Concrete strength development and sustainability: the limestone constituent cement effect

In this paper, a systematic analysis, evaluation and modelling of the sourced global strength data of concrete where Portland cement (PC) is partially replaced with ground limestone (GLS) is presented. The data – sourced from literature published in English language since 1976, by 250 researchers working at 160 institutions in 43 countries – yielded a matrix of 14 707 data points. The effect of the addition of GLS together with its fineness, concrete design strength, curing duration and water/cement (w/c) ratio are studied. It is shown that concrete strength decreases with the addition of GLS, and at an increasing rate with GLS content. However, this loss in strength of concrete may, to a limited extent, be modified by means of GLS fineness, design strength, curing and the w/c ratio. At a fixed w/c ratio, the GLS content would most likely limit strength development, with the mix unable to develop an equal strength to that of the control PC mix. It is also shown that perceived sustainability benefits would be negated where concrete mixes are designed for specific 28 d strength. This is the case particularly for high-strength PC–limestone cement (PLC) concrete. Notwithstanding this, the use of PLC at higher content than in the corresponding PC can be beneficial with low-strength, S4 slump class or self-compacting concrete, where the filler effect of GLS ensures production of stable concrete mixes free from bleeding and segregation risks and the specified strength is achieved by reducing the w/c ratio of such mixes.