Materials and mix proportions

The
details of mix proportions used in this research are given in Table 1. Ordinary
Portland cement type (I) with high grade 52.5N and silica fume (SF) were used
as cementitious materials. The chemical compositions and physical properties of
the cementitious materials used are listed in Table 2. For all test specimens,
a W/C of 0.18 was applied. Sand with grain size smaller than 0.6 were used.
Natural crushed basalt graded from 1.18 mm to 10.0 mm (max. nominal size) was
used as a coarse aggregate. To improve fluidity, a high performance
water-reducing agent, Sikament – NN super plasticizer (SP) was added. to
investigate the effect of steel fiber volume fraction and aspect ratio on the
mechanical properties, steel fibers with a length of 30 mm and a diameter of
1.0 mm and steel fibers with a length of 50 mm and a diameter of 1.0 mm were considered
in three different volume fractions (0%,1%, 2% and 3),with aspect ratios (50
and 30) leading to seven series of test specimens. The properties of steel
fiber are presented in Table 3. The test specimens were cured at clean tab
water for 28 days.

Compression test

The
compression test was carried – out on cube specimens (100 * 100 * 100 mm) and
cylinders with (100 mm diameter and 200 mm height) after 28 days curing. The
preparation of the cylinders for testing was somewhat more involved than that
normally used for cylinder testing. The largest difference is that the end
planeness of the cylinders was ensured through the use of an end grinder.
Compression tests were completed primarily according to the ASTM C39 standard
test method for cylinders and the ASTM C109 standard test method for cubes. A
slight modification to ASTM C 39 and ASTM C109 was made to make the testing of
UHPFRC more practical, namely the increase of the load rate applied to the
specimen. The current standard sets the load rate at 35 ± 7 psi per second
which would dictate that a specimen of UHPC could take up to 15 minutes to
break. This lengthy time period would be unacceptable for the time required to
break specimens for production use.

Modulus of Elasticity and Poisson’s Ratio

The modulus
of elasticity and Poisson’s ratio were conducted on 100 mm diameter and 200 mm
height cylindrical specimens. Specimen ends were prepared as described for
compression testing. The testing process followed ASTM C 469, except the load
rate was increased to 150 psi per second as mentioned for the compression
testing. In this test, electrical strain gauge was located on the face of
cylinder specimens in order to measure transverse and vertical displacements.
The specimens were completely unloaded at approximately the same rate and the
gauges zeroed. This process occurred three times for each specimen, following
the ASTM procedure. The initial loading was used to seat the gauges. Data from
the second and third loading was averaged and reported as the results for the
specimen. Strain for each 0.50 Mpa stress was recorded and were used to
calculate the modulus of elasticity. Calculate of elasticity and Poisson’s
ratio according to ASTM C 469, equations 1, 2.

E =
(S2-S1)/ (?2?0.000050) . ……………………..Equation 1

 Where: E = chord modulus of elasticity

 S2 =stress corresponding to 40% of the
ultimate load of the concrete

S1=stress
corresponding to a longitudinal strain of ?1at 50 millionths

 ?2=longitudinal strain produced by S2
Poisson’s ratio, to the nearest 0.01, as follows:

? =
(?t2 – ?t1)/ (?2 – 0.000050) ) ………….. Equation 2

Where:
? = Poisson’s ratio, ?t2 = transverse strain at mid height of the specimen
produced by stress S2, and ?t1 = transverse strain at mid height of the
specimen produced by stress S1.

Flexure strength

Testing
was conducted on 100 x 100 x 500 mm prism specimens. The specimens were
demoulded after 24 hours of casting and were transferred to curing tank where
in they were allowed to cure for 28 days. ASTM C 1018 (Using a Beam with Third
Point Loading) was used to determine the flexural strength. This test consists
of loading a small prism at the third points, to create a constant moment
region, and recording the load and deflection so the data can be analyzed to
give the flexural cracking stress, flexural strength of the fiber reinforced
concrete. This configuration loaded the specimens at the third points of the
span and created a simple support condition as outlined in ASTM C 78 where the
specification for the loading apparatus is given. The deflection measuring was
secured to the prism at the neutral axis of the prism, directly above the
support points. In each category three beams were tested and their average
value is reported. The flexural strength was calculated as follows:was
conducted on 100 x 100 x 500 mm prism specimens. The specimens were demoulded
after 24 hours of casting and were transferred to curing tank where in they
were allowed to cure for 28 days. ASTM C 1018 (Using a Beam with Third Point
Loading) was used to determine the flexural strength. This test consists of
loading a small prism at the third points, to create a constant moment region,
and recording the load and deflection so the data can be analyzed to give the
flexural cracking stress, flexural strength of the fiber reinforced concrete.
This configuration loaded the specimens at the third points of the span and
created a simple support condition as outlined in ASTM C 78 where the
specification for the loading apparatus is given. The deflection measuring was
secured to the prism at the neutral axis of the prism, directly above the
support points. In each category three beams were tested and their average
value is reported. The flexural strength was calculated as follows:

x

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