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Key Engineering Materials
ISSN: 1662-9795, Vol. 677, pp 53-56
doi:10.4028/www.scientific.net/KEM.677.53
© 2016 Trans Tech Publications, Switzerland
Submitted: 2015-09-12
Revised: 2015-09-23
Accepted: 2015-09-24
Online: 2016-01-27
Multi-Functional High-performance Cement Based Composite
BAŽANTOVÁ Zdeňka1, a, KOLÁŘ Karel1,2,b, KONVALINKA Petr2,c
and LITOŠ Jiří1,d *
1
Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7/2077, Prague 6,
166 29, Czech Republic
2
University Centre for Energy Efficient buildings, Czech Technical University in Prague, Třinecká
1024, 273 43 Buštěhrad, Czech Republic
a
zdenka.bazantova@fsv.cvut.cz, bkarel.kolar@fsv.cvut.cz, cpetr.konvalinka@fsv.cvut.cz,
d
litos@fsv.cvut.cz
Keywords: Strength development, rheology of fresh mixture, setting time, precast mixture.
Abstract. The paper introduces development of new type of high-performance Portland cement
based composite applicable for number of practical utilization. The fundaments of performed
research was to design mixture with controlled process of hydration, easy production, suitable time
of setting, good workability and rapid evolution of mechanical properties as well as satisfactory
long-term stability of hardened composite. Selected mixture were evaluated by means of
mechanical properties and volume changes determination.
Introduction
Application of commonly produced siliceous cement declared as pure Portland cements or blended
and standardized cements according to CSN EN 197-1, or any other additional standards brings for
the formulation of special cementitious composites number of difficulties resulting from basic
standard requests for physic-chemical parameters of commonly produced cementitious binders.
Reliable system of hydration regulation, hardening, suitable workability of fresh mixture, easy way
of placing, volumetric stability and reaching of required resistance to the designed environment
condition are the crucial parameters of the successful development of cement based composites.
Various ways for the control of the above mentioned properties are documented is the research
works [1, 2] for different binder siliceous systems. Gypsum or non-gypsum cements signify some
specifics and necessity of adjustment or corrections for practical use in case of special cementitious
composite [3, 4].
Varied possibilities of setting time regulation is described by use of plasticizers, retardants,
accelerators and other types of admixtures and various regimes of mixing as well. It is necessary to
pass the particular requirements for mixture homogeneity, reaching of final mechanical parameters
and workability with respect to the used technical devices in the real time.
Formulation of the Multi-functional Composite
Current approach to the design and material formulation of the composite materials exploits both
natural and artificial filler resources of granular or fibrous character, binding matrix usually based
on the siliceous cement which ranks to the most popular binder system. It is presented by the pure
Portland cement or so called blended cements containing various types of hydraulic or inert
additives due to technical, environmental or economic reasons. Applied additives could be latenthydraulic, pozzolanic or inert ones and their suitable granularity could contributes to the optimal
granulometry of the entire mixture and to increase total effectivity of particular components
utilization [5, 6].
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
Tech Publications, www.scientific.net. (#103440547, Technische Universitaet Muenchen, Muenchen-13/11/17,09:06:30)
54
Special Concrete and Composites 2015
Natural or artificial resources of mineral additives such as micronized limestone, silica fume, fly
ash, blast furnace slag, aluminosilicates are used to for the choose of fine or superfine parts of
siliceous composites. It is necessary to respect their basic chemical and physical properties to
prevent their potential negative impact on the final technical parameters such as setting time,
sudden loss of workability. Modern commonly used admixtures like plasticizer often contain
number of chemical substances to ensure sufficient resistance to variation in the chemical
composition of used binder [4, 6, 7].
Additional fine components over 0.1 mm are often considered as inactive parts, toward binder
system, and are usually represented by the pure silica sand however number of other rocks or
mineral base could be used, such as chamotte, carborundum, basalt, corundum, glass, etc. [4, 8].
Their technical properties determined by their structural properties it is necessary to take into
consideration during the mixture composition design [9, 10, 11]. Coarser fractions of aggregates,
over 1-2 mm, are used for economic reasons. In case of porous natural or artificial aggregates is
possible to reach interesting values of thermal conductivity and bulk density or increased resistance
to thermal loading [12, 13].
The aim of present research work was to develop the precast multi-functional concrete mixture
of easy application and high mechanical and basic physical properties. Binder system is controlled
by the traditional cement technology and regulated by at least one type of plasticizer. Air-separator
was incorporated together with fillers of optimized granularity. Granularity of studied mixture was
developed to be compatible with high doses of fibers which ensure resistance to impact and shock
loading [6, 14].
Experimental
Binding components are the products of cement companies acting on the national market which are
specific by their mineralogical composition: Čížkovice, Prachovice, Mokrá, Hranice na Moravě a
Radotín. Admixtures in the powdered form was selected from the offer of companies Sika, Basf,
Stachema, Chryso, Radka and others to cover the wide spectrum of products. Micro-fillers and
coarser aggregates were selected on the base of their economic parameters.
There are introduced results of selected recipes of the precast multi-functional concrete mixture
which were prepared by the mixing in the slow-rotary mixer for 1.5 min. Final fresh mixture was
prepared by adding water is dose 0.1 by mass. Setting time, workability and the flow test were
performed according to traditional laboratory procedures used for cement. Prismatic specimens of
dimension 40x40x160 mm were used. Evolution of mechanical properties was studied as well as the
total volume changes. Flexural test and compressive strength determination was organized
according to commonly used test [5, 15] and procedures developed on authors’ department [3].
Volume changes determination is organized as a non-contact measurement by using laser sensor
which allows data recording including the initial phases of hydration. Tested sample is inserted into
the waved molding of vertical orientation. Upper surface is equipped by the reflex plate which is
necessary to signal transfer.
Three concrete mixtures with different setting time were chosen from the large experimental
program to document process of composite development. Various setting time was obtained by
using different way of regulation. Changes in the mixture rheology were reached by the application
of super-plasticizer on the base of polycarboxylates in the combination with various proportions of
regulation system. Present simple way of modification made possible wide range of setting time –
from 10 minutes up to 5 hours. Obtained results are introduced in Table 1.
Detailed results of the evolution of mechanical properties, compressive strength fc and flexural
strength ft, are shown in Table 2. Record of volume changes is showed in Fig. 1, where is also
mentioned setting time of particular mixtures.
Key Engineering Materials Vol. 677
Flow test [mm]
Setting time [minutes]
55
Table 1. Rheology properties of studied mixtures.
Mixture
1
2
280
280
20
130
3
280
330
Table 2. Evolution of studied mechanical properties in time.
Mechanical properties [MPa]
Mix. 1
Mix. 2
Mix. 3
ft
fc
ft
fc
ft
[MPa]
0.9
1.4
3.7
8.1
13.2
19.7
1 h.
2 h.
5 h.
10 h.
15 h.
1 day
7 days
28 days
[MPa]
5.8
8.0
22.1
47.4
79.4
106.1
[MPa]
0.3
4.5
8.7
13.1
16.2
[MPa]
1.6
26.1
50.2
78.3
95.6
[MPa]
0.1
1.6
7.6
11.2
19.2
fc
[MPa]
0.8
9.5
45.5
65.3
95.5
Results of mechanical properties well documented significant influence of the properties of fresh
mixture and regulation of hydration process respectively on the final values.
Volume changes [mm/m]
0.2
Mix. 1 - 20 min
0.0
-0.2
0.0
20.0
Mix. 2 - 130 min
40.0
60.0
Mix. 3 - 330 min
80.0
100.0
-0.4
-0.6
-0.8
-1.0
-1.2
-1.4
-1.6
Time [hod]
Fig. 1 Record of volume changes of studied mixtures with different setting time.
Conclusion
The developed mixture was created by the combination of commonly used components what
significantly increases its economic aspects. Mixtures exhibited high level of workability with
respect to the very low water/cement ratio. Multi-functional composite made from the precast
mixture is well applicable for practical use, its hydration process could be simply regulated
according to actual requirements. This fact allows its wide industrial utilization. Developed
composite passed all requirements for high-performance composites – high mechanical properties
and suitable workability.
Acknowledgement
Present work was supported by the project No. CZ.1.05/3.1.00/14.0301.
56
Special Concrete and Composites 2015
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