In this article we will determine how much of cement , sand and coarse aggregates will be required to construct a slab of length;10m, width; 5m and thickness 0.15m(150mm)

 Reinforced concrete is in the ratio 1:2:4.

Meaning one part of cement to two parts of fine aggregates to four parts of coarse aggregates.

Volume of the slab is length x breadth x thickness.

I.e 10 x 5 x 0.15= 7.5m³.

Dividing this volume in ratio 1: 2: 4

Volume of cement is;

(1/7)x 7.5=1.07m³

The density of cement is 1500kg/m³

 density= mass/ volume

Therefore mass of cement ;

1500x 1.07= 1605kg

A bag of cement weights 50kg so dividing 1650/50= 33 bags.

Mass of sand;

Volume of sand is( 2/7 )x 7.5= 2.14m³

Density of sand is 1700kg/m³

Therefore mass of sand = density x  volume;

1700 x 2.14= 3638kg

Mass of coarse aggregates;

Volume of coarse aggregates is (4/7)× 7.5= 4.29m³

Density of coarse aggregates is 1650kg/m³

Therefore mass of coarse aggregates,

1650 x 4.29= 7078.5 kg

The RCC 71 is an excel software developed by the Reinforced concrete council for the design of staircase. It designs to BS 8110: 1997. It can be used to design stairs, flight and landing.Upon starting the program you might see a macros warning. Enable macros if possible.

All blue text data are editable. Data which you will be required to enter include, dimensions of the staircase, concrete parameters and loading.

You do not need to do any previous major calculation before using RCC 71.

In the Flight tab of RCC 71, there are 4 input sections. They are the;

Project Name Title 

Materials

Dimensions

and Loading sections.

In the Project title section you can input the name of the project and so on

In the materials  section you can enter parameters such as strength of concrete, strength of steel, diameter of reinforcement and so on

The dimension section is where you enter the staircase dimensions such as length of thread, riser, thickness of waist..etc. 

In the loading section, you input the imposed loading and any other additional dead loads.

The design is longitudinal so the main bars are along the length of the stairs.

The software is a free to use version. A public release version.

To download RCC 71 and other structural design excel programs 

CLICK HERE 

What is bamboo scaffolding? 

Bamboo scaffolding is simply scaffolding using bamboo stems. It is a cheaper alternative to the conventional scaffolding that uses hollow steel columns and struts.

How is bamboo scaffolding constructed?

The bamboo stems are connected together using big five inches long nails and binding wire. The column bamboo stems must be braced. The column stems are usually spaced 1.5m apart..For added strength and rigidity, bamboo struts that support the platform on which workmen will stand are bored into the wall.

 How reusable is bamboo scaffolding?

Bamboo is still reusable a few times. You can also dismantle bamboo scaffolding and erect in another section of the building if you don’t have enough scaffolding to go round the whole building.

How much bamboo stems is need for a typical building?

The number of bamboo stems a building will need depends on the perimeter of the building and its height. A typical story building that is about 6m high will need about 120 bamboo stems to construct scaffolding for it at once.

How to construct bamboo scaffolding based on its properties.

Bamboo stems are very strong in compression and rigidity. Bamboo stems good for scaffolding should be at least 6cm and above.Use bamboo stems with higher diameter for struts, beams and bracings. 

Plaster sand is usually mixed in the ratio 1:6. That is, one part of cement to six parts of sand. Calculating the amount of these materials allows 25% bulking of sand. There is not much difference between the densities of cement and sand so the density of sand will be indirectly used to determine mass of sand required. Recall that a standard bag of cement weighs 50kg and it has a volume of 0.033m³

Example;

Let’s say you want to determine the amount of cement and sand necessary to plaster a wall of area 900m² and the thickness of plaster is 15mm thick.  This is how you do it.

first determine the volume of plaster which is

AREA x THICKNESS

= 900×0.015= 13.5m³

since its in ratio 1:6, you use this information to find the volume of cement and that of concrete.

volume of cement is;

(1/7 )× 13.5= 1.93m³

therefore volume of sand is 13.5-1.93= 11.57m³

Increasing the sand volume by 25% to cater for bulking we have: 

1.25 x 11.57= 14.46m³

The volume of cement previously calculated is 1.93. Dividing this volume by the volume of one 50kg bag of cement we get:

1.93/ 0.033= 58.48 bags, approximately 59 bags.

let’s indirectly use the density of cement to approximately determine the mass of sand required

recall that a 50kg bag of cement has a volume of 0.033m³

so dividing the volume of sand previously calculated by the volume of one 50kg bag of cement ,we have;

14.46/ 0.033=439 (50kg bags).

therefore mass of sand is;

439 x 50= 21950 kg or 21.95 tons

Our calculation so far shows that 59 bags of cement and 21.95tons of plaster sand is required to plaster a wall of 900m² with plaster thickness of 15mm. ( mass of sand increased by 25% to cater for bulking).

However, plastering usually results in considerable amount of waste. Coupled with wall irregularities such as holes and joints that need filling. Let’s increase the amount of cement and sand needed by 30% to cater for this;

i.e 1.3×59 bags of cement = approximately 77bags

and 1.3 x 21.95 tons of sand = 28.54tons.