8.11
Kürleme Yöntemleri
Küçük yüzey-hacim oranına sahip beton elemanlar, beton eleman dökülmeden önce kalıpların yağlanması ve nemlendirilmesi ile kürlenir. Bu kalıplar, nem…
Beton dökülmeden önce yağlama ve nemlendirme formları, küçük bir yüzey-hacim oranına sahip beton elemanların kürlenmesine yardımcı olur.
Bu kalıplar belirli bir süre yerinde bırakılabilir ve ahşaptan yapılmışsa ıslatılabilir veya erken çıkarılırsa betonun nemlendirilmesi ve polietilen levhalar kullanılarak kaplanması gerekir.
Beton sertleşene kadar kuru havaya maruz kalan yeni döşenmiş geniş yatay beton yüzeylerin üzerine bir kaplama asılır, ardından ıslak kürleme yapılır.
Bir nozul sistemi kullanarak suyun püskürtülmesi veya sislenmesi ve beton yüzeylerin suyla göllenmesi veya su basması ıslak kürlemeyi kolaylaştırır.
Alternatif olarak, betonun nemli talaş veya samanla kaplanması veya periyodik olarak sulanan veya bir polietilen film ile kaplanmış ıslak kendir veya pamuklu paspaslar gibi doymuş nem tutucu kumaşlarla kaplanması, su-beton temasını sağlar.
Beton üzerinde geçirimsiz membranlar sağlamak, nemin buharlaşmasını en aza indirebilir ancak nem girişini önleyebilir. Bunlar, manuel olarak uygulanan veya nemli beton yüzeylere püskürtülen su geçirmez kağıtlardan, plastik levhalardan veya membran oluşturan sızdırmazlık bileşiklerinden yapılabilir.
Betonun laboratuvar test numunelerinin kürlenmesi, suya daldırılarak elde edilir.
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Q1: Why should concrete forms be oiled and moistened before pouring?
Oiling and moistening forms before pouring concrete aids in curing concrete members with a small surface-to-volume ratio. This preparation helps prevent moisture loss from the freshly cast concrete and facilitates easier form removal. Proper form conditioning ensures better moisture retention during the critical early curing period.
Q2: What are the main methods for wet curing concrete surfaces?
Wet curing concrete is achieved through spraying or fogging water using nozzle systems or by ponding and flooding concrete surfaces with water. Alternatively, covering concrete with moistened sawdust, straw, or saturated moisture-retaining fabrics like wet hessian or cotton mats maintains water-concrete contact. These methods ensure continuous moisture availability during the curing process.
Q3: How do impervious membranes affect concrete curing?
Impervious membranes made of waterproof papers, plastic sheets, or membrane-forming sealing compounds minimize moisture evaporation from concrete surfaces. However, these membranes prevent moisture ingress and cannot replace moisture lost through self-desiccation. They are applied manually or sprayed onto damp concrete to reduce surface water loss.
Q4: What should be done if concrete forms are removed early?
If concrete forms are removed early, the concrete must be moistened and covered using polyethylene sheets to maintain moisture content. This protective covering prevents rapid evaporation and ensures adequate hydration during the critical curing phase. Early form removal requires immediate protective measures to preserve concrete quality.
Q5: How are large horizontal concrete surfaces protected during curing in dry weather?
A temporary covering is suspended above freshly laid large horizontal concrete surfaces exposed to dry weather until the concrete sets. After the concrete hardens, wet curing is initiated using spraying, fogging, or ponding methods. This staged protection prevents rapid moisture loss during the vulnerable initial setting period.
Q6: Why is immersion in water used for laboratory concrete specimens?
Immersion in water is the standard curing method for laboratory test specimens of concrete because it provides complete and uniform moisture saturation. This method ensures consistent hydration conditions and allows accurate measurement of concrete properties under controlled curing environments. Water immersion represents ideal curing conditions for standardized testing.
Q7: Can wooden forms be left in place during concrete curing?
Yes, wooden forms can be left in place for a prolonged period and periodically wetted to prevent moisture loss from the concrete. Keeping forms in place protects the concrete surface and maintains moisture content during curing. If forms are made of suitable materials, they can be an effective moisture-retention strategy.