Synergistic-effect of iron-filing and silica-fume on the absorption and shrinkage of cement paste
This study investigated workability, water absorption, and drying shrinkage performances of the synergy of iron filing (IF) with silica fume (SF) in the ordinary Portland (OPC) cement paste. IF varied from 0 to 15wt. % while SF was kept constant at 10wt % of the binder. The finding revealed that at low water/binder (w/b) ratio of 0.25, the synergistic effects of the combination of IF and SF reduced the workability and shrinkage of the paste exponentially but increased water absorption. Besides, an increase in absorption was due to non-absorbent nature of IF and proliferation of interfacial transition zones (ITZ) within the matrix while addition of SF caused the increase in pore tortuosity through secondary pozzolanic reaction accompanied by its micro-filling effects. Moreover, bond characterization showed that drying shrinkage reduction was due to IF retention of evaporable water within the matrix, and the removal of hydroxyl precipitated together with an improved polymerized units of silicate. Scanning electron micrograph indicated the improvement in the microstructural density due to the formation of CASH or CSH and restriction of internal strain deformation due to the formation of Fe-infused product (CAFSH). The least shrinkage value was observed at the IF substitution level of 15% with the SF of 10%. Therefore, synergistic effects of SF and IF could enhance production of more durable concrete more especially in the hot weather climate.