What is Rice husk ash ( RHA)? its uses, How RHA produce, advantage/disadvantage & more

What is Rice husk ash ( RHA)

Obtained from burning protecting outer cover of rice husk

It consists of non-crystalline silicon dioxide (SiO2) with high specific surface area and high pozzolanic reactivity.

The RHA can be found as natural materials, by-products or industrial wastes Chemical propertie so fare closer to micro silica ,silica fime

HOW RHA PRODUCE

Chemical compositions of RHA are affected due to burning process and temperature

RHA produced by burning rice husk between 600 to 700°C temperatures for 2 hours

Table 1 Physical and Chemical Properties of RHA

How RHA improves concrete

OPC reacts with water to form two products

Calcium silicate hydrate :it gives strength and durability to concrete

Calcium hydroxide

• reacts with CO2 causing effloresce
• It creates negative effects on concrete

Addition of RHA

1. Increases calcium silicate hydroxide
2. Decreases calcium hydroxide

Ca(OH)2+SiO2=H2O+CaSiO3

The major benefits of the reaction are

High strength

Reduced efflorescence

Reduce sulphate attacks

Reduce chemical attacks

Uses of RHA

RHA can be used in the 2 distinct ways

1. To create HPC –RHA can be added to cement to increase high strength concrete
2. To create Green Concrete-RHA can be used as an substitute to reduce amount of cement with higher strength

Carbon credits

• The production of 1 Tons of cement contributes to 1 tons of co2 in atmos,
• Worldwide 7% of carbon dioxide emission for production of OPC
• The utilization of RHA in concrete production is solution to reduce the cement

ADVANTAGES

• Improves compressive strength, flexural strengths and split tensile strength.
• RHA mixed concrete shows better bond strength as compared to OPC concrete.
• Permeability of concrete decreases chloride diffusion and chloride permeation reduces (30%) replacement.
• RHA makes a role to increased resistance to chemical

DISADVANTAGES

• Suitable incinerator/furnace as well as grinding method is required for burning and grinding rice husk in order to obtain good quality ash.
• Strength of concrete is reduced for larger (beyond 30%) replacement.
• There is a little transportation problem.
• Unburnt RHA is not suitable for concrete production

CONCLUSION

• To study the effect of RHA as substitute for fine aggregate in concrete mixture.
• The properties of concrete containing RHA had been successfully studied.
• The use of RHA in civil construction, besides reducing the environmental polluters’ factors, may bring several improvements fotg544r the concrete characteristics.