Natural analogs of belite sulfoaluminate cement clinkers from Negev Desert, Israel

Abstract

Ye’elimite-larnite rocks in the Hatrurim formation of the Negev Desert, Israel, are natural analogs of belite sulfoaluminate (BSA) cement clinkers. They have been produced by ultrahigh-temperature combustion metamorphism at ambient pressure of a calcareous sedimentary precursor. Their mineralogy consists of 35-50 vol% β-Ca2SiO4, 15-20 vol% ye’elimite, 7-15 vol% ferrites, and 15-20 vol% fluorapatite and/or fluorellestadite. A few grains of hatrurite (Ca3SiO5) and α′-Ca2SiO4 have been observed as well. The composition of α′- and β-Ca2SiO4 polymorphs by EPMA are near Ca1.96-1.98Na0.01-0.02 Si0.96P0.03Al0.01O4, whereas ye’elimite has an approximate composition by EPMA of Ca3.99Mg0.02Ba0.01 Na0.02K0.02Al5.73Fe3+0.16Si0.10S0.97P0.02O16. The Al content of brownmillerite Ca2(Fe1-xAlx)2O5 ranges from x = 0.20-0.27. Fe-analog of shulamitite (Ca3Fe2TiO8) contains up to 15.1 wt% TiO2. Ye’elimite-larnite rocks were derived from chalky sediments by burning of combustible gas with a Tmax at 1200-1350 °C. The mineral content, microstructure, and texture/fabric of the ye’elimite-larnite rocks imply that chalky and/or marly sediments with randomly distributed clay, phosphorite, and gypsum may be utilized as cheap naturally homogenized and pulverized mixtures for industrial production of BSA cement clinker, as an environment-friendly alternative to ordinary Portland cement (OPC).