**4. Hexagonal Model for Cost–Strength–Workability–Durability Relationship**

An increased upfront cost must be expected for HPSCC, especially for better performance, enhanced quality control, along with better-quality formwork to withstand higher pressures. On the other hand, the incorporation of industry by-products increased productivity, reduced labor, and energy consumption, and fewer post-construction repairs can balance the final cost. The HPSCC is much more economical in certain applications on a basis of the original cost, and also in a point of view the durable upkeep, and more ecological than the usual concrete. Moreover, the lifespan of HPSCC is estimated at two or three times than on a usual concrete. The major obstacles that prevent a wider implementation of HPSCC in construction are its high cost (+25 to 50%), and the lack of knowledge of the properties. In Table 11 the major parameters (strength, workability, durability, and cost) are been considered simultaneously on a scale of 0–10. The strength and durability results were converted based on the highest value obtained among the four concrete types.

**Table 11.** Comparison scales and rating for the four concrete mixes.


S.N. standardized number.

For comparing the workability results, SCCs were considered as perfectly workable, while the vibrated concretes can achieve 6 points for a 200 mm slump. Decreasing the slump has to decrease in the scale by one point for each additional 25 mm. The cost is negatively influencing the concrete selection; therefore, the lowest price was divided by the cost of other concrete types and multiplied by 10. The shown values of the concrete cost are based on the local prices for the preparation of 1 m<sup>3</sup> of concrete. The average results of multi-parameter assessment scale (MPAS) are showing that the HPSCC is the best option (MPAS = 196.6) in selecting a mix among the tested classes (Figure 9).

**Figure 9.** Hexagonal model for multi-parameter comparison of different concrete classes (W—workability measures; FT—tensile strength; FC—compressive strength; C—economic considerations; RH—residual strength after heating to +700 ◦C; RF—residual strength after 50 cycles of freezing and thawing).
