Energetically Modified cement (EMC) containing up to 70 % of pozzolans have been tested to have the ability to deliver long term pozzolanic reactions (calcium oxide + wateer + silicon dioxide) leading to the formation of additional amounts of C-H-S gel. This can fill voids and cracks of widths up to 0,2 mm, up to twice the crack width that usually can be healed. EMC is Portland cement mechanically activated in a process with a pozzolan, silica sand or blast furnace slag. The process was discovered 1992 at Luleå University of Technology and has been further developed since then.

Self-healing can increase the lifetime and durability of concrete structures. The self-healing properties of concrete made with Energetically Modified Cement (EMC), which has a pozzolan content of up to 70%, have been investigated. In such concretes, pozzolanic reactions within the cement cause the gradual formation of fresh C-S-H gel, which seals cracks as they form. The self-healing of small EMC concrete samples was tested in a laboratory, and field observations of an EMC concrete highway pavement were made. The EMC concrete exhibited fewer cracks than conventional concrete, and was observed to self-heal cracks with widths of up to 0.2 mm.

High Volume Pozzolan Concrete (HVPC) can be manufactured with low carbon dioxide footprint and energy consumption with the help of a new technology based on Energetically Modified Cement (EMC). The technology consists of mechanical processing a blend of ordinary portland cement (PC) and a pozzolan (Class F fly ash) through multiple high intensity grinding mills. The process imparts an increased surface activation of the PC and the pozzolan particles. Fly ash may be processed with all cements forming ready-to-use cement. Alternatively, fly ash can be processed with a small amount of cement (circa 5% by weight) and used as a pozzolan added to the concrete mixer. The latter product is called CemPozz and has been produced from 2004 by Texas EMC Products, Ltd, at the Limestone plant in Jewett, Texas. It can replace up to 60% of the PC in concrete. The performance of CemPozz (mechanically processed pozzolan) in concrete is equivalent to Grade 100 blast furnace slag in accordance with ASTM C 989 "Standard Specification for Ground Granulated Blast-Furnace Slag for Use in Concrete and Mortars."Th e strength of HVPC with 50% CemPozz is comparable to concrete made of ordinary portland cement, the setting time is similar, with improvements to alkali-silica reactivity mitigation and drying shrinkage. Concretes produced with CemPozz also have much higher sulfate resistance, very low permeability to chloride ions and are characterized by a signifi cantly reduced cracking.Th ere are three environmental benefi ts with the EMC-based HVPC: (i) You can activate a fl y ash that otherwise would not be suitable for high replacement of PC in concrete, (ii) You can reduce the CO 2 footprint by using a much less amount of clinker as concrete binder, and (iii) You can reduce the energy consumption associated with the binder. Calculations show that as much as 45% can be saved in energy with 45% less CO2 emissions when 50% fl y ash of cement mass is used with the EMC technology. During the period 2004-2007, over two million cubic yards (1.5 million cubic meters) of High Volume Pozzolan Concrete (HVPC) made with CemPozz have been manufactured in Texas and eff ectively used for different applications in Texas (highway paving, housing concrete, shotcrete and blocks). TX DOT and PENNDOT have included CemPozz in their specifications, which allow 50% replacement of portland cement by weight. Udgivelsesdato: March/April

Energetically Modified Cement (EMC) consists of a mechanochemical processed blend of ordinary Portland Cement (OPC) and filler or pozzolan. The process is carried out in multiple high intensity grinding mills to increase surface activation of the OPC and filler/pozzolan particles. Performance of EMC with 50% quartz or fly ash is compared with simple blends of same components. Examples are also shown where fly ash of low reactivity can be activated as pozzolan by the same process and used as additive to concrete.

Energetically modified cement (EMC) has been produced by high intensive grinding/activation of normal portland caemnet (NPC) together with 20% and 50% quartz sand. EMC concretes were compared to NPC based concrete using the k-factor concept. The k-factor for concrete with w/c = 0.60 - 0.45 was 0.7 - 0.9 for 1 day and 1.1 - 1.3 for 28 days compressive strength. k > 1 for both capillay suction, porosity, vapor diffusion and chloride permeability. For carboantion resistance k was approximately 0.55.Microstructure of EMC paste with 50 % quartz sand and w/c = 0.40 showed that the quartz was extensively ground and formed agglomerates with concrete having a high inner surface. The degree of hydration of the cement in EMC was as high as 71 % after 1 day comparted to 45 % for untreated blend. Refind pore sizr distribution of EMC versus blend means that even for equal hydration at higher ages EMC will perform better.

The microstructure of cement paste of 50/50 mixes of cement/quartz and cement/fly ash, both ground in a special mill [energetically modified cement (EMC) process] and simply blended, have been studied under sealed curing conditions. The grinding process reduced the size of both cement grains and quartz/fly ash markedly and created flaky agglomerates of high inner surface for the finer particles. EMCs had much higher degree of hydration at 1 day, but similar as blends at 28 days. The pores were much finer for EMC paste due to smaller particles as also reflected in the strength. The morphology of calcium hydroxide in EMC paste appeared more mass like. Pozzolanic reaction was insignificant for quartz in EMC, but increased for fly ash. Thus, improved performance of EMC versus OPC can be explained by increased early hydration and extensive pore size refinement of the hardened binder resulting in reduced permeability and diffusivity for concrete.

The demands of the modern building industry require development of new types of binder materials with improved properties for high and ultra high strength concretes and with significantly improved durability. They will provide new potential possibilities for the controlling of high performance concrete technology. In the Department of Civil Engineering at Luleå University of Technology a study of energetically modified cement (EMC) indicates that it is possible to obtain much more rapid hardening cement than the original cement used. As an example the strength of EMC-concrete increases about 100 per cent at the age of one day compared with a conventional high strength concrete.A new type of the cement gives possibilities to obtain required workability of the concrete mixtures with low water to binder ratios (w/B < 0.24) and achieve the strength levels up to 200 MPa with binder content not exceeding 550 kg/m3. The modification process used in this study means a special mechanochemical treatment in vibrating milling equipment of the blend containing Ordinary Portland Cement (OPC) and silica fume (SF), which increases the surface energy and the chemical reactivity of the newly obtained binder. This results in an accelerating effect, which maintains at least for nine months. According to ongoing investigations the energetically modified cement appears to give a considerable acceleration effect in the whole range of studied temperature. Concretes produced with EMC cement demonstrated very high durability at very severe testing conditions, including drying, saturation in sodium chloride solution and freezing-thawing. These results are very promising and it might be used in a lot of applications as winter concreting, precast element production, special structural elements, repair of buildings, rehabilitation, topping of concrete, floors, roads, etc.