Strength development of concrete balancing production requirements and ecological impact

The effective production of concrete structures requires adequate control of strength development in order to realise the scheduled production cycles. Demoulding of elements can take place only when sufficient strength is gained and the production cycle has to be maintained with seasonal changes of temperature. The use of Portland Cement promotes high early age strengths, but comes with a relative high impact on the environment since decarbonation and a high energy demand come along with cement production. Supplementary cementitious materials have been widely applied to improve the sustainability of concrete but the rate of early age strength development often is compromised to some degree. An experimental study was executed with the aim to maintain a similar strength level at early age but lowering the content of Portland clinker in concrete. Parameters of the study were the replacement level of Portland Cement, the curing temperature and the use of strength accelerator. At a comparable workability level, specimens were produced of which the compressive and flexural strengths were determined at different ages after casting. The Dutch CUR tool 'Green Concrete 3.2' was used to determine the environmental impact of the mixtures. The results show that concrete can have a much lower impact on the environment without compromising on the production conditions. Quantifying the trade-off between the use of Portland Cement and other mixture components and adding heat in the process is important information in order to balance production requirements and the ecological impact of concrete structures.

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