Self Compacting Concrete (SCC): A Reliable Methodology In The Production Of Wind Turbine Towers

What is Self-Compacting Concrete (SCC)?

Recognizing the lack of uniformity and compaction of concrete by vibration technique, researchers at the University of Tokyo, Japan started in the late 1980s to develop SCC. By the early 1990s, Japan has used SCC that does not require vibration/minimum compaction to achieve full uniformity. By the year 2000, SCC had become popular in Japan for prefabricated products and ready-mix concrete. Recently in India, SCC has become Engineers/Designer's first choice of concrete for pre-cast products, areas with heavy/dense reinforcement, structures using MIVAN/Tunnel formwork for construction works and in areas where the conventional process of vibration is physically not possible

Self-Compacting Concrete (SCC) offers a rapid rate of concrete placement, with faster construction time and ease of flow around congested reinforcement, with fluidity & segregation resistance of SCC ensures a high level of homogeneity, minimal concrete voids, and uniform concrete strength, providing the potential for a superior level of finish and increased durability to the structure. SCC is often produced with a low water-cement ratio providing high durability.(Source ijamtes.org/gallery/585-dec.pdf)

The elimination of vibrating equipment improves the environment near construction and pre-cast sites where concrete is being placed, reducing the exposure of workers to noise and vibration.(Source : iopscience.iop.org/article/10.1088/1755-1315/140/1/012138/pdf)

The improved construction practice and performance, combined with the health and safety benefits, make SCC a very attractive solution for both precast concrete and civil engineering construction.

Self Compacting Concrete (SCC) In The Production Of Wind Towers – An Innovative Initiation In India

TUV India Private Limited is involved in the complete inspection of the production of Precast RCC (Reinforce Cement Concrete) wind tower which shall be erected as a wind mast in the Wind farms across India. The wind farms consist of several RCC wind towers with a total height of 120 meters.

Each Precast RCC wind tower comprises of 5 different profile segments naming them as KEYSTONES and each keystone type varies in the shape, size, and reinforced structural steel. The challenge is to precast the keystones in the prescribed standard steel moulds using SCC of M60 grade in controlled environmental conditions.

Tests Performed In SCC:

Currently, Indian Standards does not offer testing procedure and hence the European standards were adopted and the following code was followed to determine the fresh concrete properties,

EN 12350-8 TESTING FRESH CONCRETE –SCC- SLUMP FLOW TEST

EN 12350-9 TESTING FRESH CONCRETE- SCC- V-FUNNEL TEST

EN 12350-10 TESTING FRESH CONCRETE –SCC- L-BOX TEST

EN 12350-11 TESTING FRESH CONCRETE –SCC- SIEVE SEGREGATION TEST

EN 12350-12 TESTING FRESH CONCRETE –SCC- J-RING TEST

Properties Of SCC:

FLOWABILITY:

The slump value describes the flow ability of a fresh mix in unconfined conditions, it is a sensitive test that will be normally specified for SCC as a primary check to know whether the fresh concrete consistency meets the specification visual observations during the test and /or measurement of the T500 time, which can give us the additional information on the segregation resistance.

VISCOSITY:

Viscosity can be assessed by the T500 time during the slump flow test or assessed by the V-funnel flow time. The time value obtained does not measure the viscosity of SCC, but is related by analyzing the rate of flow. Concrete with low viscosity will have a very quick initial flow and then ceases. Concrete with high viscosity may continue to creep forward over an extended time. (Source : https://www.academia.edu/)

PASSING ABILITY:

Passing ability describes the capacity of the fresh mix to flow through confined spaces and narrow openings such as areas of congested reinforcement without segregation, loss of uniformity or cause blocking. In defining the passing ability, it is necessary to consider the geometry and density of the reinforcement, the flow ability / filling ability, and the maximum aggregate size.

SEGREGATION RESISTANCE:

Segregation resistance is necessary for SCC in situ with homogeneity and quality. SCC can suffer from segregation during placing and after placing but before stiffening. Segregation which occurs after placing will be most detrimental in tall elements but even in thin slabs, it can lead to surface defects such as cracking or a weak surface.

COMPRESSIVE STRENGTH:

SCC with water-cement or cement binder ratio will usually have slightly higher strength compared to traditional vibrated concrete, thus the lack of vibration provides an improved interface between the aggregate and the hardened paste. The strength development will be similar, so the maturity testing will be an effective way to control the strength development whenever accelerated heating is used or not.(Source : https://www.thebalancesmb.com/self-compacting-concrete-844767)

Advantages Of RCC Wind Turbine Towers Over Conventional Wind Turbine Towers:

• As RCC towers can be built up to greater heights of 120 meters, resulting in power generation output to be remarkable as compared to conventional wind towers.
• The RCC towers were found to be more economical than conventional wind turbine towers; the cost and the operational maintenance expenses incurred were considerably reduced in RCC wind turbine towers.
• The raw materials available which are used in the proximity help in low volatility in the project cost.
• Faster construction methodologies adopted ensure project completion on time.
• Most reliable and developed technology guarantees safety standards as prescribed.
• Minimal rate of pollution is involved in the production, construction, and operation of RCC wind turbine towers.

TUV India Pvt. Ltd., part of TUV NORD GROUP provides Construction Services by assuring quality of construction from the commencement to completion of the project. We at TUV India support you to overcome constraints and bring your plans to reality, thus assuring Construction Quality and Safety. Construction Quality Assurance minimizes the risks and damages in advance and avoids unnecessary costs due to rework and delay in construction & subsequent operation.