Construction Chemicals and Mortars

Admixtures for Concrete  Ready-to-use Mortars  Tunnelling

Admixtures for Concrete

Technologies:
The use of cement, mortar and concrete admixtures to seal against water pressure to increase water-tightness of plaster, to prepare air-entrained concrete, to improve the workability of fresh concrete, or to achieve other specific properties - both of fresh as well as hardened concrete or mortar - has become an obvious necessity today for most construction experts.
Concrete consists of aggregates, cement, water  and admixtures. The aggregates are the  matrix of the  concrete, cement mixed with water, forms the binder; first as cement glue, later as cement 'stone'. The water acts as well  as a processing material. The admixtures, on the other hand, take the function of active ingredients.
The aggregate has a decisive effect on the properties of a concrete. The matrix endows the final product with strength, density, permanence and appearance, -the cement is the binder for the framework (glue) and, therefore has the major responsibility for the properties of the concrete.
Admixtures  Have significant influence on both, the fresh and the hardened concrete properties. They are added in an amount of less than 5% on weight of cement.

Applications:

High performance full range standard admixtures for concrete and mortar and tailor made admixtures for big job sites.

• Low cost admixture range with multipurpose use.
• Environmentally friendly admixtures which show biodegradability or are not leachable from concrete.
• Admixtures to be added at the cement plant to modify cement properties, including grinding agents.
• Corrosion inhibiting admixtures for cement, mortar, concrete and auxiliary products.
• Basic investigations on cement hydration and mode of action of admixtures for the development of new products and systems.

Innovation:
Superplasticizers :
High-range water-reducing admixtures (HRWR) or superplasticizers (SP) have been widely used since their introduction in the late 60's in Japan. They can be used either to reduce the amount of water and thereby the amount of cement or to produce high strength concrete with increased service life of the resulting structure. Used as superplasticizers the flow of a concrete with a given w/c could be increased to produce flowing concrete.
However with the upcoming new construction technologies mostly coming from Japan, the need for new admixtures was evident.

New cost-effective polycarboxylate based polymers  with a low environmental impact, are replacing conventional admixtures  such as lignin sulphonate, naphthalene- and melamine sulphonate derivatives. This new product technology has a wide range of uses: from construction concrete through specific concrete qualities to prefabrication applications and highest-quality Self Compacting Concrete (SCC).

The product technology is now to be globally anchored and introduced to our subsidiary companies with the help of extensive for local specialists.

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Ready-to-use Mortars
Technologies:
Our buildings and the infrastructure are permanently exposed to wear and tear, climatic changes and or aggressive environments. High performance ready-to-use mortars for repair and maintenance, mortars for industrial applications or high performance grouts are being used for this purpose.

Applications:

• non sagging polymer modified cementitious mortars, for repair of verticals, highly performing  when structural demands apply, light weight mortars for applications like facades where the ease of application is important.
• The repair system includes bonding bridge as well as rendering mortar and coatings.
• The mortars can be handapplied or machine applied by wet spraying.
• a special range of Gunite mortars covers dry spray applications, main use is repair of large structures like bridges or cooling towers, fast setting gunites are used in tunnelling, to stop water ingress and to solidify rocks.
• free flowing polymer modified cementitious mortars, for horizontal applications such as finishing coat in ice rinks, or for bridge deck repairs.
• epoxy modified cementitious mortars, for applications with increased chemical attack, (waste water sewage plants, e.g.), or when rapid curing for overcoating is required (SikaFloor EpoCem)
• water proofing mortars for clean water and drinking water reservoirs, with and without polymer modification.
• flowable grouting mortars, with rapid strength evolution and high strength potential, for anchoring and casting.
• various speciality products, like
     - low density flooring mortars for ship decks
     - high density mortars for counterweights and noise dampening
     - cosmetic mortars
     - rapid setting mortars
     - powerpacks for other Sika companies or job site blends

Characteristics:
Ready-to-use mortars have to meet narrow specifications, in many cases according to national (ZTV-SIB in Germany, e.g.) or international (upcoming EN, ASTM, e.g.) standards.
Use of polymers, as plasticisers or modifiers, is compulsory, in order to meet the specifications which are in many cases contradictory. The main effort in the last years was to adapt the products to powder polymers, thus reducing the liquid polymer component, in order to improve ease of application and to reduce the packaging waste.

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Tunnelling + Mining

Sprayed Concrete Technology:
The enormous advantages of sprayed concrete as a construction and rock support process and the improvement of equipment, materials and application know-how have made it an important tool for various types of work.
Approximately 30 years ago, the only method available for the application of sprayed concrete was via the dry-mix process. This remained the dominant method until the mid nineties, when eventually the wet-mix process began to be used more widely. Currently the wet-mix method is being adopted on a world-wide basis as the preferred choice.
The wet-mix sprayed concrete process uses concrete that is batched in a similar way to conventional concrete, making it possible to check and control the w/c ratio and thus the quality at any time. The consistency can be adjusted by means of admixtures. With the wet-mix method, it is easier to produce a homogenous product with uniform quality throughout the spraying process. The ready-mix concrete is emptied into a pump and forwarded through a hose by pressure (thick stream transport). Today, piston pumps dominate the wet-mix sprayed concrete pump market.

Innovations
The role of the shotcrete accelerators
Sika has developed a wide range of shotcrete accelerators. In the past aluminate based materials were used.  Today, due to safety and ecological concerns, it has become dominant in the sprayed concrete accelerator market, that applicators have started to be reluctant to apply aggressive products. In addition, requirements for strength and durability of concrete structures are increasing. Strength loss or leaching effects suspected to be caused by strongly alkaline accelerator has forced our industry to provide products with better performances.
Due to their complex chemistry, alkali-free accelerators are more expensive than traditional accelerators. However, accelerator prices have very little influence on the total cost of on-place sprayed concrete. Of much greater consequence are the time and rebound savings achieved, the enhancement of the quality, and the safe working environment.