Abstract
This paper investigates the behavior of calcined powder made of natural magnesite and natural steatite. The magnesite and steatite are made into a powder of ratio 3 : 1 by weight proportion, and the combination is thermally decomposed at a temperature of 1200° Celsius. The calcined powder along with and without Sodium Tripolyphosphate (STPP) salt is tested for its microscopic structural development, consistency, initial setting time, final setting time, and heat of hydration. The powder is made into paste with water/powder ratio as 0.25 and the hardened samples are tested for its compressive strength, drying shrinkage, pH value, SEM analysis, and XRD analysis. The results show that adding phosphate salt increases the hydration process, setting time, and strength aspects. The test samples are found with hydration products such as magnesium hydroxide and struvite. Thus, the present work shows that natural metamorphic magnesite and natural metamorphic steatite can be the potential alternative resource for the production of magnesium‐based binder.
Highlights
Alternative binders are a type of manmade mineral material which can react with water and/or CO2 and get hardened and can be later used to concrete or mortar as binder. e magnesium-based binders are considered to be the carbon negative as the water usage is reduced in comparison to Portland cement and the energy spent on preparing the magnesium-based cement will be lesser than calcium-based cement. is is due to lesser calcination temperature of magnesium-based cement with 650°C to 1200°C [1], when compared to calcium-based cement which has reacting temperature above 1300°C [2]. e magnesium from reject desalination brine is studied and found that it can react with CO2 in atmosphere at 25°C to 65°C which is a breakthrough in carbon capture and utilization [3]
Magnesium-based minerals are good alternative to calcium-based minerals which influence the strength development, microstructure, and pH of binders [4, 5]. e magnesium oxychloride cement has higher strength due to the formation of magnesium hydroxide [6], and the mechanical behavior of magnesium oxysulfate cement is based on the relative contribution of porosity, pore size, and higher interparticle bonds [7]. e magnesium phosphate cement (MPC) has rapid setting, light weight properties, and higher strength gain, and the MPC has a potential future of replacing the conventional cement [8]. e early studies show that the calcined magnesite has hydration reaction and this calcined magnesite can even replace 50% of ordinary portland cement [9]. e
It is observed that the requirement of water is reduced by 40% to 50% compared to Ordinary Portland Cement
Summary
E test samples are found with hydration products such as magnesium hydroxide and struvite. Us, the present work shows that natural metamorphic magnesite and natural metamorphic steatite can be the potential alternative resource for the production of magnesium-based binder. A new kind of binder material, i.e., Magnesium Silicate Hydrate (MSH) gel is found when cement is partially replaced by steatite [17].
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