Requirements

Requirements for sprayed concrete and basic control tests

The purpose of using shotcrete methods in repairs of damaged concrete or reinforced concrete surfaces is to obtain a layer of sprayed concrete that will reflect the parameters set forth by the designer. The basic rule of such repair consists in good selection of repair material so that its properties are similar to properties of the structural concrete. Actually, there are no such materials that would meet all the requirements of each repair case. When deciding on repair with the use of shotcrete the designer determines final parameters of shotcrete and the contractor must select an adequate mix formula to comply with them.
The mix’s usability for repairs should be judged basing on the shotcrete complying with specific requirements.  Concrete made pursuant to the formula should prove adequate mechanical and physiochemical properties. The following should be tested:

• compressive strength,

• frost resistance,

• adherence to mineral base.

Sometimes, additional tests should be performed:

• water permeability,

• coefficient of elasticity E,

• shrinkage,

• tensile strength,

• protection efficiency (e.g. resistance to CO2 and chlorides),

• ageing resistance.

Tests

The final effect of the repair that was carried out is a resultant of all control activities performed in order to secure adequate technological conditions during spraying.
It is very important to carry out continuous control and supervision over the ongoing works. Tests performed directly on the structure guarantee the required qual