Energetically modified cements (EMCs) are a class of cements made from pozzolans (e.g. fly ash, volcanic ash, pozzolana), silica sand, blast furnace slag, or Portland cement (or blends of these ingredients). The term "energetically modified" arises by virtue of the mechanochemistry process applied to the raw material, more accurately classified as "high energy ball milling" (HEBM). At its simplest this means a milling method that invokes high kinetics by subjecting "powders to the repeated action of hitting balls" as compared to (say) the low kinetics of rotating ball mills. This causes, amongst others, a thermodynamic transformation in the material to increase its chemical reactivity. For EMCs, the HEBM process used is a unique form of specialised vibratory milling discovered in Sweden and applied only to cementitious materials, here called "EMC Activation".

By improving the reactivity of pozzolans, their strength-development rate is increased. This allows for compliance with modern product-performance requirements ("technical standards") for concretes and mortars. In turn, this allows for the replacement of Portland cement in the concrete and mortar mixes. This has a number of benefits to their long-term qualities.

Energetically modified cements have a wide range of uses. For example, EMCs have been used in concretes for large infrastructure projects in the United States, meeting U.S. concrete standards.

The term "energetically modified cement" incorporates a simple thermodynamic descriptor to refer to a class of cements produced using a specialised highly intensive milling process first discovered in 1992 at Luleå University of Technology (LTU) in Sweden. The transformatory process is initiated entirely mechanically as opposed to heating the materials directly. The mechanisms of mechanochemical transformations are often complex and different from "traditional" thermal or photochemical mechanisms. HEBM can transform both the physical and thermodynamic properties that for example, "can lead to glass formation from elemental powder mixtures as well as by amorphization of intermetallic compound powders". The effects of HEBM-transformation cause a thermodynamic change that resides ultimately in a modified Gibbs Energy. The process increases the binding capacity and chemical reactivity rates of the materials transformed.

Continuing academic work and research regarding "self-healing" properties of energetically modified cements is ongoing at LTU. For example, EMCs has received awards from the Elsa ō Sven Thysells stiftelse för konstruktionsteknisk forskning (Elsa & Sven Thysell Foundation for Construction Engineering Research) of Sweden. The contribution of EMCs to the domain of mechanochemistry itself has also been recognised.

The term "energetically modified cement" was first used in 1992 by Vladimir Ronin, introduced in a paper by Ronin et al. dated 1993 and presented at a formal meeting of the academic Nordic Concrete Research group. The process was refined by Ronin and others, including Lennart Elfgren (now Professor Emeritus of LTU, Department of Civil, Environmental and Natural Resources Engineering). In 2023, LTU awarded Elfgren the "Vice-Chancellor's Medal for Merit for outstanding and meritorious work" by virtue of his work "...for the spread of new knowledge and understanding of, in particular, the concrete construction field".

At the 45th World Exhibition of Invention, Research and Innovation, held in 1996 in Brussels, Belgium, EMC Activation was awarded a gold medal with mention by EUREKA, the European inter-governmental (research and development) organisation, for "modification énergique de ciments".

The term "energetically modified" has been used elsewhere—for example as recently as 2017—although such usage does not denote the method used was EMC Activation as defined here.