Introduction

Founded by Kaspar Winkler in 1910, the name Sika today stands for waterproof and durable solutions. Beginning with rendering mortar, used for the first time in the waterproofing of the old Gotthard Railway Tunnel, and extending to entire waterproofing systems for a wide number of applications, which also currently includes the Gotthard Base Tunnel, the longest high-speed railway tunnel in the world, Sika products contribute to building success. To seal durably against penetrating water, while in other instances to protect precious water and prevent its leakage; two sides of a comprehensive challenge present complex interfaces.

Designing an entire watertight building from the basement to the roof requires the development of solutions for the widest range of applications, solutions which can be installed practically and provide permanent protection. For a complete structure this means the sealing of surfaces such as roofs, underground walls or foundation plates. It also means assuring the watertightness of construction joints and of movement joints. Furthermore, waterproofing solutions in visible areas must meet high aesthetical requirements.
Alongside water, building structures are exposed to a broad range of forces and strains, starting with mechanical stresses resulting from the type of construction and extending to various external attacks. Extreme hot or cold temperature conditions, aggressive water or other chemicals, continually rolling, abrading or pulsating strains on surfaces, or in extreme cases the impact of fire, places enormous stresses on structures as a whole and on building materials.

Concrete has shaped Sika’s development sustainably, and since 1910 Sika has made a notable contribution to the development of concrete as a durable building material!

Terms

Three main constituents are actually enough to produce concrete:

  • Binder (Cement)
  • Aggregates
  • Water

Due to continually increasing demands for the concrete quality (mainly durability) and huge advances in admixture and concrete technology, it is now possible to produce many different kinds of concrete.

Sand and gravel

The aggregates (sand and gravel) are the main constituents of concrete, at over 70% by volume. The type and quality of the aggregates are therefore vitally important for the properties of the concrete, both fresh and hardened.

 

Standard concrete Concrete with a maximum particle diameter > 8 mm
Density (kiln dried) > 2'000 kg/m³, < 2'600 kg/m³
Heavyweight concrete Density (kiln dried) > 2'600 kg/m³
Lightweight concrete Density (kiln dried) > 800 kg/m³ and < 2'000 kg/m³
Fresh concrete Concrete, mixed, while it can still be worked and compacted
Hardened concrete Concrete when set, with measurable strength
‘Green’ concrete Newly placed and compacted, stable, before the start of detectable setting (green concrete is a precasting industry term)

Other terms in use are shotcrete, pumped concrete, craned concrete etc. they define the placement into the formwork, working and/or handling to the point of installation.

In addition to the three main components of concrete, concrete admixtures and additives are also used in concretes with higher performance specifications again both fresh and hardened.

Sika began developing the first admixtures for cementitious mixes in 1910, the year in which it was founded. At that time the main aims were to shorten the setting time of mortar mixes, make them waterproof or increase their strength. Some of these early, successful Sika products are still in use today. Water is necessary in concrete for consistence and hydration of the cement, but too much water is unfavorable for properties of the hardened concrete, so Sika products were also developed to reduce the water content while maintaining or even improving the consistence (workability).

Date   Product base   Typical Sika product   Main effects  
1910 Aqueous alkaline solution Sika®-1 Waterproofing
1930 Lignosulfonate Plastocrete® Water reduction up to 10%
1940 Gluconate Plastiment® Water reduction up to 10% plus retardation
1960 Mix of carbohydrate and polyphosphates

Mix of synthetic surfactants

Sika Retarder®


Sika-Aer®

Retardation


Air-entrainment

1970
1980
1990
Naphthalene
Melamine
Vinyl copolymers

Sikament®
Water reduction up to 20%
Water reduction up to 20%
Water reduction up to 25%
2000 Modified Polycarboxylates
(PCE)
Sika® ViscoCrete® Water reduction up to 40%
2010 Modified Polycarboxylates
(PCE)
Sika® ViscoFlow® Slump retention up to 7 hours

Ever since the company was founded, Sika has always been involved where cement, aggregates, sand and water are made into mortar or concrete – the reliable partner for economic construction of durable concrete structures.

Main Uses of Concrete

It makes sense to classify the uses of concrete on the basis of where and how it is produced, together with its method of application, since these have different requirements and properties. The sales of cement in four different countries in 2010 are given as an example of how the percentages vary for the different distribution and usage channels for the overall methods of use:

Germany   USA   China   India  
  • Approx. 45%
    to ready-mix plants
  • Approx. 70%
    to ready-mix plants
  • Approx. 40%
    to ready-mix plants
  • Approx. 10%
    to ready-mix plants
  • Approx. 30%
    precast component
    and concrete product
    producers
  • Approx. 10%
    precast component
    and concrete product
    producers
  • Approx. 10%
    precast component
    and concrete product
    producers
  • Approx. 15%
    precast component
    and concrete product
    producers
  • Approx. 15%
    contractors
  • Approx. 10%
    contractors
  • Approx. 30%
    contractors
  • Approx. 20%
    contractors
  • Approx. 10%
    other outlets
  • Approx. 10%
    other outlets
  • Approx. 20%
    other outlets
  • Approx. 55%
    other outlets

The requirements for the concrete differ for each of these applications. The right planning and preparation of the concrete works are crucial for the successful use of this fantastic building material.

Preparation steps

When preparing the concrete design, the concrete performance must be defined by the specific project requirements. The following parameters should be defined:

  • Strength requirements
  • Durability requirements
  • Aesthetic requirements
  • Maximum aggregate diameter
  • Method of placement
  • Placing rate
  • Concrete consistence
  • General boundary conditions (temperature etc.)
  • Delivery method and time
  • Curing/waiting time
  • Definition of test requirements
  • Mix design and specification
  • Preliminary testing
  • Mix design adjustment if necessary
Production

Production of concrete is a critical factor for the resulting concrete and consists basically of dosing and mixing the components. The following parameters can affect the concrete properties during mixing:

  • Concrete mix design
  • Type and dosage of admixture
  • Type and size of mixer
  • Mixing intensity and mixing time
  • Concrete mixer operator
  • Cleaning/maintenance of mixer
  • Addition of raw materials
  • Plant quality control
Preparation on site

The preparation on site includes the following:

  • Installation of the concrete handling/placing systems
  • Preparation of the formwork (including release agent application)
  • Reinforcement check
  • Formwork check (fixing, integrity, form pressure)
  • Supply of tools for compacting (vibrators etc.) and
    finishing (beams and trowels etc.)
Delivery

When the concrete is supplied, the following additional criteria must be considered:

  • Delivery time (traffic conditions, potential hold-ups, etc.)
  • Define the necessary drum revolutions during the journey
  • Do not leave the ready-mix truck standing in the sun during waiting periods
  • For a fluid consistence (SCC), define the maximum capacity to be carried
  • Do not add water or extra doses of admixture (unless specified)
  • Mix again thoroughly before unloading (one minute per m³)
Placing the concrete

The concrete is generally placed within a limited and defined time period. The following factors contribute to the success of this operation, which is critical for the concrete quality:

  • Delivery note check
  • Use of the right equipment (vibrators, etc.)
  • Avoid over handling the concrete
  • Continuous placing and compacting
  • Re-compaction on large pours
  • Take the appropriate measures during interruptions
  • Carry out the necessary finishing (final inspection)
Curing

To achieve constant and consistent concrete quality, appropriate and correct curing is essential. The following curing measures contribute to this:

  • Generally protect from adverse climatic influences (direct sun, wind, rain, frost, etc.)
  • Prevent vibration (after finishing)
  • Use a curing agent
  • Cover with sheets or frost blankets
  • Keep damp/mist or spray if necessary
  • Maintain the curing time relevant to the temperature