Synergistic effect of dry sludge from waste wash water of concrete plants and zeolitic by-product on the properties of ternary blended ordinary Portland cements

Abstract

This paper analyses the use of two types of supplementary cementing materials, – dry sludge from waste wash water of concrete plants and zeolitic by-product – for producing hardened cement paste specimens. X-ray powder diffraction, scanning electronic microscopy, energy-dispersive X-ray spectroscopy, and thermal analysis were used as investigation methods. Test results showed that the addition of dry sludge reduced the compressive strength of hardened cement paste at both 7 and 28 days. In hardened cement paste specimens where Portland cement was substituted with 5 %–30% of dry sludge the compressive strength decreased significantly after 7 and 28 at days. After 28 days blended Portland cement containing up to 10% of supplementary cementing materials ((SCM) - dry sludge and zeolitic by-product) demonstrated higher compressive strength than the reference specimen as a result of synergistic interactions, whereas higher replacement levels led to reduction in compressive strength.