Success with siloxane
Published by Alfie Lloyd-Perks,
Editorial Assistant
World Cement,
The production of cement is a major contributor to CO2 emissions, consequently, the cement and concrete industry, including members of the Global Cement and Concrete Association (GCCA), have an array of initiatives aiming to achieve net-zero emissions by 2050.
One of the methods of achieving this is by reducing the overall clinker content in cement and consequently also concrete. For example, over the past three years, the US cement industry has quickly shifted from Ordinary Portland Cement (OPC) to Portland limestone cement (PLC). According to the Portland Cement Association, lower-carbon cements like PLC which contain 10% or more of limestone are helping to reduce CO2 emissions. Last year, the use of PLC in the US surpassed OPC use, a change that reduced CO2 emissions by more than 4 million t, more than twice the CO2 savings over the previous year.
The other method for reducing CO2 emissions is by increasing the concrete life cycle as pointed out in the recent publication by Olsson et al. The addition of some supplementary cementitious materials (SCM) such as fly ash, or slag and specialty siloxane chemicals can extend the life time by mitigating Alkali Silica Reaction (ASR), as well as increasing freeze thaw resistance. This article will illustrate methods being used by industry to increase cement shelf life, increase freeze thaw resistance, and mitigate ASR which will increase the life cycle of cement/concrete reducing significantly GHGs.
Increasing shelf-life and improving grinding efficiency of clinker
The current cement production process is to grind the clinker, gypsum and limestone using either a horizontal ball mill or a vertical mill, which is then transferred to silos and subsequently packaged into bags or bulk. Many cement plants are located in hot, humid areas, and therefore, in a short period of time, the cement begins to form hardened clumps (hydrated cement particles) in silos and in bags. The shelf life of these cements can be reduced to less than 3 months, which decreases confidence in the quality and causes an overconsumption of the cement as well as an increase in waste. However, the use of new oligomeric siloxane grinding enhancers reduces the amount of hydration occurring in the stored cement as well as increasing the free flow properties of the cement. The industry has found that the incorporation of 500 ppm or less of new oligomers (such as SILRES® BS 8083 US or BS 8010) provides enough hydrophobic properties which mitigates the unwanted early hydration and increases the shelf life by more than 1 year. In addition, the increase in grinding efficiency and transportation out of the mills and silos increases production output.
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Read the article online at: https://www.worldcement.com/special-reports/25092024/success-with-siloxane/
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