Influence of Anticorrosive Surface Treatment of Steel Reinforcement Fibers on the Properties of Ultra-High Performance Cement Composite

Abstract

The influence on the bond between the steel fiber and the matrix of the anticorrosive treatments of steel used for concrete reinforcement is not yet fully understood. The topic of steel fiber treatment was not also studied clearly in terms of brass removal before. This paper deals with how the brass on the surface of steel fibers behaves in the UHPC matrix and how it affects its properties. The steel fibers were firstly modified with a number of surface treatments to remove brass on their surface. Some of the treatments have never been tried before for this purpose. Secondly, the surface of the fibers was analyzed by SEM, EDS, XRF, and stereomicroscopy. Lastly, the properties of the composites were analyzed. It was found out that the majority of brass on the surface of the fibers could be removed by mixture of NH3 and H2O2 with a ratio of 3:1 (v/v). It was also found out that the surface treatment slightly affects the mechanical properties, but it does that only by mechanical interlocking between the fiber and the matrix. No dissolution of the surface treatment was observed under the given conditions. According to the results, steel fibers without surface treatment should be used in UHPC if available.

Influence of Fumed Nanosilica on Ballistic Performance of UHPCs

“…The composition of each mixture can be seen in Table 1 . One could find the mixture similar to that used in [ 49 ], but with the main difference that K 2 SO 4 was not used. This chemical was not used in this study because the presence of K 2 SO 4 caused the mixture to be very difficult to work with after only a few minutes of mixing.…”

“…Three mixes (6 specimens from each mix) were made from each type of mixture; so, 3 slump flow values were obtained for each mixture. The pouring into the moulds was conducted in the same way as in [ 49 ], in a fashion that the fibers were oriented along the longest dimension of the specimens. After pouring the mixtures into the moulds, the moulds were vibrated for 30 s and left to harden for 24 h, after which all the samples were demoulded, and specimens unsubjected to the evaluation of mechanical properties were cured under water for 7 and 28 days.…”

“…Some of the results are supported by BSEM imaging. It should be noted that we do not only present a set of never-before-published data in terms of ballistic resistance, we also degas each fabricated composite, which is rarely used in literature on UHPC and never used in case of FNS addition to UHPC [ 49 ]. At the same time, there is a clear lack of results on the influence of FNS addition on the UHPC bending strength of UHPC.…”