Effect of Petroleum Products on Steel Fiber Reinforced Concrete

This Investigation aims to study the effect of adding Steel fibers with different volume fractions V f (o.5, 0.75, and 1% by volume of concrete) with aspect ratio 100 on mechanical properties of concrete, and also finding the influence of petroleum products (Kerosene and Diesel) on mechanical properties of Steel Fiber Reinforced Concrete (SFRC). The experimental work consists of two groups: group one consists of specimens (cubes and prisms) plain and concrete reinforced with steel fiber exposed to continuous curing with water. Group two consists of specimens (cubes and prisms) plain and concrete reinforced with steel fiber exposed to kerosene and diesel after curing them in water for 28 days before exposure


INTRODUCTION
The long life of many reinforced concrete structures which have been exposed to aggressive environment for years shows that concrete has a significant durability in these environments .This has encouraged the tremendous developments in the use of large concrete structures, reinforced or pre-stressed, for the production, storage and transportation of oil products, to overcome the shortage in steel materials in some parts of the world.A Reinforced concrete tanks are used instead of steel tanks for petroleum products storage.Change from steel to concrete for storage purpose was due to low cost of repair, maintenance, and construction.In addition, concrete offers considerable resistance to fire and explosive during war times.
Steel tanks and pipes have traditionally been used for storage and transportation of petroleum products around the world.However, in many countries especially those which do not have steel industry, storage in these structures could occur.In addition, the high costs of construction and maintenance, the need for larger capacities and safety requirements for steel tanks have urged the people concerned to look for new alternatives of constructional materials.Concrete oil-storage tanks have been tried for at least seventy years and would have many advantages if adequate impermeability could be assured without the use of expensive impermeable liners.The critical storage and cost of steel during the Second World War expanded progressively the use of concrete for the construction of oil tanks.Before 1914, many concrete tanks were built in the USA for storage of heavy oils and during the Second World War the USA navy built concrete tanks for fuel oil Storage (Spamer 1944)&( Shepard 1944).
The main problems that restrict the successful use of concrete to store fuel oil are: the leakage of oils especially the lighter products (that having specific gravity 0.875 at temperature 15C) through the pore structure, shrinkage cracks and joints (Lea 2004).

RESEARCH SIGNIFICANCE
Concrete is the most commonly used material in construction industry.There are a number of reasons for this such as high strength, ease of production, low cost, good compatibility with other materials, especially with steel, durability under aggressive conditions.Ordinary concrete includes cracks with large width and has low tensile or flexure strength, but when Steel Fibers added to concrete can improve its properties like compressive strength, flexural strength, impact resistance, ability to control cracks and products cracks with small width, and also improve the toughness.The essential objective from this research to study the mechanical properties of steel fiber reinforced concrete when exposed to kerosene and diesel.

STEEL FIBER REINFORCED CONCRETE
Although concrete is a widely used construction material, it has major disadvantages such as a low tensile strength and low strength to weight ratio, and it is liable to cracking (Cement& Concrete Institute 2010 ).
Fiber reinforced concrete (FRC) is Portland cement concrete reinforced with randomly distributed fibers.In FRC, of small fibers are dispersed and distributed randomly in the concrete during mixing, and thus improve concrete properties in all directions.Fibers help to improve the post peak ductility performance, pre-crack tensile strength, fatigue strength, impact strength and eliminate temperature and shrinkage cracks (Nemati 2010).
The brittle nature of plain concrete cannot be neglected and an approach to make concrete a ductile material is necessary.In this regard, steel is no doubt a useful reinforcement material for concrete whether it is in the form of a SF or a reinforcing bar.The addition of SF to concrete can improve the tensile strength and ductility, but it will also reduce the workability (Chang et al., 2009) The addition of SF in the concrete mix allows the development of tensile stresses along the entire cracked depth of a section.These stresses can provide the required ultimate bending strength.SF provides also other properties that improve the structural behavior under service loads, for instance (ACI 544(1996)) • Crack width reduction The use of SFRC in building construction has increased continuously due to its better mechanical properties, mainly, the energy absorption capacity.The energy dissipated to pull out the fibers from the cracked concrete is much higher than the Energy dissipated to crack the concrete matrix.Therefore, the energy absorption capacity is the main material property benefited by fiber reinforcement (Barros and Cruze (1998)).

Compressive Strength
Fibers do little to enhance the static compressive strength of concrete, with increases in strength ranging from essentially nil to perhaps 25%.Even in members which contain conventional reinforcement in addition to the steel fibers.The fibers have little effect on compressive strength.However, the fibers do substantially increase the post-cracking ductility, or energy absorption of the material (Neves et and Fernades (2006)).

Direct Tension
In direct tension, the improvement in strength is significant, with increases of the order of 30 to 40 % reported for the addition of 1.5% by volume of fibers in mortar or concrete (ACI 544 1R-96).

Flexural Strength
Increases in the flexural strength of SFRC are substantially greater than in tension or compression because ductile behavior of the SFRC on the tension side of a beam alters the normally elastic distribution of stress and strain over the member depth.The altered stress distribution is essentially plastic in the tension zone and elastic in the compression zone, resulting in a shift of the neutral axis toward the compression zone strength concrete.The main reason for the discrepancy in fiber cement

Asst.Prof.Dr. Nada Mahdi Fawzi
Effect of Petroleum Products on Steel Fiber Reinforced Concrete Sara Alaa Abed AL-Ameer 16 composite is that the post-cracking stressstrain curve on the tensile side of the fiber cement or fiber concrete beam is very different from that in compression (Snyder and Lankard (1972)).

EFFECT OF CRUDE OIL OR ITS PRODUCTS ON PROPERTIES OF PLAIN AND REINFORCED CONCRETE
Meissner et al. (1944) have studied the influence of high octane gasoline on mechanical properties of mortar cubes (50 mm) soaked for 180 days.He has investigated that small reduction in compressive strength and no effect in tensile strength for the specimens.
Al -Saraj (1995) has studied the mechanical properties of concrete exposed to gas oil and aircraft engine fuel for soaking period of water -cured specimens, he found: 1. was also reduced by about 18 and 18.3% for kerosene and gas oil exposure respectively.3. The modulus of rupture of steel fiber concrete exposed to kerosene and gas oil was reduced after 30 days of exposure.
Blaszczynski (2002) has investigated that the durability analysis of concrete exposed to a crude oil products environment shows that significant reduction in compressive strength and its bond to reinforcement can occur.

EXPERIMENTAL WORK Materials Cement
The cement used is an Ordinary Portland Cement taken from one stocked quantity and supplied from (Taslooja) factory; it is used in casting all specimens throughout the experimental work.

Fine aggregate (Sand)
Al-Akhaidhur well-graded natural sand used of 4.75-mm maximum size was used for concrete mixes of this investigation.

Steel Fiber
High tensile steel fibers crimped type was used in this research with 0.5, 0.75 and 1% by volume of concrete (V f =0.5, 0.75 and 1%).Table ( 7) shows the properties of the used steel fibers as given by the manufacture.

Petroleum Products Kerosene and Diesel
Kerosene and diesel product from AL-Daura refinery was used.Tables ( 8) and ( 9) show the chemical analysis of the Kerosene and diesel used in this study.

Mix Design and Mixture
In this research, there are two groups of concrete mixes according to the type of exposure.Group one consists of two series have tested with compressive strength, air dry density, and flexural strength (modulus of rupture) exposed to continuous curing with water tested at age (30, 60, 90 and 120) days.
Group two consists of two series have tested with compressive strength, air dry density, and flexural strength (modulus of rupture) exposed to kerosene or diesel (after curing them in water for 28 days before exposure) tested at age (60, 90 and 120) days.All the concrete mixes are designed according to (ACI 211) by the volume method with the target strength (30 MPa) at 28 days and the mix proportions of the concrete are given in Table (9).All the concrete in this research had the same volumetric proportion of fine and coarse aggregate, and the amount of water (mix water) is kept the same in these concrete mixes, resulting in a constant W/C of (0.54) for all mixes.

Compressive strength
The result of compressive strength of concrete mixes (reference and reinforced concrete with different volume fraction of steel fiber (0.5, 0.75 and 1% by volume of concrete)) are shown in Tables from ( 10) to ( 12) and plotted in The test results present that the compressive strength of reference concrete is increased as the time of continuous curing in water increase , this is due to continuous hydration of cement paste, then, increases the bond between cement paste and aggregate (Shetty 2000) and (Neville 2010).
From the test results, it can be seen that the concrete mixes reinforced with SF is increased continuously with the time of curing in water was increase.The maximum increase was 48% when using 1% SF at 120 days as a compared at 30 days of curing.
From test results it can be seen that the compressive strength of the cubes (reference and reinforced with SF V f (0.5, 0.75, and 1%)) mixes exposed to kerosene or diesel, at 60 days the compressive strength of them is greater than the compressive strength of the cubes (reference and reinforced with SF V f (0.5, 0.75, and 1%)) cured in water.This is due to the pores inside the concrete which was still partially filled with water and leads to further hydration that delay the deterioration of concrete (AL-Harby 1998).
But at 120 days of exposure to kerosene or diesel, the compressive strength of concrete cubes (with and without SF) is decrease.The decreased in compressive strength for plain and for steel fiber reinforced concrete exposed to kerosene or diesel may be attributed to the weakening in the bond strength between cement paste and aggregate and between concrete matrix and fibers with the time of exposure.

Density
The result of density of concrete mixes (reference and reinforced concrete with different volume fraction of steel fiber (0.5, 0.75 and 1% by volume of concrete) are shown in Tables from ( 13) to ( 15) and plotted in From test results it can be notice that: The specimens cured in water show an increase in density as the time of curing period increased too, this is due to continuous hydration of cement, and this is in complete comply with other researches like (Shetty 2000) The density of the cubes exposed to kerosene or diesel at age 60 days (after curing them in water for 28 days) is higher than the density of those cubes curing in water for the same ages.The maximum increased when used SF 1% with rates 0.65% and 0.35% for kerosene and diesel respectively.This is due to the inside pores which were partially filled with water and let to continuous hydration of cement.
At 120 days from exposure to kerosene or diesel, the density of the specimens (with and without SF) is decreased.This happens because the harmful effect of petroleum products on the bond between aggregate and cement paste and between the SF and matrix, so this led to increase porosity and decrease the strength and density (Matii 1976) and (AL-Harby 1998).
The increase or decrease in density for the reinforced cubes exposed to kerosene or diesel is higher than the density for plain concrete.

FLEXURAL STRENGTH (MODULUS OF RUPTURE)
The result of Flexural strength of concrete mixes (reference and reinforced concrete with different volume fraction of steel fiber (0.5, 0.75 and 1% by volume of concrete) are shown in Tables from ( 16) to ( 18) and plotted in Figure from (7) to (9).
The test results show that, the flexural strength is increased as the curing period with water or exposed to kerosene or diesel is increase.The largest increase happens at 120 days of curing are 32.6%, 46.8%, 54% and 57.5% for plain and reinforced concrete using SF with V f (0.5, 0.75 and 1%) curing with water respectively.
The results show that, the flexural strength of the specimens (with and without SF) exposed to kerosene or diesel increase with the time of exposure and the maximum increase at 120 days of exposure with rates 12%, 32%, 33% and 36% and 19%, 33%, 35% and 37% for plain and reinforced concrete with SF with V f (0.5, 0.75 and 1%) exposed to kerosene and diesel respectively.The increase in flexural strength of concrete specimens exposed to kerosene and diesel are due to closing and autogenously healing of crack and flaws in concrete due to possible volume change by effect of products.

(Matti 1976).
The test results also show that, the Flexural strength of specimens reinforced with SF is greater than the flexural strength of plain concrete specimens, this behavior is due to the increase in crack resistance of the composite and ability of fibers to resist forces after the concrete matrix has cracked.(Salih et al.,

CONCLUSIONS
1.The maximum increase percentage in compressive strength for specimens reinforced with SF with V f (0.5, 0.75, and 1%) and continuously cured in water at 120 days was 9.1, 11.9 and 18.9 respectively as compared with plain concrete.2. The decreasing or increasing in compressive Strength for specimens reinforced with SF and exposed to kerosene or diesel is better than the plain concrete exposed to same conditions.The percentage increases in compressive strength 3.8, 6.5, and 9.3 and 8, 10.9 and 16.5% at 60 and 120 days for 0.5, 0.75, and 1% Steel Fiber content by concrete volume respectively as compared with plain concrete exposed to kerosene and the percentage increases in compressive strength 3.9, 5.3 and 8.4% and 6.5, 10.4 and 15% at 60 and 120 days for 0.5, 0.75, and 1% Steel Fiber content by concrete volume respectively as compared to plain concrete exposed to diesel.
3. The density of reinforced specimens cured in water is increased as the percentage of SF increase and the maximum increase was 4.9% when SF 1% is used.4. The density of the specimens exposed to kerosene or diesel at age 60 days (after curing them in water for 28 days) is higher than the density of those specimens cured in water for the same ages.The maximum increase when used SF 1% is used with rates 0.65% and 0.35% for kerosene and diesel respectively.5.At 120 days from exposure to kerosene or diesel, the density of the specimens (with and without SF) is decreased.6.The flexural strength of the prisms cured in water was increased as the curing period increased.The maximum increasing happen at 120 days of curing are 32.6%, 46.8%, 54% and 57.5% for plain and reinforced concrete using SF with V f 0.5, 0.75 and 1% cured with water respectively.7. The flexural strength of the prisms (with and without SF) exposed to kerosene or diesel increased with the time of exposure and the maximum increase was at 120 days of exposure with rates 12%, 32%, 33% and 36% and 19%, 33%, 35% and 37% for plain and reinforced concrete using SF with V f (0.5, 0.75 and 1%) exposed to kerosene and diesel respectively.8. Flexural strength of prisms reinforced with SF is greater than the flexural strength of plain concrete prisms cured in water or exposure to kerosene or diesel.The maximum increasing percentage in flexural strength was when used 1% SF at 120 days.The rates were 41.8%, 55.6% and 48.5% for water, kerosene and diesel respectively.
It stored in laboratory by plastic containers were used to enclose the cement in order to minimize the effect of humidity throughout the experimental work.The physical and chemical properties of the cement are shown in Tables (1) and (2) respectively, with the estimated cement compounds based on Bogue's equations given in (ASTM C 150-00).This cement complied with the (Iraqi specification No.5/1984).

Figure ( 1 )
Figure (1) Effect of Steel fiber content on compressive strength of concrete cured in water.

Figure ( 2 )
Figure (2) Effect of Steel fiber content on compressive strength of concrete exposed toKerosene.

Figure ( 7 )
Figure (7) Effect of Steel fiber contents on Flexural Strength of concrete cured in water.

The disadvantages of used reinforced concrete tanks as follows: (Matti 1976) & (Faiyadth 1985)
Table (3) shows the sieve analysis of this aggregate and Table (4) which represented the properties of the used sand.The grading is lied in (Zone No. 1) and conformed to the limits of Iraqi specification No. 45/1984.
The Coarse Aggregate used in this research is crushed washed aggregate brought from Al-Nibaii area of maximum size 10mm.Table(5)shows the sieve analysis of this aggregate and Table (6) which presented the properties of coarse aggregate.It conforms to the Iraqi specification I.S.O.45/1984.Water Water is used in this research for mixing and curing.It is ordinary potable water for Baghdad City.