PACKING ISSUE IN CEMENT BLENDING FOR SUSTAINABILITY DEVELOPMENTS - APPROACH BY DISCRETE ELEMENT METHOD

Abstract

Common cement blending materials for concrete like fly ashes, blast furnace slag, silica fume, metakaolin and rice husk ash have been investigated experimentally as to their impact on concrete’s mechanical, physical and sustainability capabilities. Such efforts offer but case-related information on involved materials and used procedures. Generalizations will be difficult because also contradicting information is provided: a weak basis to guide further developments. Published research data on blends with inert components (carbon black) confirm fineness to be the leading parameter governing their mechanics. Experimental efforts revealing blending effects on durability issues are more scarce because of their complicated, laborious and time-consuming nature. Hence, generalization capabilities are even more restricted. An approach is therefore presented for studying cementitious materials in the virtual reality, employing the concurrent algorithm-based dynamic discrete element method (DEM), HADES. Hydration simulation of the simulated (blended) Portland cement grain mixture is thereupon accomplished with an extended version of the vector approach. Robotics-based pore delineation provides topological information, while geometric characterization of the pore networks is accomplished by star volume measurements. Topological and geometric parameters can be combined in a hydraulic model for durability estimation. This approach allows covering a wide range of parameters. This would render possible more systematic and economic development of such materials for sustainability purposes, among other things. The production stages (DEM and hydration simulation) and the analysis stages (pore delineation and topology and geometry assessment) are briefly outlined. Application of the methodology is illustrated on finer and coarser grained cements blended with rice husk ash produced with different fineness. The effects of the gap in grading on the pore network characteristics relevant for transport-based durability items are outlined.