Contd. from Part-II….
Pre-packed, ready-to-use grouts have many advantages over ordinary grouts prepared in-situ with OPC. One need not worry about procuring ingradients or mix proportion etc. as everything come ready in bags and it just needs to be mixed with water or the prescribed fluid as per manufacturer’s literature. These grouts are readily available with non-shrinking or free flowing characteristics, eliminating issues like shrinkage of grout, workability etc. substantially. Many of these grouts are tailor-made for specific purposes offering plenty of varieties to choose from for various purposes. Most of these compounds offer quite high strength and could be choosen as per strength criteria as well. Procedures for storing, mixing, grouting, testing etc. are usually well laid down in manufacturer’s specifications and one just needs to follow those carefully.
Some useful points about these grouts are briefly discussed here:
While purchasing packaged grout, relevant test certificates from the manufacturer should be scrutinised & collected.
Grout’s brand name, type, date of manufacture, batch number, date of expiry etc. usually come clearly printed in the bags containing grout. The same should be checked properly.
Grout bags should be stored in a dry & cold place protected well from moisture. Well stored grouts can be used upto 6 months from the date of manufacture.
Similar to w/c ratio in the case of grouts prepared in-situ with OPC, these grouts correspond to water to powder (w/p) ratio.
Restricting w/p ratio is quite important and normally the manufacturer’s specifications prescribe clear guidelines on it.
Some structures may call for grout of flowable consistency while some other may need grout of pourable consistency.
Flowable grout has higher w/p ratio as compared to pourable one. In other words the former is more workable than the later. A smaller or complicated gap could ask for a flowable one rather than a pourable one from workability point of view.
The optimum w/p ratios for both flowable & pourable conditions of a grout mix and the corresponding minimum cube compressive strengths for 1, 3, 7 and 28 days are usually clearly specified in manufacturer’s technical literature or similar quality assurance documents. Tests are conducted accordingly as part of quality control measures.
W/p ratio prescribed should be strictly adhered to. Trial mixes may be conducted in order to confirm desired fluidity or workability, strength etc. with prescribed w/p ratio.
In certain cases it may become quite necessary to use workability enhancing admixtures. However, such additives should only be used if manufacturer’s technical liturature on the product mentions provision for the same.
Concluded in Part-IV…..