Random Rubble Masonry (RR Masonry) is a type of construction technique used in building walls, foundations, and other structures. It involves the use of irregularly shaped and sized stones or rocks that are laid together without any definite pattern or uniformity. Instead of carefully cut and shaped stones or bricks, random rubble masonry uses the natural shape and size of stones found in the surrounding area.
In RR (random rubble masonry), the rough, irregular and unequal size of stones are used to build the wall structures. The typical stones are arranged by irregular dressing without any layers in the construction works. Or the stones are arranged in courses of equal height by neatly dressing & hammering them. The stones of equal size are selected to build the outer face of the retaining wall & to maintain the layers.
Due to unequal layers of RR masonry, it is difficult to estimate amount of mortar, cement, sand and stones. However, the certain thumb rules are used in the estimation of stones, cement, sand and mortar for RR masonry works.
RR Masonry (Random rubble masonry)
The thumb rules for RR masonry are following:
1) the amount of stones required for the random rubble masonry is 1.25 times the total volume of the structure. For example, suppose, if the volume of the stones masonry wall is = 20 cubic feet, then you need the volume of the stone requires to build the wall is 1.25 × 20 cu ft. = 25 CFT.
2) The dry volume of the mortar required for the stones or RR masonry (random rubble masonry) structure will be 40% of the total volume of the RR masonry. For example, suppose, if the volume of the RR masonry wall is 20 CFT, the amount required dry volume of the mortar will be 20 × 40% = 8 CFT.
If your volume of RR masonry work is 1m3, then as per thumb rule you need about 1.25 m3 (1 × 1.25 = 1.25 m3) of stones and 0.4 m3 (1 × 40% = 0.4m3) of dry volume of mortar.
The typical amount of stones and dry volume of mortar required for 1 m3 (cubic meter) of RR masonry is about 1.25 m3 of stones and 0.4 m3 of dry volume of mortar. Thus, a typical 1m3 of RR masonry requires 1.25 m3 of stones and 0.4 m3 of dry volume of mortar.
The typical amount of stones and dry volume of mortar required for 1 cubic foot (CFT) of RR masonry is about 1.25 CFT of stones and 0.4 CFT of dry volume of mortar. Thus, a typical 1 CFT of RR masonry requires 1.25 CFT of stones and 0.4 CFT of dry volume of mortar.
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RR masonry 1:6 ratio cement and sand calculation
If your volume of RR masonry work is 1m3, then as per thumb rule you need about 1.25 m3 (1 × 1.25 = 1.25 m3) of stones and 0.4 m3 (1 × 40% = 0.4m3) of dry volume of mortar.
Given ratio of cement to sand is 1:6, total proportion = 1+6 = 7, part of cement = 1/7, and parts of sand = 6/7. Sand density = 1600 kg/m3 and cement density = 1440 kg/m3.
Required cement quantity in kg = 1/7 × 0.4 × 1440 = 83 kg, cement amount in bags = 83/50 = 1.66 bags.
Required sand quantity in kg = 6/7 × 0.4 × 1600 = 550 kg, sand amount in CFT = 550/45 = 12 CFT.
RR masonry 1:6 ratio cement and sand calculation: with a mix ratio of 1:6, you required 1.66 bags of 50kg cement, 12 CFT of sand, 1.25 m3 of stones, 0.4 m3 of dry volume of mortar for 1 m3 of RR masonry.
RR masonry 1:5 ratio cement and sand calculation
If your volume of RR masonry work is 1m3, then as per thumb rule you need about 1.25 m3 (1 × 1.25 = 1.25 m3) of stones and 0.4 m3 (1 × 40% = 0.4m3) of dry volume of mortar.
Given ratio of cement to sand is 1:5, total proportion = 1+5 = 6, part of cement = 1/6, and parts of sand = 5/6. Sand density = 1600 kg/m3 and cement density = 1440 kg/m3.
Required cement quantity in kg = 1/6 × 0.4 × 1440 = 96 kg, cement amount in bags = 96/50 = approx 2 bags.
Required sand quantity in kg = 5/6 × 0.4 × 1600 = 534 kg, sand amount in CFT = 534/45 = approx 12 CFT.
RR masonry 1:5 ratio cement and sand calculation: with a mix ratio of 1:5, you required 2 bags of 50kg cement, 12 CFT of sand, 1.25 m3 of stones, 0.4 m3 of dry volume of mortar for 1 m3 of RR masonry.
RR masonry 1:4 ratio cement and sand calculation
If your volume of RR masonry work is 1m3, then as per thumb rule you need about 1.25 m3 (1 × 1.25 = 1.25 m3) of stones and 0.4 m3 (1 × 40% = 0.4m3) of dry volume of mortar.
Given ratio of cement to sand is 1:4, total proportion = 1+4 = 5, part of cement = 1/5, and parts of sand = 4/5. Sand density = 1600 kg/m3 and cement density = 1440 kg/m3.
Required cement quantity in kg = 1/5 × 0.4 × 1440 = 115 kg, cement amount in bags = 125/50 = approx 2.3 bags.
Required sand quantity in kg = 4/5 × 0.4 × 1600 = 512 kg, sand amount in CFT = 512/45 = approx 11 CFT.
RR masonry 1:4 ratio cement and sand calculation: with a mix ratio of 1:4, you required 2.3 bags of 50kg cement, 11 CFT of sand, 1.25 m3 of stones, 0.4 m3 of dry volume of mortar for 1 m3 of RR stones masonry.
RR masonry 1:8 ratio cement and sand calculation
If your volume of RR masonry work is 1m3, then as per thumb rule you need about 1.25 m3 (1 × 1.25 = 1.25 m3) of stones and 0.4 m3 (1 × 40% = 0.4m3) of dry volume of mortar.
Given ratio of cement to sand is 1:8, total proportion = 1+8 = 9, part of cement = 1/9, and parts of sand = 8/9. Sand density = 1600 kg/m3 and cement density = 1440 kg/m3.
Required cement quantity in kg = 1/9 × 0.4 × 1440 = 64 kg, cement amount in bags = 64/50 = approx 1.28 bags.
Required sand quantity in kg = 8/9 × 0.4 × 1600 = 570 kg, sand amount in CFT = 570/45 = approx 12.6 CFT.
RR masonry 1:8 ratio cement and sand calculation: with a mix ratio of 1:8, you required 1.28 bags of 50kg cement, 12.6 CFT of sand, 1.25 m3 of stones, 0.4 m3 of dry volume of mortar for 1 m3 of RR stones masonry.
How much cement required for 1000 sq ft house
How much sand do you mix with cement
What is the quantity of stone required for 10 m3 of rubble masonry?
With a standard mix ratio of 1:4, you need about 23 bags of 50kg cement, 110 CFT of sand, 12.5 m3 of stones, 40 m3 of dry volume of mortar for 10 m3 (cubic meter) of RR stones masonry.
Conclusions:-
In RR masonry (random rubble masonry), the rough, irregular and unequal size of stones are used to build the wall structures.