March  2003  

Make RMC mandatory - why and how?

Sanjay Bahadur

Ready mixed concrete (RMC) is an appropriate technology for growing metropolitan cities. In this paper**, the author provides a glimpse of the Chinese experience in expanding the use of bulk cement and RMC in some of their provinces. He stresses the need of evolving a suitable Indian model, taking into consideration the conditions prevailing in the country.

 

 

 

 

 

Ready mixed concrete in Bangalore - A success story

Raj Pillai

The ready mixed concrete (RMC) industry has successfully blossomed in Bangalore, where nearly 50 percent of the concrerte requirement is met with RMC. In this paper**, the author chronicles the initiation of this industry and the long term strategies adopted to encourage RMC's further growth in Bangalore.

 

 

 

 

 

 

Rapid estimation of concrete strength using predictive tools

M.S. Nagesha, Prashant P. Ramugade, Rohan Potdar and Sameer V. Patil

The strength of concrete is influenced by many factors that are primarily guided by the relative proportions of the ingredients of concrete and curing. This feature adds further scope for research for establishing ready-to-use relationship between the strength of concrete and the properties of ingredients. Use of regression analysis and an artificial intelligence-based technique, namely, artificial neural network (ANN) to accomplish this is demonstrated in the present work. It is aimed at complementing the existing quality control approaches by way of predicting the strength of concrete well ahead of performing the destructive tests. A simplified equation is also suggested for use at construction sites.

 

 

 

 

 

 

A spectacular collapse: Koror-Babeldaob (Palau) balanced cantilever prestressed, post-tensioned bridge

Brian McDonald, Vijay Saraf and Bernard Ross

The 385.6 m (1265 ft) long, 18-year old, Koror-Babeldaob bridge (KB bridge) collapsed abruptly and catastrophically on September 26, 1996. The failure occurred during benign weather and loading conditions, less than three years after two independent teams of bridge engineers had evaluated the bridge and declared it safe, and less than three months after completion of a strengthening programme to correct a significant midspan sag that was continuing to worsen. The present paper** describes findings of an on-site inspection and structural analyses performed to assess long-term behaviour of the bridge, the increment of internal forces and deflections produced by the 1995 bridge retrofit repair, and principal factors that contributed to the collapse. Results of this investigation confirmed, both qualitatively and analytically, that the most probable cause of the KB bridge collapse was damage engendered by removal of the original concrete roadway surface.









Thermal reinforcement steel in concrete silos storing hot materials

B.G.K. Murthy and P.D.P. Bhushan

One of the causes of cracking of concrete silos storing hot materials, like clinker, cement etc. is inadequate provision of temperature reinforcement needed to resist thermal stresses, that develop in walls and roofs. In case of large storage silos, critical areas are not only the wall in contact with the material, but also the area above the top of the hot material surface. Measurements of temperatures and studies carried out by several investigators indicate significant temperature differential in walls/roof elements above the surface. Guidelines are not available in codes of practice, like ACI, for the zone above the hot surface including upper portion of the walls and the roof. Considering the studies/measurements made by investigators like Ogniwek, Blight, Sindel etc., a simplified approach to compute the additional temperature steel in upper zones of the walls and roof has been suggested in this paper. At higher reaches the additional reinforcement required to take care of thermal stresses is significant.






 

Point of View: Manpower training for durable structures

R.K. Dhiman

There is an urgent need of manpower training to keep pace with mechanisation in concrete construction. This is required not only to have a faster progress but durable and maintenance-free structures. There are cases where the post-construction scenario is quite painful as the structure has shown distress prematurely. There is a need to improve the quality of manpower involved in concrete construction to have better understanding of the constructional intrinsics from the laying of concrete till completion. Quality assurance can be better enforced with training and education of personnel involved in the field of concrete technology. Quality requirement needs to be attended to from the conceptual stage itself. The essence of training of personnel has been discussed in this paper for overall achievement of durable structures.




 

2001, Research & Consultancy Directorate of The Associated Cement Companies Ltd, Thane, India.
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