Ea Design a concrete mix for the volume method: ollowing conditions and constrai

Question

Ea Design a concrete mix for the volume method: ollowing conditions and constraints using the absolute Design Environment 1- Exterior column above ground level wet exposed to freezing 2- Required design 30 MPa 3- Column dimensions are 0.3 m*0.3m 4-Standard deviation of compressive stengh of 3 MPa is expected (more 5-Only air entrainer is allowed 6-Cement :Select Type l sp.gr.= 3.15 7- Coarse aggregate 19 mm maximum size, river gravel (round) Bulk oven dry specific-2.68 Absorption= 1% surface moisture= 0.5% based on SSD Oven dry-rodded density 1602 kg/m 8-Fine aggregate Natural sand Bulk ovendy specific gravity =263 Absorption= 1 .39 surface moisture content-4.2% Fineness modulus 2.70

Explanation / Answer

SOLUTION :

Target Mean Strength = 30 + 3 = 33 Mpa

ABSOLUTE VOLUME (V)

Absolute Volume = weight of material / (specific gravity of material x unit weight of water)

Take unit weight of water = 998 kg/m3

Absolute Volume for Coarse Aggregate = (1602 ) / (2.68 * 998) = 0.599 m3

Take Natural sand  unit weight = 1520 kg/m3

Absolute Volume for Fine Aggregate = (1520 ) / (2.63 * 998) = 0.579 m3

Absolute Volume for Cement = (1440 ) / (3.15 * 998) = 0.458 m3

So total Volume = 0.599 + 0.579+0.458 = 1.636 m3

Water is assumed to be 5% = 1.636 * 1.05 = 1.72 m3

Air is only entariner is allowed so assumed as 4% = 1.72 * 1.04 = 1.79m3

So the Volume of Air is = 1.79 - 1.72 = 0.07 m3

To find

BULK SPECIFIC GRAVITY SATURATED SURFACE DRY (Gs(ssd)) for CA

Gs(ssd) = (1 + Absorption) x Gs(dry)

= (1+0.005) * 2.68 =2.693

BULK SPECIFIC GRAVITY SATURATED SURFACE DRY (Gs(ssd)) for FA

Gs(ssd) = (1 + Absorption) x Gs(dry)

= (1+0.013) * 2.63 =2.66

WATER-CEMENT RATIO (w/c) = 0.5

Weight of Fine Aggreagate = 0.579 * 2.66 * 998 = 1537.06 kg

Weight of Course Aggreagate = 0.599 * 2.693 * 998 = 1609.88 kg

Weight of Cement = (0.458 * 3.15 * 998) / 4.2 = 342.8 kg

Observations should be conduct with the above mix proportions

we should get with more than 30 samples 33Mpa. If not achived we should increase the ceemnt and water by 2.5% and again test with obserations.

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