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Ultra high performance fiber concrete (UHPFC) is an advanced formula concrete that is proven to be more superior than conventional concrete because it embrace the qualities of steel and concrete. Therefore UHPFC properties which include high durability and strength are fully exploited in the research of rehabilitation and strengthening in concrete and even non-concrete structures. This article presents the findings of an experimental study carried out to examine the bonding strength behaviour between normal concrete (NC) substrate and UHPFC as a repair material, under flexural strength test by using third-point loading beam test method. Three types of NC substrate surface preparation were used: as-cast (without surface preparation) as a reference, wire-brushed, and sand-blasted. The flexural test results clearly indicated that all failures occurred through the NC substrate and no 

Abu Bakar, Badorul H

Azmi, Megat

Johari, MA Megat

Tayeh, Bassam A.

Zeyad, Abdullah M

English

Institutional Repository of the Islamic University of Gaza

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Flexural Strength Behavior of Composite UHPFC - Existing Concrete
Article · May 2013
DOI: 10.4028/www.scientific.net/AMR.701.32
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Flexural Strength Behavior of Composite UHPFC - Existing Concrete 
Bassam A. Tayeh2, a, B. H. Abu Bakar1, b, M. A. Megat Johari1, c  
and A.M. Zeyad3, d 
1School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, 
Pulau Pinang, Malaysia  
2Engineering Division, Islamic University of Gaza, Gaza, Palestine 
3Department of Civil Engineering, University of Science and Technology, Sana'a, Yemen 
abtayeh@iugaza.edu, bcebad@eng.usm.my, ccemamj@eng.usm.my, dzeyad_eng@yahoo.com 
Keywords: Flexural strength; UHPFC; Existing concrete; Bond strength; UHPFC; Repair material; 
Substrate; Silica fume.  
 
Abstract. Ultra high performance fiber concrete (UHPFC) is an advanced formula concrete that is 
proven to be more superior than conventional concrete because it embrace the qualities of steel and 
concrete. Therefore UHPFC properties which include high durability and strength are fully 
exploited in the research of rehabilitation and strengthening in concrete and even non-concrete 
structures. This article presents the findings of an experimental study carried out to examine the 
bonding strength behaviour between normal concrete (NC) substrate and UHPFC as a repair 
material, under flexural strength test by using third-point loading beam test method. Three types of 
NC substrate surface preparation were used: as-cast (without surface preparation) as a reference, 
wire-brushed, and sand-blasted. The flexural test results clearly indicated that all failures occurred 
through the NC substrate and no de-bonding was observed in the interface between NC substrate 
and UHPFC. The results of the flexural strength confirmed that adhesion bond strength between NC 
substrate and UHPFC was stronger than the substrate regardless, the substrate roughness. This 
proves that UHPFC is able to link and bond strongly with the substrate.  
Introduction: 
The deterioration of reinforced concrete structures is a major social problem. To minimize this 
problem and ensure effective structural management, the number and extent of repair interventions 
must be kept at the lowest probable level [1]. 
In the field of rehabilitation, the bond strength between the new and existing concrete generally 
presents a weak link in the repaired structures [2]. Good bond is one of the paramount importance 
for the success in repair works [3]. 
The extremely low permeability characteristic of UHPFC jointly with their outstanding 
mechanical properties reinforce the idea to use UHPFC to rehabilitate and strengthen the zones 
where the structures are exposed to high mechanical loading and severe environmental [4]. UHPFC 
could be used as a repair materials as it has strong mechanical bond, which formed between the 
UHPFC as an overlay material  and the substrate material [5]. 
A number of studies have used UHPFC as a repair or composite material to strengthen normal 
concrete (NC) members. However, few recent studies have evaluated the slant shear and splitting 
tensile strength of the bond between UHPFC and NC as repair material and substrate material, 
respectively [5-7]. Thus, the objective of the present study is to examine the bonding strength 
behaviour between normal concrete (NC) substrate and UHPFC as a repair material, under flexural 
strength test by using third-point loading beam test method. Three types of NC substrate surface 
preparation were used: as-cast (without surface preparation) as a reference, wire-brushed, and sand-
blasted. 
 
Advanced Materials Research Vol. 701 (2013) pp 32-36
© (2013) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.701.32
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 TTP,
www.ttp.net. (ID: 113.210.136.83-29/04/13,15:45:08)
 
 
Experimental Programme 
Normal concrete substrate and UHPFC properties. Normal concrete substrate (NC) was used as 
an existing concrete. The mixing design of NC used in this study ensures average compressive 
strengths 45MPa at 28 days. The NC used contains Type-I ordinary Portland cement, river sand 
with fineness modulus of 2.4, coarse aggregate (granite) with a maximum size of 12.5mm, a water-
to-cement ratio of 0.5 and a slump value between 150-180 mm.  The mix proportion of the NC 
substrate is presented in Table 1. A prism with dimensions 100 mm × 100 mm × 400 mm was used 
as a control. The NC prisms were tested for 28 days strength and experimental results showed the 
NC has an average flexural strength of 4.76 MPa. 
     
Table 1. NC substrate mix design 
Item Mass (kg/m
3
) 
OPC 400 
Coarse Aggregate 930 
Fine Aggregate 873 
Water 200 
Superplasticizer 4 
 
 
Table 2. UHPFC mix design 
Item Mass (kg/m
3
) 
OPC 768 
Silica Fume 192 
Sieved Sand 1140 
Micro-Steel Fiber 157 
Superplasticizer 40 
Free Water 144 
 
The mix design of UHPFC used as a repair material contains Type-I ordinary Portland cement, 
densified silica fume, well graded sieved and dried mining sand, very high strength micro-steel fiber 
and polycarboxylate ether based (PCE) superplasticizer. The steel fiber used has a fiber length and 
fiber diameter of 10mm and 0.2mm, respectively, and the steel fiber has ultimate tensile strength of 
2500 MPa. The UHPFC used has achieved an average 3 days cube compressive strength of fc’ = 165 
MPa. The mix design of the UHPFC is presented in Table 2. A prisms of UHPFC with dimensions 
100 mm × 100 mm × 400 mm were tested for 3 days strength and experimental results showed the 
UHPFC has an average flexural strength of 18.90 MPa. 
Specimens Preparation. Each of the tested specimen comprised of two different materials, being 
the NC as a substrate and UHPFC as a repair material. To fabricate the composite UHPFC/NC 
substrate, the NC substrate prism was cast with similar dimensions as the control prism, with an 
additional wide-mouthed notch of 200 mm (length) 100 mm (width) 10 mm (depth). The fresh NC 
was sealed and left to set in its moulds for 24 hours after casting. After 24 hours the NC specimens 
were demoulded and were cleaned and cured for another two days in a water curing tank. At the age 
of three days, the NC substrate specimens were taken out from the water tank for surface 
preparation. In this study, the experimental parameter is the surface texture of the substrate. Three 
different types of surface were prepared, that is (i) as cast without roughening (AC), (ii) sand 
blasting (SB) and (iii) wire brushing (WB). 
Fig. 1.a, shows the roughened surfaces of the NC substrate specimens. These specimens 
represent the substrate for the flexural test. Prior to the casting the UHPFC onto this roughened NC 
surfaces, the NC specimens were further cured in a water tank until the age of 28 days since the 
casting date. At the age of 28 days, the NC substrate specimens were left to dry for two months. 
Before casting the UHPFC, the surfaces of the NC substrate specimens were moistening for 10 
minutes and wiped dry with a damped cloth. The NC substrate specimens were then placed into 
their respective moulds with the roughening side facing upward to be overlaid with the UHPFC.  
Mixing of the UHPFC was carrying out using a pan mixer. The moulds were then filled with 
UHPFC. The composite UHPFC/NC substrate specimens were steam cured for 48 hours at a 
temperature of 90°C. At age 3 and 7 days, the third point bending strength test was performed for 
the composite UHPFC/NC substrate specimens using AUTOGRAPH AG-X, having a capacity of 
100 kN and loaded at the rate of 1 MPa/min. Fig. 1.b shows the flexural test set-up for composite 
UHPFC/NC substrate specimens. 
Advanced Materials Research Vol. 701 33
 
  
(a) (b) 
Fig. 1: (a) NC substrate with different surface treatment and (b) the third-point loading beam test 
set-up for the composite UHPFC/NC substrate specimen. 
 
Third Point Loading Beam Test Method (Flexural Strength). This test was performed to 
investigate the bonding behavior between UHPFC and NC substrate. In this test, the UHPFC is 
applied to a recess made on bottom of a prismatic NC substrate. A third point bending strength test, 
according to ASTM C 78 [8] was used to test the composite specimens. Flexural strengths of NC 
and UHPFC was tested by a third point bending strength test, according to ASTM C 78 [8] and 
ASTM C 1018 [9] respectively. In this test method, the geometry of concrete prisms 400 mm in 
length with a cross sectional area of 100 mm x 100 mm was used. The test procedure requires that 
the prism span length to be at least three times it’s depth as indicated in Fig.1.b. The load is applied 
through two points that are located at one-third of the span length from each support. As a result, 
the maximum stress is induced in the middle third of the prism. 
2bd
PL
F =  
F  flexural strength, (MPa),  
P  maximum applied load indicated by the testing machine, (N) 
L  span length, (mm)  
b  average width of specimen, (mm) 
d  average depth of specimen, (mm) 
Results and Disscusion  
The results of flexural test are shown in Table 3. The results clearly showed that all failures 
occurred via the NC substrate, as shown in Fig. 2. This behaviour was the same for the test ages 3 
and 7 days, and for all types of surface roughness, as-cast, wire-brushed and sand-blasted. These 
results in general agreed with those of R.R. Pattnaik et al. [10], who studied the bonding between 
normal concrete and different types of epoxy, for very rough substrate surface. In that study, when 
the compressive strength of the epoxy was stronger than the normal concrete substrate, the failure 
mode was through the normal concrete.  Likewise, the UHPFC used in this study had a compressive 
strength stronger than the NC substrate, so the failure occurred through the substrate. This proved 
that UHPFC was able to link and bond strongly with the substrate, particularly the bonded surface 
located in tension side. The failure generally occurred at the middle of the prism as in monolithic 
prism of NC substrate and UHPFC. These results also proved that binder materials would not be 
needed if UHPFC is used as overlay material. 
The results of the flexural strength confirmed that adhesion bond strength between NC substrate 
and UHPFC was very strong, and was stronger than the substrate regardless the substrate 
roughness.  In case of as-cast surface, although the substrate surface was not rough, the adhesion 
SB 
AC 
WB 
34 Key Engineering Materials III
 
 
bonding was stronger than the substrate, with evidence the failure occurred via the substrate as 
shown in Fig. 2.a. This can be attributed to the chemical  adhesion bond due to the action of the 
silica fume in the UHPFC along with the calcium exist in the substrate surface which together forms 
the calcium silicate, leading to improvement in the interface [11,12]. In addition, the application of 
steam curing significantly improves the hydration process [13] as well as the properties of silica 
fume thereby leading to the formation of more densified cement matrix microstructure. 
 
Table 1: Flexural strength and failure modes of composite UHPFC/NC substrate specimens 
Test 
age 
Surface 
Treatment 
Sample 
No. 
Max. 
Load 
(kN) 
Max. 
Stress 
(MPa) 
Average 
(MPa) 
Standard 
deviation 
(MPa) 
COV 
(%) 
Failure 
Mode 
3
 d
a
y
s 
As-cast 
surface 
AC1 14.24 4.27 4.27 0.00 0.04 Substrate 
AC2 14.23 4.27    Substrate 
Wire- 
brushed 
WB1 19.19 5.76 5.34 0.60 11.18 Substrate 
WB2 16.38 4.91    Substrate 
Sand-blasted 
SB1 13.84 4.15 4.64 0.69 14.84 Substrate 
SB2 17.08 5.12    Substrate 
7
 d
a
y
s 
As-cast 
surface 
AC1 16.52 4.96 5.07 0.17 3.30 Substrate 
AC2 17.31 5.19    Substrate 
Wire- 
brushed 
WB1 13.61 4.08 4.74 0.92 19.49 Substrate 
WB2 17.96 5.39    Substrate 
Sand-blasted 
SB1 18.74 5.62 5.09 0.75 14.80 Substrate 
SB2 15.19 4.56    Substrate 
 
 
   
(a) (b) (c) 
Fig. 2: Flexure failure of composite UHPFC/NC substrate, (a) as-cast surface, (b) wire-brushed 
surface and (c) sand-blasted surface. 
Summary  
As a conclusion, it can be said that: 
The results of the flexural test clearly indicated that all failures occurred through the NC 
substrate and no de-bonding was observed in the interface between NC substrate and UHPFC. The 
results of the flexural strength confirmed that adhesion bond strength between NC substrate and 
UHPFC was very strong, and was stronger than the substrate regardless the substrate roughness.  In 
case of as-cast surface, although the substrate surface was not rough, the adhesion bonding was 
stronger than the substrate, with evidence the failure occurred via the substrate.  This proves that 
UHPFC is able to link and bond strongly with the substrate, although the bonded surface located in 
tension side, no separation between the NC substrate and the UHPFC which indicates that superior 
bond behaviour of UHPFC. 
 
 
Advanced Materials Research Vol. 701 35
 
References  
[1] E. Denarié, E. Brühwiler, Structural rehabilitations with Ultra High Performance Fibre 
Reinforced Concretes, International Journal for Restauration of Buildings and Monuments, 
Aedificatio, 12 (2006) 453-465. 
[2] B.A. Tayeh, B.H. Abu Bakar, M.A. Megat Johari, Y.L. Voo, Utilization of ultra high 
performance fibre concrete (UHPFC) for rehabilitation – a review. , in:  The 2nd  International 
Conference on Rehabilitation and Maintenance in Civil Engineering (ICRMCE-2), 8-10 March 
2012 Solo, Indonesia, 2012, pp. 533-546. 
[3] H. Beushausen, The influence of concrete substrate preparation on overlay bond strength, 
Magazine of Concrete Research, 62 (2010) 845-852. 
[4] E. Bruhwiler, Rehabilitation and strengthening of concrete structures using ultra-high 
performance fibre reinforced concrete. , in:  International Conference on Concrete Repair, 
Rehabilitation and Retrofitting, 02-05 September 2012, Cape Town, South Africa, 2012. 
[5] B.A. Tayeh, B.H. Abu Bakar, M.A. Megat Johari, Y.L. Voo, Mechanical and permeability 
properties of the interface between normal concrete substrate and ultra high performance fiber 
concrete overlay, Construction and Building Materials, 36 (2012) 538-548. 
[6] B.A. Tayeh, B.H. Abu Bakar, M.A. Megat Johari, Mechanical properties of  old concrete - 
UHPFC interface. , in:  International Conference on Concrete Repair, Rehabilitation and 
Retrofitting III (ICCRRR 2012), 02-05 September 2012, Cape Town, South Africa., 2012, pp. 
1035-1040. 
[7] B.A. Tayeh, B.H. Abu Bakar, M.A. Megat Johari, Characterization of the interfacial bond 
between old concrete substrate and ultra high performance fiber concrete repair composite, 
Materials and Structures, DOI 10.1617/s11527-012-9931-1 (2012). 
[8] ASTM-C78, Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with 
Third-Point Loading). in:  American Society for Testing and Materials, West Conshohocken, 
PA 19428-2959, United States, 1994. 
[9] ASTM-C1018, Standard Test Method for Flexural Toughness and First-Crack Strength of Fiber-
Reinforced Concrete Using Beam with Third-Point Loading, American Society for Testing and 
Materials, West Conshohocken, PA 19428-2959, United States, (1997). 
[10] R.R. Pattnaik, P.R. Rangaraju, Analysis of compatibility between repair material and substrate 
concrete using simple beam with third point loading, Journal of Materials in Civil Engineering, 
19 (2007) 1060. 
[11] H.C. Shin, Z. Wan, Moisture effects on the interfacial shear bond strength of SCM concretes 
International Review of civil Engineering, 2 (2011) 129-136. 
[12] B.A. Tayeh, B.H. Abu Bakar, M.A. Megat Johari, A.M. Zeyad, The role of silica fume in the 
adhesion of concrete restoration systems  Advanced Materials Research, 626 (2013) 265-269. 
[13] L.K. Askar, B.A. Tayeh, B.H. Abu Bakar, Effect of different curing conditions on the 
mechanical properties of UHPFC, in:  Awam International Conference on Civil Engineering 
(AICCE’12) and Geohazard Information Zonation (GIZ’12) , 28th-30th 2012, Penang, 
Malaysia., 2012, pp. 444-449. 
36 Key Engineering Materials III
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