PSI - Issue 28

Chbani Hamza et al. / Procedia Structural Integrity 28 (2020) 430–439 Author name / Structural Integrity Procedia 00 (2019) 000–000

438

V

V

V





(13)

absolute

aggrgate

ciment

Where

V

V

V

V







(14)

aggregate

0 / 4

3 / 8

8 / 16

sand

gravel

gravel

(15)

  1000 8 /16

V V  sand 0/4

V

V





3/ 8

gravel

gravel

ciment

Table 6 gives the weight dosage of the different constituents (aggregates, cement, water and admixture) for one cubic metre of ordinary C25/30 concrete. The required weight of admixture is 0.9 of the cement weight(according to NM 10.1.260 (2000). Table 6. Formulation of ordinary concrete Concrete constituents Weight (kg/m 3 ) Sand 0/4 563,35 Gravel 1 3/8 889,95 Gravel 2 8/16 464,33 Water 199,68 Cement CPJ 55 MPa 275 Admixture 2 ,475 If the verification of the concrete workability by the Abrams cone test shows a concrete that is too viscous or had a fluidity more than the intended objective and therefore not plastic enough, it should not have the reflex to add water. Indeed, the addition of water causes a drop in strength; for example, for a C25/30 type concrete, adding 20 L per meter cube results in a 5 MPa drop in strength Stefan (2009). During the formulation phase, it is necessary to review the granular mixture in order to make it more compact and/or to use a plasticizer (2000). If, on the other hand, the concrete is too plastic, check the moisture content of the aggregates, remove water and compensate by adding aggregates (gravel and sand) Aıtcin (2003). 4. Conclusion This paper has detailed the different steps in the formulation of an ordinary concrete. This formulation is based on several technical, standardise and economic criteria and is mainly related to well-defined mechanical and physical characteristics. The dosage of each element in the concrete mixture must be controlled in order to obtain the desired characteristics. The determination of a formulation for targeted concrete can only be achieved after an exact knowledge of the physical and mechanical properties of its primary components (gravel, sand, cement). In a first step, the aggregates were characterized using the density and compactness tests. The result of the coefficient of water absorption is considered low, therefore, no correction for the water/cement ratio was considered. Subsequently, a granulometric analysis was carried out in order to evaluate the dimensional homogeneity of the constituent grains of the aggregates. Knowledge of the dimensional distribution of the aggregates makes it possible, in addition to knowing the targeted compressive strength and the consistency class of the concrete, to define the cement/water (C/W) ratio required for the mixture. The Dreux-Gorisse formulation method was adopted in order to define the proportions of the aggregates from the superposition between the granular curve corresponding to the aggregates used, the reference granular curve and the dividing lines. Finally, once the concrete formulation has been defined, it must be adjusted experimentally according to the results obtained from laboratory tests (study tests) or under site conditions (suitability tests).