cement additives/concrete additives

What is Expansive Agent for Concrete

It is one kind of concrete admixtures which, when added to concrete, mortar or paste, produce ettringite, calcium hydroxide or ettringite and calcium hydroxide after hydration reaction, making the concrete volume expand. The normal concrete usually cracks due to shrinkage, resulting leakage and low function and durability. The key to improve the durability of concrete structure is to control the cracks. The compensating concrete obtained by adding expansive agent for concrete at the rate of 6%-12% can greatly improve the waterproofing ability and crack resistance of concrete structures.

The expansive hydration products from the hydration reaction between expansive agent for concrete and cement and water can efficiently compensate the shrinkage of ordinary cement concrete during the water hardening, preventing the cracks caused by such shrinkages. The expansive agent contains no sodium salt and never causes alkali-aggregate reaction. The shrinkage compensating concrete prepared by expansive agent has good durability, steady expansive ability and continuously ascending strength. The expansive agent for concrete can be used to improve the waterproofing ability of the structure (even cancel the application of external waterproof material under certain situation), extend the pitch of post pouring joint, low down the chances of cracks of crack caused by different in temperatures of mass concrete and high-performance concrete.

Classification of expansive agent concrete

1.Calcium Sulphoaluminate Hydrate Expansive Agent for Concrete

The expansive agent for concrete which, when mixed with cement and water produces hydration production of ettringite, code A.

2. Calcium Hydroxide Expansive Agent for Concrete

The expansive agent for concrete which, when mixed with cement and water produces hydration production of calcium hydroxide, code C.

3. Calcium Sulphoaluminate Hydrate-calcium Hydroxide Expansive agent for concrete

The expansive agent for concrete which, when mixed with cement and water produces hydration production of ettringite and calcium hydroxide, code C.

Technology Characteristics

1. Using dosage: add 8%-12% of the gel materials.
2. Compressive strength: not lower than base concrete, with same setting time as base concrete but no obvious compact on slump constant.
3. Good adaptability with other chemical additives, low alkali, and remarkable improvement of temperature shrinkage due to hydration heat of gel materials.
4. Performance Index of expansive agent for concrete

Application Scope

Because of the extraordinary functions of crack resistance, waterproofing, anti-seepage, corrosion resistance and strength reinforcement, the expansive agent for concrete is widely used to prepare shrinkage compensating concrete for concrete self-waterproofing, jointless concrete design and construction of super-long reinforced concrete, mass concrete and other special constructions and parts with requirements of anti-crack and anti-seepage. Following constructions are extremely applicable:

1. Underground structures: underground parking garage, underground air defense facilities, underground storeroom, underground walkway, foundation ditch, pile foundation work and so on.
2. Water pool, swimming pool, treatment tank, water tower, storage tank, grain store and so on.
3. Metro, tunnel, water conservancy and hydropower, marine works, port, water plant, generating plant, reservoir dam and some other waterproof structures.
4. Super long structure floor, stadium stand, radiation shielded concrete structure and so on.
5. Rigid self-waterproof roof, mortar impermeable layer, slurry moistureproof layer.
6. Beam-to-column connection, filling concrete for post-cast strip, mechanical equipment, reinforced second perfusion, pre-stressed concrete.
7. Cement products, self-stressing, pre-stressing and steel pre-stressed concrete, concrete-filled steel tube.
8. Airfield runway, highway pavement, bridge concrete, arch culvert.

Usage

1. Using dosage: 6%-12% of the gel materials.
2. When preparing shrinkage compensating concrete, accurate measurement is required, and the expansive agent for concrete, sands and gravels are added into the mixer at the same time, and the mixing time needs to be lasted 30-60 seconds more comparing to ordinary concrete.
3. When pouring, the concrete should be vibrated compactly without honeycombs and holes, well water curing in the early stage. The concrete with expansion agent demands more water when hydrates and the hydration is brought into full play only under good moisture condition. So concrete added expansive agent needs to keep the surface wet and pay more attention to water curing (such as watering, covering) comparing to ordinary concrete. The curing should last for 7-14 days, at least 7 days under the best curing condition. Ensure sufficient time for water curing even it is time for form removal. The water curing can be started 2 hours after final setting.

Package and Storage

1. Packed by coated woven bags.
2. During storage and transportation, the product should be put in dry place, keeping from moisture and other foreign substances. Different types of products should be stored separately.
3. Handle with caution, protecting the bags from damaging and damping. The heap layer never beyond 10 bags.
4. The shelf life of the product is 6 months under sealed state. Product exceeding shelf life must be retested before using, consultant the manufacturer about the usage.