About Microsilica

Our Micro Silica is a by-product material which consists of non-crystalline silicon dioxide with high specific surface area and high pozzolanic reactivity. Use of it in concrete as pozzolanic material has demonstrated significant influence in improving the mechanical and durability properties.

Our Micro Silica is a highly pozzolanic material. The non-crystalline silica and high specific surface area of our product are responsible for its high pozzolanic reactivity.

Pozzolanic Effect :-

A pozzolanic reaction occurs when a siliceous oraluminous material get in touch with calcium hydroxide in the presence of humidity to form compounds.. The C-S-H gel (calcium silicate hydrate ) generated by the hydration of C3S (tricalcium silicate )and C2S (dicalcium silicate) is the main strengthening constituent.Calcium hydroxide and Ettringite that are crystalline hydration products are randomly distributed and form the frame of the gel-like products.Excess calcium hydroxide can be detrimental to concrete strength, due to tending the crystalline growth in one direction.It is known that by adding pozzolanic material toconcrete mix, the pozzolanic reaction will only start when CH is released and pozzolan/CH interaction exist.

The crystallized compound of C-S-H and C-A-H,which are called cement gel, hardened with age to form a continuous binding matrix with a large surface area and are components responsible for the development of strength. Pozzolan-lime reactions are slow, generally starting after one or more weeks. The behavior of the delayin pozzolanic reaction will result in more permeable concrete at early ages and gradually becomes denser than plain concrete with time. This behavior is due to two reasons:-

  • Firstly, pozzolan particles become the precipitation sites for the early hydration C-S-H and CH that hinders pozzolanic reaction.
  • Secondly, the strong dependency of the breaking down of glass phase on the alkalinity of the pore water which could only attain the high pH after some days of hydration. Pozzolan can partially replace cement in concrete mix without affecting strength development. The effect of the pozzolanic reaction produces more cement gel reducing the pore size, blocks the capillary and produces denser concrete thus making it stronger and more durable.

The use of our product decreases the formed CH by the pozzolanic reaction to produce more C-S-H gel that can improve the strength and durability of concrete . The pozzolanic nature of our product reacts with lime more rapidly. Use of our product accelerates the early hydration of C3S. The increase in the early hydration rate of C3S is attributed to the high specific surface area. This phenomenon specially takes place with fine particles of our product. Finer particles of our product speed up the reactions and form smaller CH crystals.

Workability :-

Water demand and workability of the concrete are significantly influenced by particle size distribution.present in the solid system. Typical concrete mixtures do not have an optimum particle size distribution, and this accounts for the undesirably high water requirement to achieve certain workability. Secondly, to plasticize a cement paste for achieving an acceptable consistency, much larger amounts of water than necessary for the hydration of cement. However, there is the possibility of water reduction higher than 20% in case of the use of our Micro Silica. This is because fine particles of our Micro Silica get absorbed on the oppositely charged surfaces of cement particles and prevent them from flocculation. The cement particles are thus effectively dispersed and will trap large amounts of water meaning that the system will have a reduced water requirement to achieve a given consistency. The more the fineness the more is the number of contacts among the particles and hence the more is the resistance to flow.

Setting time :-

Initial and final setting time of concrete depend on the particle size & surface area. Our product with finer particles exhibits superior setting time.

Pore size distribution :-

Use of our Micro Silica produces more homogenous hydration products by filling and segmentation of the capillary voids and produce ultimately more denser andimpermeable concrete. When the percent of our product is increased, the total porosity is decreased.

Water absorption and sorptivity :-

One of the main sources of contamination of concrete in structures is water absorption which influences durability of the concrete and also has the risk of alkali aggregate reactions . The more impermeable the concrete, the greater will be its resistanceto deterioration. The use of our product in the composites could cause an extensive pore refinement in the matrix and in the interface layer, thereby decreasing water permeability. The permeability willdecrease rapidly with the progress of the hydration, Our product more effectively block the pores helping to reduce permeability.

Compressive strength :-

Normally use of our Micro Silica in the below mentioned percentages enhances the compressive strength.

10% to 15% - High strength structural columns

10% - Flatwork

8% to 10% - High durability / Low permeability such as bridge decks or parking structures

8% to 15% - by weight of cement but as an addition not replacement.

Note :- The usage will absolutely depend upon the requirement of the quality of the concrete as per the requirement of the Customer.

Moreover, using 30% of our product could be considered optimum for all content of W/C ratios in investigated concrete because of its high value of compressive strength. Use of our product could help to achieve higher compressive strength and decrease of permeability due to reduced porosity, reduced calcium hydroxide content and reduced width of the interfacial zone in the aggregate. The development of more CS-H gel in concrete with our product may progress the concrete properties. Concrete with our Micro Silica had higher compressive strength at 91 days in comparison to that of the concrete with other Micro Silica. In the long term, the compressive strength of that concrete with our product produced by controlled incineration shows better performance.

Tensile and Flexural Strength :-

Tensile strength of concrete increased systematically with increasing use of our product . The use of our material also resulted in significant improvement in flexural strength as the finer particle size of our product increases the pozzolanic reaction.

Durability properties of concrete containing our Micro Silica :-

Alkali-silica reaction :-

Our Micro Silica is used to prevent or minimize cracking in concrete due to the expansive gel formed by the alkali—silica reaction.

Chloride-ion diffusion :-

It is approved that the long term deterioration of concrete and corrosion of reinforcing steel commonly occurs by entrancing the chloride ions into body of concrete structures. It is also well known that the rate of chloride ion diffusion into concrete is related to the permeability and pore size distribution. The ability of our Micro Silica mixtures to reduce the potential detrimental effects of chloride intrusion into concrete. There are significant reductions in chloride ions permeability due to use of our product. Consequently, they concluded that concrete containing our Micro Silica may require less depth of cover to protect the reinforcing steel. Concrete mix with our product will effectively reduce the pore sizes, permeability, and diffusivity of chloride ions in concrete.

Sulfate resistance :-

Concrete mixed with our Micro Silica has good resistance to sulfate attack.

Corrosion resistance and drying shrinkage :-

Use of our material reduces the chloride penetration, decreases permeability, and improves strength and corrosion resistance properties.

Conclusions :-

Our material is an effective pozzolan which can contribute to mechanical properties of concrete.Use of our product in concrete can decrease the temperature effect that occurs during the cement hydration. It can improve the workability of concrete. It can also increase the initial and also final setting time. Additionally, our material blended concrete can decrease the total porosity of concrete and significantly reduce the permeability which allows the influence of harmful ions leading to the deterioration of the concrete matrix. It can improve RHA the compressive strength as well as the tensile and flexural strength of concrete. It helps in enhancing the early age mechanical properties as well as long-term strength properties of concrete. It also reduces the water penetration into concrete by capillary action. It is effective for improving the resistance of concrete to sulfate attack.