Page 451 - New Trends in Eco efficient and Recycled Concrete

402 New Trends in Eco-efficient and Recycled Concrete

(A) (B)

Yield stress, depending to: σ = shear stress γ = shcar ratio γ (s –1 ) or σ (Pa) η (Pas)

1
Time (s) η = σ/γ γ (s ) or σ (Pa)
Figure 13.31 (A) Loop test and (B) example of results for a non-Newtonian and time-
dependent sample (Leonelli and Romagnoli, 2015).

(A) (B)

Yield stress, depending to: σ = shear stress γ = shear ratio σ or γ σ or γ

Time (s) Time (s)
Figure 13.32 (A) On off and (B) steps procedures (Leonelli and Romagnoli, 2015).

(Fig. 13.32B), consists of subjecting the sample to shear rates (or shear stresses),
the times are gradually increasing to get the balance. The resulting viscosity allows
show of the time-dependence in different flow regimes and the viscosities at differ-
ent shear rates at the same time.
Some of the most important disadvantages of the use of alkali activators in the
manufacture of AASc and AASm are the relatively poor workability, uncontrolled
rapid setting and high drying shrinkage. The result of previous studies showed that
AASm and AASc rheology depended on the nature of the activator used (Palacios
et al., 2006). Different factors influence the rheology behaviour of new mortars and
concrete:

The nature of the activator. In function on the nature of the alkaline solution the shear
stress versus shear rate curves could fit the Bingham model or a Herschel Bulkley model
(Palacios et al., 2008; Nath and Sarker, 2014).