Use of Secondary Slags in Completely Recyclable Concrete

Abstract

A completely recyclable concrete (CRC) is designed to have a chemical composition equivalent to the one of general raw materials for cement production. By doing so, this CRC can be used at the end of its service life in the cement clinkering process without need for ingredient adjustments, and with improvement of the resource efficiency of cement and concrete production. Copper slag is interesting as an iron source for the production of such a CRC and can be added to concrete, either as alternative binder or as aggregate. By isothermal calorimetry and compressive strength tests it was found that the addition of copper slag as cement replacement is of minor interest. But a study toward the compressive strength and durability of concrete with copper slag as aggregate replacement had promising results. The performance of these concretes was comparable with or even better than the reference concrete, regarding strength and most durability aspects such as porosity and permeability, and resistance against carbonation and chloride ingress. Only the resistance to freezethaw attack with deicing agents was inferior.

Mechanical Properties and Durability of Concrete with Water Cooled Copper Slag Aggregate

“…Most mixes showed almost no signs of carbonation except for some local carbonation mostly around microcracks or aggregates, which is consistent with concurrent research findings by [25]. The results of the average carbonation depths d kmean (recorded to the nearest 0.5 mm) of the tested copper slag mixes for duplicate specimens per mix are presented in Table 6.…”

“…It is possible that slumps were affected to some extent by the angular shape of the copper slag aggregate as discussed later. It is interesting that [25] also found a decrease in workability when fine aggregate was replaced by copper slag, against initial expectations. Overall however the workability results show that workable mixes can be achieved for all sand replacement levels if the w/c ratio is carefully controlled.…”

“…[17][18][19][20][21][22]) but that overall the air-cooled slag appears to be the type of slag used in most publications; this is either mentioned explicitly (e.g. [6,[23][24][25]-the latter paper uses both air cooled and water cooled slag for the partial replacement of coarse and fine aggregate respectively-) or can be inferred based on the supplier's details and material characteristics (e.g. specific gravity).…”

“…Finally, there is little information widely available on various durability aspects of concrete with copper-slag fine aggregate, with few exceptions [e.g. 6,23,25]. In the former two papers concrete sand was partially replaced by copper slag and the water absorption, corrosion of reinforcement, chloride permeability and acid and sulphate resistance of the resulting concrete were studied.…”

The impact of slag fineness on the reactivity of blended cements with high-volume non-ferrous metallurgy slag

“…The effect of some iron-rich NFM slags on the cement hydration has been investigated in the past as well. De Schepper et al [12] and Edwin et al [13] reported a retarding effect of copper slag on the hydration of cement, which was attributed to the heavy metal content of the slag, in particular Zn, which was present in considerable amounts (> 5 wt%).…”