RECYCLED CONCRETE POWDER AS PARTIAL CEMENT REPLACEMENT IN FINE-GRAINED CONCRETE

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7408-06-5 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 41, 169-176 pp, DOI: 10.5593/sgem2017/41/S18.022

ABSTRACT

The paper presents the research on the use of a waste material (a recycled powder) which partially replaces cement in fine-grained concretes. The powder was obtained in the thermo-mechanical treatment of concrete rubble, which this article describes. Roasting made a cement paste partially dehydrated and consequently activated the cement’s binding capacity. The recycled powder was tested in terms of a sieve analysis, the Blaine surface area method, density and a thermal analysis. Then the statistical experiment considered the impact of three factors on selected physical and mechanical properties of the fine-grained concretes. These factors included: contents of the recycled powder (10, 20, 30 % of cement’s weight), grinding time of the recycled powder (0, 30, 60 min) and a pressing force of the samples’ compaction (150, 200, 250 kN). The tested features are as follows: the concrete compressive strength after 28 days of curing, density, water absorption and water capillarity expressed in the percentage of weight change. The presence of recycled powder generally deteriorated all studied physical and mechanical fine-grained concrete properties. However, when the content of the powder was up to 10 % or even up to 20 % by cement weight, concrete parameters similar to those of the control were obtained. The promising results open the way for managing the fines concrete waste and for searching other possible applications of recycled concrete powder in construction, where its hydraulic properties may be used.

Keywords: fine-grained concrete, recycled powder, dehydration of cement paste, thermal treatment