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Boriding is a thermochemical surface treatment used to improve corrosion and wear resistance of hardened steels. In this work, we study the effect of boriding treatment in solid medium on the cyclic fatigue resistance of C20 carbon steel. Specimens of untreated and borided C20 steel in a solid medium consisting of 5% B4C, 5% NaBF4 and 90% SiC were subjected to rotating-bend fatigue device. The results showed that the improvement in fatigue resistance carried by the boriding treatment on C20 steel is low. This was explained by the presence of FeB boride in addition to Fe2B boride, which leads to surface cracking.

Self-compacting concrete (SCC) production is a complex operation that requires finding a good combination and a suitable dosage of each of its constituents. Several formulation methods have been developed to meet the workability requirements of SCC. In this paper, the relationships between the fresh properties of SCC based on local metakaolin (MK) and the spreading of its mortar was investigated. The results showed the existence of good correlations between the spreading of the mortar and the fresh state properties of the related SCC and that the MK substitution rate did not affect these correlations. The choice of the mortar flow rate should target appropriate fresh properties of the SCC and a viscosity enhancing agent (VEA) could be used if the mix is too fluid and present an instability.