Method of Determination of Compressive Strength of Concrete Cores

 NAME OF TEST:-       Method of Determination of Compressive Strength of Concrete Cores     OBJECT:                      The Compressive Strength of concrete core samples drilled from the structure is performed to assess the quality and strength of concrete.                                        

THEORY:                     
          The estimated in-situ cube strength can be determined from the measured compressive strength of core using the following formula:                      

x Measured Compressive strength of      core strength

D       1.5 + 1/ λ

Estimated in-situ cube strength =

                       

 

 

                                     D = 2.5 for cores drilled horizontally

                                    D = 2.3 for cores drilled vertically

λ  =

                                            Length after preparation

                                            Diameter of core sample    

             APPRATUS:

           

                  -Cutting & grinding equipment,

                  -Capping equipment & Material

                  -Compression testing machine

                  - Vernier Calipers

                  - Weighing balance

 

Reference Standard – BS 1881 – Part 120 - 1983 

 PROCEDURE

·         Take out core samples from curing tank at 20+2⁰C after two days.

·         Allow the core samples to dry for 2 to 3 hrs. in ambient condition.

·         End preparation for sample to be done either by capping or grinding.

·         For end preparation by capping, heat the capping material to approximately 130⁰C to 150⁰C and stir continuously.

·         Pout the mixture into a level machined steel plate thinly coated with paraffin.

·         Place core sample into this layer with its axis vertical.

·         Cut away surplus material around specimen with a sharp knife and lift specimen off the plate.

·         Test the core in compression in compression testing machine.

·         Apply load without shock and increase the load continuously at a constant rate within 0.2 N/mm²-S to 0.4N/mm²-S till failure.

·         Record the maximum load.

·         Determine compressive strength and estimated in situ cube strength.

PRACTICAL CIVIL ENGINEERING