Expected increase C-S-H volume in cement based mixture as a result of High - Energy Mixing based on Penetration Resistance development in conditions below -8 degree Celsius.

1. vfrid38@gmail.com
© Copyright 2016 by Vladlen Fridman
Expected increase in the volume of C-S-H gel with High-Energy Mixing (HEM)
“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)
The HEM technology (see the invention US2013-0305963A1) is an effective way to increase and/or establish a
required quantity of C-S-H gel starting from the volume observed in conventional mixing technology. The HEM
technology begins and ends during the process of mixing. The main idea of HEM is to provide the most favorable
conditions for absorption of the mechanical energy by the mixture. With increased energy absorption, cement particles
attract more water, resulting in deeper and faster hydration of cement accompanied by an increased volume of nano-
structured C-S-H gel.
Thus, it is necessary to evaluate the effectiveness of different HEM processes and compare them with conventional
mixing.
According to R.A. Olson et al. “Interpretation of the impedance spectroscopy of cement paste via computer
modeling” in Journal of Material Science 30, 1995, page 5081, the process of cement hydration continues at the
temperature below 0o
C, where the freezing of bulk water in the macro-pores ends at -8o
C because of the high ionic
strength of the pore solution.
The supersaturated solution filling smaller capillary pores of the C-S-H gel freezes between -23o
C and -40o
C.
Therefore, the reactions of cement hydration are able to continue there at the range of temperature from - 8o
C to -23o
C
where the aforementioned solution doesn’t freeze.
How penetration resistance (ASTM C403) develops characterizes setting and hardening of cement paste or mortar.
One indicator of the cement hydrations in capillary pores of C-S-H gel is the continuing increase in penetration
resistance at the range of temperature shown above.
To compare the process of C-S-H gel formation in the mixtures activated with HEM with conventionally mixed, the
author placed samples of both mixes in a freezing camera at temperature -15o
C during 96 hours, determining
penetration resistance after every 24 hours. These tests were done after thawing frozen samples during approximately
one hour with the increase of temperature of mixes from -15o
C to +15o
C. See results Fig 1, 2.

2. Fig 1. Penetration Resistance development at temperature below -8o
C 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 expected increase of
C-S-H gel volume is almost 2 times as a result of High-Energy Mixing.
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 20 40 60 80 100
PenetratiionResistance,psi
Hours
Penetration Resistance at -15oC
Act. Psi
Contr. Psi

3. Fig 2. Penetration Resistance development at temperature below -8o
C 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 expected increase of
C-S-H gel volume as a result of High-Energy Mixing is more than 3 times.
CONCLUSION: An increase in the volume of the nanostructured C-S-H gel is the basic result of The High-Energy
Mixing of cement based mixtures under the conditions of quasi laminar flow when the Re number less than 800
according the invention US 2013-0305963A1.
0
1000
2000
3000
4000
5000
6000
7000
0 20 40 60 80 100 120
PenetrationResistance,psi
Hours
Penetration Resistance at -15oC
Act.psi
Contr. Psi