PRODUCTION OF FOAMED CONCRETE

Production of foamed concrete is different compare to conventional concrete production.

It has different constituents and different mix design. A conventional concrete have basic

constituents of cement, fine aggregate, coarse aggregate, water and other admixtures,

depending on the design of the concrete. A foamed concrete compose of constituents of sand,

water, cement, and foam. It does not consist of coarse aggregate, a characteristic that leads to

its low density. However, due to the fact that it has no coarse aggregate, it posses low

compressive strength compare to conventional concrete.

There are no detailed mix designs stated in standards such as ASTM and British Standard,

however, the past workable design stated in literatures are useful to be used.

The initial step of mix design is to decide the wet density and how much foamed concrete

you require. After planning of amount of materials required making the foam concrete, dry of

the sand and cement. Mix dry constituents for a few minutes and add water in stages and

make sure the mixing is thorough. Then, foam is added to the wet slurry and foam must be

ensured has been completely mixed with the mortar.

After mixing is completed, the wet density of the foamed concrete is to be checked that it

is close to what is required. The dry density (oven dried) of foamed concrete is normally less

than its wet density, depending on w/c ratio, and density. The foam concrete must be target a

value of wet density much higher than what we actually require (dry).

Mix proportion to be used: 1:1.5 (Cement: Sand) or 1:1.5:0.45 (cement, sand and foam

mixture)

W/C ratio: 0.45

Foam percentage: 14%

Decide the wet density and how much foamed concrete you require.

Example for rectangular prism foamed concrete specimen.

Volume of foamed concrete required = 5.3 x 104 mm3 or 5 x 10-5 m3

Wet density of  foamed concrete required = 1000 kg/m3

Therefore materials required,

Cement = 0.0169 kg

Sand = 0.025 kg (dry sand)

Water = 0.008 kg (including water in foam)

Then from the target volume of foamed concrete (5 x 10-5 m3), calculate foam content. Foam

content in mix = 0.000007m3 (0.07liters)

3.1 EXPERIMENTAL SET-UP

Experimental set-up is sets of procedures to achieve the objectives. The experimental will be

procedure guildlines and it must be followed according to sequences. The experimental set-

up is such as below.

3.1.1 PREPARATION OF FORMWORK

Four types of formwork must be prepared for four types of specimens; rectangular

prism, triangular prism, solid cylinder and hollow cylinder.

Steel mould of rectangular prism with dimensions of 100 x 100 x 500 mm and solid

cylinder steel mould with dimensions of 150 mm and 300 mm in length are to be used as

formwork for rectangular prism and solid cylinder specimens.

Formwork for triangular prism is to be created according to the dimensions of the

specimen. The specimen have the dimensions of 11250 mm2 (1/2 x 150 mm x 150 mm) area

and 500 mm in length. The formwork of the specimen will be made by modifying a steel

rectangular prism mould by adding plywood to the side of the mould. . Other than ply wood,

polystyrene can be used as materials for the formwork.

PVC pipe is used to create hollow cylinder specimen. The pipe is placed inside the

cylinder steel mould before the foamed concrete is poured into the mould. The specimen have

diameter of 150 mm and 300 mm in length. The void will be made by attaching a PVC pipe

of diameter 50 mm to the cylinder steel mould. These moulds had to be brushed with oil to

prevent from sticking to the moulds.

3.1.2 PREPARATION OF FOAMED CONCRETE

It is important to be precise in preparing foamed concrete. The materials used must be

according to the designated mix and lag of time will affect the mix. The procedures of

preparation of concrete are as below.

1. Prepare the sand before undergo mixing stage for 24 hours. Fill the mixer with sand,

and put some water while the mixer drum is running. After the wet is suitable, take

designated portion of the sand and put into oven. Put a wet towel on the mixer drum

which contains the rest of the sand.

2. Take the hot dried sand, weighing it and record the reading to determine the condition

of the sand after 24 hours.

3. Measure the cement, sand, and water following the mix proportions. Weigh the

designate portion of the cement, and sand, and use measuring cylinder to measure the

water.

4. After that, put the cement and sand together into the mixer drum.

5. After a few minutes, add the measured water together with the mixing. Mix dry

constituents for a few minutes and add water in stages and make sure the mixing is

thorough.

6. Add the foam into the mixer for sample. For the foam, the controlling technique will

be used to measure the density. The technique is use 1 liter fresh concrete and take the

reading from it until the reading is achieved 1 kg which is equal with 1000kg/m3. The

foam is put into the mixer stage by stage until the density is determined. Adding the

foam caused the mixing is decreasing the weight because the void.

7. After mixing is completed check that the wet density of the foamed concrete is close

to what is required. The dry density (oven dried) of foamed concrete is normally less

than its wet density, depending on w/c ratio, density and also on the cellular structure

obtained. 

8. Lets the mixes mix for another a few minutes and after that the mixing is ready for

cast into formwork.