# Experimental Study on the Flexural Behavior of Alkali Activated Fly Ash Mortar Beams
## 2 Experimental Procedure
### Production of Beams  
The cement mortar was produced at Department of Civil Engineering of the University of Coimbra, as well as the tests carried out on small specimens (cubes and prisms) and on the beams. To follow the initial objectives, an average strength of 35 MPa was targeted for the beams. For this purpose, a mixture was carried out. The mix proportions were 270 kg of sand, 60 kg of cement, 30 kg of water, and 0.54 kg of superplasticizer Sika ViscoCrete 20 HE. This mixture was sufficient for casting five beams, twelve 150 mm cubes, and six \(40\times 40\times 160\) mm prisms. After three days of curing, the beams, cubes and prisms were demolded.  
The fly ash based mixture was done with: 200 kg of sand, 80 kg of fly ash, and 40 kg of compound activator. These proportions were those adopted from a base recipe suggested by [PERSON] [27]. With this mixture, five beams, twelve \(40\times 40\times 160\) mm prisms, and five 150 mm cubes were cast and demolded five days later.  
Table 3 shows the weight and real dimensions, measured after the construction of the beams. The height (h) and the width (b) result from an average of three measurements made in the central area of the beam (the most important area of the tests). L represents the length of the beam. It appears that the greatest deviations occurred for the height (h).  
Control tests were carried out on cubes and prisms, on different days, in order to evaluate the evolution of the strength.  
Regarding the cement mortar tests, the results on cubes gave very close results to the expected average compressive strength of the concrete, an exponential curve proposed by [PERSON] [28] (see Figure 2). In this figure, fcm indicates the average value of the compressive strength of concrete for the time T in days.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Beam** & **Weight [kg]** & **b [mm]** & **h [mm]** & **L [mm]** \\ \hline Cem-2F6 & 52.1 & 98.1 & 152 & 149.5 \\ \hline Cem-3F6 & 53.9 & 100 & 153 & 149.5 \\ \hline Cem-4F6 & 54.9 & 100 & 154 & 149.5 \\ \hline Cem-3F8 & 54.6 & 101 & 153 & 149.5 \\ \hline Cem-4F8 & 53.4 & 97.4 & 152 & 149.5 \\ \hline FA-2F6 & 51.9 & 104 & 152 & 149.6 \\ \hline FA-3F6 & 51.7 & 99.3 & 152 & 149.6 \\ \hline FA-4F6 & 52.2 & 99.2 & 153 & 149.5 \\ \hline FA-3F8 & 52.7 & 102 & 153 & 149.5 \\ \hline FA-4F8 & 53.2 & 103 & 152 & 149.5 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Effective dimensions of the beams.  
Regarding the fly ash specimens, compression and/or tension strength tests were performed on twelve \(40\times 40\times 160\) mm test specimens, following NP EN 196-1 and NP EN12390-5 [29; 30], to determine the mechanical characteristics of this material. The value for the modulus of elasticity of this material was about 20 GPa in non-destructive cyclic tests and about 18 GPa in failure tests. The average compressive and tensile strengths were 15.1 and 3.2 MPa at 23 days old and 23.5 and 4.0 MPa at 32 days old, respectively. The corresponding maximum stresses were respectively, 17.8 and 3.3 MPa at 23 days and 30.7 and 4.6 MPa at 32 days. From the compression tests of 150 mm cubes, an average compressive strength of 23.8 MPa, was obtained at 32 days, with a maximum value of 27.2 MPa. The standard deviation of the results was 2.6. It should be noted that all ash beams were tested between days 31 and 33 after pouring.