Calculate Sand & Gravel per 50kg Cement Bag in Volume & Weight

Calculate Sand & Gravel per 50kg Cement Bag in Volume & Weight

Proper batching of cement, fine aggregate(sand) and coarse aggregate(gravel or jalli) are important to get a good quality of concrete. This article will show you how to calculate sand and gravel needed per bag of cement (50kg) to prepare concrete as per the codebook.

Let’s first understand the role of different ingredients in making concrete. Cement is the active ingredient that binds the inactive ingredients and gives strength to concrete, whereas aggregates like sand and gravel act as filler materials to reduce the usage of cement and decrease the shrinkage in concrete.

Based on strength, concrete is classified into different grades like M5, M7.5, M10, M15, M20, etc.. Number in the grade denotes the strength of the concrete is 28 days. We can achieve targeted strength by using proper quantities of materials to prepare concrete.

Weight of Sand and Gravel (Jalli) needed for 1 bag of Cement

Calculating ingredients in terms of weight is called weigh batching. They are used in places like ready mix plant and laboratories to get accurate results. Codebook suggests the following total aggregates (sand + gravel) per 50kg bag of cement. It does not give separate values for sand and gravel so we have to find them on our own.

Table 9 Proportions for Nominal Mix Design – IS456

CONCRETE GRADE	CEMENT (BAGS)	TOTAL AGGREGATES (SAND + GRAVEL)
M5	1	800 kg
M7.5	1	625 kg
M10	1	480 kg
M15	1	330 kg
M20	1	250 kg

The ratio of fine aggregate to coarse aggregate to be used in concrete is 1:2, which means that for every 1 part of sand we have to take 2 parts of gravel. Hence we have to divide the Total Aggregate into 3 parts and take 1 part as sand and 2 parts as coarse aggregate.

Let's calculate the weight of sand and gravel needed for M15 Grade concrete.

Weight of Sand required per bag of cement = (330/3) x 1 = 110 kg

Weight of gravel required per bag of cement = (330/3) x 2 = 220 kg

Therefore to prepare M15 Grade concrete, use 110 kg of sand and 220 kg of gravel per bag of cement.

Weight of sand and gravel needed per bag of cement for different concrete grades

CONCRETE GRADE	CEMENT (BAGS)	SAND (KG)	GRAVEL (KG)
M5	1	265	535
M7.5	1	210	415
M10	1	160	320
M15	1	110	220
M20	1	85	165

The volume of Sand and Gravel needed for 1 bag of cement in cubic feet CFT

Calculating ingredients in terms of volume is called volume batching. Volume batching is preferred for the onsite preparation of concrete. It is easy and faster than weigh batching. Codebook suggests the following volumetric mix ratio for different grades of concrete.

Let's calculate the volume of sand and gravel needed to prepare M15 grade concrete

Mix Ratio of M15 grade concrete is 1:2:4. Hence for every 1 part of cement, we have to use 2 parts of sand and 4 parts of gravel to get M15 ratio concrete. The volume of the 50 kg cement bag is 1.25 CFT. We can check this value by dividing the weight of the cement bag by the bulk density of cement. The volume of batching box used in the construction site is also 1.25 CFT.

Mix Ratio of M15 Grade concrete = 1:2:4

Volume of sand needed = Volume of cement bag x Ratio of sand

Volume of sand needed = 1.25 x 2 = 2.5 CFT

Volume of Gravel needed = 1.25 x 4 = 5 CFT

Therefore to prepare M15 Grade concrete, use 2.5 cubic feet of sand and 5 cubics of gravel per bag of cement.

The volume of sand and gravel needed per bag of cement for different concrete grades

CONCRETE GRADE	CEMENT (BAGS)	SAND (CFT)	GRAVEL (CFT)
M5	1	6.25	12.5
M7.5	1	5	10
M10	1	3.75	7.5
M15	1	2.5	5
M20	1	1.88	3.75

Please note that the above quantities are only prescribed quantities and slight variations in the quantities are allowed, and even sometimes they are desirable. For example, a slight increase in the quantity of sand can save cost on cement and also increase the shrinkage resistance. But, quantities of aggregates should not be increased by more than 20% than the prescribed quantities given above. Always consult the engineer for making any changes in the quantities given above.

Liters of water needed per 50kg bag of cement

W/C ratio is not applicable for nominal mix ratio concrete. IS456 Table 9 suggests the following liters of water for M5, M7.5, M10, M15, M20 grade concrete. Normally, Engineers use the known volume of containers or buckets to measure water for concrete.

CONCRETE GRADE	LITRES OF WATER PER 50KG CEMENT BAG
M5	60 Liters
M7.5	45 Liters
M10	34 Liters
M15	32 Liters
M20	30 Liters

Also Read: 

Cement Sand and Aggregate needed for concrete in volume and weight

 http://civilbaselife.blogspot.com/2020/04/cement-sand-and-aggregate-needed-for.html 

Er.SP.ASWINPALANIAPPAN., M.E.,(Strut/.,)

Structural Engineer

Madras Terrace Architectural Works

www.civilbaselife.blogspot.in

M35 Grade Concrete Mix Design with Fly Ash – IS10262

M35 Grade Concrete Mix Design with Fly Ash – IS10262

This article covers the mix design calculation of M35 Grade Concrete with Ground Granulated Blast Furnace Slag (GGBS) admixture and Poly Carboxylite type superplasticizer as per Indian Standard Codebook IS10262(2009) – Guidelines for Concrete Mix Proportioning.

Mix Design calculation procedure is the same when either GGBS or Fly ash is used, the only change will be the specific gravity of the admixture. The specific gravity of fly ash ranges from 2.1 to 3 whereas the specific gravity of GGBS is 2.85. Superplasticizers are required for all high strength concrete to get good workability and good strength in concrete.

I. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE

This section deals with the conditions and requirements of the concrete to be made.

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A	Grade Designation	M35
B	Type of Cement	OPC 53
C	Type of Admixture	Fly ash
D	Maximum Nominal Size of Aggregate	20mm
E	Minimum Cement Content	340kg	Table 5-IS456
F	Maximum Cement Content	450kg	As per code
G	Partial replacement of cement by Fly ash	30%	as per requirement
H	Maximum W/C ratio	0.45	Table 5-IS456
I	Workability	100mm
J	Chemical Admixture	PCS Type

II. TEST DATA FOR MATERIALS

Materials should be tested in the laboratory as per tests given in the codebook and their properties should be found. The values of the material properties will be used in the design process and to check the quality of the material with the help of codebook standards. Standard values are taken here for calculation purposes.

A	Cement Used	OPC 53	Confirming to IS8112
B	Specific Gravity of Cement	3.15	Test – IS: 2720
C	Mineral Admixture	Fly ash	Confirming to IS12089
D	Specific Gravity of Fly ash	2.90
E	Chemical Admixture	@0.6%	IS9103
F	Specific Gravity of		Test – IS 2386
	Coarse Aggregate	2.74
	Fine Aggregate	2.74
	Admixture PCE based	1.12
G	Water Absorption		Test – IS 2386
	Coarse aggregate	0.5 %
	Fine aggregate	1 %
H	Sieve Analysis		Test – IS 2386
	Coarse aggregate		Confirming to Table 2-IS383
	Fine aggregate	Zone II	Confirming to Table 4-IS383

III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

The strength of the concrete may deviate slightly depends on the quality of the material, method of mixing, and construction practices. Hence target strength (F_ck) should be higher than the required strength of the concrete (f_ck). The value of standard deviation(s) for different grades of concrete is given in Table 1 of IS456.

Fck	= fck+1.65s	“S” from Table1-IS10262
Fck	= 35+1.65×5
Fck	= 43.25 N/mm2

IV. SELECTION OF WATER-CEMENT RATIO

The maximum water-cement ratio for different grades of concrete is given in Table 5-IS456. You can reduce the water-cement ratio based on your requirements. The Water-cement ratio directly affects the strength of the concrete.

Maximum W/C ratio	=0.45	Table 5-IS456
Adopted W/C ratio	=0.45

V. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2-IS1026

Above water-content is for 25 to 50mm slump but the slump we require is 100mm. hence we need to increase the water content to get the required slump for good workability. Clause 4.2 of IS1026 suggests an increase of 3% of water content from its original value for every increase of 25mm. Here we have a 50mm increase in the water content hence we have to increase the water content by 6 %.

Water-content for 100mm Slump	=186+(0.06*186)
	=197.16 L

Since superplasticizers are used water content can be reduced to get good strength of concrete. The percentage of reduction of water depends on the type of superplasticizers used in the concrete.

Percentage of Reduction in water content	=20%
Water content requirement after SP	=198 – (0.20*198)
	=157.73
Adopted Water Content	=160 L

VI. CALCULATION OF CEMENT AND FLY ASH CONTENT

Adopted Water Cement Ratio	=0.45
Total Cementitious (Cement +Fly ash) requirement	= Water Content / WaterCement ratio
	=160/0.45
	=355.55 kg

Since Fly ash is used the amount of Cementitious content (Cement+Fly ash) shall be increased to get good workability and strength. the percentage of increase depending on experience and research. Here we increased the cementitious content by 1.1 %.

Final Cementitious Content (Cement+Fly ash)	= 356*1.1
	=391.6 kg
Minimum Cement Content required for ‘severe’ exposure	=340kg	Table 5-IS456
Adopted Cementious content	=391.6 kg	> 340kg

Fly ash content requirement	= 391.6 * 0.30	30% replacement
	= 117.48 ~ 118 kg
Cement Content requirement	=Cementious content – Fly ash
	=391.6-117.48
	= 274.12

Calculation of Super Plasticiers @ 0.6 percent to the mass of cementitious content = = 391.6*(0.6/100) = 2.35 kg

VII COARSE AND FINE AGGREGATE

Coarse Aggregate ratio	= 0.62	Table3-IS10262 (For W/C =0.5)
Coarse Aggregate ratio for 0.45 w/c ratio	= 0.63	(adding 0.01 for every decrease .05 and vice versa)
Final Fine Aggregate ratio	= 0.37	(1-0.63) = 0.37

VIII MIX CALCULATIONS OF M35 GRADE CONCRETE

A	Volume of Concrete	= 1 cu.m
B	Total Volume of Cement	= Cement/(S.G*1000)
		= 275/(3.15*1000)
		= 0.087 cu.m
C	Total Volume of Fly ash	= Flyash/(S.G*1000)
		= 118/(2.5*1000)
		= 0.041 cu.m
D	Volume of Water	=Water /(S.G*1000)
		= 160/(1*1000)
		= 0.160 cu.m
E	Volume of Superplasticizers	= Superplasticizers /(S.G*1000)
		= 2.35/(1.12*1000)
		= 0.002 cu.m
F	Total Aggregates requirement	= A – (B+C+D+E)
		=1 -(0.087 +0.041+0.160+0.002)
		=0.71 cu.m
G	Coarse Aggregate (C.A)	= F * C.A ratio * S.G * 1000
		= 0.71*0.63 *2.74 *1000
		= 1225.6 kg
I	Fine Aggregate (F.A)	= F * F.A ratio * S.G * 1000
		= 0.71*0.37*2.74 *1000
		=719.8 kg

Cement Flyash Sand Aggregate Water and Superplasticizer needed for M35 grade concrete

S.No.	MATERIALS	QUANTITY
1	Cement	275 kg
2	Fly ash	118 kg
3	Fine Aggregate	720 kg
4	Coarse Aggregate (20mm)	1226 kg
5	WATER	160 L
6	PCE based SuperPlasticizer	2 L

To find the design mix ratio divide the calculated value of all materials by the weight of cement. Therefore Mix Ratio of M35 Grade concrete by weight is Cement : Flyash: F.A: C.A: Water = 1:0.4:2.6:4.46:0.58

Er.SP.ASWINPALANIAPPAN., M.E.,(Strut/.,)

Structural Engineer

Madras Terrace Architectural Works

www.civilbaselife.blogspot.in