Ursula P ott, Clemens Ehm, Cordula J ak ob, Dietmar Stephan
In vestigation of the Earl y Cement Hydration with a
Ne w P enetration T est, Rheometr y and In-Situ XRD
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P ott, U ., Ehm, C ., J akob , C ., & Stephan, D . (2019). Inv estigation of the Ear ly Cement Hydration with a Ne w
P enetration T est, Rheometr y and In-Situ XRD . In RILEM Bookseries (pp . 246–255). Spr inger Inter national
Pub lishing. https://doi.org/10.1007/978- 3- 030- 22566- 7_29.
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Investigat ion of the early cement hydr ation with a new pe netration
test, rhe ometry and in - situ XRD

U rsula Pott 1 , C lemens Ehm 1 , Cordula Jakob 2 , D ietmar Stephan 1
1 Building Materials and Construction C hemistry, TU Berlin, Berlin, Germany
2 G eoZentr um Nordbayern, Mineralogy, FA U Erlangen - Nuernberg, Erlangen, Germany

Abstract
To gain more information about the relationship between ear ly c ement hydration and
rheolog ical behavior of the corresponding cement pas te , a new penetrati on test device,
with the n ame “Multip urpose Incre mental Loadin g device” (MIL D ), has been devel-
oped. The construction and the mechanical properties of the device are described in
detail. F urthermore, the implementati on of a measu rement and firs t results will b e dis-
cussed, and the new device is compared with the standard ized Vicat test. I n addit ion, a
comparison of the measuremen t results with rheological invest igations is made and the
results of quantitative in- situ XRD and ca lorimetry are integrated for a deeper u nder -
standing. We show that it is possible to get more info rmation abo ut the structur e for-
mation with the new device tha n with the Vi cat test. Moreover, a comparison with th e
rheological propert ies of a cement paste was don e. Both methods show two periods
with diffe rent rheologic al behavior . Duri ng the first two hours the paste show s a slow
increase of v iscosity which is followed by a strong increase . T he results of the penetra -
tion test an d the rheometer are l inked with the for mation of hydration products and the
heat flow development . This com parison shows that the l ink between the two peri ods
is the beginning of the acceleration p eri od. Finally, it is conc luded that it is possible to
get precise information about the early cement hydration with a p enetr ation test.

Keywords : Penetration test ; early cement hydration ; phase forma tion; Rheology.
1. Introducti on

The early cement hydration and the developi ng rheological and mechanica l properties
of the fresh mate rial have a sign ificant imp act on many applications of cementitious
products. Neverth eless, the complex process es especially during early cement h ydra-
tion are barely understood. However, in many areas, it is important to know in detail
how a fresh paste or concret e will behave, and wh ich properties can be expected. T he
relationships between the processes of ear ly cement hydration and the rheological prop-
erties of a cement paste a re of importa nce in view of the increasing deve lopment of 3D
printing of concrete [1,2]. There are several commonly used penet ration tests in th e
field of civ il engineering like the Vic at needle, the Hilti nail gun an d the Gillmore ne e-
dle . Moreover, there are two diffe rent types of penetration tests. S ome devices measure
the penetratio n resistance at a given speed and oth er devices measure the penetration
depth at a given load [3] . In this paper , we will co mpare the new device with the most
widely used and standardized Vicat test . Th is method measure s the pene tration depth
whereas the Multipurpo se Incremental Loading device ( M ILD ) measur e the penetra-
tion resistance. Penetration tests can also b e considered as rheological investigations
[4] . During penetration tests where the penetration depth is measured, the needle is
hindered from further penetration by the yield point of the paste . Consequently, the

resistance to needle penetration at a given speed is also affected by the yield point [3].
For this stu dy, the chemical pro cesses of early cement hydratio n are particularly i m-
portant. These processes is desc ribed by Jansen et al. [5].
2. Materials

2.1 Materia ls
Ordinary Portland cement (OPC, CEM I 42.5 R) provided b y HeidelbergCement was
used and its chemical and minera l composition are given in Table 1. The specif ic sur-
face measured by Blain e is 3699 cm²/g ± 23 cm²/g and d eionized w ater was used .
Table 1. Phase con tent (QXRD) and chemical composit ion ( XRF ).
Phase

wt. -%

Phase

wt. -%

Oxide

wt. -%

Oxide

wt. -%

Alite

57.4

Anhydrite

2.5

CaO

64.33

Na 2 O

0.20

Belite

14.0

Bassanite

2.5

SiO 2

20.51

K 2 O

0.74

C 3 A cubic

6.6

Gypsum

-

Al 2 O 3

5.28

SO 3

2.96

C 3 A orth.

3.1

Calcite

3.4

Fe 2 O 3

2.49

TiO 2

0.29

Ar canite

0.7

MgO

1.4

2.2 Sample preparati on
Cement paste w as prepared with 650 g cement and a water to cement ratio of 0.36 under
20.0 °C ± 0.3°C and a relative humidity of 65 %. A stand mixer (Kitchen Aid, Type
5K45) w as used to prepare the sample with the f ollowing process: The mixing proce-
dure started after the wat er addit ion. It started at le vel 1 (58 rounds per minute (rpm))
for 15 s. After that the sp eed was increased to level 4 ( 125 r pm ) for 45 s and then level
10 (220 rpm) f or 30 s. This was followed by a 90 s brea k to rid the edges of the bowl
of cement paste. The last step involves mixing at level 10 for another 60 s.
3. Methods

3.1 Multipurpose Inc remental Loading D evice (MIL D)
3.1.1 Constructi on
The MIL D was designed and built at the TU Berlin. With this device two different
measurements can be performed. The fir st one is a compress ive strength test for s mall
sample cubes and the second one is a penetration t est with constant penet ration speed .
In this paper, we will focus on the penetration test of cement past . The device is com-
bined by the following part s: T he ste pper motor drive , the pistil with the pe netration
needle, the casing of electronic control unit , the sample tab le and the can tilever under
the table (F ig. 1a ) . The stepper motor drives the vertically mounted revolving ball spin-
dle (propulsion acc uracy >200 μm). On the spindle, a head is attached with a stam p
plate , which can move up and down. In t his stamp different needles can be clamped
(Fig. 1b). The do wnward movement forces the ne edle into the sample, which is loc ated
on the sample table. The table is fit ted on a cantilever . On the top of the cantilever are
electrical condu ctors t hrough which an electri c current flow . Stretching the cantilever
also stretches the co nductor. As a result, the volta ge and thus the resistance increases.
Once calibrated, this a llows the measurement of the applied f orce by the analysis of the
resistance. Through the progress of hydration, the resi stance to penetration of the sam-
ple increase s. This increasing force i s measured as a function of time .

a) b)
Figure 1 . a) MIL D (1) step per motor drive (2 ) needle (3) e lectronic cont rol unit (4)
sample table (5) can tilever under the table b) needle 1 (left), needle 2 (rig ht) .
3.1.2 Implemen tation
For a measurement a mo u ld with a diameter of 9 cm and a h eight of 3 cm was filled
with ceme nt paste direc tly after mix ing. The mea surement sta rted 10 min after water
addition. The head with the need le automatically goes up and down (speed: 0,7 mm/s) .
However, the sample ha s to be m oved manually, and the needle must be cleaned after
each measurement. The maximum force that can be measu red is 100 N.
3.1.3 Error Analysis
When developing a prototype, taking errors into account is essential. A corr ect inter-
pretation of the results can only be ensured by a comprehensive examination of the
errors. A major error du ring a measu rement is the fact that th e table, which is fixed on
a cantilever, travels under the load. Due to the force exerted by the needle on the mould
and thus on the table and the cantilever, the table moves down wards by a certain length.
Therefore, the needle does not reach the set dept h, but only the depth minus the defor-
mation of th e cantilever . Consequently, it is possible tha t the force at the exact depth
would be greater than the force at the indeed depth. To evaluate this error, the defor-
mation of the cantilever is recorde d prior to each measurement. A c alculation has
shown that this leads to an error of 0.5 %. T h e measurements of the cantilever a re
dependent on the temperature. Since the de vice is operated in an air -conditioned room
this error is negligible. Another error can be c aused by the stepper motor drive system.
There is a speed range where the motor runs smoothly. If the motor is forced to move
in very h igh or low spe eds it is pos sible that the motor skip s teps. Due to t est runs w ith
high and low speeds , it is expected t hat this error is neg ligibly smal l in the performed
experiments. Since the MIL D is a prototyp e, further errors may occu r which have not
been considered before. For this reason, a maximum error of 0.5 is increased tenfold,
so that an error of 5.0 % is assumed.
3.2 Vic at
The method for the determination of the initial and the fina l setting of a cement paste
is a standard ized procedure ( EN 196 -3) [6]. According to this standard, the procedure
must be carr ied out at the w /c- ratio determined by the standard sti ffness , defined by the
same standard, w hich was in this case at a w/c - ratio of 0.31 . To ens ure comparab ility
with the other tests of this work, i t has deviated from the st andard and th e Vicat metho d
was carried out at a w/c - ratio of 0.36. In addition, the sample preparation was carried
out as described in section 2.2. Initial and final setting were deter mined as described in
the standard.

3.3 Rheology
The rheological measurements are carried out using a spe ed controlled rotational rhe-
ometer (Vi skomat NT, Schleibinger , Germany). During a meas urement the ce ment
paste flows around the stationary paddle and generates a torque, which can be meas-
ured. The measuring range of the torque is between 0 and 500 Nmm and the range of
the speed is between 0.001 rpm and 400 rpm. The used geometry is a fish bone paddle.
For the in vestigation o f the early cement hydrat ion longer mea surements were p er-
formed. F or this purpose, a velocity of 0.001 rpm was run every half hour. Since the
first formed crysta ls should not be destroyed, pre - shear was waived. For e ach measure-
ment a new sample w as prepared and stored at 20 °C.
3.4 In - situ Q XRD
In order to examine the phase evolution in the first hours of the cement hydration in-
situ XRD measure ments were perfor med (20°C ± 0.2 °C) . The sample was covered by
a 7.5 µm thick Kapton® polyimide film to avoid water evaporation and CO 2 intake o f
the paste. The diffract ion patterns were recorded every 1 0 min by a Bruker AXS D8
Advance d iffractometer in Bragg- Brentano geometry from 7° to 55° 2Θ and a step
width of 0.0236° 2Θ. Three preparations were measured over a time frame of 6 h. The
Rietveld analysis was performed using the software TOPA S 5.0 (Bruker AXS). The
external stan dard G - Factor method [7] was used to gain absolute amounts of the crys-
talline phase s present in the paste.
3.5 Heat flow c alorimetry
A TAM Air calorime ter was used to measure th e heat flow evolution o f the system a t
20 °C ± 0.2°C. A custom made InMixEr [8] device was u sed which allows equilibra-
tion, inje ction of water and mixing i nside the cal orimeter. Th is experimenta l setup en-
ables the p roper detect ion of the heat flow direct ly from the time of mixin g on. Cement
and water were mixed to a paste at 860 rpm for 1 min. Th ree measurements were per-
formed.
4. Results and discussion

4.1 MIL D
Two needle sizes were teste d, and the results are show n in Fig. 2. T he trend line can be
determined by using a power - law formul a of the type 𝑓𝑓 ( 𝑥𝑥 ) = 𝑎𝑎 ∗ 𝑥𝑥 𝑏𝑏 [9,10]. It is easy
to see tha t the repro ducibility o f both needle geometries is very good. As expected, the
figure shows that the needle geo metry is directly rela ted to the dura tion of the meas -
urement. The smaller th e surface of the needle, the longer a measur ement takes. I t c an
be clearly se en that the early p eriod of the measurement c an’t be described by an ex-
ponential function. Based on the results, one can therefore recognize two different pe-
riods . In the first period , t he force shows a rather small increas e and after a certain time,
the force increases sign ificantly faster. T he second period can be described by an ex-
ponential function. A distin ction in t hese two periods wa s also done by M antellato et
al. [10] . At this p oint, it can b e stated that n eedle 1 is advantageous if a longer period
is interesting. On the other hand, it is les s sensitive during the first hou rs of cement
hydration. In this period needle 1 shows almost a plateau . Needle 2 is advantageous if
the early cement hydration is important. In the f irst period it shows a steady increase .
The influenc e of the surface and the angle of the need le tip must be furthe r investigated .

a) b)
Figure 2. Results of the MIL D test in a logar ithmic scale .
4.2 Compar ison to Vicat
Fig. 3 shows the resu lt of a Vicat - test and the fitte d curves of the MIL D. Based on t he
Vicat - test th e initial setti ng (IS) and the fina l setting (FS) c an be determi ned. The IS
occurs after about 4.8 h and ends after 6.5 h. Up to a time of about 4.5 h, nothing can
be measured w ith the Vicat method. The surface of the needle is too small and ful ly
penetrates the paste. Fro m the IS the penetration decreases, which ends with the FS.
In compari son one can g et more info rmation about th e structure fo rmation and the fol-
lowing inc rease of the strength and viscosity wi th the resu lts of the MIL D . In the te st
results of the MIL D no significant p oints can be seen at th e time of the in itial and final
setting determined by Vicat. For that reas on, one can conclude that the setting accord-
ing to Vicat is not caused by a signification change of the structure [11].

Figure 3. Results of a Vicat - te st and the MILD.
4.3 Rheological Mea surements
The rheological measu rements were carried out up to 4h after water addition and with
a speed of 0.001 rpm. Saake et al. found out that at low speeds it is possible to measure
the elasti cally deform ation of the fir st formed hydration products till they reach their
elastic l imit and the bon ds start to break [12]. Such a measured curve can be seen in
F ig . 4a. Based on th is investigation, w e assume that we can use thi s method to measure
the micros tructure form ation (mainly ettringite) . How ever , the peak as shown in Fig .
4a can’t be seen so clearly in every measurement. For this re ason, the mean of the five

last values is used for the evaluation. The results of the rheolo gical measurement show
an increas ing curve with two different periods (Fig. 4b) . The first period starts after th e
water addition and ends after about 2 .15 h. This pe riod is characterized by a rathe r slow
increase in torque and thus in visco si ty. The second period sta rts after about 2 .15 h.
This period sh ows a large inc rease in torqu e over time. It is intere sting to see that the
rheological measuremen t shows t he same kink at about 2.15 h like the MILD results.
a) b)
Figure 4. a) Result of a rheological measurement after 30 minutes at a speed of 0.001
rpm b) Rheolo gical meas uremen t of a cement paste at 20 °C at a speed of 0.001 rpm.
4.4 In - situ XRD a nd calorimetry
Fig . 5 shows the phase development measured by in - situ QXRD and the heat flow evo-
lution of the cemen t paste dur ing the first 6 h of hyd ration. In th e first 2 .15 h no signif-
icant decrea se in the amount of alite can be observed. After wards it shows a steadil y
increasing reaction r ate. In the first hours th ere is no s ignificant pr ecipitatio n of port-
landite. The determined contents are below the detection lim it of 0. 5 wt. -%. Over the
whole measured time f rame no C -S-H- Phase can be detected, even though it can be
expected from the dissolution of alite and portlandite precipi ta tion. This is caused by
the used phase model published by Bergold et al. [13] for th e Rietveld refineme nt which
is just capab le for the dimeric or “lo ng- range ordered” C -S- H. The earlier precipitated
monomeric or “s hort - range ordered” C -S - H can’t be detected by this model [1 4] , but
occurs simultaneously with alite dissolution and portlandite precipitation [15].

Figure 5. Alite, C -S - H, portlandit e and ettringite ( QXRD) and heat flow (c alorimetry) .

The onset of the acceleration period of the silicate rea ction is related to the beginning
of the second heat flow event. After a very high initial heat flow and a subsequent
period of low heat release the heat flow starts to increase at 2 .15 h. The experimental
results so far show n o evolution in the silic ate reaction (dissolu tion of alite respectively
precipita tion of CH and C -S- H) in the fi rst 2 .15 h. Alite content is constant up to 2. 15 h.
The only phase which develops considerably during this perio d is t he hydration product
of the alu minate reac tion, ettring ite. The precip itation of ettringite s tarts direc tly after
the addition of water . After around 2. 15 h the second peri od starts. Ettr ingite conte nt is
still inc reasing during th at period . Now alite is d issolving af ter about 2. 1 5 h and the
formation of portlandite can be detected after 3.5 h indicating the start of the formation
of C-S- H.
5. Conclusion

5.1 Advantages of the new penetration test dev ice
In this study a new penetration test device was investigated. Based on th e results, the
development of early cement hydration can be better investigated than with the stand -
ardized Vicat te st. It is possible to me asure the early and sen sitive phase format io n with
a penetration test device and to determine the beginning of the acceleration period. By
being able to use different needle geometries very sensitive c hanges i n cement hydra-
tion can be measured. T he results correlate perfectly with tho se of other mea surement
methods such as rheometry , Q XRD and calori metry ( Fig. 6) . Consequent ly, this device
can lead to a better understanding of early cement hydration.
5.2 Comparison with the formation of hydrati on products
According to the present data two periods of dif ferent rheological regimes can be ob-
served by either MIL D or rheometer as shown in Fig. 6. Period 1 (0 - 2.1 5 h) with low
slope for MIL D and rheometer meas urements is du e to formation of ettr ingite. Period 2
(2.15 h - 6 h) with high slope for MIL D and rheometer measurements is c orrelated with
ongoing formation of ettringite and additionally related to the C -S- H formation (indi-
cated by d issolution of a lite).

Figure 6. Conclusion o f the results o f QXRD, ca lorimetry, MIL D and rheometry.

6. Acknowledgement

The author would like to thank the German Research Foundation (DFG) for funding
the p riority program Opus Fluidum Futurum – Rheology of reactive, multiscale, multi-
phase construction materials (SPP 2005) (STE 1086/181; NE 813/7 -1) and Heid el-
bergCemen t for providin g the materi al s.
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