The bio-activation of pozzolanic activity of circulating fluidized-bed fly ash by Paenibacilllus mucilaginosus.

[Display omitted] • P. mucilaginosus destructed anhydrite of circulating fluidized-bed fly ash. • Active SiO 2 and Al 2 O 3 was increased by P. mucilaginosus. • Pozzolanic activity was improved by P. mucilaginosus. • P. mucilaginosus promoted fly ash hydration and ettringite earlier formation. • The compatibility of circulating fluidized-bed fly ash with cement was improved. The present investigation reports an eco-friendly biotechnology applying Paenibacilllus mucilaginosus (P.m), a silicate solubilizing bacteria, to activate pozzolanic activity of CFA. The results show SiO 2 and Al 2 O 3 dissolution rate of CFA treated by P.m and its Ca2+ absorption capacity in saturated Ca(OH) 2 solutions are increased compared to raw CFA indicating that pozzolanic reactivity of CFA is improved by P.m. One reason is destruction of the anhydrite coating layer of CFA particles surface through P.m erosion. Another reason is promotion of SiO 2 dissolution caused by deformation and destruction of Si-O-Si (Al) bonds by P.m. Carbonic anhydrase activity of P.m is one of the main factors involved in dissolution of SiO 2 , which also induces CaCO 3 mineralization. The hardening characteristics and hydration products of CFA-15% lime system with different content of P.m further confirm the effects of P.m on pozzolanic activity of CFA. 40% P.m incorporation is conducive to promote CFA hydration, ettringite earlier formation and bio-mineralization, thereby improving the mechanical properties of hardened mortar. Incorporation of 40% P.m in cement blended with CFA results in that CFA content is increased by 5–20% and the 28d strength improved by 11.5–23.9 MPa. This is the first report of microbial activation of CFA pozzolanic activity. [ABSTRACT FROM AUTHOR]