Contd. from Part-III ….
Some ready-to-use grouts prescribe mixing of small sized stone chips for certain cases, usually for larger gaps, in order to induce additional strength apart from reduction of cost. Normally, good quality stone chips of sizes varying from 6mm to 10mm are suitable for the purpose. However, grout manufacturer’s specifications usually provide clear guidelines on the same.
Most of the points regarding surface preparation, mixing or placing of grout are more or less same as discussed earlier for ordinary grout. Any special care, if suggested in manufacturer’s technical literature, should be diligently taken.
For certain grouts, mixing & placing may involve special mixing & vibrating equipments and grout manufacturer may advise deploying their own skilled personnel for better results.
Methods of testing common ready-to-use grouts are more or less same as discussed earlier. Relevant quality assurance documents e.g., codes, manufacturer’s specifications etc. are referred to for that purpose. As already mentioned, 3 & 7 days compressive strengths are the most referred ones. For approximate or general idea, the minimum cube compressive strengths for a common high strength ready-to-use industrial grout can be 23 N/sq.mm & 34 N/sq.mm for 3 & 7 day cubes respectively.
For large pours, it could be more appropriate to adopt pumping rather than manual pouring. For such purposes, various kinds of pumps, such as, diaphragm pump, screw feed & piston pumps etc. are available. Various types of pressure grouting methods or equipments are also available which may have to be choosen for certain cases.
Formwork should be rigid and rendered leak-proof using mastic sealant, foam rubber strip etc. In certain cases, it could be more appropriate to use well pre-soaked sacrificial cement-sand formwork. Sometimes, grout manufacturer’s literature provides guidelines on that as well.
Transferring of load to foundation is done as per specifications. Normally, the same is done after 3 to 7 days after completion of grouting depending on the type of the structure, characteristics of the grout used etc.