Abstract
The decades-long use of supplementary cementitious materials (SCMs) as replacements for ordinary Portland cement (OPC) by the cement and concrete industry is undergoing a resurgence in research activities related to goals addressing circular economy activities, as well as reduction in CO2 emissions. Differences in the chemistry, mineralogy and reactivity of SCMs compared to OPC impact the fresh properties of concrete. Some SCMs exhibit greater initial water uptake and thus compete strongly with OPC for water during hydration. This study focuses on the early interaction with water as a primary factor that determines the resulting fresh properties and workability. Currently, no test (standard or otherwise) is available for quantifying initial interactions between water and cementitious materials. A quick and reliable method to measure the initial water uptake of SCMs is presented herein, which relies on their affinity to water. The method enables the calculation of water-to-binder ratios for different SCMs required to achieve the same workability as a reference OPC. The results are then well correlated to measured slump and bleed properties. We propose this simple technique to be used by researchers and industry practitioners to better predict the fresh properties of concretes, mortars, or pastes with SCMs.
Highlights
The enormous quantities of cement used worldwide, amounting to 4 gigatons/year [1], results in contributions of approximately 8% of global anthropogenic CO2 emissions by the cement and concrete industry [2]
SCMs are used for different reasons: to name a few, calcined clay in cementitious blends have been shown to reduce the porosity of mortars and concretes and improve some durability properties [9,10]; blends containing good quality fly ash, on the other hand, are often applied where a higher level of workability with the same water-to-binder ratio is required [11]; and limestone and limestone calcined clay cement (LC3) blends are often utilized in applications where the reduction in the carbon footprint is the main priority [3]
The as-received clay, limestone and gypsum were separately milled in a planetary ball mill l (ND0.4L, Torrey Hills Technologies, LLC, Across International Australia, Melbourne, Vic., Australia) to obtain similar particle size distribution (PSD) to that measured for ordinary Portland cement (OPC)
Summary
The enormous quantities of cement used worldwide, amounting to 4 gigatons/year [1], results in contributions of approximately 8% of global anthropogenic CO2 emissions by the cement and concrete industry [2]. SCMs are used for different reasons: to name a few, calcined clay in cementitious blends have been shown to reduce the porosity of mortars and concretes and improve some durability properties [9,10]; blends containing good quality fly ash, on the other hand, are often applied where a higher level of workability with the same water-to-binder ratio is required [11]; and limestone and limestone calcined clay cement (LC3) blends are often utilized in applications where the reduction in the carbon footprint is the main priority [3]. This research responds to one of the main research requirements of “mastering the workability of fresh concrete” listed in the United Nations’ 2017 report on eco-efficient cements and in Scrivener et al (2018) [3], and helps to increase concrete quality, reduce waste, and saves time and money
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