Análise da influência da adição de resíduos metálicos nas propriedades do concreto autoadensável - CAA

Abstract

This work aimed to analyze the influence on the mechanical, rheological and durability properties of a Self Compacting Concrete - SCC that had different percentages of sand replaced by metal slag and the simultaneous use of marble powder residue as a filler. To this end, a SCC Mix Reference was developed to meet all parameters of the ABNT NBR 15823: 2017. This SCC-REF was changed with the inclusion of four increasing proportions of metal slag (MS) (25, 37.5, 50 and 75%), then these new concretes were tested, and its properties, both fresh and hardened, were compared. The elaboration of the mix control assumed the principle of particle packing and paste optimization. The SCC-REF had the factor water/cement a / c = 0.35, silica fume SF / cement = 0.06, superplasticized/cement SP / c = 0.008. A new sequence of mixing concrete components in the concrete mixer was adopted in this research, which proved to be very efficient. The paste and mortar tests of the SCC-REF demonstrated the characteristics of a high flowability and moderate viscosity. The SCC-REF achieved all parameters of a fresh and hardened self-compacting concrete where it presented excellent results for parameters such as strength and durability. For the production of the mixtures aces with metal chips, small corrections of SF / c and a / c were necessary in some substitutions. Every SCC -MS mix reached all parameters of a fresh state SCC, with the exception of the SCC -MS 75, which did not reach the parameters of the L box. Comparing the results of all concretes, it can be concluded that the replacement of sand by MS is very viable and with replacement up to 50% does not significantly change any of the properties registered by the SCC-REF in both fresh and hardened state. According to the ABNT NBR 8953:2015 all concretes have achieved resistance to a compressive that classify them as structural and high performance. The splitting tensile strength of every concrete is around 10% of its compressive strengths. The values of the module of elasticity decreased with the increment of the substitution. The SCC -MS 75 presented a module of elasticity 20% lower than the mix REF. The surface hardness of concrete grows up to 37.5 of substitution, above this value, it decreases, but maintains a value equivalent to the SCC -REF. The Absorption A% and void index Iv% of concretes increased with the enhance of the substitution, but their low values indicate a durable concrete. Only the SCC -CM 75 is classified as inefficient. All concretes presented low capillary absorption values. Every concrete presented electrical resistivity at 28 days between 100 and 200 Ω.m. Meaning low probability of corrosion. The SCC -CM75 had a high probability of corrosion.