| Abstract [eng] |
The main aim of the project was to evaluate the possibility of using smectite clay waste (SMA) which is obtained from the vegetable oil bleaching process as a pozzolanic additive for Portland cement. It was found that smectite clay consists of montmorillonite, quartz, anorthite and calcium sulphate and SiO2. Although it has an average pozzolanic activity (117 mg CaO/g), organic impurities need to be removed. When the hexane method for waste treatment was selected, it was found that the best results were achieved by mixing the SMA with hexane at a ratio of 1: 7 and extracting for 40 minutes. It has been investigated that extraction with hexane does not change the mineral composition of SMA, and pozzolanic activity increases from 117 mg CaO/g to 216 mg CaO/g, but after this process a large amount (12,7%) of organic impurities (oil) remain in the smectite clay. It has been determined that the extracted smectite clay waste extends the induction period of the Portland cement hydration, slows down the initial cement hydration and reduces the compressive strength of the Portland cement samples, therefore the extracted smectite clay is not a suitable additive for Portland cement. Using the thermal activation method, the best results are achieved by calcining SMA granules at 600°C for 1 hour. During combustion, the mineral composition of SMA changes slightly but the intensity of montmorillonite peaks is much lower than the untreated waste on the XRD curve, pozzolanic activity increases to 320 mg CaO/g,. Sample strength analysis showed that after 7 day of hydration, the highest compressive strength had sample with 10% SMA600 additive (76,97 MPa), and the compressive strength of the specimen decreases by increasing the amount of additive. After 28 days of hydration, the highest compressive strength (98,85 MPa) is also present with a sample of 10% SMA600. The positive effect of the SMA600 additive on the compressive strength of the specimens is attributable to the pozzolanic reaction in these samples, which was clearly identified by the VTA analysis method. |
