ICE SKATING RINK DESIGN CONSIDERATIONS
C.J Hewetson
Date 14/2/03
Revised 5/12/04 added additional concrete notes para 13.
1) General
Ice skating rinks can be used for a number of purposes and uses throughout the year
- Curling
- Hockey
- Speed skating
- Figure skating
- General leisure
- Non skating activities by removing the ice or covering it.
Each of the above requires a different ice surface temperature and thickness. The ice temperature determines the
hardness of the ice and therefore the friction between ice and skates and the thickness determines the weight the
ice sheet can support without cracking and to some extent the thicker the ice the softer it is. Ice rink sizes can be
made to suit the developer's needs and financial investment and required returns. They can be square, rectangular,
oval or round. International Hockey rinks are 200' x 85' (60 x 25mtr) (17,000ft2/1,500M2) Olympic size rinks are
200' x 100' (60 x 30mtr) (20,000sqft/1,800M2) with 28ft (8.4mtr) diameter radiused corners. Rinks can be stand
alone indoors or outdoors, located in shopping malls or exhibition halls. They can be temporary using mat systems
or permanent and both systems can be multi functional multi purpose.
Figure skaters and hockey skaters have different ideas of what good ice and bad ice is. Figure skaters prefer an ice
temperature of 26 to 28 F (-4 to – 2degC). Ice in that temperature range is softer, so it grips the skate edges better.
It is also less likely to shatter under the impact of jumps. Hockey players though, prefer a harder colder ice
temperature of 24 to 26degF (-6 to -4degC). With many skaters on the ice simultaneously, it's easy for the ice
surface to get chewed up at the temperatures preferred by figure skaters.
2) Skater density
In terms of skater density an approximate figure of 1 skater/3.5M2 should be used for estimating heat loads, and
for rink operators information, in terms of revenue calculations and safety on the ice pad. Too many skaters are a
danger to themselves and other rink users.
3) Ice Temperature & thickness, making ice
Ideal ice surface temperatures for public skating would be -4degC and ideal ice thickness is 1" (25mm). The ice
sheet is laid and built up in several layers 8-10 in total and it has to be undertaken with care to get it right. Making
an ice rink isn't as simple as flooding the floor with gallons of water. The operators must apply the water carefully
and slowly, in order to insure ideal thickness. An ice surface that is too thick requires more energy to keep frozen
and is prone to softening on the surface. A surface that is too thin is also dangerous because skaters risk cutting
straight through the ice and cracking of the ice.
It takes between 12,000 and 15,000 gallons (45,000 to 57,000ltrs) to form a 60 x 30m rink surface. The
maintenance operators form the ice in several different layers, in many steps:
1) Once the rink pad is down to an even -2degC, the first 2mm layer of ice is built up using a hose and fine
spray nozzle jet over the entire rink area.
2) Once this ice layer is hardened, a second layer of ice is built up to 2mm in the same way.
3) Once hardened the entire rink surface can be painted white, using 300 gallons (about 1,300 liters) of waterbased white paint. The paint is available in liquid or powder form and should be sprayed on with a hand
pressurized industrial type portable sprayer. The manufacturers directions should be followed for mixing
and application and drying times.
4) Once dried another third layer 1.5mm is built up in the same way to seal the paint surface.
5) Once hardened the lines and logos can then be painted using stencils or paper rolls or painted by hand.
6) The ice surface is built up in layers to a final 25mm, maybe upto 8 layers each 2mm
The final ice thickness is achieved slowly applying the remaining 45,000ltrs with a large hose at a rate of around
2000 to 3000 ltrs/h until the remaining layer is complete. That means 15 to 20 hours (1 hour/2000-3000ltrs) for the
final layer. Each of those layers is allowed to freeze before putting the next 2000 to 3000 ltrs on. The less water
you put on the floor at one time, the better the ice will be.
Experience will determine a reliable ice thickness and temperature for individual rinks and usage. If the ice is too
thin or too thick it is liable to crack and if it is too thick the thermal conductance will increase requiring a lower
Glycol supply temperature and increased energy, additionally if the ice is too thick say 2"(50mm) the ice surface
will be softer. However for Rubber or Polymer mat systems laid in a Sand bed, the ice should be 1.5-2" thick to
provide adequate protection to the mat.
4) Ice building
The ice plant should be commissioned upon completion of the installation and all necessary pressure and leak tests
plus curing of the concrete. Initial curing of the concrete to achieve the design strength is 28days. During
commissioning, the rink pad temperature must not under any circumstances be lowered too fast and should be
bought down to -2 degC from ambient in increments of 5-10degC over a period of at least 4 days. Reducing the
pad temperature too fast will cause plastic stress cracks in the concrete. Once the temperature of the pad has
stabilised at -2degC de ionized or fresh filtered water can be sprayed on to create the ice pad as described above.
5) Water requirements
For crystal clear Ice sheets, de ionised/de mineralised water should be used. In any event approximately 0.65
gallons/sqft (24ltr/m2) of water will be required to produce a 1" (25mm)thick ice sheet. For a standard Olympic
size rink this equates to around 45,000ltrs in total.
6) Refrigeration requirements
The rink refrigeration system requirements vary between 75-300sqft/TR (7.5-30m2/TR) dependant upon
- Location.
- Lighting.
- Ambient conditions.
- Number of people on the ice.
- Whether the rink surround is air-conditioned to maintain temperature and humidity or whether the ice pad
itself is used for de humidification. Chart 1 provides an insight into the make up of the ice rink heat loads.
For indoor rinks in Saudi Arabia an average total heat load value for estimating the refrigeration load is
260watts/m2 for pads on first floors of malls and 280watts/m2 for pads laid at ground level.
Chart 1: Refrigeration Loads
The system may be Direct refrigerant, circulating refrigerant directly through the pad using mechanical pumps or
Pumper drums, using discharge pressure as the motive force or Indirect using Brine or 35% Aqueous solution
Inhibited Ethylene Glycol with mechanical pumps to circulate the liquid through the evaporator and rink pad. (
Brine by the way is a salt/water solution, Glycol solutions are not Brines and should not be referred to as such).
The temperature differential between flow and return should be designed for 1.5degC with a maximum of 3degC
in order to provide an even ice temperature across the entire rink surface. The Liquid supply temperature would
depend upon a number of factors
- Type of usage and associated ice surface temperature.
- Ice thickness and thermal conductivity 'k' factor.
- Rink pad thickness and material and associated thermal conductivity 'k' factors
- Overall 'U' factor or heat transmission factor of the Ice plus Rink pad.
Typically a LMTD of 6degC would be considered adequate for most circumstances. The glycol or Brine flow and
return temperatures would be -12/-9degC based upon ice temperature of 6degC and temperature differential of
6degC. Obviously the lower the supply temperature of the liquid the greater the energy usage of the refrigeration
plant and circulating pumps, therefore it makes sense to operate with the highest liquid supply temperature
commensurate with the desired rink usage and ice temperature. The ideal and highest liquid supply temperature
will be found by trial and error by the rink operator during operation.
In terms of refrigerant, R717 provides the highest COP and lowest KW/TR figures but where such refrigerant
cannot be used R22 provides a suitable alternative. R717 is generally the lowest cost refrigerant in most countries
including the Middle East. It is however toxic and flammable in concentrations above 16% in air and therefore
special safety measures have to be provided, such as
- Plant room extract ventilation system interfaced with a leak detection sensor.
- TEFC IP55 electrical enclosures.
- Ammonia masks at entrance & exit to plant room.
- Limiting the refrigerant charge (use Plate Heat Exchangers)
In terms of Refrigeration chillers, industrial chillers with open drive duplex screw compressors should be the
preferred choice to provide a well engineered reliable system, capable of operating at high heads and peak
demands. An industrial chiller should provide at least 20-25 years reliable operation with low maintenance and
running costs. Screw compressors are preferred over reciprocating compressors for the following reasons
a) Reduced number of moving parts
b) Reduction in maintenance costs
c) Longer mean time between breakdowns and service intervals
d) Compressor turndown to 10% load without any discharge temperature limitations
e) Direct drive @ 2 pole speed 3560RPM
f) Reciprocating compressors may incur unloading limitations, typically 50% or 150degC discharge
temperature
g) Reciprocating compressors operating on 60hz frequency are limited in general to 1450RPM which requires
belt drive using 4 pole motors or direct drive @ 1200RPM using 6 pole motors
h) Oil carryover is less with screw compressors
Developers and operators should be aware that low cost air conditioning chillers, whilst providing an initial cost
saving will be expensive to operate and repair, provide a shorter working life typically around 10 years,
particularly in the Middle East. They are not designed for the industrial demands of Ice rink duties and typically
use semi hermetic or hermetic compressors which again are not designed for industrial duty 24 hrs/day 7
days/week. Such chillers will incur considerably higher Kw/TR penalties due to the lower COP's at the higher
compression ratios and the daily running costs are likely to be substantially higher than for an industrial
compressor/chiller. Rink developers who have been persuaded to use commercial air conditioning chillers, have
generally lived to regret the decision and we know of few ice rinks around the world which use or would consider
such chillers. In view of the requirement for a temperature differential of 1.5degC, plate heat exchangers are the
preferred choice from a design and operational point of view. PHE's can accept high flow rates and velocities,
offer reduced fouling and pressure drops and increased system COP in comparison to commercial air conditioning
chiller DX Shell & Tube heat exchangers. Additionally PHE's reduce the refrigerant charge volume. DX chillers
require higher refrigerant charge, lower heat transfer rates and are limited to around 4 deg C temperature
differentials due to velocity/PD limitations. Too, Brine flow is on the shell side rather than tube side, which means
the tubes cannot be inspected or cleaned (apart from Acid cleaning). Should developers consider commercial air
conditioning chillers they should pay close attention to the COP/KW/TR figures plus flow rate and temperature
differentials and if semi hermetic compressors are used consider the costs of clean up, motor replacement, loss of
refrigeration in the event of a motor burnout.
7) Low Emissivity Ceilings
Low emissivity ceilings should be considered for energy savings in all ice skating rinks, especially for rinks
operating in the Middle East. Low emissivity ceilings are normally suspended ceilings supported from the main
roof structure and are essentially foil faced radiant barriers. They nearly eliminate the radiant heat load in an ice
rink which typically represents 25-40% of the overall refrigeration load. This radiant heat load naturally occurs
when a large ice surface directly faces a large relatively warmer ceiling surface. Low emissivity ceilings can
reduce this load by up to 95%.
8) Ice Temperature Controls
All ice rinks should have a means of measuring the ice thickness and measuring and controlling the ice pad
temperature to provide energy saving. Plates should be affixed to the concrete slab in various locations across the
rink to allow drilling down through the ice to measure the thickness. The ice should be no more than 25mm thick.
Thicker ice will cost more energy to maintain the ice temperature. For example ice at 2" thick will cost
approximately 10-15% more in refrigeration costs compared to ice at 1" thick
A one degree (1 F) increase in ice temperature will save approximately 6% annually in refrigeration energy costs.
Most ice rink refrigeration control systems control the temperature of the slab, or brine / glycol temperature below
- not the ice. They are typically set to maintain the same temperature 24 hours a day whether the ice needs it or
not. As a result, much more energy is used than necessary. Installing a control system that controls the actual ice
temperature will prevent this unnecessary over cooling. Such ice temperature control systems can also be used to
raise the ice temperature up at night and unoccupied periods for even more energy savings. With an ice
temperature control system, energy savings from 5-15% can be expected. The ice temperature sensor should be
installed on the surface of the rink or in the ice sheet.
9) Rink construction
The rink pad construction can use Sand or Concrete with either permanently installed 1"nb piping grids or
temporary pipe grids e.g. Polymer or Rubber Ice mats with 1/2" nb pipes which are laid in rolls of 4-7ft wide by
the length of the rink. Permanent rinks now use Polyethylene 1"(25mm) nb pipe laid in a number of individual
circuits spaced at between 3-4" (75-100mm) centres. The closer the centres the better, as this reduces the wash
board effect which arise if the centres are too great. However reduced pipe centres increases costs as more pipe is
laid the closer the centres. 31/2" (87mm) centres are ideal. The number of circuits is important as this effects
pressure drop; the greater the pressure drop the higher the temperature differential between flow and return which
leads to uneven ice surface temperatures and increase pumping costs. In general a permanent 5" reinforced
concrete rink pad construction, with 1" piping is preferable for many reasons (note temporary 1/2"nb mat systems
such as ITT/Calmac can be permanently installed)
- 1" pipes embedded in a 5 or 6" reinforced concrete slab provides a huge thermal mass and flywheel which
reduces temperature fluctuations, reduces plant operation time and maintains a more even ice surface
temperature.
- 1" Polyethylene pipes provide reduced friction losses over 1/2 " pipe moulded in a 'mat' system and
provide lower pumping costs and more even ice surface temperature.
- 1" Polyethylene pipes are corrosion proof, have a low coefficient of friction and Reynolds number, provide
good chemical resistance to Concrete, Glycols, Brines and Inhibitors. Certified pipe pressure rating should
be 100psig (690kpa). CSA certified pipe has a safety factor of 4 x the pipe pressure rating. It provides
excellent pliability, thermal expansion & contraction properties with a modulus of elasticity of 80,000psig
which allows the pipe to expand & contract, resist tension plus compressive forces without breaking.
(expansion/contraction loops must be provided on both flow & return connections to the respective
headers).
- 1/2" moulded pipes in a mat, are prone to greater fouling or potential blockage.
- Temporary mats deteriorate over time.
- A permanent concrete ice pad provides greater protection to the pipe grid than a rubber or polymer mat in a
Sand pad.
- Permanent concrete pads provide an extremely level rink pad compared to a sand pad.
- Thicker ice pad is required for temporary roll out mat systems or sand pads to provide adequate protection
to the mat.
- Concrete pads allow accurate ice thickness determination, by drilling through the ice with a cordless drill.
- Concrete floor pads will cost up to $65,000 more than sand floors, however they provide a more even
surface, provide greater flexibility and durability and do not need to be replaced. Too, a concrete pad
provides the ability to use the arena for other activities & events, especially events which require load
bearing.
- A sand floor is difficult to maintain level and for maintenance procedures when the ice is melted, may
require the sand bed to be replaced.
The rink pad should comprise 2 layers 50mm thick Styrofoam insulation with staggered joints, vapour barrier with
sealed joints, reinforcing bars and reinforcing mesh, 1"nb PE brine piping and appropriately sized flow and return
headers. PE piping joints should be fusion welded or insertion fittings used. The concrete rink pad should be 5"
(125mm)thick, waterproof, with minimum compressive tensile strength of 4,000lbs, laid in one Monolithic pour
and laid level to within +/-5mm from end to end and side to side using laser alignment tools. The rebars shall be
laid with suitable spacers to provide the correct height on top of the insulation, the rink piping should be affixed to
the rebars and steel wire mesh should be affixed on top of the rink piping. The rink circumference between the
rink and perimeter pads should have a 3/4" thick minimum expansion joint filled with waterproof sealant, the rink
tubing should not extend outside the rink pad. Concrete samples should be provided for slump and strength tests
from each and every batch delivered to site and suppliers certificates of conformity should be provided. Concrete
batch deliveries should be pumped into the rink and vibrated to remove air pockets. A minimum of 28 days should
be allowed for the concrete pad to cure prior to making ice. The rink floor should be covered with strategically
placed scaffold boards to facilitate concrete pouring, under no circumstances are contractors allowed to walk over
the wire mesh/pipework or barrow concrete into place.
Stainless steel drill plates should be installed on the finished floor slab at designated locations across the floor slab
to facilitate ice thickness measurements.
During ice building 4 days should be allowed to reduce the rink pad down to design temperature in 10degC
increments.
10) Header trenches
The header trenches are designed to contain the main flow and return glycol headers to which the rink cooling
pipes are connected to. The header trenches may be located in many ways
- Length ways parallel to the rink length
- Widthways parallel to the rink width
- At one end only
- Flow and return header at opposite ends
- In the ice floor slab
- In the apron outside the ice rink pad
Ideally the header trench should run width ways, the flow header trench at one end and the return header trench at
the opposite end and the trench should be located in the rink perimeter apron not in the rink itself. This design
concept means there are no joints or connections in the concrete rink pad itself and any leaks can be repaired
without digging up the rink ice and concrete pad. Additionally this concept reduces pressure drop and provides a
more even ice pad temperature across the rink. If the flow and return headers are located at one end or side only, a
"U" bend has to located in the concrete pad, this will involve a welded or insert joint x 2 which are subject to
potential leaks.
By running the cooling pipes lengthways along the length of the rink to a flow and return header at opposite ends
there can only be 2 joints, not 4 as would be the case if headers were in a common trench at one end. If the header
trench is laid lengthways along one or both sides of the rink, the header trench and header piping will be longer
plus incur greater cost, but most importantly the number of joints will be increased.
Most importantly is how to hydraulically balance the flow rates across the rink circuits to ensure the rink piping
grid provides equal pressure drop and flow across each cooling pipe. Without a means of balancing, the cooling
flow will take the path of least resistance thereby increasing flow on the paths of least pressure drop & decreasing
flow of highest pressure drop. There are only two ways to ensure the circuits can be hydraulically balanced, either
a) A reverse return header must be used or b) 25mm regulating valves must be installed on the every connection
from the flow header to the rink tubing to facilitate balancing during commissioning.
11) Underfloor heating
Frost heave is a major concern if the rink pad is to be laid at grade level. A proper soil analysis should be
undertaken to establish whether the type of sub soil is frost susceptible and establish the water table height.
Normally frost heave is not an issue if the soil is not frost susceptible e.g. gravel, coarse sand or a water source is
not available. If the soil is frost susceptible underfloor heating will be required. Underfloor heating can be
provided either by low voltage heater mats or hot water circulated through 25mm PE piping laid in sand. For ice
rinks located on first or second floors frost heave is not a concern, however condensation on the ceiling of the
floor below will be a concern and under floor heating will be required under the rink insulation and above the main
floor slab.
12) Dasher boards
Dasher boards should be permanently installed around the Apron perimeter floor slab of the rink pad rather than
the ice rink slab itself. This is the recommended method as the anchor bolts can be installed after the apron has
cured, there are no pipes to avoid and the expansion joint is in front of the dasher boards and cooling pipes due not
have to penetrate through the expansion joint and under the dasher boards. The dasher boards can be cantilevered
out upto 3/4" to cover the expansion joint and ensure freezing right up to the dasher board edge.
If the cooling pipe grid in the 5" concrete slab is correctly designed the slab will perform at an even temperature
right up to the rink pad periphery (edges) & hard ice will exist.
Alternatively some rink designers mount the dasher boards around the perimeter of the ice rink slab itself, however
this means that the dasher board post anchors have to be cast in the concrete slab during pouring very accurately.
Accuracy is difficult to achieve when anchors are set in wet concrete, if the hole centres are more than 2-3 mm out
it will not be possible to locate the dasher posts in line or pick up the hole centres in the post base. The anchor
holes cannot be drilled after curing the concrete slab as a danger exists of penetrating a cooling pipe/s.
Additionally with this method the expansion joint will be behind the dasher boards plus the cooling pipes will run
under the dasher boards. This is not recommended as the all the pipes will penetrate through the expansion joint
(not just the pipes connected to the flow/return headers), water seepage under the dasher boards may freeze and a
danger exists the dashers will heave. If the cooling pipes are extended too far out into the surrounding apron, frost
may arise in areas behind the dasher board unless adequately insulated with rubber matting.
The board height should be 1.2m above the refrigerated floor slab and board frame length will be approximately
2.4m long with two vertical support frames. The frames should be 5" galvanized hollow steel or Aluminium
construction. A total of three gates should be provided for entrance – exit + ice resurface machine. Gates, frames,
panels should be provided with all necessary hardware e.g. hinges/latches/gate locks/castors plus foundation bolts
and anchors, these should be galvanized steel or stainless steel. Kick boards are added to the dasher panels to
protect the panels from skate damage. Unless the rink is be used for sport e.g. Hockey, there is no need to provide
any plastic glass above the dasher boards.
13) Concrete specification
The concrete for Ice rinks must be poured and laid in one continuous series of pours in one day. Failure to do
so may result in stress cracks due to plastic shrinkage and different exothermic heat rates. (Note depending on the
header design, see para 6, if any pipe joints are located in the ice rink pad itself, the piping circuit should be
pressure and leak tested prior to carrying out concrete placement).
The concrete specification is critical and should comply to the latest ASTM C150 cement/C33 aggregates/C494
admixtures type A,F,G, C260 air entrainment, C94 proportioning and design of mixes.
Test cylinders or cubes must be supplied from each and every batch of concrete delivered to site for independent
laboratory compression tests. The newly laid concrete pad should be maintained damp over the 28 days curing
time by using wetted Hessian sacks or water spray. Failure to do so will result in the concrete not achieving its
strength over the correct time frame and will result in plastic cracking.
Concrete is not generally waterproof or vapour proof unless an admixture is added to the concrete mix and the
floor sealed after curing. Waterproof concrete is concrete which is impervious or unaffected by water or prevents
the penetration of water. The term “waterproof” is frequently used inaccurately with regards to concrete floor
slabs. Waterproof concrete or waterproofing concrete does not stop water vapor movement. Concrete must be
“vapour proof” with the application of admixtures, surface coatings and correct water-cement ratio.
If the ice rink reinforced concrete floor slab is not vapourproof, moisture will migrate from the rink surface and
from the underslab, condense & freeze in the concrete slab capillaries. This will eventually cause the slab to crack
as well as cause reinforcing bar corrosion & expansion.
Vapourproof concrete restricts or prevents the passage of water vapor & water whereas waterproof concrete is not
necessarily vapourproof. Vapourproof concrete is always waterproof.
Water Cement Ratio - This property is the most important factor in producing quality concrete. The water to
cement ratio of concrete is simply the weight of the water divided by the weight of cement.
The water to the cement ratio is relative to the local aggregates and sand available. Porous aggregates will require
higher water to cement ratios to achieve a workable slump. Denser aggregates, being less absorptive, will require
lower water to cement ratios to maintain a given slump. The resulting concrete, with porous aggregates and a
higher water to cement ratio, will naturally have greater permeability due to a higher percentage of interconnecting
capillary voids.
Hydrating Free Mix Water - Hydrating free mix water is the excess concrete mix water outflow from newly laid
concrete. In actual field conditions, new concrete construction may take five years or more,depending on the water
to cement ratio of the concrete, for this free water to completely hydrate based on Portland Cement Association
Research.
Capillaries - Capillaries form within concrete in direct relationship to the water to cement ratio, the higher the
water-cement ratio (more water) the greater volume of interconnecting capillaries, producing a more porous
concrete making concrete inherently weaker.
Permeability - Concrete by its very nature is permeable. The interconnecting capillaries formed when concrete
cures provides the perfect medium for water vapor transmission. The free mix water necessary for the placement
of concrete is much higher than is necessary for the complete hydration of concrete. It is the process of the
hydrating cement and the curing of concrete that forms these weakness planes and permeability.
Capillary Action - Capillary action (wicking action) attracts moisture from below and above the ice rink slab
through the interconnecting capillaries in the concrete slab. Moisture within the slab will condense and freeze.
Curing - Curing is a process which maintains the proper internal moisture level in concrete. The one significant
variable which directly effects permeability, quality and the ultimate strength properties of concrete is curing.
Prolonged and thorough moist curing is the most significant factor in producing waterproof and watertight, high
quality, high strength concrete. One form of prolonged moist curing is to apply moist burlap/hessian to the
concrete surface, continually keeping it moist for a period of 28 days. Research shows that concrete continuously
moist cured for a period of 28 days resulted in compressive strengths exceeding 4,500 psi. Yet, the same concrete
air cured for the same period achieved only 2,550 psi. Furthermore, the compressive strengths at 180 days were
actually lower for the air cured concrete, 2,500 psi, where the continuously moisture cured concrete achieved an
ultimate compressive strength of over 5,750 psi.
Enhancing the Moist Curing Process - Although prolonged and thorough moist curing produces concrete far
superior in all respects over air cured concrete, prolonged moist curing cannot produce concrete which prevents
water vapor transmission. Interconnecting capillaries are formed in the cement hydration process. Slow, moist
curing is the most significant factor in producing high quality, high strength, waterproof and watertight concrete
yet without an enhancement to this curing process it is impossible to produce concrete which is impermeable to
water vapor transmission.
A Pozzolanic chemical admixture like MOXIE 1800 super admixture should be added by the concrete supplier.
These complex, hydrous silica, pozzolanic chemical compounds react in a time-released fashion, depending on
their specific application, prior to, during, or and after hydration with the calcium hydroxides and by-products of
hydration to form additional cementitious (cement-like) materials. This conversion of all available calcium
hydroxides (free lime) into insoluble calcium silicates eliminates potential efflorescence.
During this period the controlled loss of water slowly moist cures the concrete. The additional cementitious
materials by their very chemical and physical nature produce concrete and Portland cement based applications
with a much higher density and surface hardness, a dramatic increase in bond, flexural, tensile and compression
strength while achieving a near-zero capillary void state.
The initial phase of chemical reactions create colloidal gels prior to initial set, instead of the typical bleed water,
which prevents internal segregation and settling of the concrete components, and after initial set allows for
immediate or almost immediate finishing. At initial surface set, the gel-like characteristics of the concrete,
provide the properties of a thermal barrier restricting rapid evaporation of the surface water which prevents
shrinkage and slab curl, and reduces or eliminates plastic cracks. These colloidal gels also protect the reinforcing
steel from internal corrosion and ultimately form additional cementitious materials that provide further protection
from externally caused corrosion.
During the critical three to seven day period after placement, and throughout the process of hydration, the thermal
barrier properties continue to compensate for shrinkage by creating a stable and controlled environment which
conserves the heat generated by hydration in low ambient temperatures and reduces the amount of heat absorption
in high ambient temperatures.
After the cement hydration process is complete, at the 28-day period, the final stages of the initial phase take place
and these colloidal gels react with what would usually be the remaining byproducts of hydration and the free mix
water to form the last of the cementitious materials. This timed-release process takes an additional 31 days
approximately to complete its initial phase & the continuing process becomes complete when all the calcium
hydroxides & by-products of hydration have formed additional cementitious (cement-like) materials.
The absence of interconnecting capillary voids also means that excess free mix water, typically present after
hydration of the cement, would be eliminated, reducing the internal free humidity to a level that no corrosion can
take place. It takes approximately 850 days, under controlled laboratory conditions, for the internal humidity of
standard concrete to reach a point where it no longer corrodes the reinforcing steel. If unprotected during this
period of time corrosive expansion of the reinforcing steel has already taken place, creating pressure & the onset
of structural cracks.
Using the correct admixture will ensure the concrete moisture is used to provide the proper, prolonged, slow, moist
curing which enhances, improves, & provides a Portland cement based material which is impervious to the
transmission of water and water vapor, as well as other contaminants such as oil, petroleum & acids.
The basic specification for concrete pads should be based on the following specification which I discussed &
agreed with RMC in UK in 1986.
- Concrete placement temperature.
15degC
- Cement type.
Portland cement type 1
- Aggregates.
Natural clean sand as fine aggregate passing Number 4 sieve,
good quality limestone ¾" as course aggregate. No Calcium
Chlorides/alkalis/mica/loam/clay/sulfates/sulfides/silt shall be
allowed.
- Cement water ratio.
> 0.45
- Concrete compressive strength.
4,500lbf/sq"at 28 days.
- Mimimum cement content.
330kg/m3 (550lb/yd3)
- Slump.
<3"on trucks
- Air entrainment
4.5% +/-11/2 %
- Water.
Clean potable water
- Admixtures for vapourproofing concrete.
Admixture to be included
14) Snow pit and Ice resurfacing
In order to maintain the ice sheet in pristine condition, at the design thickness, flat & even with no gouges, holes or
bumps, the ice pad must be resurfaced daily, dependant on usage upto 5 x/day. For this purpose various makes of
Ice resurfacing machines are available such as Zamboni or Olympia. These can be battery or gas powered & work
by scraping/shaving the ice surface with a blade and spraying warm water @ 60degC onto the ice surface to melt
the top few mm's of ice surface & bond a new layer of ice on top. The water has to be warm to remove as much air
as possible & melt the ice surface. Water temperature should not be higher than 60degC to avoid evaporation &
raising of the design 40-50% RH around the rink arena. The water should be de ionized & deaerated to provide
clear ice. The resurfacing machine cannot resurface right up to the edge of the rink dasher boards & therefore a
power hand 'edger' machine is also required to complete the resurfacing right to the ice surface edges. Ideally the
resurface machine should be electrically operated, many rink operators are expressing concerns at environmental
issues arising when using petrol or gas engine driven resurface machines.
The ice or snow removed from the rink requires a 'Snow pit' from 3 - 4m3 to melt snow removed during
resurfacing operations. The snow pit has to be heated & this can be achieved using a hot water pipe circuit
embedded in the base and sides to provide the heating means. The heating load is around 50kw based on
maximum 4 hour melt time. Hot water may be recovered via a heat interchanger located in the compressor
discharge line & a circulating pump. (Note care must be taken using screw compressors & discharge line heat
exchangers due to the lower gas discharge temperatures & enthalpy). Alternatively an inline electric resistance
heater can be used. Condenser water from the cooling tower circuit would not be a suitable source of heating due
to its low temperature e.g. 40degC. Using concrete pits a temperature differential of at least 55degC is required
due to the thermal resistivity of the concrete + PE heating piping + film coefficients.
The sketch below indicates how an ice resurfacer machine works
A blade shavesthe surface of the ice.
After a horizontal screw gathers the
shavings, a vertical screw propels them into the snow tank .
Water is fed from a wash-watertank
to a squeegee-like "conditioner" , which smooths the ice. Dirty water is vacuumed, filtered, and returned to
the tank.
Clean hot water is spread on the ice by a towel behind the conditioner.
The resurface machine blade (1) will need to be removed at least once per week & a spare blade should be on
hand to facilitate this. The resurfacer blade is over six feet long & needs to be sharp to insure a quality ice sheet. It
is located behind the horizontal auger just in front of the squeegee & is bolted onto the conditioner. At most
arenas, the blade is changed once a week at the same time that other maintenance is performed on the resurfacer.
The resurfacer blade is extremely sharp so it must be changed with caution.
15) Facilities
Generally a permanent ice rink will require the following facilities
- Snow pit.
- Skate boots for hire, for entry level + advanced level for boys/girls/adults
- Ice resurface machine, edger & garage.
- Shop for skate boot sale & hire, skater accessories.
- Blade sharpening facility for skates & resurface machine.
- Toilets.
- Good lighting with low emissivity.
- Changing room & lockers.
- Cafeteria.
- Audience seating arrangements & viewing facilities.
- Ticket booth & office.
- Maintenance engineer for refrigeration plant plus ice resurfacing.
- Dasher boards around the rink circumference.
- Rink non slip matting for rink surround & skate facilities.
- Audio system for music & announcements.
- Workshop for day to day running repairs and storage of rink sundries such as ice paint, spare parts,
refrigerant, glycol, tools.
16) Ice removal
Occasionally the ice sheet may have to be entirely removed to facilitate
- Maintenance or clearing discoloured or dirty ice.
- Temporary alternative use of the rink surface which requires removal.
- Repair of ice pad or tube leak.
The ice can be removed by switching off the refrigeration plant & breaking up the ice sheet & physically removing
it. Alternatively if drains are provided the ice can just be left to melt, in which case drain/s should be provided at
the rink periphery or centre of rink pad suitably insulated, with trace heating tape and solid covers. Drains should
also be provided in the header trenches.
17) Ice arena airconditioning, ventilation and dehumidification
The ice rink arena and surrounding spectator area and other associated facilities will require air conditioning to
maintain the design internal conditions and dew point temperature.Of particular importance is dehumidification
and dew point. The internal design conditions should be < 20degC 40%RH and ideally 15degC DB 8degC WB
(40%RH) which provides a dew point of 5degC.
Moisture is introduced from 5 main areas
 Ventilation fresh air
 Skaters
 Spectators
 Resurface water evaporation
 Refreshment and other ice auxiliary facilities
If the design conditions are not maintained, moisture will condense out on any surface below the dew point &
particularly on the ice rink itself. This increases the refrigeration load on the rink refrigeration system & creates
fog above the ice surface, due to the difference in vapour pressures of dry cold air above the ice & moist warm air
falling. The moisture condensed on the rink surface creates frost and an uneven ice surface.
For an average rink the water evaporated during a single resurface operation is approximately 25Lbs. To provide
an average hourly water evaporation load in Lbs/hr multiply 25Lbs x the resurface frequency (say 5) divided by
the hours of rink operation ( say 10hrs) e.g. 25 x 5/12 = 10.4lbs/hr.
In terms of the moisture load from skaters and spectators this can be calculated by multiplying the number of
skaters by 1.05Lb/person and the number of spectators by 0.1Lbs/person or a latent load in Kw or Btu can be
directly taken from the ASHRAE manual. As the numbers of skaters and spectators is variable over the daily rink
usage the average hourly moisture load can be calculated by dividing the total number of anticipated skaters or
spectators/day by the hours of rink operation e.g. 1,000skaters/day /10hrs = 100 skaters/hour.
To calculate the ventilation latent load the formulae for Lbs water is Fresh air CFM x 4.5 x Grains/lb difference
between fresh air & internal design conditions/7000. Alternatively the load can be calculated directly in terms of
refrigeration load by taking the enthalpy content difference of fresh & return air.
The fresh air ventilation load should be based only on the times of rink occupancy. ASHRAE 62 requires 0.5
cfm/sq ft of ice sheet & 7.5 cfm/person or spectator if they are in the arena for less than three hours.
In the Middle East ceiling insulation should not be a problem as the internal film surface temperature will not
approach the skating hall design dew point temperature.
18) Advertising
The ice can be painted any colour using brush or spray after the first two layers are laid using water soluble paints.
Additionally advertising may be provided by painting on the required logo using a template & brush or spray or
using pre-made canvas logos.
19) Investment and operating costs
It is difficult to predict budget costs due to the number of variables, e.g temporary or permanent, indoor, outdoor,
direct or indirect, type of refrigerant & chiller, rink construction and pipe arrangement, heat load, inclusion of
sundries like resurface machine & dasher boards, actual rink area. Costs/sqft do not reduce proportionately, so if
the cost of a 20,000sq ft (2,000m2) Olympic rink cost SR300/sqft (SR3,000/m2) a 10,000sqft would not cost
SR150/sq ft. Purely for feasibility purposes, an approximate figure to cover the refrigeration plant, dasher boards,
condensers, pumps, pad and installation would be SR300/sqft (SR3,000/m2) excluding the civil, building,
architectural costs, land purchase cost & debt service cost.
In Middle Eastern countries where few entertainment facilities are available, land generally is low cost relative to
Europe and USA, the potential return on investment should be higher. (In Europe & USA the ROI is generally low
due to high land, construction & operating costs plus debt servicing costs and many competing Ice Rinks in each
city or surrounding cities). If the rink is incorporated into an existing facility like a shopping mall or exhibition
hall the returns will be greater as the land, building, civil & architectural costs are already accounted for in the
mall costs and a rink can be added at little additional cost. In Europe entrance fees to Ice Rinks are typically
around SR20 and typical spending with skate hire, food & beverages is around SR40/person on average.
Additionally advertising revenues may be generated plus rental income from skate hire/sales, clothing sales, skate
sharpening. Shopping malls are an ideal location for Ice Rinks, as there is the benefit of attracting shoppers & their
children on top of dedicated skaters who would use the facility regardless of location. The income of course is all
cash & there are no provisions for bad or doubtful debts or receivables issues.
Al Salem Refrigeration division & York have a long history of Ice Rink design & refrigeration, with a large
majority of Ice rink developments around the world using York Industrial Refrigeration equipment. In particular
York has been the preferred company of choice for the supply of all the Olympic and Winter Olympic skating &
Bob sleigh events.