Types of modern cement

Portland cement

Main article: Portland cement

Cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 °C in a kiln, in a process known as calcination, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide, or quicklime, which is then blended with the other materials that have been included in the mix. The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum into a powder to make 'Ordinary Portland Cement', the most commonly used type of cement (often referred to as OPC). Portland cement is a basic ingredient of concrete, mortar and most non-specialty grout. The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, High Temperature Cement and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Portland cement may be grey or white.
[edit]Energetically Modified Cement ("EMC Cement")


Proving Energetically Modified Cement's "self-healing" capabilities...



PHOTO A: Proving Energetically Modified Cement's "self-healing" capabilities. Mechanically-induced cracking in concrete comprising EMC Cement, caused by RILEM 3-point bending induced after ~3 weeks of water curing (September, 2012). Cracks had an average width of 150-200 μm.
The photo above depicts a concrete test-beam made from EMC Cement undergoing RILEM 3-point bending at Luleå University of Technology in Sweden (February, 2013). This treatment induces cracks so as to test for EMC Cement's "self-healing" capabilities.



PHOTO B: Former cracks in concrete comprising EMC Cement, taken 5 months after PHOTO A. The photograph shows that the former cracks had undergone a complete "self healing" process without any intervention, by virtue of newly-synthesized CSH gel — itself a product of the ongoing pozzolanic reaction.
Concrete (total cmt: 350 kg/m³) containing 40% Portland cement and 60% EMC Cement made from fly ash was used. Cracks of average width 150-200 μm were induced after ~3 weeks of water curing. This is depicted in PHOTO A.

Control cubes were tested for compressive strength at different ages.

As expected, without any intervention the high volume pozzolan concrete exhibited the gradual filling-in of the cracks with newly-synthesized CSH gel (a product of the ongoing pozzolanic reaction). These were completely filled-in after ~4.5 months. This is depicted in PHOTO B.

During the observation period, continuous strength-development was also recorded by virtue of the ongoing pozzolanic reaction. This, together with the observed "self healing" properties, both have a positive impact on concrete durability.

All photos courtesy of Dr. V. Ronin
An alternative fabrication technique EMC (Energetically Modified Cement) produces cementitious materials made from pozzolanic minerals that have been treated using a patented milling process ("EMC Activation").[13] The resultant concretes can have the same, if not improved, physical characteristics as "normal" concretes — at a fraction of the Portland cement. Note, although Energetically Modified Cement is able to replace Portland cement in concrete to high levels, it cannot fully replace it.
Energetically Modified Cement is better known as "EMC Cement". EMC Cement may be classified both as an "Alternative Cementitious Material" and as a "Supplemental Cementitious Material", on account of the range of the Portland cement replacement-ratios offered. Colloquially, EMC Cement may be referred-to also as a "Green Cement", on account of the significant energy and carbon dioxide savings yielded by EMC Activation as compared to Portland cement production.
The trade name for EMC Cement is "CemPozz". At the 45th World Exhibition of Invention, Research and Innovation, held in Bruxelles, Belgium, EMC Activation was awarded the Gold Medal "with mention" by the EUREKA Organisation (the pan-European research & development funding and coordination organization, comprising all 27 EU Member States). High Temperature Insulation

Put simply, EMC Activation is a patented, cost– and energy–efficient, near zero-emission technology for the high replacement of Portland cement in concrete.

Materials that are used to replace Portland cement in concrete (such as fly ash, blast furnace slag, natural pozzolans – e.g. volcanic ash – and silica sand) are mechanically activated in proprietary milling systems.EMC Activation increases the amount of Portland cement that can be replaced over and above "traditional" replacement methods (which typically replace an average of circa. 15% of the Portland Cement in concrete). By contrast, up to 70% of the Portland cement in concrete can be replaced using EMC Cement.
EMC Activation generates high-energy particle impacts. This leads to deep transformations in the particle micro-structure in the form of (among others) sub-micro cracks, dislocations and lattice defects that significantly increase reactivity, with no material increase in overall powder fineness.
EMC Cements comply with relevant normative standards and specifications. For example, where EMC Cement is made from fly ash, high Portland cement replacements (i.e., the replacement of at least 50% Portland cement) yield concretes that exhibit consistent field results.This is also the case for EMC Cement made from natural pozzolans (e.g., volcanic ash).

For example, volcanic ash deposits situated in Southern California of the United States were tested by independent consultants, according to the relevant normative standards. EMC Activation was then applied to the raw materials. At 50% Portland cement replacement, the resulting concretes exceeded the normative requirements. At 28 days, the compressive strength was recorded at 4,180 psi / 28.8 MPa (N/mm²). The 56-day strength exceeded the requirements for 4,500 psi (31.1 Mpa) concrete, even taking into account the safety margin as recommended by the American Concrete Institute.

EMC Cement presents dramatic savings both in terms of carbon dioxide and energy-savings. The figures vary slightly depending on the source material used. For example, if volcanic ash is used, the resulting compound has to be dried. This drying process consumes about 150,000 Btu per ton of EMC Cement produced.

All in all, as compared to a total energy consumption of ~1,000 to 1,400 KWh for each ton of Portland cement produced:
For each ton of EMC Cement made from fly ash, the energy requirement is usually ~25 KWh. There are no direct CO2 emissions.
For each ton EMC Cement made from volcanic ash, the energy requirement (including drying, as above) is no more than ~80KWh, with direct emissions of only 8 kgs CO2 per ton.

The performance of concretes made from EMC Cement can also be custom designed. Hence, concretes can range from those exhibiting superior strength and durability that reduce the carbon footprint at up to ~70% as compared to concretes made from Portland Cement, through to the production of rapid and ultra-rapid hardening, high-strength concretes (for example, over 70 MPa / 10,150 psi in 24 hours and over 200 MPa / 29,000 psi in 28 days).This allows EMC Cement to yield High Performance Concretes (HPCs).
EMC Cement exhibits a high resistance to chloride and sulfate ion attack, together with a low Alkali–Silica Reactivity (ASR).These features allow concretes made from EMC Cement to exhibit superior durabilities as compared to concretes made from Portland cement. For example, an early project using EMC Cement was the construction of a road bridge in Karungi, Sweden, with Swedish construction firm Skanska. The Karungi road bridge has successfully withstood the tests of time, despite Karungi's harsh subarctic climate and extremely divergent diurnal temperatures.

EMC Activation and EMC Cements are well-proven to an "industrial scale". In the United States, EMC Cement has been approved for usage by PennDOT (Pennsylvania Department of Transportation), TxDOT (Texas Department of Transportation) and CalTrans (California Department of Transportation). As a result, hundreds of miles of highway paving have been laid, together with assorted highway bridges, using concretes made from EMC Cement — including large sections of Interstate 10, which is the main U.S. Interstate highway linking Miami, Florida with Los Angeles, California.
Another notable project in the United States includes the extension of the passenger terminals at the Port of Houston, Texas. This project fully exploits EMC Cement's known propensity to yield concretes that exhibit high-resistances to chloride– and sulfate–ion permeability (i.e., increased resistance to sea waters), as compared to concretes made from Portland cement.