Properties of Tungsten Mine Waste Geopolymeric Binder- Experimental Work IV

Properties of tungsten mine waste geopolymeric binder

Mix proportion and strength testing

In this investigation the mortar was a mixture of aggregates, waste mud, calcium hydroxide, alkaline silicate solution and water. The mass ratio of mine waste mud: activator was 1:1. Calcium hydroxide was used with a percentage substitution of 10%, because it was found that percentage lead to the highest compressive strengths. An activator with sodium hydroxide (24 M) and sodium silicate solution (Na₂O = 8.6%, SiO₂ = 27.8%, Al₂O₃ = 0.4% and water = 63.2%) was used with a mass ratio of 1:2.5. Previous investigations showed that this ratio lead to the highest compressive strength results in alkali-activated mine waste mud mortars. Distilled water was used to dissolve the sodium hydroxide flakes to avoid the effect of unknown contaminants in the mixing water. The alkaline activator was prepared prior to use. The sand, mine waste mud and calcium hydroxide were dry mixed before added to the activator, which according to Pinto et al. is the mixing option that leads to the best results. To produce a workable mix extra water has been added as stated by Jahanian and Rostami. The mass ratio of water/ dry solid binder content was 3.6% in most of the samples, except for samples with an aggregate/binder mass ratio of 1.5 or 1.7. In those cases, the extra water percentages were respectively 7 and 10% . TMWM binders using schist (SC) fine aggregates with an aggregate/binder ratio of 1.5 were named SC – AG/B 1.5. Similarly when limestone (LS) or granite (GR) aggregates were used were named respectively LS – AG/B 1.5 and GR – AG/B 1.5. TMWM mixtures made with 2% superplasticizer by mass of binder lime and mine waste mud, were named respectively SC/SP, GR/SP and LS/SP.

Compressive strength data was obtained using 50x50x50 mm3 cubic specimens according to ASTM C109 . The fresh mortar was cast and allowed to set at room temperature for 24 h before being removed from the moulds and kept at room temperature until tested in compression. Compressive strength for each mixture was obtained from an average of three specimens.

 

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