Use of Effective Micro-organisms (EM) technology and self-compacting concrete (SCC) technology improved the response of cementitious systems

Effective Microorganism technology (EMT) is of Japanese origin and has found useful applications in agriculture and water treatment works. This study reports the response of self-compacting paste systems with the addition of a mixture containing three micro-organisms namely lactic acid bacteria, photosynthetic bacteria and yeast all present in a suitable liquid medium. Two types of Effective Microorganisms (EMs) consortia, EM-Light (EML) having light brown color and low microbial cell concentration and EM-Dark (EMD) having dark brown color with high microbial cell concentration in a suitable liquid were used to study a total of seven self-compacting paste (SCP) formulations. These seven formulations include a control formulation and six EM modified SCP formulations containing 5, 10 and 15% (by wright content of cement) of both EM liquid consortia. The results showed that both EM consortia modified the plastic viscosity, delayed setting times and hydration kinetics, modified volume stability, reduced water absorption of SCP systems in hardened state and enhanced the compressive strength of SCP systems. Especially strength of SCPs with EMD seem to depend on fresh density of the paste to a large extent while with EML it shows different response. An increase of 26% in strength was observed compared to the control formulation with 15% EMD amendment at similar water-cement ratio along with a reduction in water absorption of hardened SCPs which may be attributed to the refinement in microstructure obtained by the production of calcium carbonate predominantly as a result of the reaction between microorganisms and calcium hydroxide. Scanning electron microscopy (SEM) and XRD results also suggest improvements in strengths of SCPs due to calcite (calcium carbonate).