why we do multiply 1.54 for dry volume of concrete?

Answer Posted / bhupinder salwan

For converting wet volume of concrete to dry volume of material mix we multiply it by 1.52 to 1.54. As water is added in dry material to make it wet concrete and then placed in shuttering particles slides to readjust in pores and voids reducing the volume of it. The void ratio compressibilty of stone aggressive is 32 to 33% where as that of sand is 20%. Assumig the cement particles being very fine get adjusted in compressed voids total volume of dry material (having 0.33 +0.20=0.53 voids) has nearly 52 to 54 % more volume than when in wet state.So volume of dry material for concrete is arrived at by multiplying wet concrete qnty by 1.54. Based on same reason if we want to get volume of dry material for mortar wet volume should be multiplied by 1.20. However some engineers add 5% to 10% to multiplicative figure of 1.54 or 1.20 to account for wastage and poor workmanship. Hope it is clear.

By Bhupinder Salwan Executive Engineer Indian Railways.

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