9. Practical Guidelines for the Mix Design of Grouts in Masonry Strengthening

In this Chapter, the scientific approach followed in this book finds its justification: The rational and detailed examination of all properties of a grout, offers now the possibility to follow a practical step-by-step procedure of mix-design, permitting to handle numerous parameters in a logical sequence. Thus, this chapter contains more practical guidelines for the mix-design of grouts used in masonry strengthening. The use of Tables and empirical formulae included in previous Chapters, greatly facilitate the selection of (i) the type of the binders and the final grading of the solids, (ii) the minimum acceptable fluidity factor, depending on the finest discontinuities width class (W_nom), (iii) the zero-bleeding and the critical-bleeding (W/S) expressions (with or without superplasticizers), as a function of the calculated average specific surface S_A of the solid phase, and (iv) the limit value W/S against segregation. Subsequently, a practical procedure for the selection of the final (W/S) ratio of the mix is described, respecting all the aforementioned limits. Corresponding remedy-measures are presented in case such a complete respect is not feasible. Moreover, for masonries of minor historical importance and with representative W_nom ≥ 0.25 mm, a Table is offered, containing approximate compositions of grouts for three different required grout strength ranges. Experimental verification of the required grout-performances will be in any case necessary.