Release Agents and Admixtures for Concrete and Mortar

A release agent is applied to the formwork before the pour, so the concrete does not stick to it when the shuttering is removed. It protects timber, steel and panels and helps to give a clean cast surface. The collection includes formulations for timber, steel and concrete formwork, suited to different uses. Apply it in a thin, even coat, following the instructions on the product's technical data sheet.

The concentrated release agent, such as Nuovo Disarmoil for timber formwork, must be diluted before use. The pre-emulsified type, such as Emulsform, is ready to apply, while Ecofinish, a water-based emulsion, is applied straight from the container. The creamy Prontosform is intended for exposed concrete faces. The choice depends on the type of formwork and the finish required. For dosages and timings, always read the technical data sheet.

The formwork material guides the choice. Timber absorbs more and needs a release agent designed for this surface, such as Emulsform. For steel, a low-viscosity product such as Sformacer is better, applied in a thin coat. Alchioil 100 is suitable for timber, steel and concrete, so it is a good choice for mixed formwork. Before using it on new formwork, check on the technical data sheet which surfaces are compatible.

Admixtures are added to the mix to change how it behaves. The collection includes setting accelerators, such as Siriomix, surface retarders such as EXP 50 for concrete, integral water-repellent admixtures such as Hydromas for mortars and concrete, and the Sirio Silicafume silica fume. The type should be chosen according to the effect you want to achieve, and the dosage should be checked against the technical data sheet and with a preliminary trial.

Some synthetic resins are mixed into the mortar during batching. These include Kimitech BC, designed for powder mortars, Kimitech ELASTOFIX for waterproofing mortars and adhesives, and Kimitech EP-RG for mortars that need to be made more waterproof and better bonded. Resivil vinyl latex is a waterproofing adhesive for mortars and concrete. Too much resin can alter the set, so the dosage must be respected.

Polypropylene fibres, such as Siriofibre, are added to the mix during batching and are distributed throughout the mass. In the first hours of curing they help to counter plastic shrinkage and surface cracking. Structural fibres, such as Siriofibre STX, have a different function and must be chosen according to the design. For dosages and mixing times, follow the technical data sheet and, for structures, the advice of the designer.

The first step is the technical data sheet, which gives the dosages relative to the cement and the type of application, such as mortar, concrete or exposed-face casting. It is then advisable to test a small batch before the real job, to check setting, workability and the final appearance. Admixtures should not be mixed with one another without checking, because the reactions can change the result. If in doubt, ask the manufacturer or the technical dealer.