Energetically modified cement

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Pictorial insert: Demonstrating EMC's "self-healing" ("biomimetic") propensity...

PHOTO A: Testing energetically modified cements' "self-healing" capabilities. Mechanically-induced cracking in concrete comprising EMC, caused by RILEM 3-point bending induced after circa three weeks' water-curing (September, 2012). Cracks had an average width of 150-200 μm.
A concrete test-beam made from energetically modified cement (EMC) undergoing RILEM 3-point bending at Luleå University of Technology in Sweden (September, 2012). This treatment induces cracks to test for energetically modified cement's "self-healing" ability. The study of such "biomimetic properties" of certain materials is relatively newly-emerging in civil engineering and advanced material sciences.[1]
PHOTO B: Former cracks in concrete comprising EMC, 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 synthesised CSH gel — itself a product of the ongoing pozzolanic reaction.

Here, 60% of the Portland cement has been replaced with EMC:

1. Concrete (total cmt: 350 kg/m³) of 40% Portland cement and 60% EMC made from fly ash was used.

2. Cracks of width 150-200 μm were induced after circa 3 weeks' water-curing. See PHOTO A.

3. Without any intervention, the high volume pozzolan concrete itself gradually filled-in the cracks with new CSH gel (a product of the ongoing pozzolanic reaction) to cause complete re-healing after about 4.5 months. See PHOTO B.

4. 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, have a positive impact on concrete durability.

Energetically modified cements (EMC) are a class of cementitious materials each made from a raw ingredient that typically is either a pozzolan (e.g. fly ash, volcanic ash, pozzolana), silica sand or blast furnace slag (and their blends). In every case, these raw materials are treated with a patented process that is entirely mechanical in nature, as opposed to thermal or chemical (in this article, "EMC Activation"). This process, together with its effects, were first discovered in 1992 at Luleå University of Technology in the far north of Sweden.[4]

Energetically modified cements can replace more Portland cement in concrete than untreated pozzolans. This permits:

  • Performance improvements that are well-documented across a broad range of applications, and "tried and tested" in the application-environment (see final section, "Normative standards and notable U.S. projects using EMC");[5]
  • Environmental considerations — with energy and carbon dioxide (CO2) savings, without noxious emissions (see sections, "Energy and carbon dioxide savings" and "No noxious emissions and low leachability of EMCs");[6]
  • Sustainability benefits — requiring less water, and providing better durability.[7][8]

By replacing Portland cement with energetically modified cements, the resultant concretes can have the same or better physical characteristics as "normal" concretes made from Portland cement, with lower costs in terms of carbon dioxide, water and energy.[9] Accordingly, EMC Activation may be described as an "environmental technology".

Classification and field-usage potential

An energetically modified cement is a cementitious material that has been produced using the EMC Activation process (see section below, "The EMC Activation Process"). As such, the term "energetically modified cement" refers to a distinct class of cementitious materials.[8][10] Strictly speaking therefore, there are several different energetically modified cements, depending on the raw materials used. These are commonly abbreviated to "EMC" and "EMC cement" — the commonality being that all are derived from raw materials that have been treated with the EMC Activation process:

  • Although the term "energetically modified cement" may imply that such compounds are "cements", they may be more accurately be described as "cementitious materials". As such, EMC cannot fully replace conventional Portland cement in concrete, unless Portland cement itself is the raw material undergoing EMC Activation.
  • Where raw materials other than Portland cement undergo EMC Activation, the resultant energetically modified cements may be classified as "Alternative Cementitious Materials" and as "Supplemental Cementitious Materials".
  • Colloquially, energetically modified cements not made from Portland cement may be referred to as "Green Cements", on account of the significant energy and carbon dioxide savings.[11] As such, EMC Activation may be viewed as a contributor to the emerging field of eco-design.[7]

The usefulness of energetically modified cements depends on the performance characteristics required, based on the mechanical loads expected and the ambient environment. The most useful EMCs are those made from fly ash and natural pozzolans — on account of their relative abundance, the performance characteristics of the respective EMC, the relatively high Portland cement replacement-ratios made available by EMC Activation using these raw materials, together with the associated energy and carbon dioxide savings.

EMC products have been extensively tested by independent labs, including Caltrans and other concrete producers.[3][12]

History, recognition and wider resonance

The main campus of Luleå University of Technology (LTU) in Luleå, Sweden where EMC Activation was discovered in 1992. LTU is one of four universities included in Sweden’s "Universities of the Built Environment" (SBU), the aims of which include materials that "reduce energy consumption, cost and the use of resources". SBU is a cooperative between LTU, Royal Institute of Technology (Stockholm), Chalmers University (Gothenburg) and Lund University. [Note 1]

The term "energetically modified cement" (in Swedish: energimodifierad cement) is widely accepted in the academic community, first acquired in Sweden where the EMC Activation process was discovered in 1992 by Vladimir Ronin at Luleå University of Technology (LTU). Subsequently, the EMC Activation process was refined there by Dr. Ronin and others, including Lennart Elfgren (now Professor Emeritus of LTU, Division of Structural Engineering, Department of Civil, Mining and Environmental Engineering).[13]

The term "energetically modified cement" was used first in a paper by Ronin et al., in 1993.[14]

At the 45th World Exhibition of Invention, Research and Innovation, held in Brussels, Belgium, EMC Activation was awarded a Gold Medal "with mention" by EUREKA, the European inter-governmental (research and development) organisation.[15]

Given that the EMC Activation process is entirely mechanical in nature (as opposed to thermal), its potential to cause significant energy-savings has been further recognised independently for a number of years (see section below "Energy and carbon dioxide savings").[6][7] This recognition continues.[10]

In terms of energetically modified cements' potential for wider environmental benefits and EMCs' place in "low carbon" growth and development initiatives, a lecture at the Imperial College London by the former World Bank Chief Economist Baron Stern of Brentford (in Stern's capacity as a professor of the London School of Economics), was repeated by Stern when he gave the annual Sir Douglas Robb lectures at the University of Auckland, New Zealand in September 2010.[16]

Continuing academic work and research with energetically modified cements is ongoing at LTU, including work within the auspices of the Sveriges Bygguniversitet (SBU - see picture insert) and wider afield. The nascent "self healing" properties of EMCs have some resonance within the emerging field of biomimetics in the advanced material sciences and civil engineering disciplines. For example, in March 2013 Elfgren presented LTU's perspective at the Future Infrastructure Forum (FIF) held at Cambridge University, upon the invite of FIF's Chairman Campbell Middleton (Laing O'Rourke Professor of Construction Engineering, University of Cambridge).[17]

The research work connected with EMCs has received numerous awards through the years from the Elsa & Sven Thysell Foundation for Construction Engineering Research (in Swedish: Elsa ō Sven Thysells stiftelse för konstruktionsteknisk forskning) — in terms of further understanding EMC Activation together with its effects and, more recently in 2012 and 2013, towards a greater understanding of the "self-healing" capabilities of energetically modified cements (see main pictorial insert above).[18]

The EMC Activation process

In concrete, the more the Portland cement is replaced with pozzolans, the better the concrete's durability.[19] This is facet is well-settled and not controversial (the chemical basis, is set out in the section below). In sum, EMC Activation has a three-fold effect on the mineral treated: as compared to using (say) untreated fly ash, EMC Activation allows a treated fly ash to yield a faster and greater strength-development of the resulting concrete — at higher replacement-ratios. This higher replacement ratio means that the chemistry of the concrete is improved—and improved by a greater extent than just using (say) raw fly ash—nevertheless, at all times ensuring that the resulting concrete conforms to modern "21st Century" performance-requirements.[20][21]

Put simply, EMC Activation is a patented, water–, cost–, and energy–efficient, zero-emission technology intended primarily (but not exclusively) for the high replacement of Portland cement in concrete.[22] Although EMC Activation is a mechanical process, it results in a compound (typically, a processed pozzolan) which has with no material increase in overall powder fineness.[14] As such, whereas grinding techniques elsewhere rely on an increased fineness to achieve the required results (i.e., an increase of particulate surface area), by comparison EMC Activation relies on the surface activation of the particles themselves.[14] In effect, EMC Activation increases a particle's "surface energy and chemical reactivity" using "a large number of impact impulses".[23] This is quite distinct from grinding per se.

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 and surface area for the purposes of the necessary pozzolanic reactions.[24] As a technology, EMC Activation is readily and highly scalable, being well-proven to an "industrial scale".[25]

EMC Activation can transform minerals that otherwise have zero or relatively very weak "pozzolanic" characteristics. Silica sand is a case in point, which comprises an inert filler within a crystalline structure. As a result, silica sand has zero pozzolanic activity in its untreated state, yet displays a significant transformation having undergone EMC Activation. For example, silica sand undergoing EMC Activation has produced results showing that, at 50% Portland cement replacement, the degree of hydration after 1 day was 71% as compared to 45% for a silica sand blend not treated by EMC Activation — and that "even for equal hydration, at higher ages EMC will perform better".[26]  In other words, EMC Activation is able to transform "inert" silica sand into a cementitious material that exhibits "pozzolanic" characteristics.

EMC Activation allows for the higher replacement of Portland cement in concretes that nevertheless exhibit performance characteristics that fall within a project's required specifications. For example, for untreated (but refined) fly ash, the replacement of Portland cement in concrete is typically about 15-20% in order to meet such requirements.[27] By contrast, using fly ash that has undergone EMC Activation, up to 70% of the Portland cement in concrete can be replaced.[3]

Effect of EMCs on a concrete's chemistry and "self-healing"

In simple terms, using pozzolans in concrete provides a number of chemical-pathways whereby porous (reactive) Portlandite, rather than producing porous and soft (relatively reactive) calcium carbonate (that can be produced using "ordinary" concrete in a process called carbonatation), instead is transformed into a number of hard and impermeable (relatively non-reactive) compounds.[19] Many of the end-products of such a "pozzolanic" chemistry are a range of materials which share the same chemical composition as certain gemstones, with some commonly exhibiting a hardness greater than 7.0 on the Mohs scale. By comparison, Tungsten is 7.5 on the same scale.[28]

The greater the replacement in the concrete of Portland cement with pozzolanic cementitious materials (of which EMCs are an example), the greater the propensity for the foregoing.[19] EMC Activation is a process which is thought to increase a pozzolan's affinity for such pozzolanic reactions.[9][23] This is yields a faster and greater strength-development of the resulting concrete—at higher replacement-ratios—than untreated pozzolans.[20][21] As such, EMCs may be classified also as "highly reactive pozzolans". Highly reactive pozzolans are thought to yield further "stabilisation benefits" upon the pozzolanic reaction-pathways themselves (see below).

A simplified explanation for the benefits of EMCs (Pozzolanic) chemistry

In common with all pozzolanic cementitious materials (as opposed to Portland cement), EMCs improve a concrete's overall chemistry.[19] The full extent of the effects is not entirely known.[3] For the sake of this article therefore, what follows is a general example of one aspect common—to varying degrees—in all concretes comprising pozzolanic cementitious materials.

In concrete (including concretes with EMCs), Portland cement reacts with water to produce a stone-like material — in the context that the "setting" of cement, when mixed with water and aggregates to form concrete, involves a complex series of chemical reactions, the full mechanics of which are still not fully understood. That chemical process, called hydration, forms two cementing compounds in the concrete: (i) calcium silicate hydrate (C-S-H) and (ii) calcium hydroxide (Ca(OH)2). This reaction can be noted in three ways, as follows:[29]

  • Standard notation:  Ca3SiO5  +  H2O   →   (CaO) · (SiO2) · (H2O)(gel)  +  Ca(OH)2
  • Balanced:  2Ca3SiO5  +  7H2O   →   3CaO · 2SiO2 · 4H2O(gel)  +  3Ca(OH)2

In sum, the "underlying" hydration reaction forms two products:

  1. Calcium silicate hydrate (C-S-H), which gives concrete its strength and dimensional stability. The crystal structure of C-S-H in cement paste has not been fully resolved yet and there is still ongoing debate over its nanostructure.[30]
  2. Calcium hydroxide (Ca(OH)2), which in concrete chemistry is known also as Portlandite. In comparison to calcium silicate hydrate, Portlandite is relatively porous, permeable and soft (2 to 3, on Mohs scale).[31] It is also sectile, with flexible cleavage flakes.[32] Portlandite is soluble in water, to yield an alkaline solution which can compromise a concrete's resistance to acidic attack.[33]

Portlandite makes up about 25% of "ordinary" concrete.[19] In such "ordinary" concretes (i.e. made with Portland cement without pozzolanic cementitious materials), carbon dioxide is slowly absorbed to convert the Portlandite into insoluble calcium carbonate (CaCO3), in a process called carbonatation:[19]

Ca(OH)2  +  CO2   →   CaCO3  +  H2O      (cement chemist notation: CH + C  →  CC + H)

In mineral form, calcium carbonate can exhibit a wide range of hardness depending on how it is formed. For example, at its softest, calcium carbonate can form in concrete as chalk (of hardness 1.0 on Mohs scale). Like Portlandite, calcium carbonate in mineral form can also be porous, permeable and with a poor resistance to acid attack (whereupon it releases carbon dioxide).

By comparison, as a continuing part of the hydration process (and in common with all pozzolanic concretes), concretes comprising EMCs continue to consume the soft and porous Portlandite — instead turning it into additional hardened concrete as calcium silicate hydrate (C-S-H) rather than calcium carbonate.[19] This results in a denser, less permeable and more durable concrete.[19] This reaction is an acid-base reaction between Portlandite and silicic acid (H4SiO4) that may be represented as follows:[34]

Ca(OH)2  +  H4SiO4   →   Ca2+  +  H2SiO42-  +   2H2O   →   CaH2SiO4 · 2H2O      (cement chemist notation: CH + SH  →  C-S-H) [Note 2]

Further, many pozzolans contain aluminiate (Al(OH)4-) that will react with Portlandite and water to form:

  • calcium aluminiate hydrates, such as calcium aluminium garnet (hydrogrossular: C4AH13 or C3AH6 in cement chemist notation, hardness 7.0 to 7.5 on Mohs scale);[35]  or
  • in combination with silica, to form strätlingite (Ca2Al2SiO7·8H2O or C2ASH8 in cement chemist notation), which geologically can form as xenoliths in basalt as metamorphosed limestone.[36]

Pozzolanic cement chemistry (along with high-aluminiate cement chemistry) is complex and per se is not constrained by the foregoing pathways. For example, strätlingite can be formed in a number of ways, including per the following equation which can add to a concrete's strength:[37]

C2AH8  +  2CSH  +  AH3  +  3H    →    C2ASH8    (cement chemist notation) [38]

The overall role of pozzolans in a concrete's chemistry is not fully understood. For the sake of illustration, only one aspect has been considered, which alone is complex-enough. For example, strätlingite is metastable, which in a high temperature and water-content environment (that can be generated during the early curing stages of concrete) may of itself yield stable calcium aluminium garnet (see first bullet point above).[39] This can be represented per the following equation:

3C2AH8    →    2C3AH6  +  AH3  +  9H    (cement chemist notation) [40]

Per the first bullet point, although the inclusion of calcium aluminium garnet per se is not problematic, if it is instead produced by foregoing pathway, then micro-cracking and strength-loss can occur in the concrete.[41] However, adding high-reactivity pozzolans into the concrete mix prevents such a conversion reaction.[42] In sum, whereas pozzolans provide a number of chemical pathways to form hardened materials, "high-reactivity" pozzolans such as blast furnace slag (GGBFS) can also stabilise certain pathways. In this context, EMCs made from fly ash have been demonstrated to produce concretes that meet the same characteristics as concretes comprising "120 Slag" (i.e., GGBFS) according to U.S. standard ASTM C989.[20][43]

There are many other benefits to pozzolanic chemistry.[Note 2] For example, Portlandite can also react with sulphate ions to cause efflorescence, typically as either: (i) calcium sulphate (in hydrated form as gypsum or, in a sufficiently dry environment, as anhydrite); or (ii) copper sulphate (in hydrated form as a blue crystalline solid that, when exposed to air, dehydrates to form its white anhydrous counterpart). These reactions are induced by low temperatures, moist conditions and condensation. Pozzolanic chemistry reduces the amount of Portlandite available, to reduce efflorescence.[44]

"Self-healing" (Autogenous effects)

It is for the foregoing reasons (and others) that it is thought pozzolanic mortars and concretes have been observed to "self-heal".[45][46] This effect is considered a natural autogenous property.[47] By virtue that EMC Activation is a process which is thought to increase a pozzolan's affinity for such pozzolanic reactions, concretes made from EMCs are no different in this regard (see major pictorial insert above).[9][23] The same autogenous tendency been noted and studied in the various supporting structures of Hagia Sophia built for the Byzantine emperor Justinian (now, Istanbul, Turkey).[48] There, in common with most Roman cements, mortars comprising high amounts of pozzolana were used — in order to give what is thought to be an increased resistance to the stress-effects caused by the various earthquakes that have disrupted the region throughout the millennia (see also, below, "Historical context of the EMC California results").[49]

Range of concretes produced

The performance of concretes made from energetically modified cements can 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).[50] This allows energetically modified cements to yield High Performance Concretes (HPCs - see section below, "Durability of concretes produced and High Performance Concretes").[51]

Portland cement replacement-capabilities (and limitation considerations)

Generally, the strength and strength-development of pozzolan concretes depend upon the "pozzolanic" characteristics of the raw material that is employed to make it. For example, fly ash in its natural state is typically more "pozzolanic" than volcanic ash — although care should be taken not to necessarily imply that all fly ashes are per se more "pozzolanic" than all volcanic ashes. In a similar vein, the nascent characteristics of the raw material undergoing EMC Activation may also act as a consideration as to the upper limit of Portland cement replacement by an energetically modified cement.

Moreover, in practical "everyday" terms, the key consideration is a concrete's strength-development within a specified time period. In a project environment, this means a concrete will need to develop a strength within a given time period that either matches or exceeds a project's specifications. For this reason, although the replacement-ratio of an EMC made from fly ash may exceed even 70%, by comparison the current upper-limit using EMC made from natural pozzolans is 60% for practical large-scale usage.[3]

No noxious emissions and low leachability of EMCs

Unlike Portland cement production which can release a number of noxious particulate and gaseous pollutants (including mercury), EMC Activation releases no noxious pollutants.[52] It is known that noxious emissions can be caused by Portland cement production — and also that noxious emissions may be caused by the burning of fly ash. For example, in the United States:

  • Such noxious pollutants are now the subject of control, which, via the (U.S.) Environmental Protection Agency, are subject to the 2013 National Emissions Standards for Hazardous Air Pollutants (NESHAP).[53]
  • As of 2013, the implementation of the NESHAP controls have been delayed to 2015, as "it was unclear how many [Portland cement] plants would be able to comply with the new limits; the mercury limits were expected to make it difficult for cement plants to continue to burn fly ash as a raw material for clinker manufacture." [52] [Emphasis added].

By contrast, the EMC Activation of fly ash does not involve any heating or burning at all.[11] This is because EMC Activation is entirely mechanical in nature (i.e, and uses no chemicals either).

Leachability tests were performed by LTU in 2001 in Sweden, according to normative standard NEN 7345:1995, on behalf of a Swedish power production company.[54]  These tests confirmed that EMC made from fly ash "showed a low surface specific leachability" with respect to "all environmentally relevant metals." [55]  This concords with the observed impermeability of energetically modified cements.[22]  In other words, EMC Activation produces no noxious emissions, and to any meaningful degree, any heavy metals such as mercury are likely locked inside energetically modified cements — on account of encapsulation caused by EMC Activation.

Energy and carbon dioxide savings

EMC Activation's potential to cause significant energy-savings has been further recognised independently for a number of years.[6][7] This recognition continues.[10]

The sustainability and environmental savings (in terms of energy and carbon dioxide savings) that may be achieved by replacing portions of Portland cement in concrete is well understood and uncontroversial.[27] The need for the Portland cement industry to move towards greater sustainability, together with the industry's potential for an adverse impact on climate change, was acknowledged by the industry itself in 2002, via a series of independent studies commissioned via the World Business Council for Sustainable Development (WBCSD) — in which EMC Activation was discussed as a possible route for mitigating the environmental effects of the Portland cement industry.[8]

Of itself, EMC Activation produces no direct CO2 emissions. Hence, energetically modified cements present the opportunity for dramatic savings both in terms of carbon dioxide and energy-savings.[22] 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 (43.96 kWh) per ton of energetically modified cement produced.[56]

For each ton of Portland cement produced, total energy consumption is ~1,000 to 1,400 kWh.[57] The generally accepted figure for carbon dioxide production is ~1000 kg CO2 per ton of Portland cement produced.[Note 3] Whereas, all in all:

  • For each ton of EMC made from fly ash, the energy requirement for EMC Activation itself, typically can be as low as ~25 kWh. There are no direct CO2 emissions.[58]
  • For each ton EMC made from volcanic ash, the energy requirement (including drying, as above) is no more than ~80 kWh, with direct emissions of only 8 kg CO2 per ton for the drying process.[58]

Global context of projected environmental savings

In 2011, the World production of Portland cement stood at 3.6 billion tonnes.[52] An accepted figure for the energy consumed during the production of Portland cement, is 1,378 kWh per tonne produced.[57] Using these figures, together with a 25 kWh energy-requirement for EMC Activation per ton of fly ash, and the generally-accepted figure of 1000 kg CO2 for every tonne of Portland cement produced, makes it possible to approximate various savings both on a per tonne basis and extrapolated Globally — if EMC Activation was deployed to achieve various replacement-ratios of Portland cement in the concrete poured:

EMCs using Californian volcanic ash and significance

Natural Pozzolan (volcanic ash) deposits situated in Southern California in the United States. In a year-long independent study, these deposits underwent extensive testing before undergoing EMC Activation. The study found that, upon treating such volcanic ash deposits with EMC Activation, the resulting concretes exceeded the relevant normative strength-requirements, at 50% Portland cement replacement (see, accompanying text in this section).[2]

Energetically modified cements have been used in large infrastructure projects in the United States.[3] When EMC is made from fly ash, high Portland cement replacements (i.e., the replacement of at least 50% Portland cement) yield concretes consistent field results in high-volume applications.[20] This is also the case for EMC made from natural pozzolans (e.g., volcanic ash).[21]

For example, volcanic ash deposits from Southern California of the United States were independently tested. At 50% Portland cement replacement, the resulting concretes exceeded requirements:[2]

The results demonstrated that:

  • EMC Activation "has a sufficient positive impact on the water requirement to obtain satisfactory workability and strength of concrete, at about 50% replacement of Portland cement."
  • the "index of pozzolanic activity at 7 days was 80% and at 28 days was 88%, which exceeded the relevant standard's requirements (75% at both ages)." [2]

The particle-size distribution and morphology of the EMC produced were studied by Luleå University of Technology. Those studies "evidenced the improvement in the surface smoothness of particles of natural pozzolans processed by the proprietary EMC method." [2]

Historical context of the EMC California results [Note 4]

California—indeed in common with much of the western United States—has a copious abundance of natural pozzolans yet relatively very little fly ash.[60]

Although little-used today, the usage of natural pozzolans per se is not new and dates back at least 6000 years. During the 600 years or so of the Roman Empire, the Romans discovered and developed a variety of pozzolans for usage in construction throughout their empire, including the Pantheon in Rome, Italy.[61] For example, according to the Roman engineer Vitruvius Pollio, who lived in the first century B.C., the cements made by the Greeks and the Romans were of superior durability, because "neither waves could break, nor water dissolve" the concrete.[62] In describing the building techniques of masonry construction, Vitruvius indicated that the Romans developed superior practices of their own from the techniques of the Etruscans and the Greeks.[62] For example, the Greek masons discovered pozzolan-lime mixtures sometime between 700-600 B.C. and later passed their use of concrete along to the Romans in about 150 B.C.[61] Many of these ancient structures remain in good condition today, which is testimony to the durability of concretes made of such volcanic materials.[63]

In the recent times, the modern-usage of such materials figure extensively in the development of the many notable U.S. public works completed during the first-half of the 20th Century — especially in California where fly ash is relatively rare.[60] For example, in the 1920s and 1930s natural pozzolans were used as a mineral admixture in concrete, for the construction of dams and other structures then being constructed by the Los Angeles County Flood Control District and the Central Valley Project— an example of the latter being the Friant Dam in Fresno.[64] Further, during the 1930s and 1940s, a cement containing 25% interground calcined Monterey shale was produced, which was used by the then California Division of Highways (now Caltrans) as a cement in several structures, including the Golden Gate Bridge and the Oakland Bay Bridge.[65]

The usage of natural pozzolan cementitious materials continued in the 1960s and '70s, with the construction of the Second Los Angeles Aqueduct and the longer California Aqueduct.[60] Further afield, the Glen Canyon Dam in Arizona was also constructed using such materials.[60] This said, although the usage of natural pozzolans in California reached their modern-day height during the first-half of the 20th Century, the limitations were two-fold.[60] First, relatively low replacements of Portland cement (~25% maximum) were recorded.[60] Second, the raw materials were required to undergo the process of calcination — a process which of itself uses significant amounts of energy, to release significant amounts of CO2.[60] Hence, to produce concretes using ratios of volcanic materials higher than 25%, yet to concord with modern performance requirements—but without the need for any calcination process whatsoever— remained elusive throughout the United States for the entirety of the 20th Century.

By contrast, natural pozzolans undergoing EMC Activation (i.e., without any calcination process) produce concretes which meet the most stringent and recent modern-day performance requirements as stipulated by ASTM International (formerly, the American Society for Testing and Materials) and the American Concrete Institute — while allowing for the replacement of Portland cement at a ratio more than double than that achieved in the various notable U.S. civil engineering works of the 20th Century that nevertheless relied upon calcination.[3] Further, the energy requirement for EMC Activation itself is a fraction of that used during calcination, producing no direct CO2 emissions (see section immediately above).

Durability of concretes produced and High Performance Concretes (HPCs)

Diagram: "Bache method" for testing concrete durability, which simulates daily temperature variations in brine. Test 1 or 2 (each 24 h) may be used, or both performed sequentially during a 48-hour period. The chosen cycle is repeated ad nausem in order to determine the mass-loss, as an analogue for durability.

All concretes comprising energetically modified cements are highly durable: any cementitious material undergoing EMC Activation will likely marshal improved durability concretes — including concretes made with Portland cement treated with EMC Activation.

Treating Portland cement with EMC Activation will yield High Performance Concretes. These HPCs will be high strength, highly durable, and exhibiting greater strength-development in contrast to HPCs made from untreated Portland cement, which can have moderate to challenging durability impairments by comparison.[50]

For example, durability tests were been performed according to the "Bache method" (see diagram).[50] The Bache method induces the sequence of saturation by salt water of 7.5% sodium chloride (i.e., a brine, which by definition is of greater salt concentration than sea waters), followed by freezing or heating in a 24-hour cycle, in order to simulate high diurnal temperature ranges.[66] Concrete made from ordinary Portland cement without additives, has a relatively impaired resistance to salt waters.[66] Hence, the Bache method is generally accepted as one of the most severe testing procedures for concrete.[50]

Samples made of high performance concrete comprising (a) EMC (comprising Portland cement and silica fume both having undergone EMC Activation) and (b) Portland cement, having respective compressive strengths of 180.3 and 128.4 MPa (26,150 and 18,622 psi) after 28 days of curing, were then tested using the Bache method.[50] The resulting mass-loss was plotted in order to determine durability. The test results showed:

  • EMC high performance concrete showed a "consistent high-level durability" throughout the entire testing-period. For example, "practically no scaling of the concrete was been observed", even after 80 Bache method cycles.[50]
  • Whereas, the reference Portland cement concrete had undergone "total destruction after about 16 Bache method cycles, in line with Bache's own observations for high-strength concrete." [50][66]

In other words, treating Portland cement with the EMC Activation process, may increase the strength-development by nearly 50% and also significantly improve the durability, as measured according to generally-accepted methods.

All energetically modified cements also exhibit high resistances to chloride and sulphate ion attack, together with low Alkali-Silica Reactivities (ASR).[20] These features allow concretes made from energetically modified cements to exhibit superior durabilities as compared to concretes made from Portland cement, a feature common to all concretes comprising pozzolans.[33]

The characteristics of energetically modified cements are suited also to cold weather climates — a feature that has been noted by the American Society of Civil Engineers (ASCE) at least since 1997.[67] For example, an early project using EMC made from fly ash 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 annual and diurnal temperature ranges.[11][56]

Energetically modified cements' "self healing" capabilities also contribute to enhanced field-application durabilities (see major pictorial insert above) where mechanical stresses may be present.

Normative standards and notable U.S. projects using EMC

Photographic record taken from an academic paper (2010) written by Ronin and Elfgren. The photo records the large-volume application of EMC made from fly ash onto IH-10 (Interstate Highway), Texas, United States. EMC replaced not less than 50% of the Portland cement in the concrete poured — circa 2.5 times the amount of raw fly ash typically used. The project was approved by TxDOT (Texas, U.S.A) and the U.S. Federal Highway Administration (see, accompanying text in this section).[3]

Energetically modified cements comply with relevant standards and specifications.[68] In the United States, energetically modified cements have been approved for usage by a number of State wide Department of Transport agencies, including PennDOT, TxDOT and CalTrans.[3][12]

In the United States, highway bridges and hundreds of miles of highway paving have been constructed using concretes made from EMC derived from fly ash.[3] These projects include the paving of large sections of Interstate 10, which is the main U.S. Interstate highway linking Miami, Florida with Los Angeles, California.[3] In these projects, EMC replaced at least 50% of the Portland cement in the concrete poured.[20] This is roughly 2.5 times more than the Portland cement replacement typically offered by untreated fly ash per se.[27] In all projects the 28-day strength requirements were exceeded. For example, independent test-data records the highest 28-day strength at 8015 psi (55.26 MPa) against a project requirement of 4400 psi (30.34 MPa).[20]

By September 2010, over 4,500,000 cu yd (3,440,496 m3) of concrete made from EMC had been poured in such large scale projects.[3] To place this into context, that is more than the entire construction of the Hoover Dam, its associated power plants and appurtenant works, where a total of 4,360,000 cu yd (3,333,459 m3) of concrete was poured — enough to pave a standard U.S. highway, 16 feet (4.9 m) wide, from San Francisco to New York City.[69]

Another notable project is the extension of the passenger terminals at the Port of Houston, Texas. This project fully exploits energetically modified cement's ability to yield concretes that exhibit high-resistances to chloride– and sulphate–ion permeability (i.e., increased resistance to sea waters), as compared to concretes made from Portland cement.[3]

Notes

  1. ↑
  2. ↑ 2.0 2.1
  3. ↑
  4. ↑

See also

Background science to EMC Activation:

Academic:

References

  1. ↑ See, for ex., Lark, B et al., (Gardner, D.; Harbottle, M.; Jefferson, T.; and Al-Tabbaa, A.; Lees, J.; Oyen, M.; Abell, C.; and Paine, K.; Cooper, R., Heath, A.); Future Infrastructure Forum, Cambridge University (27–28 March 2013). Materials for Life (M4L): Biomimetic multi-scale damage immunity for construction materials. 
  2. ↑ 2.0 2.1 2.2 2.3 Stein, B (2012). A Summary of Technical Evaluations & Analytical Studies of Cempozz® Derived from Californian Natural Pozzolans. San Francisco, United States: Construction Materials Technology Research Associates, LLC. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 Ronin, V; Elfgren, L (2010). An Industrially Proven Solution for Sustainable Pavements of High-Volume Pozzolan Concrete – Using Energetically Modified Cement, EMC. Washington DC, United States: Transportation Research Board of the National Academies. 
  4. ↑ "Performance of Energetically Modified Cement (EMC) and Energetically Modified Fly Ash (EMFA) as Pozzolan". Justnes, H and Ronin, V SINTEF, Oslo, Norway. 
  5. ↑ Hu, J; Huang, Z; Ma, N (May 2009). "Effects of EMC Technology on the Fluidity and Strength of RPC". Journal of Hunan University (Material Sciences) (in Chinese) 36 (5): 16–20. 
  6. ↑ 6.0 6.1 6.2 Hasanbeigi, A; Price, L; Lin, E; Lawrence Berkeley National Laboratory, LBNL Paper LBNL-5434E (2013). "Emerging Energy-efficiency and CO2 Emission-reduction Technologies for Cement and Concrete Production". Renewable and Sustainable Energy Reviews (London: Elsevier Ltd) 16 (8): 6220–6238. doi:10.1016/j.rser.2012.07.019. ISSN 1364-0321. 
  7. ↑ 7.0 7.1 7.2 7.3 Kumar, R; Kumar, S; Mehrotra, S (2007). "Towards sustainable solutions for fly ash through mechanical Activation". Resources Conservation and Recycling (London: Elsevier Ltd) 52 (2): 157–179. doi:10.1016/j.resconrec.2007.06.007. ISSN 0921-3449. 
  8. ↑ 8.0 8.1 8.2 Humpreys, K.; Mahasenan, M. (2002). Toward a Sustainable Cement Industry Substudy 8: Climate Change. Geneva, Swtizerland: World Business Council for Sustainable Development (WBCSD). 
  9. ↑ 9.0 9.1 9.2 Justnes, H; Elfgren, L; Ronin, V (2005). "Mechanism for performance of energetically modified cement versus corresponding blended cement". Cement and Concrete Research (Elsevier (London) and Pergamon Press (Oxford)) 35 (2): 315–323. doi:10.1016/j.cemconres.2004.05.022. ISSN 0008-8846. 
  10. ↑ 10.0 10.1 10.2 Harvey, D (Prof., University of Toronto) (2013). Energy and the New Reality 1 - Energy Efficiency and the Demand for Energy Services. Taylor & Francis. ISBN 9781136542718. 
  11. ↑ 11.0 11.1 11.2 Hedlund, H; Ronin, V; Jonasson, J-E; Elfgren, L (1999). Grönare Betong ("Green Cement") 91 (7). Stockholm, Sweden: Förlags AB Bygg & teknik. pp. 12–13. 
  12. ↑ 12.0 12.1 United States Federal Highway Administration (FHWA). "EMC Cement Presentation January 18, 2011". Washington, DC. 
  13. ↑ LTU website. "Professor Lennart Elfgren". http://www.ltu.se/staff/e/elfgren-1.10884. 
  14. ↑ 14.0 14.1 14.2 Ronin, V.; Jonasson, J.E. (1993). New concrete technology with the use of energetically modified cement (EMC). Proceedings: Nordic Concrete Research Meeting, Göteborg, Sweden. Oslo, Norway: Norsk Betongforening (Nordic concrete research). pp. 53–55. 
  15. ↑ EUREKA is the pan-European research & development funding and coordination organization, comprising amongst others, all 27 EU Member States. See: EUREKA. EUREKA Gold Award for EMC Cement. 
  16. ↑ Stern, N (9 September 2010). "Managing the risks of climate change, overcoming world poverty and creating a new era of growth and prosperity: The challenges for global collaboration and rationality". Douglas Robb Lectures. Lecture 2, Policies for low-carbon growth and development: creating a new era of progress and prosperity (University of Auckland, New Zealand). 
  17. ↑ Eflgren, L.; Future Infrastructure Forum, Cambridge University (28 March 2013), Future Infrastructure Forum: Scandinavian Points of View 
  18. ↑ See, for example, LTU weblink (in Swedish) from 2009 available here.
  19. ↑ 19.0 19.1 19.2 19.3 19.4 19.5 19.6 19.7 Baroghel Bouny, V (1996). Bournazel, J., P., and Malier, Y., ed. Texture and Moisture Properties of Ordinary and High Performance Cementitious Materials (in PRO 4: Concrete: From Material to Structure). 144 at 156: RILEM. p. 360. ISBN 2-912143- 04-7. 
  20. ↑ 20.0 20.1 20.2 20.3 20.4 20.5 20.6 EMC Cement BV. Summary of CemPozz® (Fly Ash) Performance in Concrete. EMC Cement BV, 2012. 
  21. ↑ 21.0 21.1 21.2 EMC Cement BV. Summary of CemPozz® (Natural Pozzolan) Performance in Concrete. EMC Cement BV, 2012. 
  22. ↑ 22.0 22.1 22.2 Ronin, V; Jonasson, J-E; Hedlund, H (1999). "Ecologically effective performance Portland cement-based binders", proceedings in Sandefjord, Norway 20-24 June 1999. Norway: Norsk Betongforening. pp. 1144–1153. 
  23. ↑ 23.0 23.1 23.2 See, patent abstract "PROCESS FOR PRODUCING BLENDED CEMENTS WITH REDUCED CARBON DIOXIDE EMISSIONS" (Pub. No.:WO/2004/041746; International Application No.: PCT/SE2003001009; Pub. Date: 21.05.2004; International Filing Date: 16.06.2003)
  24. ↑ EMC Cement BV. EMC Activation Diagram. EMC Cement BV. 
  25. ↑ Klemens, T (2004). Another Mix Option: Portland Cement Substitute Yields Economic, Environmental, and Durability Benefits. United States: The Concrete Producer. 
  26. ↑ Justnes, H; Dahl, P.A; Ronin, V; Jonasson, J-E; Elfgren, L (2007). "Microstructure and performance of energetically modified cement (EMC) with high filler content". Cement and Concrete Composites (New York: Elsevier Ltd) 27 (7): 533–541. doi:10.1016/j.cemconcomp.2007.03.004. ISSN 0958-9465. 
  27. ↑ 27.0 27.1 27.2 27.3 Schneider, M.; Romer M., Tschudin M. Bolio C. (2011). "Sustainable cement production - present and future". Cement and Concrete Research 41: 642–650. 
  28. ↑ About.com. "Metal Profile: Tungsten". Retrieved 10 December 2013. 
  29. ↑ "Cement hydration". Understanding Cement. 
  30. ↑ See, for ex., Thomas, Jeffrey J.; Jennings, Hamlin M. (January 2006). "A colloidal interpretation of chemical aging of the C-S-H gel and its effects on the properties of cement paste". Cement and Concrete Research (Elsevier) 36 (1): 30–38. doi:10.1016/j.cemconres.2004.10.022. ISSN 0008-8846. 
  31. ↑ Portlandite at Webmineral
  32. ↑ Handbook of Mineralogy
  33. ↑ 33.0 33.1 Chappex, T.; Scrivener K. (2012). "Alkali fixation of C-S-H in blended cement pastes and its relation to alkali silica reaction". Cement and Concrete Research 42: 1049–1054. 
  34. ↑ Mertens, G.; Snellings, R.; Van Balen, K.; Bicer-Simsir, B.; Verlooy, P.; Elsen, J. (March 2009). "Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity". Cement and Concrete Research 39 (3): 233–240. doi:10.1016/j.cemconres.2008.11.008. 
  35. ↑ Ca3Al2(SiO4)3-x(OH)4x, with hydroxide (OH) partially replacing silica (SiO4)
  36. ↑ Webmineral.com. "Stratlingite Mineral Data". Retrieved 6 December 2013. . See, also, Ding, Jian; Fu, Yan; Beaudoin, J.J. (August 1995). "Strätlingite formation in high alumina cement - silica fume systems: Significance of sodium ions". Cement and Concrete Research 25 (6): 1311–1319. doi:10.1016/0008-8846(95)00124-U. 
  37. ↑ Midgley, H.G.; Bhaskara Rao, P. (March 1978). "Formation of stratlingite, 2CaO.SiO2.Al2O3.8H2O, in relation to the hydration of high alumina cement". Cement and Concrete Research 8 (2): 169–172. doi:10.1016/0008-8846(78)90005-4. ISSN 0008-8846.  . See, also, Midgley, H.G. (March 1976). "Quantitative determination of phases in high alumina cement clinkers by X-ray diffraction". Cement and Concrete Research 6 (2): 217–223. doi:10.1016/0008-8846(76)90119-8. ISSN 0008-8846. 
  38. ↑ Heikal, M.; Radwan, M, M, Morsy, M, S (2004). "Influence of curing temperature on the Physico-mechanical, Characteristics of Calcium Aluminate Cement with air cooled Slag or water cooled Slag". Ceramics-Silikáty 48 (4): 185–196.  . See, also, Abd-El.Aziz, M.A.; Abd.El.Aleem, S.; Heikal, Mohamed (January 2012). "Physico-chemical and mechanical characteristics of pozzolanic cement pastes and mortars hydrated at different curing temperatures". Construction and Building Materials 26 (1): 310–316. doi:10.1016/j.conbuildmat.2011.06.026. ISSN 0950-0618. 
  39. ↑ Mostafa, Nasser Y.; Zaki, Z.I.; Abd Elkader, Omar H. (November 2012). "Chemical activation of calcium aluminate cement composites cured at elevated temperature". Cement and Concrete Composites 34 (10): 1187–1193. doi:10.1016/j.cemconcomp.2012.08.002. ISSN 0958-9465. 
  40. ↑ Taylor, HFW, (1990) Cement chemistry, London: Academic Press, pp.319–23.
  41. ↑ Matusinović, T; Šipušić, J; Vrbos, N (November 2003). "Porosity–strength relation in calcium aluminate cement pastes". Cement and Concrete Research 33 (11): 1801–1806. doi:10.1016/S0008-8846(03)00201-1. ISSN 0008-8846. 
  42. ↑ See, for ex., Majumdar, A.J.; Singh, B. (November 1992). "Properties of some blended high-alumina cements". Cement and Concrete Research 22 (6): 1101–1114. doi:10.1016/0008-8846(92)90040-3. ISSN 0008-8846. 
  43. ↑ ASTM International. "ASTM C989: Standard Specification for Slag Cement for Use in Concrete and Mortars". Book of Standards Volume 4.02. doi:10.1520/c0989-10. 
  44. ↑ Nhar, H., Watanabe, T., Hashimoto, C., and Nagao, S. (2007). Efflorescence of Concrete Products for Interlocking Block Pavements (Ninth CANMET/ACI International Conference on Recent Advances in Concrete Technology: Editor, Malhotra, V., M., 1st ed.). Farmington Hills, Mich.: American Concrete Institute. pp. 19–34. ISBN 9780870312359. 
  45. ↑ Yang, Y; Lepech, M. D., Yang, E., and Li, V. C. (2009). "Autogenous healing of engineered cementitious composites under wet-dry cycles". Cement and Concrete Research 39: 382–390. doi:10.1016/j.cemconres.2009.01.013. ISSN 0008-8846. 
  46. ↑ Li, V., C.; Herbert, E., (2012). "Robust Self-Healing Concrete for Sustainable Infrastructure". Journal of Advanced Concrete Technology (Japan Concrete Institute) 10: 207–218. doi:10.3151/jact.10.207. 
  47. ↑ Van Tittelboom, K.; De Belie, N. (2013). "Self-Healing in Cementitious Materials—A Review". Materials 6: 2182–2217. doi:10.3390/ma6062182. ISSN 1996-1944. 
  48. ↑ Moropoulou, A.; Cakmak, A.; Labropoulos, K.C.; Van Grieken, R.; Torfs, K. (January 2004). "Accelerated microstructural evolution of a calcium-silicate-hydrate (C-S-H) phase in pozzolanic pastes using fine siliceous sources: Comparison with historic pozzolanic mortars". Cement and Concrete Research 34 (1): 1–6. doi:10.1016/S0008-8846(03)00187-X. 
  49. ↑ Moropoulou, A; Cakmak, A., S., Biscontin, G., Bakolas, A., Zendri, E. (December 2002). "Advanced Byzantine cement based composites resisting earthquake stresses: the crushed brick/lime mortars of Justinian's Hagia Sophia". Construction and Building Materials 16 (8). doi:10.1016/S0950-0618(02)00005-3. ISSN 0950-0618. 
  50. ↑ 50.0 50.1 50.2 50.3 50.4 50.5 50.6 Elfgren, L; Justnes, H; Ronin, V (2004). High Performance Concretes With Energetically Modified Cement (EMC). Kassel, Germany: Kassel University Press GmbH. pp. 93–102. 
  51. ↑ United States Federal Highway Administration (FHWA). What is High Performance Concrete. Washington, DC. 
  52. ↑ 52.0 52.1 52.2 52.3 52.4 United States Geological Survey. USGC Mineral Commodity Survey CEMENT (2013). USGS, 2013. 
  53. ↑ Environmental Protection Agency, U.S. (February 12, 2013). "National Emission Standards for Hazardous Air Pollutants for the Portland Cement Manufacturing Industry and Standards of Performance for Portland Cement Plants; Final Rule". U.S. Federal Register, Part II. 40 CFR Parts 60 and 63 (U.S. National Archives and Records Administration) 78 (29): 10005–10054. 
  54. ↑ See, also, NEN 7345:1995, "Leaching Characteristics Of Solid Earthy And Stony Building And Waste Materials - Leaching Tests - Determination Of The Leaching Of Inorganic Components From Buildings And Monolithic Waste Materials With The Diffusion Test".
  55. ↑ Private study, Luleå University of Technology (2001) "Diffusionstest för cementstabiliserad flygaska", LTU Rapport AT0134:01, 2001-09-03
  56. ↑ 56.0 56.1 EMC Cement BV website. EMC Cement BV, 2013. 
  57. ↑ 57.0 57.1 1,378 kWh (5.11 MMbtu) for each ton cement (i.e., including energy used in kiln), per Nisbet, M. A. (1996). The Reduction of Resource Input and Emissions Achieved by Addition of Limestone to Portland Cement. Portland Cement Association. p. 4.  (See, also, Wikipedia entry for cement: "A cement plant consumes 3 to 6 GJ of fuel per tonne of clinker produced, depending on the raw materials and the process used").
  58. ↑ 58.0 58.1 58.2 EMC Cement BV, based upon operational data. For more information, see EMC Cement website, external link section.
  59. ↑ ACI 318 "Building Code Requirements for Structural Concrete and Commentary"
  60. ↑ 60.0 60.1 60.2 60.3 60.4 60.5 60.6 ACI Committee 232 (2012). 232.1R-12 Report on the Use of Raw or Processed Natural Pozzolans in Concrete. American Concrete Institute. 
  61. ↑ 61.0 61.1 Kirby, R. S.; Withington, S.; Darling, A. B.; Kilgour, F.B. (1956). Engineering in History. New York: McGraw-Hill Book Co. Inc. 
  62. ↑ 62.0 62.1 Vitruvius Pollio, M. (1960). The Ten Books on Architecture. Vol I, New York: G. P. Putnams & Sons. p. 31.  See, external link section.
  63. ↑ For example, during archaeological excavations in the 1970s at the ancient city of Kameiros on the Island of Rhodes, Greece, an ancient water-storage tank having a capacity of 600 m³ (785 cu yds) was found. Built in about 600 B.C., it was used until 300 B.C. when a new hydraulic system with an underground water tank was constructed. For almost three millennia this water tank has remained "in very good condition" [ see, Efstathiadis, E. (1978). Greek Concrete of Three Millennia. Athens, Greece: Technological Research, Hellenic Ministry of Public Works. ]
  64. ↑ Meissner, H. S. (1950). Pozzolans Used in Mass Concrete. Symposium on Use of Pozzolanic Materials in Mortars and Concrete, American Society for Testing and Materials, West Conshohocken, Pa. pp. 16–30. 
  65. ↑ Davis, R. E. (1950). A Review of Pozzolanic Materials and Their Use in Concretes. Symposium on Use of Pozzolanic Materials in Mortars and Concrete, American Society for Testing and Materials, West Conshohocken, Pa. 
  66. ↑ 66.0 66.1 66.2 Bache, M (1983). "Densified cement/ultra fine particle-based materials". Proceeding of the Second International Conference on Superplasticizers in Concrete. 
  67. ↑ Freitag, D.; McFadden, T. (1997). Introduction to Cold Regions Engineering. American Society of Civil Engineers (ASCE). p. 738. doi:10.1061/9780784400067. ISBN 978-0-7844-0006-7. 
  68. ↑ United States Federal Highway Administration (FHWA) (2005). "Long-Term Plan for Concrete Pavement Research and Technology - The Concrete Pavement Road Map". Tracks. HRT-05-053. Vol. II (Washington, DC). 
  69. ↑ "Lower Colorado Bureau of Reclamation: Hoover Dam, Facts and Figures". FAQ. U.S. Bureau of Reclamation. 
  70. ↑  Swedish Universities of the Built Environment (SBU) is a cooperative organisation that includes the activities of research and education, connected with the "education of civil engineers". The stated aim of the SBU is to produce machines and materials which "reduce energy consumption, cost and the use of resources."   As of November 2013. See, Swedish Universities of the Built Environment, available here. LTU's core aims: of its declared 9 declared "Areas of excellence in research and innovation" two areas are comprised (i) "Attractive built environment" and (ii) "Smart machines and materials", with the ambition "be a recognised national and international research centre in the area of the built environment."  [ As of May 2013. See, Luleå University of Technology, external link, no longer available.
  71. ↑  Further notes on pozzolanic chemistry: (A) The ratio Ca/Si (or C/S) and the number of water molecules can vary, to vary C-S-H stoichiometry. (B) Often, crystalline hydrates are formed for example when tricalcium aluminiate reacts with dissolved calcium sulphate to form crystalline hydrates (3CaO·(Al,Fe)2O3·CaSO4·nH2O, general simplified formula). This is called an AFm ("alumina, ferric oxide, monosulphate") phase. (C) The AFm phase per se is not exclusive. On the one hand while sulphates, together with other anions such as carbonates or chlorides can add to the AFm phase, they can also cause an AFt phase where ettringite is formed (6CaO·Al2O3·3SO3·32H2O or C6S3H32). (D) Generally, the AFm phase is important in the further hydration process, whereas the AFt phase can be the cause of concrete failure known as DEF. DEF can be a particular problem in non-pozzolanic concretes (see, for ex., Folliard, K., et al., Preventing ASR/DEF in New Concrete: Final Report, TXDOT & U.S. FHWA:Doc. FHWA/TX-06/0-4085-5, Rev. 06/2006). (E) It is thought that pozzolanic chemical pathways utilising Ca2+ ions cause the AFt route to be relatively suppressed.
  72. ↑  Two aspects: (I)  2011 Global Portland cement production was approximately 3.6 million tonnes per United States Geological Survey (USGS) (2013) data, and is binding as a reasonably accurate assimilation, rather than an estimate per se. Note also, that by the same report, for 2012 it is estimated that Global Portland cement production increased to 3.7 billion tonnes (a 100 million tonne increase, year-on-year).  (II)  2011 Estimate of Global total CO2 production: 33.376 billion tonnes (without international transport). Source: E.U. European Commission, Joint Research Centre (JRC)/PBL Netherlands Environmental Assessment Agency. Emission Database for Global Atmospheric Research (EDGAR), release version 4.2. The 2009-2011 trends were estimated for energy-related sectors based on fossil fuel consumption for 2009-2011 from the BP Review of World Energy 2011 (BP, 2012), for cement production based on preliminary data from USGS (2012), except for China for which use was made of National Bureau of Statistics of China (NBS) (2009, 2010, 2011).   [As of May 2013. See, EDGAR, external link section].
  73. ↑  The oldest example of hydraulic binder, dating from 5000-4000 B.C., was a mixture of lime and natural pozzolan, a diatomaceous earth from the Persian Gulf. The next oldest reported use was in the Mediterranean region. The pozzolan was volcanic ash produced from two volcanic eruptions: one, sometime between 1600 and 1500 B.C. on the Aegean Island of Thera (now called Santorini), Greece; the other in 79 A.D. at Mount Vesuvius on the bay of Naples, Italy. Both are volcanic ashes or pumicites consisting of almost 80% volcanic glass (pumice and obsidian). [See, Malinowski, R., Frifelt, K. (in cooperation with Bonits, Hjerthem, and Flodin), (1993) "Prehistoric Hydraulic Mortar: The Ubaid Period 5-4000 years BC: Technical Properties", Document D12, Swedish Council for Building Research, Stockholm, Sweden, 16 pp.]

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