textile cement bond enhancement

1. • Name: Muslim Hussaini Adam
• Department: Civil Engineering and Mechanics
• ID: 5102220322
• Topic: Textile-cement bond enhancement: Sprinkle
some hydrophilic powder

2. outlines
1. Introduction
2. Experimental
2.1. Materials
2.2. Bundle yarns coating
2.3. Pull-out specimen preparation
2.4. Pull-out test procedure
3. Results and discussion

3. Cement and Concrete Composites
Volume 120, July 2021, 104031
Textile-cement bond enhancement: Sprinkle some hydrophilic powder
Abstract: Textile reinforced concrete (TRC) has recently
gained significant attention in the field of construction. The
textile is made of multifilament yarns that exhibit telescopic
pull-out behavior reducing its reinforcing efficiency. The
remedy lies in epoxy coating, which facilitates full utilization
of all filaments within the yarn during loading. Nevertheless,
the obtained interfacial bonding between the hydrophilic
cementitious matrix and hydrophobic epoxy coating is
rather weak. In this study, several coating strategies were
employed to enhance the interface bonding by modifying
the textile surface with graphene oxide or cement powder.

4. Keywords:
• Textile reinforced concrete
• Bond strength
• Single-yarn pull-out test
• Textile-cement interface
• Material surface modification
• Epoxy coating

5. • 1. Introduction:
In recent years, there has been considerable interest in developing textile-
reinforced concrete (TRC) composites as a means to modify brittle cementitious
matrices into ductile composite with high tensile strength and enhanced energy
absorption. In parallel, TRC is also being considered as an alternative to steel-
reinforced concrete structures. For enhancing the performance of structural
elements vs the conventional steel rebar, carbon-based textiles are the most
promising candidates due to their lightweight, non- corrosive, and flexible nature
and their high strength/weight ratio.
An additional advantage of TRC lies in the reduced quantity of cement required for
a given construction task in comparison to conventional rebar-based methods in
which a rather thick concrete coating (50–75 mm) is required over the re-bar to
protect it against corrosion. Among the examples of built TRC-based structures
reported in the literature are a pedestrian bridge in Dresden (Germany), a curtain
wall for an office building façade in Arnhem (the Netherlands) and curved shell
elements (Germany).

6. 2. Experimental
2.1. Materials
A two-dimensional weft inserted warp knitted carbon fabric
was used (1600 tex, stitch length 4.2 mm, ITA, Germany).
As a means to isolate the influence of coating – without the
contribution of the complex fabric geometry – a single yarn
(multifilament bundle) was withdrawn from the fabric for
the pull-out tests.

7. The properties of the carbon yarn used are provided in table
1.
A two-part epoxy (EP 520, Part-A:Part-B = 10:3 (w/w), Polymer G,
Israel) was brushed on the surface of the yarn, penetrated through the
filaments and held them together as one unit. Ordinary Portland
cement CEM-I N-52.5 (Nesher Israel Cement Enterprises Ltd) was
mixed with water in ratio of w/c = 0.4 w/w to produce the cementitious
matrix. Graphene oxide (V-30, Standard Graphene, Korea), acetone
(GADOT Group, 99.8% pure AR grade), iso-propanol (Bio-Lab ltd,
Israel) were used as received.

8. 2.2. Bundle yarns coating
• As mentioned above,
individual yarns were first
separated from the fabric
and then coated. Several
yarn coating approaches
were investigated, as
detailed below and
presented schematically in
Fig. 1.

9. 2.3. Pull-out specimen preparation
• A single yarn was placed in the
middle of a silicon mold and the
cementitious matrix was then cast
into the mold. After 24 h, the
specimens were de-molded and
cured in saturated calcium-water
solution for 12 days.
• The specimens were then dried for
24h under controlled conditions
(60% humidity and 25 °C) before
testing.

10. • Fig. 2. Preparation procedure for the tested pull-out
samples: (a) cement paste cast into silicon mold with the
rigid yarn located in the center, (b) the pull-out sample
during curing in saturated Ca(OH)2 solution, and (c) the
hardened pull-out sample. Aluminum plates were used to
allow uniform stress distribution at the gripping area.

11. 2.4. Pull-out test procedure
• Pull-out tests were conducted using an
Instron 5982 instrument (Fig.3) at a
crosshead speed of 0.5 mm/min.
Aluminum plates were fastened to the long
section of the specimen with Scotch-Weld
DP 460 NS epoxy adhesive (Fig. 2c) to
allow uniform stress distribution in the grip
region. The original Instron flat grips were
used for holding the specimen (Fig. 3a).
The short section of the specimen (L = 10
mm, Fig. 2c) was held by a frame and
connected to the longer section by the
virgin yarn (Fig. 3b).

12. • Fig. 3. Pull-out test setup with the specimen. The yarn
embedded in the short section (top) was held by a frame
and pulled out by a force applied through the longer
matrix section (bottom). The dashed rectangle in (a) is
enlarged in (b).

13. • The slip of the yarn
(embedded in the hardened
cement paste matrix) as a
function of load provides
information on the pull-out
behavior of the different
systems (Section 2.2). Eight
duplicates were measured for
each coating system. A typical
load vs slip curve is shown in
Fig. 4.

14. Typical load vs slip pullout behavior of a yarn embedded in a
cement-based matrix (GO-E/NE system)
shows that the typical load vs. slip curve is divided into three
main regions. Initially, in Region I, elastic behavior follows by
partially yarn de-bonded along the yarn–matrix interface is
performed, while the end of the embedded yarn (lend, inset) is
kept stationary, i.e., no slippage (ocular observation).completely
de-bonded. Pmax – Pfr indicates the strength of the chemical
bond between the yarn and the matrix. Finally, Region III
corresponds to slippage of the de- bonded yarn, where the
resistance to the yarn slippage is due entirely to frictional
forces. Based on this behavior, four bonding parameters were
calculated:

15. The maximum bond strength (τmax) was calculated by dividing Pmax by the interfacial area
between yarn and matrix (using the average diameter of the yarn, D, and the embedded length
(L) of 10 mm)
where: Pmax – maximum pull-out load [N]; Pfr – frictional pull-out load [N]; D – average
diameter [mm] and Em –modulus of elasticity of the yarn. An average NE diameter of 1.77 mm
was used for all specimens, assuming that the additional coating (by GO and CEM) was
negligible in terms of yarn diameter; and L – embedded length [mm], 10 mm for all specimens.
These calculations assume that the bundle is a single reinforcing unit with the diameter of the
NE system.

16. 3. Results and discussion
• In TRC applications, the textile is commonly coated with epoxy to
improve the loading capacity of the yarns within the cement
matrix. Bonding all filaments into a single reinforcing unit provides
efficient reinforcement, but the hydrophobic nature of the epoxy
results in weakening the bonding between the cementitious
(hydrophilic) matrix and textile, i.e., delamination. Therefore, our
strategy was to modify the surface of the epoxy-coated carbon
yarn by decoration of the yarn with GO or cement powder
(Section 2.2) such that the decoration imparts the hydrophilicity
required for enhancing the bonding of the yarn with the cement
matrix.

17. THANKS