## 1 Introduction  
Construction activity plays an important role in the global economy, since it generates a substantial number of jobs and consumes large amounts of intermediate products (raw materials, chemicals, electrical and electronic equipment, etc.) and related services [1]. In addition, the current framework of the world economy, characterised by globalization and liberalization, has led to increasingly competitive business activity [2]. Hence, companies in the construction sector are constantly seeking cost-efficiency actions to obtain reasonable profit margins that allow them to withstand these difficult conditions, and hence be more competitive in the global market [3]. This context makes it essential to optimise available resources to achieve more competitive prices for the manufactured product [4]. In concrete manufacturing, one of the main lines of action is the technical-economic optimization of the different components involved in the dosage of the concrete mixture. Here, the most important costs are those of the cement and chemical additives, which have a significantly higher unit cost than the raw materials (water and aggregates) [5]. Thus, these costly components are normally dosed in lower proportions, giving preference to the functional requirements of the elements for manufacture [6]. Table 1 shows a list with the average costs of each component for a standard dosage of concrete estimated for the south-east area of Spain, considering three main situations of cement richness: (a) 300;Regarding these values, the cement cost represents 62-70% of the final cost of the mixture. Thus, the cement volume is the highest cost in the concrete dosage, as suggested by various authors [7]. Therefore, the cost of the concrete mixtures increases proportionally to the growth in cement richness. An average increment of EUR 5 for each 50 kg of extra cement added could be considered, i.e., an increment of about 10% for each new addition of 50 kg used in the dosage. Cement content is typically perceived as controlling concrete strength. Based on this perception, a minimum cement content that may exceed the amount needed to achieve the desired strength and durability is often specified [8]. Previous studies [9; 10] suggest that a high cement content in a mixture does not contribute to a greater strength than the required design strength. In fact, the final strength level is controlled by the W/C ratio, which characterises the porous properties of the cementitious matrix [11; 12]. In consequence, any decision intended to optimise the cement content in the concrete mixtures should be given priority, since the economic margins involved in the construction activity are increasingly lower. However, apart from the economic criteria, other factors are equally important in many cases, e.g., the workability of fresh concrete, hardening rate, durability conditions, possibility of reusing concrete waste as new aggregates for concrete (recycled aggregates), and, last but not least, the energy cost savings [13]. Furthermore, the Portland cement used in concrete is a matter of interest due to the high greenhouse gas emissions associated with its production, which results in approximately 5% of all CO\({}_{2}\) emissions [14]. This concern has led international organisations to make suggestions aimed at improving concrete production, recommending methods to reduce the greenhouse gas emissions associated with cement production [15]. Regarding the manufacturing process, pre-casting companies typically produce their concrete elements in suitably controlled conditions that allow them to reproduce each successive concrete batch almost identically during the entire manufacturing process. This is evidently of great importance in concrete production in order to optimise the W/C ratio and to guarantee the final mechanical properties [12].