Environment-friendly Blended cement – Eases pressure on Industrial waste disposal

Environment-friendly Blended cement – Eases pressure on Industrial waste disposal and reducing emissions per unit weight of cement manufactured

Portland Cement, an essential component of concrete, hardens and become strongly adhesive after application; used for various engineering and building construction activities. It is a mixture of Calcium silicate (CaO, SiO2), Calcium aluminate (CaO, Al2O3) in varying proportion, with small amount of magnesium, iron compounds etc. To slowdown the hardening process of cement, sometime Gypsum is also used.

Production of Portland cement is highly gas pollutant; emits considerable amount of Carbon dioxide (CO2) in the atmosphere, polluting air. CO2 is well known for its ill-effects towards Global warming as greenhouse gas. In cement manufacturing plant alone, CO2 produces (a) during de-carbonation of limestone, (b) during kiln fuel combustion, (c) during transportation by vehicles in the cement plant & for cement distribution.

Considering CO2 associated with electric energy consumed by a cement plant, we have observed, for production of 1 tonne of Portland cement 1 tonne of CO2 is produced and emitted to the atmosphere. This is a quite large quantity of CO2 which a Portland cement unit pollutes. To mitigate this extent of pollution menace, many of the steps have been taken by cement industries - production and use of environment-friendly blended cement, i.e., use of alternate or supplementary cementitious materials such as fly ash and slag, is among such steps taken to bring down emission per unit weight of cement manufactured. In addition to reduction of emission per unit weight of cement manufactured, it eases problem of Industrial waste disposal; as both fly-ash and slag are the waste from thermal power and steel making industry respectively, available abundantly almost at free of cost.

Fly-ash blended cement: Fly ash is the waste generated by thermal power units, resulting from combustion of powdered coal. Fly ash consists of mostly Silicon dioxide (SiO2), Aluminum oxide (Al2O3) and Iron compounds. It is pozzolanic, i.e., it reacts with calcium hydroxide and alkali to form cementitious materials.

Activated Fly ash can replace up to 50% by mass in blended cement. It is less expensive and it is advantageous in a host of applications. Fly ash can be used to improve workability and pumpability of concrete. Due to its generally slower rate of hydration, fly ash also lowers the heat of hydration and is important in mass concrete structures, such as large foundations, bridges, and piers. High fly ash concrete shows less bleeding and shrinkage than straight cement mixes. Fly ash is also used as a component in the production of flowable fill, which is used as self-leveling, self-compacting backfill material in lieu of compacted earth or granular fill.

Due above advantages of fly ash blended cement, more and more fly ash is being used beneficially as a recycled material.

Slag blended cement: Slag is the waste product of iron making industry. These are the impurities present in iron ore and obtained from blast furnace while processing for pig iron. It was found that ground granulated slag reacts with water to produce cementitious properties. Therefore it is used in concrete in combination with Portland cement as part of blended cement. Concrete containing ground granulated slag develops strength over a longer period, leading to reduced permeability and better durability properties. Slag cement concrete is less vulnerable to alkali-silica and sulfate attack.

As with fly ash, processing blast furnace slag into slag cement or slag aggregate eases the burden on environment. Apart from reducing the burden of waste disposal, it reduces the air emissions at the cement kiln as well as the material in landfills. Most significantly, slag decreases Portland cement usage by as much as 50 percent, thereby diminishing CO2 emissions, the amount of energy required to produce concrete, and the quantity of virgin land extraction through mining raw materials for Portland cement.

Concrete made with blended cement has generally higher density than concrete made with Ordinary Portland Cement. Hence it improves the impermeability and durability. All these make for better long-term strength, dense and impermeable concrete and improved corrosion resistance and longer service life with reduced cost for repairs and maintenance.

Thus, the Blending cement is not only environment-friendly, but also make improved concrete performance.

Guidelines for making City Green

As cities are keep on growing because of urbanization, more and more cities are becoming congested. To make cities livable for the citizen and to make their life beautiful, it has been the constant endevour of the Government to encourage for green building, keep city pollution within the limit and to create sufficient green belt.

A. Green Building is a philosophy of design and construction that integrates natural resources more effectively, preserves and restores the natural and human resource base while creating healthier, more efficient “high-performance” structures, homes and communities. This philosophy incorporates the following guiding principles:

• Using natural and manmade resources efficiently;

• Considering the impact of buildings and development projects on the local, regional and global environment;

• Reducing building footprint and development size;
  

• Allowing ecosystems to function naturally;

• Conserving and reusing water; treating storm water on-site;

• Maximizing the use of local materials;

• Optimizing energy performance by installing energy efficient equipment and systems;
  

• Optimizing climatic conditions through site orientation and design;
  

• Integrating natural day-lighting and ventilation;

• Minimizing the use of mined rare metals and persistent synthetic compounds and volatile organic compounds;
  

• Minimizing construction waste by reducing, reusing and recycling materials during all phases of construction and deconstruction.

Sustainability is the practice of using resources to provide for the needs of today’s citizens while preserving the use of those same resources for the needs of future generations. Generally, objectives of green buildings are: (a) Improve work and learning environments, thus increasing worker productivity and student performance; (b) Mitigate health risks such as asthma and childhood lead poisoning; (c) Create local green building jobs within every existing industrial sector; (d) Reduce energy consumption and costs; (e) Affirm the City’s commitment to environmental conservation.

B. The creation of green-space in cities is often spoken of as if it were the result of orderly planning or regulation. Most of the cities have a plan to conserve green-space on the urban fringe. Generally, planning for creation of city green zones includes:

• Greening Commercial Corridors – This focus on landscape enhancements along strategic streets that can serve as a neighborhood's economic lifeline.

• City Parks Revitalization – This focus on maintaining and beautification of existing parks in a city.

• Setting-up of New Community Gardens;
  

• Street Beautification Projects- creation of "Garden Blocks".

· Education and Training Opportunities - Courses and workshops help city dwellers beautify their communities through horticulture.

C. Apart from setting up green buildings, green covers, strategy for implementing proper solid waste management, restricting generation of air / water pollutants and strict implementation of local emission control codes. Thus, guidelines should include:

• Utilize sites to capture environmental benefits and preserve or create new open space;
  

• Develop programs and policy to conserve potable water use, improve stormwater management and “green” the city sewage waste water system;
  

• Address city and regional transportation issues by encouraging transit-oriented development, improve public transit services and reduce dependency on individual automobile use;

• Implement citywide energy conservation programs and incentives, encourage use of renewable, non-fossil fuel energy sources and improve city performance on meeting regional clean air standards;
  

• Promote the development of local, green manufacturing industries and the use of recycled content materials or renewable materials for building, operations, and supplies for city work. Also establish more extensive recycling program to include construction and demolition waste recycling;
  

• Maintain city’s sustainable development by integrating programs, such as in workforce development, economic redevelopment, and the public school system.

D. Citywide ban on smoking in all enclosed public spaces and public vehicles, also to be imposed for long term benefit of its citizen.