Anticipated C-S-H gel volume increase in High-Energy Mixing (HEM) process

“For C-S-H it is widely accepted that the nano scale structure controls many engineering properties such as the

elastic module, creep and drying shrinkage” (Hamlin M. Jennings, Jeffrey W. Bullard “From electrons to

infrastructure: Engineering concrete from the bottom up”, Cement and Concrete Research, 2011)

Technology of HEM (see invention US2013-0305963A1) is an effective way to increase and/or establish required

level of quantity of C-S-H gel starting from the regular volume which is created in conventional mixing technology.

HEM technology begins and ends at the first step of creation cement based materials, i.e. during the process of mixing.

The main idea of HEM is to provide most favorable conditions for absorption the mechanical energy by the mixture.

With increased energy absorption more water attracts by the cement particles and the process of cement hydration

develops dipper and faster with formation additional portion of nano structured C-S-H gel.

With this point of view it is necessary to evaluate effectiveness of different variants of HEM process in comparing

with conventional mixing.

According R.A. Olson at al. “Interpretation of the impedance spectroscopy of cement paste via computer

modeling”, (Journal of material science 30, 1995, page 5081) the process of cement hydration is continuing at the

temperature below 0oC, where the freezing of bulk water in the macro pores ends at -8

oC because high ionic strength

of the pore solution.

The supersaturated solution filling C-S-H gel smaller capillary pores freeze from the temperature below -23oC and

above -40oC. Therefore the reactions of cement hydration are able to continue there at the range of temperature from

minus 8oC to -23

oC where the solution said above doesn’t freeze.

The determination of the Penetration Resistance developing in setting and hardening of cement past or mortar is

the convenient method for determination the kinetics of cement hydration in order to compare different mixtures

placed in different conditions. At the range of temperature shown above increase of the Penetration Resistance will

give evidence about continuous cement hydrations in capillary pores of C-S-H gel and developing its nanostructure.

To compare the process of C-S-H gel formation in the mixtures activated with HEM and conventionally mixed author

contained samples of both mixes in freezing camera at temperature -15oC during 96 hours with determination of the

Penetration Resistance after every 24 yours. The tests with the Penetration resistance determination were fulfilled after

thawing of frozen samples during approximately one hour with the increase of temperature of mixes from -15oC to

+15oC. See results Fig 1, 2.

Fig 1. Penetration Resistance development at temperature below -8oC for cement-water mixture.

Conditions: W/C = 0.297, Superplasticizer SiKa 6100-1ml/kg of activated and control mix,

Time of activation 3.5 min,

Average speed N = 2464 rpm,

Average Absorbed Power = 407 wt/Kg, Efficiency coefficient = 0.63,

Average Re number = 161,

Average Power number = 1.48.

Increase of graph area (Fig 1) for activated mix in comparing with regular one is 96%. Thus the anticipated increase of

C-S-H gel volume is almost 2 times as a result of High-Energy Mixing.

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Penetration Resistance at -15oC

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Fig 2. Penetration Resistance development at temperature below -8oC for cement-sand-water mixture.

Conditions: C/W/S = 1.0/0.376/2.0, Superplasticizer ADVA-190 4 ml/kg of activated mix, 1.8 ml/kg of control mix.

Time of activation 4 min,

Average speed N = 1695 rpm,

Average Absorbed Power = 132 wt/Kg, Efficiency coefficient = 0.39,

Average Re number = 141,

Average Power number = 0.73.

Increase of graph area (Fig 2) for activated mix in comparing with regular one is 213%. Thus the anticipated increase

of C-S-H gel volume as a result of High-Energy Mixing is more than 3 times.

CONCLUSION: The volume increase of nanostructured C-S-G gel is a main result of The High-Energy Mixing in

conditions of quasi laminar flow of the cement based mixtures when Re number less than 800 according the invention

US 2013-0305963A1.

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