Performance of energetically modified cement (EMC) and highly reactive pozzolan based on fly ash

The Energetically Modified Cement (EMC) technology consists of processing a blend of ordinary Portland Cement (OPC) and a pozzolan through multiple high intensity grinding mills to impart increased surface activation of the OPC and pozzolan particles. In this study a fly ash of low reactivity as such was selected as pozzolan. Fly ash may be ground together with all cement forming ready cement or with a small amount of cement (approximate to 5%) and used as a pozzolanic additive. The environmental benefit is three-fold; 1) activation of fly ash that otherwise is not suitable for concrete addition, 2) reduced CO₂ emission to the atmosphere by using much less amount of clinker as concrete binder and 3) reduce the energy consumption in binder production. Calculations show that savings can be at least 40% on CO₂ emissions and 46 % on energy consumption with EMC technology when 50% fly ash of cement mass is used.The performance of EMC with 50% fly ash is compared to OPC and simple 50:50 blends of OPC and fly ash as binder in mortar and concrete in terms of setting time, strength development, drying shrinkage, sulphate resistance and alkali-silica reactivity. The strength of EMC with 50% fly ash is comparable to OPC, the setting time is similar, and alkali-silica reactivity is lowered as well as drying shrinkage. Activated fly ash as pozzolan may replace up to 70% of cement in concrete.The improved performance in spite of only modest increased fineness (+18%) is explained by formation of agglomerates of cement/fly ash grains of high inner surface. Breaking of closed glassy aluminosilicate spheres in the fly ash will also improve its reactivity.Full scale industrial projects in Texas, USA, with concrete based on EMC with 50% fly ash show remarkable low cracking tendencies. Photographs from a parking lot and highway pavements are presented.