PSI - Issue 11

Bárbara Belén Raggiotti et al. / Procedia Structural Integrity 11 (2018) 36–43 Raggiotti et al./ Structural Integrity Procedia 00 (2018) 000 – 000

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• Semi-quantitative microanalysis by electron probe (SEM - EDS): the zeolite appears as tiny laminar crystals grouped in the shape of added rosettes. This can be observed in Figure 3. The composition maps (Si, Al, Na, K, Mg, S, Ca, Fe, Ti) and the SEM images were obtained in gold-laminated dust samples with a Carl Zeiss FE (field emission)-SEM Zigma high resolution microscope equipped with an EDS. Around 30 mg of sample was used.

Figure 3. SEM image of the laminar crystals of clinoptilolite-Na.

Zeolite is mainly represented by the sum of Si, Al and Na maps with a lower proportion of K, Mg and Ca. Biotite is represented by the sum of Si, Al, Fe, Mg and a lower measure of Ti. Plagioclase is represented by the sum of Si, Al, Na and a little more Ca but, as it coincides with the main elements of zeolite, it might not be recognized on the maps though it was identified by EDS and XRD. Although the quartz was determined using XRD, it might not be recognized in the compositional maps because the Si is also part of the clinoptilolite, plagioclase and biotite crystal structures. With the aim of detecting additional mineral phases not identified by XRD and to assess the origin of the sulfur different from the gypsum phase, composition maps were obtained by FE-SEM- EDS of the fine fraction (≤ 1,000  m) of the pozzolanic material. Figure 4 shows the compositional maps. The gypsum is represented by the sum of the S and Ca maps. The sulfur is fully bonded to the gypsum phase.

Figure 4. FE-SEM-EDS. a) Image of the secondary electrons of the pozzolanic material (18 kV). b-f) composition maps of Si (b), of Al (c), Na (d), K (e), Mg (f), S (g), Ca (h), Fe (i)

4. Design of concrete with the addition of zeolite

Two series of concrete were posed, one for each kind of cement used, Normal Portland cement (NPC) and Compound Portland cement (CPC), to which 5, 10, 15 and 20% of the cement content in weight was replaced by the addition of zeolite, the main variable in the study. Table 4 indicates the dosages.

5. Materials

• Cement: NPC40 from the province of Catamarca, Argentina, was used; and CPC40 from the province of Cordoba, Argentina, which comply with IRAM standard 50,000 (2014). These two cements were used to analyze the