''ViscoCrete is the result of newly-developed high-performance concrete admixtures based on polycarboxylate polymers,'' explains a company spokesman. ''The three-dimensional shape of the complex molecule and its chemical composition result in a double-action dispersing effect, namely, electrostatic repulsion coupled with steric hindrance not found in conventional melamine/naphthalene-based admixtures.''

He continues: '' The formulated new-generation admixture exhibits much improved and controlled workability, allowing ultra-high water reductions and minimum slump loss even at low additions. Typical dosage ranges between 0.2 - 1.5 per cent bwoc, depending on the desired effect. Viscocrete concrete can be placed as pumped concrete, poured directly or by skip.

''ViscoCrete is, therefore, not just an admixture, it is also a new concrete design concept. Following the new guidelines of a concrete mix design, tremendous flowability and internal cohesion are possible. The result is a concrete that is self-compacting and requires no vibration.''

Self compacting concrete, according to the spokesman, is a new concept based on extremely flowable concrete with low water-cement ratios and cohesive concrete without segregation or bleeding. ''Concrete moves easily even through intricate formwork and dense reinforcement giving many new advantages for contractors, concrete producers, specifiers and clients,'' he says.

''Sika ViscoCrete SCC provides all these advanced properties and allows placement of concrete without vibration. A special mix design with increased fines (limestone dust, fly ash, slag or silica fume) content and the addition of ViscoCrete allows to minimise the water content by maximising workability to a great extent.''

''Fresh SCC has no vibration, is very fluid and soft with a slump flow of 65 to 75 cm and concrete levels with slope of 1 to 3 per cent, offers good cohesion, with no segregation, separation or bleeding and a workability time and air content as required.

''Hardened SCC gives high strength, low permeability, high carbonation resistance and a homogeneous concrete surface and matrix.''

''SCC offers benefits all round, the spokesman says. "For contractors, it offers a higher speed of concrete placement, less finishing work, especially for slabs, less manpower, and quicker use of equipment such as cranes. Placing problems caused by heavy reinforcements are minimised, a homogeneous concrete surface result in reduced cost without honeycombing, and a reduction in noise improves the environment for workers and neighbours.

Also, the 'white finger syndrome' caused by vibration can be prevented.

''Readymix producers also stand to benefit, with a faster turnaround of trucks, and easier pumping.

''For precast plants, it offers higher speeds of concreting and higher capacity, less manpower and the production of thinner elements. SCC allows a more economic production process as walls and floors of one element can be made in one step.

''All this translates into advantages for the specifier and client, with faster completion of a project, and new architectural possibilities, (because very detailed concrete surfaces can be produced). Also the smooth floor slabs make tiling possible without installing a screed.''

SCC can be used for repair work, concrete floors and slabs, structural elements with congested reinforcement, slender elements (walls), architectural specialties with complex shapes, precast concrete elements and tunnelling work.

''ViscoCrete, thus allows the economic production of self-compacting concrete and durable, ultra-high strength concrete with good surface finish,'' the spokesman says.