Why Manhole Non-Shrink Grout Shall meet the required compressive strength of 35 Mpa !!

 

 Manhole Non-Shrink Grout Shall meet the required compressive strength of 35 Mpa after casting period pf 28 Days testing will be done by laboratory. If we achieved compressive strength more than  mpa we should follow the below procedure.

 

 

 

Root Cause / Reason for Non-Conformity: -

 

• Prepared grout specimen at site is transported earlier than 24 hours after placement in which it must be cured first at site for a period of 3days.
• Molds used as forms for grout specimen are not precisely fixed with equal side before filling, when demolded dimensions are not accurately equal having a difference of 2-3mm when measured by vernier caliper.
• Prior compression testing, surface that will engage to the load cell are not uniformly levelled leading uneven stress distribution.
• Prepared grout specimen prior demoulding must be mark on the top side to indicate the surface where the load cell will engage during compressive testing.
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Correction Plan: -

• Grouted manholes affected by the failed grout compressive strengths shall be collected with a set of drilled cores for crushing tests to determine if actual site condition of placed grout meets the specified compressive strengths.

Corrective and Preventive Actions (To Avoid Recurrence): -

 

• QC shall strictly monitor the grout preparation for mixing, sampling, and testing.
• Third-party technicians shall ensure calibrated grout mold only to be used for preparing specimen.
• Demolding of specimen shall be carried out after 24hours and to be site cured in 3days prior transporting to the Third-Party laboratory for continuous curing.

Source From : Er. Munusawmy, Consultant, GOBI.