Use of Fly Ash and Cu-Slag from Mexico to Make Alkali Cements and Hybrid Cements
- PDF / 854,839 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 71 Downloads / 189 Views
CaO MgO SO3 K2O 8.63 1.92 0.78 -11.64 4.00 0.20 1.52 66.1 1.71 3.93 1.07 20.12 1.88 1.41 0.22
Na2O 1.55 1.44 0.20 1.28
TiO2 1.14 0.49 0.23 0.96
CuO Others 0.0119 1.80 0.60 4.73 0.05 0.27 0.03 1.48
LoI. = loss on ignition; FA and CS were hydrated with a 8 M NaOH (pH ≥ 14) solution. Hybrid cement was hydrated with a solution ClSNa (90% of NaCl at 5%+ 10% of sodium silicate solution, pH ~11.04) and OPC was hydrated with water (Reference). The liquid /binder ratio used to obtained similar consistency is show in Table II. The resulting mixtures pastes were poured into metallic prismatic molds (1x1x6 cm). Alkali cement (FA and CS + 8M NaOH solution) were cured in a stove at 85 °C and 95% relative humidity (r.h) for 20 h, however OPC and hybrid cement were cured at 23 ºC and 95% r.h. After demoulding, all specimens were cured in air chamber at 23 °C± 1 °C and 95% r.h. until the test age (2 and 28 days). At the test age 6 specimens were tested in compression to determine the compressive strength. Fragments of the broken specimens were finely ground for analysis. The techniques used for characterization of the raw materials and reaction products formed at 2 and 28 days were: X ray fluorescence (spectrophotometer Bruker S8 Tiger); laser ray diffraction (Mastersizer MALVERN Instruments); X ray diffraction (diffractometer BRUKER D8 ADVANCE); Scanning Electron Microscopy (microscope Hitachi S-4800). DISCUSSION The granulometry distribution of raw materials is showed in Figure 1. CS was ground in a ring mills; FA and OPC were used as received. OPC and CS have 90% of particles less than 20 µm, FA had larger particle size. Therefore, the hybrid cement (20% OPC + 80% fly ash) also had larger particle size than the OPC. Table II shows the compressive strength developed by the pastes at 2 and 28 days. Alkali cement, pastes (FA-N8) showed the greatest mechanical performance 33.8 MPa at 2 and 28 days. This value of compressive strength was comparable to OPC cement pastes (CEM 32.5), according to the UNE EN 197-1 (≥32,5 MPa at 28 days) and class 30 according to the NMX-C-414-ONNCCE (≥30 MPa at 28 days). CS-N8 pastes showed the poorest mechanical performance. According to the literature [1-3] this could be due to its lower aluminum content (see Table I). The hybrid cement pastes had the lower strength values (24.9 MPa) with respect to control OPC pastes and it was less than initially expected [1-3]. This performance was attributed to the insufficient reaction of hybrid cements with the activator (ClSNa), due to the larger particle size and also perhaps a low pH value reached in the alkali solution.
100
OPC FLY ASH COPPER SLAG HYBRID CEMENT
6
Cumulative volume (%)
Differential volume (%)
7
5 4 3 2 1 0.1
1
10
100
OPC FLY ASH COPPER SLAG HYBRID CEMENT
80 60 40 20
0.1
1000
1
10
100
1000
Particle size (µm)
Particle size (µm)
Figure 1. Granulometry distribution by laser ray diffraction. Tabla II. Mechanical strength at 2 and 28 days. Binder Alkali cement FA-N8 CS-N8 Reference OPC 40 HYBRID CEMENT (20% OPC + 80% fly as
Data Loading...
