Infra to drive cement demand
Cement demand in our country is driven by housing, infrastructure and industrial construction. Housing contributes to about 60-65 per cent; infrastructure around 10-15 per cent and the rest is by industrial and commercial buildings. India being a developing country, it is expected that infrastructure projects will be a major consumer of cement. The efforts of the Government to improve and execute infrastructure projects would be the key driver. Cement is the basic ingredient which is used in mortar, concrete, grouts - widely used in all the infrastructure projects. India´s economic growth is dependent on the need for high quality infrastructure development. It has also been reported by various researches that the country´s economic growth and cement are correlated.
As infrastructure projects are developed, the cement industry sees a lot of scope for product differentiation. There is an increasing effort to demarcate market segment in terms of product quality. Certain projects need special types of cement and the ability of a cement manufacturer to carve a niche will be one of the factors that is expected to define the dynamics of the industry.
Concrete is the largest ´man made´ material in the world and stands second to water in per capita consumption. Various estimates put the average per capita annual consumption of cement worldwide to around 500 kg against 210 kg in India.
1.Cement concrete roads
Cement is being used in the construction of concrete roads and the consumption of cement is expected to increase in the years to come as the stakeholders are being made aware of the advantages of concrete roads
Some of the advantages of concrete roads are:
a.Concrete when compared to bitumen does not have petroleum-based products and hence is considered more environment friendly. Moreover concrete is recyclable. Thus concrete in its composition does not the major import content - oil which contributes positively in terms of the foreign exchange of the country.
b.In terms of life, concrete roads lasts longer when compared to bitumen and probability of maintenance, occurrence of potholes and repair is far less. This in the long term leads to fewer traffic interruptions.
c.Concrete Roads are designed to take loads as applicable. Depending on the load of the vehicle, concrete roads can be designed for which suitable grade of concrete can be used.
d.Mileage of vehicles running on concrete roads is enhanced.
e.Concrete can be aesthetically customised in terms of colour and texture to produce attractive designs and patterns .
Increased use of white-topping in roads: Many cities of the country have adopted the practice of white-topping. White topping is the using a layer of concrete to cover an existing bitumen / asphalt pavement. This normally used on bitumen /asphalt pavement which are showing signs of deterioration. The thickness of white topping can range from two to six inches and can be very thin for roads with low traffic volume. Fibre reinforced concrete is used in some of the white-topping layers.
2.Development of smart cities
A smart city normally means a city which uses digital facilities for its operations. As part of the Government´s endeavour, a number of smart cities are being identified. Once the implementation starts this could drive the consumption of cement.
3.Precast concrete products
In India there is a huge potential for precast concrete products and the growth of this industry is expected to accelerate the consumption of cement in the years to come. Precast concrete industry began in the North America in the 1950 with the completion of the prestressed concrete bridge - Walnut Lane Memorial Bridge in Philadelphia. Now the precast concrete structures are a common place in the US.
Advantages of precast units
- It was observed that precast concrete when used in buildings and other concrete structures provides superior fire resistance and sound control for the individual units.
- Precast concrete is also a popular material for constructing office buildings as it leads to huge savings in time. The walls of the building can be manufactured while the on-site foundations are being built, providing significant time savings and resulting in early occupancy.
- The speed and ease with which precast structures can be built has helped make precast a popular building material for parking structures. Precast concrete allows efficient, economical construction in all weather conditions and provides the long clear spans and open spaces needed in parking structures. For stadiums and arenas, seating units and concrete steps can be mass produced according to specifications, providing fast installation and long lasting service. In addition, pedestrian ramps, concession stands, and dressing room areas can all be framed and constructed with precast concrete.
- Precast concrete has very good crack control and strength to weight ratio. This is being increasingly used to create longer and thinner spans than using site mixed concrete
- In terms of weight, concrete is almost 30 per cent of the weight of structural steel. Therefore when precast components are used instead of structural steel the overall weight can be decreased to a great extent.
- Precast concrete unlike site mixed concrete are manufactured in a factory environment where quality can be monitored and controlled easily. All the operations from mixing, placement and curing can be supervised effectively.
- Less labour is required as most of the operations in a precast unit are automated. Precast products of similar shape and size can be casted and number of units can be casted like in the case of hollow block or solid block components which have been able to replace bricks in the construction industry. Ability to cast similar number of units in large numbers can increase the viability of setting up a precast unit.
- The cycle time of casting precast units can be reduced to a great extent as accelerated curing can be easily adopted in a precast unit. Accelerated curing increases strength gain and productivity.
- Durability of the precast components can be enhanced as the concrete used to make precast units can be made under strict quality control supervision.
4.Hydel power projects
These projects require cements with lower heat of hydration. This is achieved through the use of blended cements like PPC (Portland Pozzolana Cement) and PSC (Portland Slag Cement)
5.Captive RMC units at sites
Penetration of RMC is higher in metropolitan cities and this is expected to increase further in other Tier 2 cities with expected increase in infrastructure development. RMC can be made under strict quality assurance measures but the transportation cost can increase the cost of delivered concrete. Therefore number of RMC units are expected to come up near the projects. This would increase the demand of cement in bulk.
With the average production of a RMC plant to be 30 cubic meter per hour huge quantities of concrete can be produced within a short span of time.
In India only 7 to 10 percent of cement is being consumed by the RMC units as against 70 percent in a country like Japan. With the increasing concrete requirement due to booming infrastructure RMC units are the solution. The Government support and tax reforms may help in accelerating the growth of concrete from RMC units.
For each infrastructure project the quality of concrete needs to be customised based on the performance required. The grade of concrete, the workability required and the degree of durability varies with the type of project and the exposure conditions. Apart from the grades of concretes which varies with the compressive strength the requirements of workability also changes depending upon the concrete mix whether its a site based mix or mix transported from an RMC plant or the degree of pump-ability required for concrete.
The various types of concrete based on the infrastructure project could be any of the following types of concrete:
- High strength concrete
- High performance concrete where strength, workability and durability of concrete are given equal importance
- High density concrete: Where the concrete has a density higher then the normal value of 2,400 kg per cubic meter
- Light weight concrete: Where the concrete is light having density as low as possible
- Self compacting concrete: Where the concrete has a workability which enables it to compact by itself without the use of vibrator
- Fibre reinforced concrete: Where fibres have been introduced so as to increase the tensile strength of concrete
Sustainability in concrete construction
Concrete is the most widely used construction material for new and replacement infrastructure. Unfortunately, concrete industry is one of the largest consumers of natural resources and energy, and is responsible for large emissions of carbon dioxide that is one of the greenhouse gases responsible for global warming. The sustainable development is frequently defined as "the development that meets the needs of the present without compromising the ability of future generations to meet their own needs."
Supplementary cementing material (SCM), such as fly ash, ground-granulated blast-furnace (GGBF) slag, or silica fume, is one of the most sustainable construction materials because it recovers an industrial by product through beneficial use when incorporate into concrete, avoids disposal of industrial byproducts, reduces Portland cement content in concrete, resulting in decreased emission of greenhouse gas and decreased use of natural raw materials, and increases structure service life by improving the durability of concrete.
Modernisation of cement plants and machinery has decreased the electricity consumption during milling of cement, with consequent reduction of CO2 emission from power plants. Recycled concrete has also been used as partial replacement of coarse aggregate for the concrete structures and concrete pavements
Role of cement and cementitious materials
If we analyse the composition of concrete; for any grade the approximate quantity can be estimated as follows:
1.Coarse Aggregates: 31-35 per cent
2.Fine Aggregates : 31-35 per cent
3.Cement & cementitious materials: 9-15 per cent
4.Water: 15-16 per cent
5.Air: Up to 8 per cent
Cement & cementitious materials are involved in the hydration process that eventually forms the structural gel uniting the aggregates together. Ordinary Portland Cement used to be the only cementitious material available about 25 years back but now we find that supplementary cementitious materials or pozzolonas like fly ash slag and silica fume is being used to enhance certain properties like durability in concrete. Fly ash and GGBS (ground granulated blast furnace slag) meeting specifications of Bureau of Indian Standards can be used to produce good quality Portland Pozzolana & Portland Slag Cement, which can be used to make a durable concrete. For instance: the typical characteristics of good quality fly ash are fineness (Blaine): 320 m2/kg (Min); lime reactivity: 4.5 N/mm2 (Min) & loss on ignition: 5 per cent (Max). Fly ash of such quality can be collected from electrostatic precipitators of thermal power stations. Similarly slag which is obtained from the steel plants can be used to produce Portland Slag cement which enhances durability of concrete. The Indian cement industry is considered to be the second largest after China and has the capability to manufacture varieties of cement customised to a particular type of concrete and structure. Infrastructure projects requires cement in bulk to be supplied to their sites and most of the major plants have facility for supplying cement in bulk.
With increase in various types of projects in different exposure conditions, there is a increasing demand for R&D in the area of concrete technology where the cement companies can support and complement the quality assurance of these infrastructure projects in terms of studies relating to mix designs.
India being a developing country has a long way to go in terms of infrastructure development and increasing per capita consumption of cement. Various Infrastructure projects are evaluated based on different quality criteria and hence there is a huge challenge facing the construction professionals. The R&D efforts of the cement industry and construction professionals are expected to provide solutions to these projects. Innovation as a result of efforts by cement technogists, concrete technolgists and civil engineers will change the face of landscape of infrastructure projects in the country. The combined efforts will result in infrastructure projects that are durable and sustainable, thereby reducing the carbon footprints. The contract specifications therefore must give more emphasis on the usage of blended cements like Portland Pozzolana Cement and the Portland Slag cement. This would be the right step to enhance the quality of concrete and also ensure availability of raw materials like limestone to manufacture the additional quantity of cement required for the execution of infrastructure projects.
Globally the Indian cement industry is not only second in terms of quantity and size but also incorporates the most advanced technology in the manufacturing process. Therefore the Indian cement industry is geared to meet the requirements of the various infrastructure projects.
1.Sustainable Concrete Technology for the 21 Century Tony C. Liu -; Jenn Chuan Chern
Types of concrete
- High strength concrete
- High performance concrete(HPC) where strength, workability and durability are given equal importance
- High density concrete: where the concrete has a density higher then the normal value of 2,400 kg per cubic meter
- Light weight concrete: where the concrete is light in weight having density as low as possible
- Self compacting concrete(SCC): Concrete has a workability which enables it to compact by itself without the use of vibrator
- Fiber reinforced concrete: Fibers are introduced in concrete so as to increase the tensile strength.
Anil Kumar Pillai avers:
"Measuring durability of concrete : The ability of concrete to withstand damaging effects of environment, thereby enhancing its service life is durability. While evaluating the durability of concrete one should take into consideration the environmental factors affecting the concrete and accordingly adopt innovative techniques to resist those factors.
Extensive amount of research and trials have been carried out to understand the mechanism of deterioration due to which basic information and knowledge about concrete durability is available. There are instances of premature deterioration of concrete structures, which increases the costs to the economy and it is clearly evident that in most of the cases that knowledge is not applied adequatelyö.