The Real Jammy Dodger

Changes to Energetically Modified Cement page

Here are my proposals The Real Jammy Dodger (talk) 13:01, 23 August 2020 (UTC)

EMC Activation

Amorphisation: A depiction the moment of impact during HEBM.

EMC Activation's purpose is to cause a fundamental destruction to the crystalline structure of the material processed, to render it amorphous. Although this change increases the processed material's chemical reactivity, no chemical reaction is caused during the EMC Activation process.

Mechanochemistry itself can be defined as a branch of chemistry which is concerned with the "chemical and physico-chemical transformation of substances in all states of aggregation produced by the effect of mechanical energy." IUPAC carries no standard definition of the term mechanochemistry, instead defining a "mechanochemical reaction" as a chemical reaction "induced by the direct absorption of mechanical energy", while noting, "shearing, stretching, and grinding are typical methods for the mechano-chemical generation of reactive sites".

More narrowly, "mechanical activation" was a term first defined in 1942 as a process "involving an increase in reaction ability of a substance which remains chemically unchanged." Even more narrowly, EMC Activation is a specialised form of mechanical actiivation limited to the application of high energy ball milling (HEBM) to cementitious materials.

Thermodynamic Justification

More particularly, HEBM can described as increasing the chemical reactivity of a material by increasing its chemical potential energy. In EMC Activation, transferred mechanical energy is stored in the material as lattice defects caused by destroying the material's crystalline structure. Hence, the process transforms solid substances into thermodynamically and structurally more unstable states, allowing an explanation for that increased reactivity as an increase in Gibbs energy:

$\Delta G=G_{T}^{*}-G_{T}$  where, for temperature $T$, the terms $G_{T}^{*}$ and $G_{T}$ are the respective Gibbs values in the processed and unprocessed material.

At its simplest, HEBM causes the destruction of crystalline bonds, to increase a material's reactivity. From the thermodynamic perspective, any subsequent chemical reaction can decrease the excess energy level in the activated-material (i.e. as a reactant) to produce new components comprising both a lower chemical energy and a more stable physical structure. Conversely, to render the pre-processed material into a more reactive physical sate, the disordering process during the HEBM process can be justified as being equivalent to a decrystallization (and hence an entropy increase) that in part yields a volume increase (decrease of bulk density). A reverse process, sometimes called "relaxation", can be almost immediate (10^-7 to 10^-3 seconds) or take much longer (e.g. 10⁶ seconds). Ultimately, any overall retained thermodynamic effect can be justified on the basis that any such reverse process is incapable of reaching an ideal thermodynamic end-state of its own accord. As a result, in the course of the mechanical activation of minerals, reverse "relaxation" processes cannot completely decrease the Gibbs free energy that has been created. Hence, energy remains in the material, which is stored in the crystal-lattice defects created.

Net Thermodynamic Effect of HEBM

Overall, HEBM renders a net thermodynamic effect:

• The structural disordering implies an increase of both entropy and enthalpy and thus stimulates the crystal properties according to the thermodynamic modifications. Only a small fraction (approximately 10%) of the excess enthalpy of the activated product may be accounted-for as surface-area enlargement.
• Instead, the main part of the excess enthalpy and modified properties can mostly be assigned to the development of thermodynamically unstable states in the material's lattice (and not as a reduction of particle size).
• Since the activated system is unstable, the process of activation is reversible—resulting in deactivation, re-crystallization, entropy loss and energy output of system. That reverse ("relaxation") process continues to a thermodynamic equilibrium, but ultimately can never reach an ideal structure (i.e. one free of defects).
• A more complete description of such an "activation" process factors-in enthalpy also, by which according to the Gibbs-Hemholtz equation, the Gibbs free energy between activated and non-activated solid state can be represented:
  
  

$\Delta G=\Delta H-T\Delta S$   where, $\Delta H$ is the change in enthalpy and $\Delta S$ the change in entropy.

Resulting Crystalline Disorder

Where the crystal disordering is low, $\Delta S$ is very small (if not negligible). In contrast, in highly deformed and disordered crystals, the values of $\Delta S$ can have a significant impact on rendered the Gibbs free energy. Leaving aside the heat generated during the process on account of friction etc. occasioned during the activation process, the excess Gibbs free energy retained in the activated material can be justified as being due to two changes, namely an increase in ($\mathrm {I}$) specific surface area; and ($\mathrm {I}$$\mathrm {I}$) defect structure. In successful HEBM processes such as EMC Activation:

• as to ($\mathrm {I}$), only about 10% of the excess energy of such an activated product may be accounted-for as a change in surface area.
  
• as to ($\mathrm {I}$$\mathrm {I}$), almost all the imparted energy is contained in the actual structural defects in the material processed.

An approximation for EMC Activation

The relatively low value of ($\mathrm {I}$) as against the high value of ($\mathrm {I}$$\mathrm {I}$) serves to further distinguish HEBM from general grinding or "milling" (where instead the only aim there is to increase the surface area of the materials processed), thereby accounting for an explanation for the change in entropy $S$ of the rendered material in the form of elastic energy (stored in lattice defects that can take years to "relax" ) that is the "source of excess Gibbs energy and enthalpy". As for enthalpy $H$, four descriptors can be derived to provide an overview as to the total change during such an activation process:

$\Delta H_{T}=\Delta H_{d}+\Delta H_{S}+\Delta H_{A}+\Delta H_{p}$  where:

• $\Delta H_{d}$  is a measure of the dislocation density;
• $\Delta H_{p}$  is a measure of new phases (polymorphic transformation);
• $\Delta H_{A}$  is a measure of the formation of amorphous material;
• $\Delta H_{S}$  is a measure of specific surface area.
  

Because the majority of the work exacted during the EMC Activation process goes to aspect ($\mathrm {I}$$\mathrm {I}$) above, $\Delta H_{S}$ is trivial. Hence the major functions for the change in enthalpy approximate to:

$\Delta H_{EMC}\approxeq \Delta H_{d}+\Delta H_{A}+\Delta H_{p}$

In EMC Activation, the foregoing terms $\Delta H_{d}$ and $\Delta H_{A}$ are seen as being particularly prominent because of the nature of the changes in the physical structure observed. Hence, the change in enthalpy $H$ occasioned during EMC Activation can be approximated to:

$\Delta H_{EMC}\thickapprox \Delta H_{d}+\Delta H_{A}$      i.e,   $\Delta H_{EMC}\thickapprox (\rho M_{V}){\frac {b^{2}\mu _{S}}{4\pi }}\ln \left({\frac {2(\rho )^{1/2}}{b}}\right)+C_{A}E_{A}$

where:

• $M_{V}$, $b$, $\mu _{S}$ and $\rho$ correspond respectively to the molar volume of the material, Burgers vector, shear modulus and dislocation density;
• $C_{A}$ and $E_{A}$ are respectively the concentration of the amorphous phase and molar amorphisation energy.
  

From the above thermodynamic construct, EMC Activation results in a highly amorphous phase that can be justified as a large $\Delta H_{A}$ and also a large $\Delta H_{d}$ increase. The benefits of the EMC Activation being large in $H$ means that an EMC's reactivity is less temperature dependant. In terms of any reaction's thermodynamic impetus, a reactant's overall $H$ is not $T$ dependent, meaning that a material having undergone HEBM with a corresponding elevation of $H$ can react at a lower temperature (as the "activated" reactant is rendered less reliant on the temperature-dependant function $T\Delta S$ for its onward progression). Further, an EMC's reaction can exhibit physical mechanisms at extremely small scales "with the formation of thin SiO₂ layers" to aid a reaction's pathway—with the suggestion that EMC Activation increases the ratio of favourable reaction sites. Studies elsewhere have determined that HEBM can siginficantly lower the temperature required for a subsequent reaction to proceed (up to a three-fold reduction), whereby a major component of the overall reaction-dynamics is initiated at a "nanocrystalline or amorphous phase" to exbhibit "unusually low or even negative values of the apparent activation energy" required to cause a chemical reaction to occur.

Overall, EMCs are likely less temperature dependent for a chemical pathway's onward progression (see next section on Pozzolanic reactions), which may explain why EMCs provide self-healing benefits even at low arctic temperatures.

Physical Justification (Amorphisation)

Large changes in $\Delta G$, more particularly in the resultant values of $\Delta H_{A}$ and $\Delta H_{d}$ provide an insight into EMC Activation's efficacy. The amorphisation of crystalline material at high-pressure conditions "is a rather unusual phenomenon" for the simple reason that "most materials actually experience the reverse transformation from amorphous to crystalline at high-pressure conditions". Amorphisation represents a highly distorted "periodicity" of a material's lattice element, comprising a relatively high Gibbs free energy. Indeed, amorphisation may be compared to a quasi-molten state.

For EMC activation, the HEBM method used is a vibratory ball mill (VBM).  A VBM uses a vertical eccentric drive-mechanism to vibrate an enclosed chamber up to many hundreds of cycles per minute. The chamber is filled with the material being processed together with specialised objects called grinding media. In their most simple format, such media can be simple balls made from specialised ceramics. In practical terms, EMC Activation deploys a range of grinding media of different sizes, shapes and composites to achieve the required mechanochemical transformation.  In simple terms, the compressive force acting between two identical colliding balls in a VBM can be expressed:

$P=\left[\left({\frac {5m}{8}}\right)^{3/5}\left({\frac {2r}{9\pi ^{2}k^{2}}}\right)^{1/5}\right]v^{6/5}$     where,  $k={\frac {1-v^{2}}{\pi E}}$

where, $m$ is the mass of both balls, $r$ the radius, $v$ the absolute velocity of impact and $E$ the Young's modulus of the balls' material.

Due to the rapid vibration, a high acceleration is imparted to the grinding media: the continuous, short, sharp impacts on the load result in rapid particle-size reduction. In addition, high pressures and shear stresses facilitate the required phase transition to an amorpohous state both at the point of impact and also during the transmission of shock-waves that can yield even greater pressures than the impact itself. For example, the contact time of a two-ball collision can be as short as 20μs, generating a pressure of 3.3 GPa and with an associated ambient temperature increase of 20 Kelvin. Because of the short duration of the impact, the change in momentum is sigificant—generating a shock wave of duration only 1-100μs but with an assiciated pressure of up to 10 GPa and a highly localised and focal temperature (i.e., at the nanoscale) up to several thousands of degrees Kelvin. To place this into context, a pressure of 10GPa is equivalent to about 1,000 kilometers of sea water.

It has been suggested that a VBM will grind at 20 to 30 times the rate of a rotary ball mill, reflecting that a VBM's mechanism is epecially rapacious. All told, in common with other HEBM processes, EMC Activation causes crystalline destruction because of extremely violent and disprutive factors that are occasioned at the nanoscale of the material being processed. Although over in short duration and highly focal, the processes are repeated at a high frequency: hence those factors are thought to mimic pressures and temperatures found deep inside the Earth to cause the required phase change. For example, Peter Thiessen developed the magma-plasma model that assumes localised temperatures—higher than 10³ Kelvin—can be generated at the various impact points to induce a momentary excited plasma state in the material, characterized by the ejection of electrons and photons together with the formation of excited fragments (see diagram above). Expermental data gathered from localised crack generation, itself an important component of EMC Activation, has confirimed temperatures in this region as long ago as 1975.

The content here belongs in your sandbox or User subpage

Hi The Real Jammy Dodger, I suggest moving your proposal to another page as your Talk page is not the appropriate place. You can read more about User pages here which also has instructions about creating sub pages. It's fairly simple. To create your general sandbox, just type User:The Real Jammy Dodger/sandbox and select "Create". If you would rather have a named Sub page, such as User:The Real Jammy Dodger/Energetically Modified Cement Proposal, it's the same method. I will also leave you some additional information about editing Wikipedia. If you have questions or need help, you can reach out to the Teahouse. S0091 (talk) 18:10, 23 August 2020 (UTC)

Welcome The Real Jammy Dodger!

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Hello, The Real Jammy Dodger. Welcome to Wikipedia!

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Sincerely, S0091 (talk) 18:10, 23 August 2020 (UTC)   (Leave me a message)

Your proposed new section

Dear sir:

On behalf of EMC Cement BV (please see talk page of the article) we have today reviewed your changes as posted here.

Because your work is substantive, we offer no validation on any of the content nor any guidance as to its suitability for inclusion on Wikipedia. Nonetheless, we wish to thank you for your efforts and consider your work is generally accurate. We would ask you to consider the following:

1. Regarding your chosen function for the force of ball collision in VBMs, we wonder if the term "P" should instead read "F".

2. In that same section, we wonder if it should be noted that velocity as incorporated into your function "k", renders a denominator for your Force equation that has the effect of increasing that Force as v inreases.

3. We believe that your thermodynamic account is accurate but we wonder whether the focus on entropy may be confusing. We have noted you state that others have commented that an amorphous state is "semi molten". We think that aspect can be further exploited in your text because we can all agree that a "semi molten state" of the same substance must be interently less stable than its crytalline state counterpart when both are at standard state conditions.

For example, you might want to consider a note section making it clear that during a phase change delta G=0 (to yield heat when moving to a more structurally stable format). Consider liquid water to ice. This may provide an insight into why the apparent increase in entropy rendered during activation of "compund A" nonetheless may add to overall momentum in any resulting reaction at a given temperature T. Recall: delta H of lattice formation is always negative, which is thermodynamically favoured. At phase change, since the process is at constant pressure, the change in enthalpy is equal to the heat transferred from the surroundings to the system

i.e. delta S = delta H / T

In sum, at phase change (because delta G = 0) one gets to assert entropy in terms of enthalpy and hence it is phase change that "connects" the two features delta S and delta H. We do not wish to subscibe to easy trpohes that "entropy" is only about "disorder" when it is clear moving to a crystalline state, heat is exuded. A crystal may be inherently more stable and less "disordered" yet still favoured thermodynamically if the temp gradient is also faovurable (ignoring pressure for a moment just to keep it simple). Again, think freezing water.

We trust the above is helpful to you and again thank you for considering this and of course your work.

Denslenovo (talk) 18:12, 24 August 2020 (UTC)

Further Comment

Dear sir:

We hope thie following is also useful to you.

In your proposed test you state: "Overall, EMCs are likely less temperature dependent for a chemical pathway's onward progression (see next section on Pozzolanic reactions), which may explain why EMCs provide self-healing benefits even at low arctic temperatures"

You then use a citation but it's not clear which one. I have been tasked to point out your proposed words are accurate and the following papers may support your assertion:

• Ronin, V, Jonasson, J-E. (1995): High strength and high performance concrete with use of EMC hardening at cold climate conditions, Proceedings of International Conference on Concrete under Severe Conditions, Sapporo, Japan, August 1995
• Ronin, V. and Jonasson, J.-E. (1994): Investigation of the effective winter concreting with the usage of energetically modified cement (EMC) - material science aspects. Report 1994:03, Div of Struct Eng, Lulea Univ of Techn, Lulea 1994, 24 pp.
  

The papers are not available generally. However, if you wish to have copies I have been authorised to email them to you if you wish. We place no obligation on you but all you need do is use the "contact form" on the external website idnetifed already on the page.

We thank you again for all your work!

Denslenovo (talk) 10:55, 25 August 2020 (UTC)

THANK YOU!

Dear sir

Thank you for letting me know and thank you for all of your careful work.

Denslenovo (talk) 22:05, 26 August 2020 (UTC)