Study Supports Spent Abrasive in Concrete

THURSDAY, JUNE 15, 2017


Copper slag abrasives are already a byproduct of another industrial process—copper smelting—but a recently published academic paper out of Brazil supports the growing practice of recycling the media again after blasting by using it to make concrete.

The paper, authored by M.A.G. dos Anjos, A.T.C. Sales and N. Andrade, all of the Department of Civil Engineering at Federal University of Sergipe, in Brazil, presents experimental data that the authors say show blasted copper slag as a “technically viable” and safe material to use as fine aggregate in concretes made with Portland cement.

Past Research

Recycling copper slag in concrete isn't a new idea. The recent research builds on past work done by other researchers looking at copper slag—straight from the smelter or post-blasting—as a potential fine aggregate.

As far back as 1996, the U.S. Navy was studying the reuse of abrasive blasting materials, including a program that used copper slag abrasives in cement manufacture. In 2009, researchers from Oman suggested the substitution of 40 percent of the fine aggregate in a high-performance concrete mixture with copper slag. One past study looked at using small amounts of blasted slag in the making of mortar.

The new study looks specifically at slag that’s already been used as blasting abrasive media, and its use as a substitute for a significant portion of the aggregate in concrete mixtures, evaluating a number of properties of the concrete that results.

Study Details

In the study, the Sergipe engineers gathered copper slag abrasive that had been used in abrasive blasting at a construction site and used it in different concentrations as aggregate in the formulation of concrete. They then tested the concrete in terms of factors including tensile strength and compressive strength, and tested for leaching of a number of substances that might pose health risks: arsenic, cadmium, lead, chrome, mercury, silver, selenium, fluoride, phenols and chlorides.

Abrasive blasting
© iStock.com / ZooCat

The new study looks specifically at slag that’s already been used as blasting abrasive media, and its use as a substitute for a significant portion of the aggregate in concrete mixtures.

One notable conclusion the researchers reached was that the inclusion of blasted copper slag in the mixture increased the workability of the fresh concrete. “Above 20 percent replacement of the natural aggregate, there was no need to add superplasticizer admixture in concretes to achieve the desired consistency,” the paper notes.

While axial and compressive strength both decreased as the percentage of blasted slag in the mixture rose, the researchers say the data shows that a partial substitution of blasted slag for natural fine aggregate could still result in concrete that’s strong enough to be used structurally. The authors note that some of the loss of strength could be attributed to organic matter, such as paint particles, from the substrate that had been blasted.

The authors also note in the paper that they found little to no leaching of the heavy metals and other substances that were tested for, meaning the concrete mixture appears to be a safe way to dispose of the slag.

The Sergipe engineers’ paper, “Blasted Copper Slag as Fine Aggregate in Portland Cement Concrete,” was published in the Journal of Environmental Management in March.

   

Tagged categories: Abrasive recycling; Abrasives; Asia Pacific; concrete; EMEA (Europe, Middle East and Africa); Latin America; North America; Surface Preparation

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