Introduction
Modern day distribution centres and warehouses have become very sophisticated. Clients are demanding very high performing floors.
This is mainly due to higher racking systems and the increased speed of the material handling equipment. Every industrial floor has its own individual specific needs and getting the design and detailing right is not simple or straight forward.
At CANZAC we understand the lower lifetime cost of an industrial concrete slab on grade and we most certainly deliver the best lifetime value.
Our engineered product offering is second to none. We have a wealth of knowledge when it comes to design input. We simply know what works and what does not work. When you consider the up-front cost of the concrete slab is about 13% of the total project value.
All too often during the design and construction process, the owners or occupiers are not aware of the issues they will be dealing with in 18-24 months’ time or the associated costs and down time that has to be paid for to repair badly designed and constructed concrete floors.
Many industry designers, owners, and occupiers of CANZAC slabs understand our true value, lowest maintenance costs, better material handling speeds and earlier project delivery.
Our well designed detailed and constructed steel fibre floors are becoming very popular. This is due to our engineering and design expertise.
Our understanding of critical control joint detailing for construction/contraction /isolation and expansion joints. Along with reinforcing detailing dowel type and spacing via our in-house load transfer programme.
As a rule of thumb, small fibres tend to be used where control of crack propagation is the most important design consideration. High fibre count
(number of fibres per kg) permits finer distribution of steel fibre reinforcement throughout the matrix – and, consequently, greater crack control during the drying and curing process. On the other hand, because they exhibit better matrix anchorage at high deformations and large crack widths, longer, heavily deformed fibres afford better post-crack ‘strength’. However, unlike shorter fibres, the dramatically reduced fibre count of longer product yields correspondingly less control of initial crack propagation.
Conventional practice usually concentrates welded wire fabric reinforcement within a single place of a floor slab.
Durability
The corrosion resistance of Danbar fibres is governed by the same factors that influence corrosion resistance of conventionally reinforced concrete.
As long as the matrix maintains its alkalinity and remains uncracked, deterioration is not likely to occur. There is a specific advantage of Danbar fibres over fabric or bar reinforcing insevere exposure environments. This is that the fibres, being unique and discrete, will not support classic galvanic corrosion cells, which are often the cause of corrosion and deterioration in fabric and bars. Hence Danbar fibres can be used to advantage in extremely aggresive environments.
Impact Strength
The drop weight test used in an investigation is not a truly scentific test as it does not give accurate quantitave values for impact resistance. However, this is a very simple test that can give a comparative example of the performance in concrete. The impact strength increases considereably with the increase in fibre content. Compared to plain concrete, the increase in impact strengths were significant, a 12kg per cubic metre increased the impact strength 10 fold. The results prove that the addition of Danbar fibres significantly increase impact resistance.
Punch & Shear
Danbar high strength steel fibres have the ability , even at moderate addition levels , to improve punch and shear. Tests have been done to compare punch and shear behaviour of.
• Plain Concrete
• Concrete reinforced with 2 layers of welded wire fabric
• Polypropylene Fibres
• Mill cut steel fibres
• High tensile deformed steel fibres
It was observed that the values of punch and shear are improved by the addition of relatively small quantities of steel fibres.
No punching was observed.
Improved Strength & Durability
Steel fibre reinforced concrete is a castable or sprayable composite material of hydraulic cements, fine, or fine and coarse aggregates with discrete steel fibres of rectangular cross section randomly dispersed through the matrix.
Steel fibres strengthen concrete by resisting tensile cracking. Fibre reinforced concrete has higher flexural strength than that of unreinforced concrete and concrete reinforced with welded wire fabric. But unlike conventional reinforcement – which strengths in one or possibly two directions – Steel fibres reinforce so tropically, greatly improving the concrete’s resistance to cracking, fragmentation spalling and fatigue.
When an unreinforced concrete beam is stressed by bending, its deflection increases in proportion with the load to a point at which failure occurs and the beam breaks apart.
A steel fibre reinforced beam will sustain a greater load before the first crack occurs. It will also undergo considerably more deflection before the beam breaks apart. The increased deflection represents the toughness imparted by fibre reinforcement.
The load at which the first crack occurs is called the ‘first crack strength’. The first crack-strength isgenerally proportional to the amount fibre in the mix and the concrete mix design.
Two theories have been proposed to explain the strengthening mechanism:
The first proposed that as the spacing between individual fibres become closer, the fibres are better able to arrest the propagation of micro cracks in the matrix.
The second theory holds that the strengthening mechanism of fibre reinforce-ment relates to the bond between the fibres and the cement. It has been shown that micro cracking of the cement matrix occurs at very small loads. Steel fibres then serve as small reinforcing bars extending across the cracks. So as long as the bond between the fibres and cement matrix remains intact, the steel fibres can carry the tensile load.
The surface area of the fibre is also a factor in bond strength. Bond strength can also be enhanced with the use of deformed fibres, which are available in a variety of sizes.
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