Rejoinder to Eenadu – Press Note from INSWAREB

Press Note from INSWAREB, Visakhapatnam

December 3, 2005

Dear Friends,

INSWAREB has been promoting the cause of fly ash utilization in construction industry on the plank of Sustainable Development. In the same spirit INSWAREB has taken initiative to motivate government for blending fly ash to cement in all the irrigation projects in order to achieve more durability.

What does it mean? It means, if a structure made out of OPC (Ordinary Portland Cement) lives for 20-30 years, by blending fly ash to cement, the longevity of structure can be enhanced to over 60-90 years. Thanks to the Government of AP, the proposal was evaluated and analysed carefully before according green signal. A lot of technical merits and data, including from international research, were taken into consideration. The subject was discussed at length at the round table meet on 3rd March at The International Symposium on Concrete Technology, participated by various ENCs, Chief Engineers of AP Government and International luminaries of Concrete Technology all over the World.

In this background a news item in the press caused a lot of concern and anxiety to us for the misleading education that it contained. So, as the proponents of the cause, and as the member of the Working Group on Fly ash Utilisation, we feel it our responsibility to clarify issues for the benefit of press and readers as follows:

  1. Blending fly ash to OPC is a value addition practice, increasing the engineering properties of concrete to enhance the long-term durability.

  2. Every OPC has about 25% surplus lime that gets released during curing. Part of this lime leaches out during curing (manifesting as white patches on the surface of structure) and balance of it remains within the concrete. This lime is detrimental in today’s context of increased levels of background pollution. Addition of fly ash converts this lime towards strength-rendering mineralogy, in turn, making the concrete more impervious. Improved impermeability prevents the ingress of moisture and atmospheric pollutants into the concrete, abating the chances of corrosion. This is how the concrete containing fly ash gets long-term durability. The chart below shows the increase in the percentage of strength-rendering mineralogy with increase in fly ash content in a typical case study.

 

Constituents OPC : Fly ash

Strength-rendering hydrated mineralogy

Surplus lime as Ca(OH)2.

100: —

75 25

85 : 15

83.6 16.4

75 : 25

90.6 9.4

65: 35

99.0 1.0

 

  1. In concrete the design strength means 28-day strength. When fly ash is added, though it is proved that ultimate strength increases greater than that of OPC, the early strengths need to be augmented. For this purpose, the mix design is redesigned targeting the design strength. In this process, the cementitious (OPC + Fly ash) content may increase and admixtures are used. In either case there are cost implications.

  2.  Moreover, in construction of big irrigation projects, batching plants are used to prepare the concrete with sustainable quality parameters. When fly ash is proposed for blending, additional facilities have to be created to store and dose the fly ash, which has additional cost implications.

  3.  Hence, it is not true to consider that cement is replaced by fly ash and commensurate cost savings would be there.

  4. In view of the contribution of fly ash to long term durability, the Works in certain countries procure fly ash at greater cost than OPC. Thus the role of fly ash has to be upheld as a value added product rather than a cheap product.

  5. It is not true that fly ash is available at a throw away price. A lot of investments are involved to collect good fly ash. Hence thermal plants are charging price for fly ash towards handling charges.

  6. In view of all these facts it should be the concern of Government to weigh the enhancement of durability by two to three fold and the macro-level contribution to the kitty of exchequer. This is colossal money in service of mankind in comparison to a few crores of gains or losses araised out of fly ash blending.

  7. At the national level, an estimated investment of Rs. 50,000 crores is made for concrete annually whose life may not be enhanced under present concrete practices with high grade OPC. Blending of fly ash would certainly achieve this object. Enhancement of service life at least by two times on a conservative basis means postponement of Rs. 50,000 crore investment annually for over 30 years. In view of this fact all world-class structures blend fly ash as mandatory exercise, the latest example being the World’s largest dam, Three Gorges Dam in China, which has added as high as 40% in concrete.

     To clarify further on these issues INSWAREB is going to conduct a lunch-on press meet on 14th at 1200 noon at Green Park. A separate invitation would be sent to you through Press Club.

     Meanwhile we solicit the press and everybody concerned to uphold the object of blending fly ash as an exercise towards Sustainable Development with macro-level benefits to the mankind, ecology and environment, giving least importance to other petty considerations.

With warm personal regards

Dr N Bhanumathidas, Director General 

N Kalidas,  Director.  (Mobile: 98481-91453)

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