One-part earth alkaline activated dry cementitious mixture was produced using thermally activated lime kiln dust (LKD) waste material as a source of CaO activator and metakaolin and natural pozzolan as a source of aluminasilicate • The proportion of LKD and metakaolin in the ternary blend and thermal activation of LKD not only increased the reactivity but also induced higher degree of alkali-activation.• Significant increase in the rate of strength development after 28 days of curing and continued until 180 days that reached 51 MPa for increased proportion of 950ºC calcined LKD and metakaolin in the blend was revealed.• Considerable changes in mineralogy and amorphicity were evidently accredited to thermal treatment.
• Increase in recycled asphalt replacement results in further reduction in strength. • Lower ultrasonic pulse velocity is obtained by the use of recycled asphalt aggregate. • Rebound number decreases with the percentage increase in recycled asphalt aggregate. • Roughening the aggregate prior to mixing increases the strength of recycled asphalt aggregate concrete. • Roughening up to 2 h can have a small influence of increasing the ultrasonic pulse velocity.
Among the several schemes that have been reported to be a satisfactory alternative to Portland cement is Alkali Activated Cement (AAC), which has recently started to gain greater consideration in construction sectors. Conventional two-part alkali activation has many drawbacks, including the activating solution being viscous, problematic and non-user friendly to handle. Thus, this research aims to produce a one-part alkali activated metakaolin/natural pozzolan, by using an earth alkaline source (rich in CaO) from waste material (lime kiln dust), as an activating precursor to break the alumina-silicate crystalline phases. Thermal treatment of materials at two levels of treatment (450 o C and 950 o C), was used as an assisted activation approach. Analytical techniques including X-Ray powder diffraction XRD, Thermogravimetric Analysis TG-DTA, Fourier Transform Infrared Spectroscopy FTIR and Scanning Electron Microscope SEM, were utilised to investigate the performance of the developed materials at a molecular level. Reduction of crystalline peaks as well as the appearance of new wollastonite minerals within the calcined lime kiln dust, contributed to the development of 27 MPa compressive strength after 28 days. The dissolution made through the pozzolanic reaction as well as thermal treatment evidently contributed to transform crystalline to amorphous phases.
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