7.3.2 Surface hardness and P-wave Velocity variations
The surface hardness (Fig. 16) and P-wave velocity (Fig. 17) decrease with increasing periods across all experiments. With an increasing number of periods, the surface hardness and P-wave velocity of samples gradually decrease, whereas the surface hardness decreases faster than the P-wave velocity implying that the deteriorations of samples start from the surface by water and transfer to the inner little. The surface hardness and P-wave velocity decreasing rate are the highest when the samples are immersed in pH=2.6; the lowest in the dry group; ranked in the middle in the dry-wet cycle and saturated group. The surface hardness and P-wave velocity deterioration of LA samples are greater than that of LB samples when other conditions remain the same.