Essentials of

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Part 1--Selecting and Mixing Mortar Materials


The overlapping arrangement of the concrete block or bricks in the wall is called a mortar bond. A bond is achieved when the mortar hardens and knits them together. The strength of the mortar bond is affected by the-

  • Type and quality of the cementing material.
  • Workability or plasticity of the mortar.
  • Surface texture of the mortar-bedding area.
  • Water retention of the mortar.
  • Quality of the workmanship.

1-9. Sand. Clean, sharp sand produces excellent mortar. Too much sand causes the mortar to segregate. You can make mortar that is easily workable by properly grading the sand and thoroughly mixing the other aggregates.

1-10. Water Retentivity. Loss of moisture due to poor water retention results in the rapid loss of plasticity and may seriously reduce the strength of the bond. To ensure the strength of the bond-

  • Keep concrete blocks dry until they are built into the wall.
  • Do not wet concrete blocks/bricks to control suction before application of mortar.
  • Use lime where weather conditions are hot and dry. Lime slows down the evaporation of moisture in mortar, since it retains water.


David L. Heiserman, Editor

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Revised: June 06, 2015