2018-11-1_PR Comm Packet - Laserfiche WebLink

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The refrigerated concrete slab was placed in 6 large monolithic pours which ultimately are joined in a way to provide a “bandy” rink slab and two end loop slabs that form the radiused ends of the speed skating oval. The bandy slab, approximately 365’ x 230’, acts as one large slab and is an assembly of four reinforced concrete rink cooling zones cold jointed together with continuous steel reinforcement bars. The two end loops are not directly connected. Rather they are seamed together with four refrigerated expansion joints at the four corners of the bandy slab. The expansion joints accommodate the large thermal movements to minimize stress in the 110,000 square-foot refrigerated concrete slab. The rink slab is generally in good shape given its 25 years of operation. There is some surface staining of the concrete, small hairline cracks in many locations, and some deterioration of the expansion joints. But it remains reasonably level over the whole of the slab. The refrigeration capability is good, maintaining skatable ice into the warm 60-degree days at the end of the skating season. The center-header trench, which runs perpendicular to the length of the Oval, has settled somewhat, but not to the point of causing any real performance issues. There have been a few leaks in the one-inch diameter rink-floor cooling tubes. The only in-slab leak occurred immediately after the rink floor was put into operation in 1993. There has been some leakage from the small diameter tubing in the refrigerated expansion joints over the years but that has been easily repaired since leakage was not actually located in the concrete refrigerated floor. Rather leakage was located in sand which is part of the expansion joint. The cooling tubes are also metric pipe manufactured in Sweden with a thinner pipe wall than what is typically used in the USA. This tubing is more easily damage during installation but because of its thinner pipe wall has better thermal heat transfer and efficiency than that currently used in the USA. The expansion joints have seen some stress over the years and currently the two southerly joints are heaving during the winter skating months while for the most part, returning to their original elevation after all the sub slab ice melts. The southeast joint has some residual displacement across the joint near the outer 8 feet due to soils that have migrated under the slab and prevented it from resettling back in place. The heave at the southwest joint has been significant and has resulted in some permanent damage to the concrete slab. The south end of the bandy rink also heaves along with a few other areas where water migrates under the slab edges from ice resurfacer water, melting snow, winter rains and other sources of perimeter moisture. The heaving is all a result of these winter water sources finding an easy path under the refrigerated slab, overwhelming the subsurface drainage systems, backing up and coming in direct contact with the refrigerated concrete surfaces, and ultimately freezing and expanding on those cold concrete surfaces. The activity is primarily the result of the degradation of the adjacent asphalt and grass surfaces that no longer are draining the water away from the refrigerated slab. 171717