Supporting Production Consistency for Cement

Published

May 12, 2025

Author(s)

Aron Newman, Cody Strack

Abstract

Concrete is the second most used substance in the world after water. Concrete manufacturers produce 14 billion cubic meters annually, with a market size of $440 billion. The concrete industry is developing new technologies to decrease its carbon footprint through new materials and manufacturing methods. The particle size and fineness of the cement and other components need to be accurately measured to produce a quality product. Cement producers across the world use the Standard Reference Material® (SRM)114r Portland Cement Fineness Standard. The high-temperature heat treatment with the primary components of limestone, which primarily consists of calcium carbonate and clay as a source of alumina-silicate, forms clinker with a size in the range of 25 mm [10.1109/CITCON.2013.6525273]. The grinding process of this clinker, including the addition of other cement ingredients, results in a particle size on the order of 3 micrometers to 30 micrometers. This particle size reduction, with its significant energy cost, is used to meet the particle fineness requirements to enable the appropriate hydration kinetics to form concrete. There are various approaches to characterizing cement powder size. The two test methods, ASTM C430-24 and C1891-20, employ a 45-micron sieve to assess the fineness of cement with a wet and dry method, respectively. Both test methods use SRM 114r as a standard. Sieving provides information on a fraction of the powder at a specific size, but more specifics are needed to have a consistent product. R. L. Blaine, working at the National Bureau of Standards (NBS), the predecessor to the National Institute of Standards and Technology (NIST), developed an air permeability test in 1943 that measures the amount of air passing through a compact of this pulverized clinker or the final cement [ASTM Bull 123 (1943): 51-55]. The variable pressure and flow rate prevents the use of the Carman-Kozeny permeability equation and requires a reference standard to perform the measurement. An alternative to the air permeability test is to measure particle size. Unfortunately, the cement grinding process results in communition and agglomeration of the particles, creating challenges for measuring particle size. Surface area can be directly measured using BET (Brunauer–Emmett–Teller) surface adsorption and indirectly by laser diffraction. The nitrogen surface adsorption method is preferred by academia for its intrinsic measurement, while the cement industry prefers laser diffraction and Blaine air permeability [https://doi.org/10.1016/j.cemconres.2014.10.009]. Laser diffraction has become a common method to provide the particle size distribution, but this does not account for surface area and particle shape, and a standard method has not yet been developed. Challenges with this method for limiting variability are the various means employed to disperse the particles in a liquid, the different algorithms used by equipment manufacturers, and the various scattering theories used to analyze the results. The Blaine permeability test is relatively simple, low cost, and repeatable, making it a good choice for quality control measurements for producers of cement powder, despite it not being fully automated. These producers require a product that leads to predictable hydration behavior and strength development of the final concrete.

Citation

150th anniversary of the Metre Convention and the BIPM with a poster on a metrology challenge

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https://thebipm150.org/posters-online/

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Keywords

cement, concrete, reference materials

Citation

Newman, A. and Strack, C. (2025), Supporting Production Consistency for Cement, 150th anniversary of the Metre Convention and the BIPM with a poster on a metrology challenge, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959790, https://thebipm150.org/posters-online/ (Accessed July 17, 2025)