Published at : 25 Jan 2021
Volume : IJtech
Vol 12, No 1 (2021)
DOI : https://doi.org/10.14716/ijtech.v12i1.2818
Chatarina Niken | Department of Civil Engineering, Faculty of Engineering, Universitas Lampung, Jl. Sumantri Brojonegoro No. 1, Bandar Lampung 35141, Indonesia |
Elly Tjahjono | Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia |
FX Supartono | Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia |
This paper discusses the shrinkage rheological model of
high-performance concrete with a compressive strength of 60 MPa. This is based
on experimental research in Indonesia. Three specimens measuring 150 mm × 150
mm × 600 mm were used. Specimens were placed in a conditioned room with a
temperature of 28 3oC and relative humidity of 72±5%. Observations were
conducted over 7–800 days using an embedded vibrating wire strain gauge for
each specimen. As a result, the shrinkage rheological model was single or multi
Kelvin-Voigt in series with time-dependent disturber flow in it. Disturber flow
depends on product hydration growth, weather, pore number, size, and
distribution. The model agrees with experimental results. Moreover, it also
fits the results using high strength concrete column and high strength self -
compacting concrete cylinder.
Concrete; Model; Rheology; Shrinkage
Shrinking and expansion
naturally occur in the process of forming concrete, mainly due to hydration
reactions. Shrinking and expanding causes deformation in concrete. Deformation is the most important
structural mechanism that influences building performance. This performance is
determined by mixture design, casting time and methods, compaction, and
treatment immediately following casting, curing, and loading.
Creep and shrinkage modeling of concrete using
solidification theory was done (Hedegaard, 2020).
A review of the shrinkage behavior of conventional and non-conventional
concrete was published (Elzokra et al., 2020).
Performance is chiefly characterized by applying a rheological model (Bentz et al., 2018). Rheology applies to mixture
design and quality control, segregation, pumping, formwork pressure, and
surface finish (Ferraris et al., 2017).
Rheology is a science of deformation and flow. Heraclitus, the Greek philosopher, has revealed: “Everything flows; everything changes,” which means something that moves will alter and can change. This statement is the basic idea of rheology (Hackley and Ferraris, 2001). Particle flow occurs in concrete since its mixing. Because the viscosity change in concrete is influenced by the hydration process and environmental humidity, the change in shear stress is not directly proportional to the shear rate, so non-Newtonian behavior occurs. Non-Newtonian particle-laden fluids are more complex due to various factors (Mau et al., 2020).
Shrinkage
can be defined as a time-dependent decrease in concrete volume (American Concrete Institute, 1992). In fresh
conditions, the paste rheological model is useful in designing SCC mixtures and
reducing the extent of laboratory work, testing time, and materials used. For
hard concrete, a long-term deformation rheological
model was mentioned by Sobotka (1962) as H-StV ?N-H ?N ?StV = H-B- (K ?StV)
(H: Hooke,
StV: St Venant, N: Newton liquid, B: Bingham, K: Kelvin solid). Sobotka (1984) and Ferraris (1999) also stated that the
long-term deformation of concrete fits well with the Bingham model (H-StV ? N). Because the first model as described above
is Hooke (H), it means that the increase in load is directly proportional to
the rate of strain. This means that the sample is under
external load, so what is happening is creep. Until now, concrete
rheological models were only for creep. This matter is based on
deformation and
particle flow caused by the
applied load. In fact, without an applied load, there are microscopic
flows in the concrete due to microprestresses-solidification. In rheology, there is no clear
border between solid and liquid. Based on this condition, shrinkage can be
modeled rheologically. By seeing the rheological model, concrete behavior can
be understood quickly and easily.
Shrinkage is a natural phenomenon
that is also due to moving particles and water. After curing, concrete starts
to deform with environmental influences; thus, shrinkage is influenced by
external supply water, so the climate plays an important role. Because the
hydration process may occur for a long time, shrinkage occurs simultaneously
with hydration, causing the shrinkage mechanism to become complex. A full
understanding of long-term shrinkage behavior is needed for concrete design
with good performance. A full understanding of
long-term shrinkage behavior is needed for concrete design to reach good
performance.
The
objective of this research is to create a shrinkage rheological model to
illustrate the deformation behavior of concrete under the influence of
hydration and climate.
The main conclusion of the study is that the
rheological model of shrinkage is a single or series
arrangement of the Kelvin-Voight model with: (1) Parameters reflecting the time
that influenced the product hydration rate, hydration product number, and its maturity
as a barrier to the viscoelastic flow; (2) Parameters that reflect the initial
strain in each phase as multipliers.
This rheological model can be applied to beam, column and cylinder, heat- and moist-cured, HSC concrete and[ET1] high-strength self-consolidation concrete, and varied maximum size aggregate.
The support from the University of Lampung and the
Structure and Material Laboratory of the Faculty of Engineering, University of
Indonesia is gratefully acknowledged.
Filename | Description |
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R1-CVE-2818-20201221185029.png | Figure 1 |
R1-CVE-2818-20201221185111.png | Figure 2 |
R1-CVE-2818-20201221185205.png | Figure 3 |
R1-CVE-2818-20201221185251.png | Figure 4 |
R1-CVE-2818-20201221185328.png | Figure 5 |
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