Types of plasticizers commonly used and their benefits

Plasticizers & super-plasticizers facilitate concrete to enhance it's workability.

Due to it’s strong fluidity, shotcrete is highly beneficial. When the homogeneous mix is applied pneumatically, it simply conforms with even rugged surfaces whereas maintaining the initial resistance to compression to offer good structural support from the beginning.

A family of chemical polymers like plasticizers and super-plasticizers are liable for the material’s fluidity. These are also called water reducers to minimize the total water-to-cement ratio, providing it a more ‘liquid’ consistency devoid of diluting the mix with water.

These additives are normally added all through the mixing process and allow the concrete mix to become yielding until application keeping its consistency unchanged.

Plasticizers and super-plasticizers provide a temporary dispersing effect, that produces a comprehensive hydration of each cement particle, making the fluidity of the mix better.

This mix is amalgamated with volcanic fly ash to form the type of hydraulic concrete, a fully hardy and weatherproof material along with extremely erosive salt water.

Plasticizers: first steps - First generation of plasticizers is known as Lignosulphonates. It belongs to a byproduct originated from wood processing that is frequently applied in recent times to form a workable mix with only basic raw materials.

These additives, known as Mid-Range Water Reducers [MRWR] affix themselves to the surface of a cement particle, that bears both positive and negative charges. Plasticizer polymers, which are negatively charged, neutralize the positive charges on the cement surface, transforming the entire surface completely negative.

It causes a physical effect that allows the negatively charged cement particles to keep away each other, providing a dispersing effect to develop better water infiltration. This mix can now function well devoid of adding more water, and allows for a cutback in the overall amount of water necessary, reducing the water-cement ratio by around 10%.

But these additives can defer the curing process, which may sequentially produce further complicacies. If curing is not done within a certain timeframe, a greater amount of hydrostatic pressure could amass in a formwork column over a long lasting period, causing the formwork to burst.

The second generation: Plasticizers 2.0: This type of plasticizer can significantly lessen the water-to-cement ratio of around 25%. Polysulfonates like naphthalene and melamine offer same type of working mechanism to the first generation of plasticizers, producing an electrical dispersing albeit of superior intensity.

These polymers conform to the cement particles, charging them negatively to form repulsion among related particles, allowing water to flow and hydrate the mix in an efficient manner.

This similar repulsion activity also activates major air occlusion, raising the workability of the mix but at the same time developing pockets of air that reduces its resistance and settle its structural integrity.

This type of polymer may also put other challenges, since it provides a very narrow window of ‘workability’: as soon as the cement is hydrated, it is likely to develop a crust-like byproduct that makes application complicated.

Super-plasticizers: the third generation - Super-plasticizers stands for the additives which bring huge benefits along with a water-to-cement ratio curtailment of around 40%.

Polycarboxylates alias High Range Water Reducers (HRWR) function on the base of sterical in spite of electrostatic repulsion. A major steric effect is steric hindrance for which a chemical reaction can’t occur. In this case it stops cement particles from agglomerating.

Polycarboxylates stands for complex co-polymers which are applied to satisfy several functions, and comprise of a negatively charged ‘backbone’ molecule with polymeric side chains.

Most of these additives can be amalgamated jointly, and blended with other types like air-entraining, accelerating and retarding additives
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Published By

Rajib Dey

www.constructioncost.co

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Some useful guidelines to substitute the spalling bricks

Freezing and thawing water in brick leads to flaking and spalling and due to these the bricks are damaged severely.

In this construction article, you will get some useful tips for recognizing spalling on bricks. Besides, you will learn how to take proper measures so that the water can’t enter into the brick walls. Otherwise, it will be necessary to substitute the damaged bricks.

How to substitute the damaged bricks

The brick retaining wall under a wood fence may be broken down. The flaking surface is a good instance of “spalling,” a type of failure resulting from moisture and the freeze/thaw cycle. Water from rainfall, melting snow or even wet soil soak the brick to some extent, and freeze inside the brick while the temperature is decreased.

The small development of freezing water will rupture the brick. If freezing and thawing occur in continuous basis, the fractures are expanded unless the brick is perfectly decomposed.

To get rid of these issues, bricks utilized on the outside should normally become tougher and solid (less moisture absorption). A softer brick in the wall that is mixed in the load may collapse. If massive failure occurs, there is serious water intrusion issue.

The outside walls should be detailed cautiously to discharge water, specifically when they’re inherent section of a retaining wall. There should be a coping or cap on the wall to discharge the rain water.

It comprises of metal flashing, concrete or special bricks which are angled to keep water far from the top of the wall. The cap exists there for one time, but it may be eliminated or tired. Besides, the wood fence over perhaps catches and directs even more water down onto the wall.

While going to reconstruct your brick wall, ensure it’s designed to reduce water penetration. Aside from a cap on the top, it should contain good draining fill (gravel) along the backside and weep holes along the bottom to lessen water pressure when the soil gets soaked.

Damp-proofing the backside of the wall will also facilitate the water to be discharged properly. There should be good drainage system around the base to resist penetration of water from below.

Necessary Tools for this Spalling Project

Given below, the detail lists of tools :-

Circular saw, Cold chisel, Dust mask, Extension cord, Hammer, Hearing protection, Level, Safety glasses, Sledgehammer, Spade, Tape measure, Trowel, Utility knife, Wheelbarrow.

A masonry blade is also necessary to cut the brick with circular saw.

Essential Materials for this Spalling Project

Brick, Drain tile, Gravel, Landscape fabric, Mortar.



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Published By
Rajib Dey
www.constructioncost.co
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The role of water in concrete

Water Cement Ratio signifies the ratio among the weight of water to the weight of cement applied in concrete mix.

Generally, water cement ratio remains under 0.4 to 0.6 with adherence to IS Code 10262 (2009) for nominal mix (M10, M15 …. M25)

The strength of concrete is directly impacted by the water cement ratio. It enhances the strength if employed in perfect ratio and if the ratio is improper, the strength will be reduced.

The importance of Water in Concrete

Concrete refers to a macro content. It comprises of micro constituents like cement, sand, fine aggregate & Coarse aggregate. With the purpose of obtaining high strength concrete to resist the desired compressive strength, it is required to set exact ratio of admixture to unite these materials.

The role of water is important here to accelerate this chemical process by adding 23%-25% of the cement volume. It produces 15% of water cement paste also called gel to fill the voids in the concrete.

Impact of too much water in concrete: If additional water is added more than the permissible limit of 23%, the strength of concrete will be significantly affected.

If the task of adding water is continued to improve the workability then the concrete contains lots of fluid materials where the aggregates will settle down. As soon as the water is evaporated it puts down lots of voids in concrete which influences the concrete strength.

But if the guidelines are followed to retain the strength of the concrete then it will change the concrete workability and makes it difficult to manage and place them.

Workability signifies the capacity of concrete to manage, convey and place devoid of any segregation. The concrete becomes perfectly workable if it can be easily dealt with, placed and transported devoid of any segregation at the time of being placed in construction site.

For this purpose, plasticisers & superplasticizers are utilized to enhance the workability by keeping the W/C Ratio unchanged.

In order to know how to work out water cement ratio, go through the following construction article www.civilology.com

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Published By
Rajib Dey
www.constructioncost.co
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