Case Study: Pop-out phenomenon

The pop-out phenomenon, i.e. the expulsion of small surface parts of concrete in floors, often associated with cracking, is generated by the reaction between a particular type of aggregate (alkali-reactive silica), cement and water in the form of rising damp. The aggregate reacts to the alkali present in the cement (potassium and sodium alkali) and by means of a hydration process causes an expansion process of the aggregate itself that leads to pop-out and cracking. This reaction is commonly called ASR (Alkali-Silica Reaction).

Unfortunately the pop-out phenomenon is still one of the less predictable deterioration causes, it can appear up to ten years after casting the floor, and the technical manuals do not provide clear systems for diagnosing the state of the floor. Consequently the progress of pop-out process is very difficult to foresee.

Prevention: Evercrete Pavishield® is very effective if used as a preventive measure, maybe combined with other technologies such as a vapour barrier;

Repair: we have experienced that Evercrete Pavishield® is equally effective in significantly slowing down or even stopping floor deterioration. Anyway we prefer to underline that each floor affected by pop-out is a specific case and that, if the ASR is in advanced state, the phenomenon cannot be stopped easily.

Evercrete Pavishield® is a special long lasting protective agent for concrete industrial floors. Its formula, based on waterglass with a special catalyst, allows the product to penetrate up to a depth of 34 mm into the concrete sealing its porosity, becoming a permanent barrier in time.

The reaction of Evercrete Pavishield® takes place between the sodium silicate and the alkali cement, always through a hydration process, but in this case not expansive. In this way you remove two of the three components necessary to trigger the pop-out (ie, water and alkali), at least for the first three centimetres of the surface. Evercrete Pavishield® also increases the resistance to surface compression of about 5-6 N / mm ², acting as a consolidating agent and then further contrasting the pop-out.

Treatment effectiveness

Evercrete Pavishield® is very effective when used as a preventive measure, also in combination with other technologies such as vapour barrier. In our experience, the product was as effective in slowing down or even stopping existing degradation. However, each floor affected by pop-up is peculiar, and sometimes if the phenomenon is in an advanced state, it is not easily stoppable.

Application

In floors affected by pop-out, the following procedure is recommended:

  1. Removal of the surface layer (quartz) via mechanical abrasion (sandpaper). The operation is necessary to ensure the penetration of the product, since quartz tends to close the pores of the concrete.
  2. Floor washing with washer dryer or pressure washer. This operation ensures a surface cleaning and the rise in the alkaline level in the concrete, as it is necessary to unleash the reaction with Evercrete Pavishield®.
  3. The surface must be damp but not wet (e.g. the day after washing). Apply the first coat of Evercrete Pavishield®, with low pressure pump (the product should be applied to saturation).
  4. After at least 3-4 hours, apply the second coat. Coverage rate is about 0.4-0.5 litres per m², depending on the porosity of the concrete.
  5. Within 24 hours after the second coat, wash the floor to remove any excess product on the surface.
  6. Repair the floor with Bonding Agent and Ercole.
  7. Apply one coat of Evercrete Pavishield® over repairs.

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