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

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-Ca 2 SiO 4 , 15-20 vol% ye’elimite, 7-15 vol% ferrites, and 15-20 vol% fluorapatite and/or fluorellestadite. A few grains of hatrurite (Ca 3 SiO 5 ) and α′-Ca 2 SiO 4 have been observed as well. The composition of α′- and β-Ca 2 SiO 4 polymorphs by EPMA are near Ca 1.96-1.98 Na 0.01-0.02 Si 0.96 P 0.03 Al 0.01 O 4 , whereas ye’elimite has an approximate composition by EPMA of Ca 3.99 Mg 0.02 Ba 0.01 Na 0.02 K 0.02 Al 5.73 Fe 3+ 0.16 Si 0.10 S 0.97 P 0.02 O 16 . The Al content of brownmillerite Ca 2 (Fe 1-x Al x ) 2 O 5 ranges from x = 0.20-0.27. Fe-analog of shulamitite (Ca 3 Fe 2 TiO 8 ) contains up to 15.1 wt% TiO 2 . Ye’elimite-larnite rocks were derived from chalky sediments by burning of combustible gas with a T max 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).