Dear reader we were discussing about admixtures for grout to be applied in micropile construction. Admixtures in concrete, mortar and grout help to overcome many limitations of cementitious materials as discussed in previous part.
All admixtures to be used in grout should comply with the requirements provided by ASTM C494, alternatively AASHTO M194.
When sealed encapsulation is filled with grout, the expansive admixture is generally used in grout. Admixture selected for grout should be compatible with it and recommendations of manufacturers are followed for mixing to ensure proper dose and quality of mixing.
The admixture required for controlling bleeding, reduction in water content, elongating setting time and improving flowability of grout should be used after reviewing and acceptance of owner. Admixture that contains chlorides should not be used in grout as it threatens the longevity of micropile reducing durability.
If required or building official have any doubt about admixture, appropriate field tests are conducted say for expansive admixture-field tests in fluid and setting of grout.
All cement to be used in micropile construction should confirm ASTM C150 or AASHTO M85 Type I, Type II, Type III and product should be of same manufacturer. However brand/type of cement may be changed during construction of project; in this case some tests like grout mix tests should be conducted to assure consistency in quality of construction and in-situ performance too.
Sometimes filler materials like sand are used in grout and before use should be approved by owner. Fillers are required in special situations like
-Larger voids are found
-To limit travelling distance of grout