المشاركة الأصلية كتبت بواسطة samersss
استكمالا لما سبق فقد كان هناك نظام تسخين للبلاطة الخرسانية.
حسب الفترة الزمنية للتشغيل التجريبي والتي كنت فيها لمدة ثلاثة اشهر لم تحصل اية مشاكل ولم اسمع بعدها انه قد حصلت مشاكل في الخرسانه( مع العلم بان قدرة الثلاجة الواحدة كان 1000طن وليس 500 طن).
بخصوص الابوكسي فقد كان الهدف منه حماية وجة الخرسانه من التاكل بسبب forcklift.
هذا مع العلم بان هذا المشروع كان عام 1996-1997 وفي ذلك الوقت لم يكن هناك انترنت للبحث عن المشاكل للخرسانه في درجات التجمد ولم يكن لدينا الخبره في الخرسانة المتخصصه .
ولكن من خلال اطلاع على الكودات العالميه فانني انصح باستخدام الهواء ,والاضافات الكيميائية وانواع الحصويات حسبما ذكر في الملف المرفق
Chapter 12 of ACI 360R-06, “Design of Slabs-On-Ground,” describes the special considerations for slab-on-ground floors in refrigerated facilities. When the final operating temperature in the refrigerated room is 32 °F (0 °C) or lower, a layer (or layers) of rigid insulation is placed beneath the floor slab, as shown in the typical floor section in Fig. 1. Insulation only slows heat transfer, so the subgrade will eventually fall below freezing, possibly leading to frost heaving. Therefore, most freezers also include a heating system within the subslab to prevent the development of frost and minimize the risk of slab heaving. The slip sheet located on top of the insulation is typically a polyethylene film at least 6 mil (0.15 mm) thick that acts as a bond breaker between the floor slab and insulation. A second polyethylene film at least 15 mil (0.38 mm) thick, a 10 mil (0.25 mm) thick polyolefin, or a 45 mil (1.14 mm) thick ethylene propylene diene monomer (EPDM) membrane is placed on the warm (bottom) side of the insulation to act as a vapor retarder that slows the transmission of moisture migrating up through the slab and freezing on the floor surface. Depending on the specific application and site conditions, some of the layers shown in Fig. 1 may not be used.
Fig. 1: Typical section through a slab-on-ground floor for a freezer facility (from Ref. 1)
Many of the special considerations specific to slab-on-ground floors for freezers are related to the insulation layer. For thickness design of the floor slab, the insulation stiffness should be evaluated on the proposed subgrade using the procedures for determining the modulus of subgrade reaction of soil given in ASTM D 1196
Insulation manufacturers will often report foundation modulus data found using the procedures in ASTM D 1621 but the results of these tests can be significantly higher than tests performed per ASTM D 1196 and should not be used for design of the slab. Compressive creep due to sustained loads on the insulation should also be considered. Limiting the live and dead loads to 1/5 and 1/3 the compressive strength of the insulation, respectively, is recommended to limit long-term creep to 2% of the insulation thickness over a 20-year period
The presence of the insulation layer also affects the tolerances for the subgrade and the slab formwork. To allow the insulation to lay flat with uniform bearing, a tolerance of +0/–1/2 in. (+0/–13 mm) from the specified elevation should be maintained for the base or subslab layer directly below the insulation. Formwork can’t be staked to the subgrade because the stakes would perforate the insulation and vapor retarder, so forms for freezer floors are typically attached to a horizontal base, such as a sheet of plywood, that is weighted down with sandbags to hold the formwork in place
Although joint spacing for freezer floors generally follows the same guidelines as for ordinary slabs, joint filling and detailing may require special consideration. Because of the additional shrinkage that will occur when the slab is cooled, joints should not be filled until the room is at its operating temperature and the slab temperature has stabilized. Anticipated joint widening and warping (curling) potential of the concrete mixture should also be evaluated and minimized by measuring the drying shrinkage of the concrete and optimizing the mixture for low shrinkage. If the floor will be subject to heavy wheeled traffic loads, armored construction joints should be considered to reduce floor maintenance that would have to be performed under freezing temperatures or while the facility is shut down
Air entrainment is generally not recommended, as freezer floors are not expected to undergo multiple cycles of freezing and thawing, and moisture is typically not present on the slab
The washdown and temperature cycling of the facility should be carefully reviewed with the owner to determine if air entrainment is appropriate. If air-entrained concrete is used, extreme care should be exercised when finishing the slab, especially if hard-troweling is performed, to avoid the development of surface delaminations. Hard troweling air-entrained concrete results in a high risk of surface delaminations, as the air is manipulated during repeated finishing and can coalesce beneath the densified surface
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مع تحياتي للجميع
م. رزق حجاوي