Concretes for Special Applications

Abstract

The paper shows the possibility to utilize, for manufacturing of concrete with aluminous cement, the clay or silicon carbide waste aggregates resulting from demolition of linings, concomitantly with the decrease of cement content by using of the cheap admixtures.

Concretes for Special Applications

“…Concrete with Recycled Clay was used as equalization layer [1] for the ladle of 180 t steel capacity at SIDEX Galatzi steelworks, Figure 4. The irreproachable behavior of tested ladles allowed the generalization of this solution at SIDEX Galatzi, (Romania), thus being saved 250,000 US dollars yearly.…”

“…In this place of use are the temperatures reaches 400 -1200 0 C, which are in "critical temperature range" when the strength of refractory concrete is decreasing drastically. These compositions of concrete are recommended to be used at significantly higher temperatures (this happens usually) [1]. The utilization of these concretes at low temperatures is sometimes imposed often by the lack of refractory concrete diversification.…”

“…On the other hand the classic concretes, with aggregates based on Al 2 O 3 , MgO, SiO 2 , etc and with the usual content of aluminous cement (20%) do not behave well in a reducing medium, as these oxides are reduced and, consequently, the initial composition of the refractory material is modified, exposing the material to a corrosive attack [2,3]. Moreover, the high cement (CaO supplying) ratio implies, in turn, both a high percentage of CaO, an oxide that is also reduced in such media, and a high porosity that represents the access gate of the corrosive agent in the material.…”

“…The microstructure analysis of the silicon carbide composition reveals following peculiarities (essential components of high compactness): an uniform distribution of the refractory aggregate in the binding matrix and hardened concrete structures with high degree of finishing. These aspects can be explained through the influence of benefic complementary binding forms (components of the complex binding system) used at the hardening of these concretes [3]. On the other part it can evaluate the nature, form and dimensions of crystalline grains, the form, dimensions and distribution of pores, the surface of inter granular limits, which determine finally all the material properties, by analyzing the microstructure of samples from refractory material using electronic microscopy, Figure 3.…”