Performance of Concrete Subjected to Severe Multiple Actions of Composite Salts Solution under Wet-Dry Cycles and Flexural Loading in Lab

Several action regimes were employed, namely, those exposed to solutions containing single and/or composite chloride and sulfate salts, and under wet-dry cycles and/or flexural loading. The variations in dynamic modulus of elasticity（Erd values） were monitored, as well as the key factor impacting on the chloride ingress when concrete subjected to multiple action regimes was identified by the method of Grey Relation Analysis（GRA）. The changes in micro-structures and mineral products of interior concrete after different action regimes were investigated by means of X-ray diffraction（XRD）, mercury intrusion technique（MIP）, and scanning electron microscopy（SEM）. The test results showed that the cyclic wet-dry accelerated the deterioration of OPC concrete more than the action of 35% flexural loading based on the results of Erd values and the GEA. The analyses from micro-structures could give certain explanations to the change in Erd values under different action regimes.

Influence of shock absorber condition on pavement fatigue using relative damage concept

Considering the importance of the road transportation nowadays, concerns related to pavement deterioration and maintenance have become relevant subjects. Especially for commercial vehicles, the vertical dynamic load （characterized by the tire-road interaction） is directly related to wear on the road surface. Given this, the main objective of this paper is to analyse effects of vertical loads applied on the flexible pavement, considering the variation of the condition of shock absorbers from a truck＇s front suspension. The mea- surements were performed on a rigid truck, with 2 steering front axles, in a durability test track located in Brazil. With a constant load of 6 tons on the front suspension （the maximum allowed load on front axles according to Brazilian legislation）, 3 different shock absorber conditions were evaluated： new, used and failed. By applying the relative damage concept, it is possible to conclude that the variation of the shock absorber conditions will significantly affect the vertical load applied on the pavement. Although the results clearly point to a dependent relationship between the load and the condition of the shock ab- sorbers, it is recommended to repeat the same methodology, in future to analyse the influence of other quarter car model variants （such as spring rate, mass and tire spring stiffness）.