Abstract
Ordinary Portland cement (OPC) manufacture determines about 8% of the global anthropogenic CO2 emissions. This has led to both the cement producers and the scientific community to develop new cementitious materials with a reduced carbon footprint. Calcium sulfoaluminate (CSA) cements are special hydraulic binders from non-Portland clinkers; they represent an important alternative to OPC due to their peculiar composition and significantly lower impact on the environment. CSA cements contain less limestone and require lower synthesis temperatures, which means a reduced kiln thermal energy demand and lower CO2 emissions. CSA cements can also be mixed with supplementary cementitious materials (SCMs) which further reduce the carbon footprint. This article was aimed at evaluating the possibility of using different amounts (20 and 35% by mass) of water potabilization sludges (WPSs) as SCM in CSA-blended cements. WPSs were treated thermally (TT) at 700° in order to obtain an industrial pozzolanic material. The hydration properties and the technical behavior of two different CSA-blended cements were investigated using differential thermal–thermogravimetric and X-ray diffraction analyses, mercury intrusion porosimetry, shrinkage/expansion and compressive strength measurements. The results showed that CSA binders containing 20% by mass of TTWPSs exhibited technological properties similar to those relating to plain CSA cement and were characterized by more pronounced eco-friendly features.
Highlights
The water potabilization sludges (WPSs) sample was heated for two hours in an electric oven at 700 ◦ C, namely, the optimal treatment temperature for its total dehydroxylation [64]; the treated WPSs (TTWPSs) were finely pestled in order to pass through the 90 μm sieve again
This paper evaluated the possibility of using water potabilization sludges (WPSs) as an alternative supplementary cementitious material in calcium sulfoaluminate (CSA)-blended cements
WPSs were thermally treated (TT) at 700 ◦ C with the aim of dehydroxylating the silico-aluminate crystalline phases to an amorphous state; TTWPSs are very interesting as their use as a secondary cementitious component can permit the saving of raw materials and the avoidance of their landfilling; its use allows for the dilution of the Calcium sulfoaluminate (CSA) cement and determines the following environmental benefits: (i) decreased CO2 emissions; (ii) energy saving per unit mass of cement; (iii) withdrawal reduction in natural resources
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The cement manufacturing industry is one of the largest consumers of fuel and raw materials, and one of the main producers of CO2 emissions [1]. In 2019, worldwide production of Portland cement was estimated at 4.10 billion tonnes, producing 8% of global anthropogenic carbon dioxide emissions [2]. The cement industry needs to reduce its carbon footprint to 1.55 billion metric tonnes per year by 2050 [3]; in order to do this, the cement producers and the research community have been striving to develop new environmentally friendly binders (low-CO2 cements [4,5,6,7,8,9])
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