Evaluation of Pozzolanic Activity of Illitic and Lateritic Raw Materials from Burkina Faso

Aims: Evaluate the potentially use as pozzolan in cement replacement of activated Lateritic and Illitic raw materials from Burkina Faso.

Place and Duration of Study: Laboratory of Molecular and Materials Chemistry-University of Ouagadougou, National Laboratory of Building and Publics Works-Ouagadougou, Burkina Faso. Between March 2015 and June 2016.

Methodology: The initial two raw materials were characterized to perform its chemical, mineralogical, geotechnical and microstructure properties. The two samples were activated at 680°C during 2 or 5 hours to produce amorphous reactive materials. The activated samples were characterized using infrared spectroscopy and the selective dissolution by HF acid. Pozzolanic activity was assessed using saturated lime test, Frattini test, mineralogical analysis and compressive strength test. Mineralogical analyses were carried out with X-ray diffraction and DTA/TG.

Results: The characterization of initial raw materials shown that lateritic material contain kaolinite (71%.wt) and Goethite (18%.wt) as the mains phases and the illitic material consisting by kaolinite (44%.wt) and illite (40%.wt). The activation of samples at 680°C, given amorphous phase (metakaolinite and silica) which amount around 74%.wt and 61%.wt respectively for lateric and illitic sample. The activated samples fixed at 7 days more than 80%.wt of lime. The DTA/TG test shown that at 8 days, lateric sample fixed between 33-37% and the illitic sample around 23% of portlandite produced by ement hydratation. The strength activity index, 91% and 97% respectively for lateritic and illitic samples exceeds require minimal value (75%) for pozzolan materials. Lateritic sample with finer particle and high amount of metakaolinite was presents a better pozzolan activity. However it strength is lower than those of Illitic sample. This inversion of previsible strength is due to the high contain of iron oxide in lateritic sample.

Conclusion: The two samples, after heat treatment at 680°C during 2 hours, can be used as pozzolan for cement partial replacement in the constructions.