**Alessandro P. Fantilli 1,\*, Francesco Tondolo 1, Bernardino Chiaia <sup>1</sup> and Guillaume Habert <sup>2</sup>**


Received: 4 April 2019; Accepted: 12 April 2019; Published: 16 April 2019

**Abstract:** If supplementary cementitious materials (SCMs) are used as binders, the environmental impact produced by cement-based composites can be reduced. Following the substitution strategy to increase sustainability, several studies have been carried out with the aim of measuring the mechanical properties of different concrete systems, in which a portion of Portland cement was substituted with SCMs, such as fly ashes. On the other hand, studies on the structural behavior of reinforced concrete (RC) elements made with SCMs are very scarce. For this reason, in this paper, a new procedure is introduced with the aim of fulfil a new limit state of sustainability, in accordance with the serviceability and ultimate limit states required by building codes. Although the environmental impact of concrete decreases with the reduction of cement content, the proposed approach shows that the carbon dioxide emission of an RC beam is not a monotonic function of the substitution rate of cement with SCMs. On the contrary, there are favorable values of such substitution rates, which fall within a well-defined range.

**Keywords:** fly ash; substitution strategy; structural concrete; steel reinforcement; limit states; RC beams in bending; carbon footprint
