / Procedia Structural Integrity 63 (2024) 51–57

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2. Materials and methods Based on the analysed properties of cement-bound mixes, a mix specified in the Polish guide for design of flexible and semi-rigid pavements was chosen of 28 day (Judycki et al., 2014) compressive strength in the range of 2.5-5.0 MPa. It should have Elastic modulus value of 4.500 MPa before cracking, dropping to 300 MPa after cracking. This is a consequence of the decrease in modulus due to repetitive loads (Judycki, 1991). The following three mixes were chosen for preliminary tests (Table 3). The road requirements were the most suitable for the project being implemented.

Table 3. Composition of tested mixtures. Mix No. [-] Sand [%]

Gravel [%]

Cem III/A 32.5 N [%]

Fly ash [%]

1 2 3

62.2 91.6 92.6

29.7

4.9 4.7 4.2

3.7 3.7 3.2

0 0

The Elastic modulus and compressive strength values were determined experimentally on  =150 mm and h =300 mm cylindrical samples made in 3-gang split design concrete cylinder moulds with top and bottom pieces. The compaction effort was 0.6 J/cm 3 ±10%. During the moulding process, samples for CBR and Proctor tests were taken. In the Elastic modulus and compressive strength test the compressive stress increased at a rate of 0.6±0.4 MPa/m 2 ꞏ s. On the cylinder side walls lines were marked to measure strain. Three measurements were carried out on these vertical lines spaced at 120° intervals around the side wall. (Fig. 2).

Fig. 2. Elastic modulus tester.

The method of loading the sample was adapted from the measurement of the modulus of elasticity of cement concretes, while simultaneously appropriately reducing the forces acting on the test samples. The gauge length centre