Viability of using limestone concrete waste from CDW to produce ternary cements type LC3

Abstract

This paper analyzes manufacture of a new eco-cement (reduced CO2 footprint and LC3 clinker content) by replacing natural limestone with fine limestone concrete demolition waste (CDWH). The ternary cement’s content was partially replaced by a binary pozzolanic admixture (10%, 20%, and 30% proportions; 1:1 by weight) composed of CDWH and commercial metakaolin (MK). Results show the ternary eco-cement meets current standards’ chemical and physical requirements. The pozzolanic synergy of the additives —CDWH and MK— is comparable to silica fume, as reflected in the new mortars’ intrinsic properties (capillary water absorption and electrical resistivity), microporosity, and physical and mechanical characteristics, achieving maximum performance at 20% replacement. Kinetically, in ternary eco-cements, the formation of monocarboaluminate and hemicarboaluminate phases, the non-conversion of ettringite to monosulfoaluminate, and the reduction of the Ca/Si ratio in CSH gels all benefit kinetically as the replacement content increases. Use of limestone concrete demolition waste in manufacture of LC3 eco-cements is a viable option.