Cement,  Concrete  and    Construction

• With a view to disseminate knowledge, information or share experience, you will see blogs by Dr J D Bapat on technical subjects or issues related to cement and concrete, which are of current interest to the manufacturers, suppliers or users.
  
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                           In the last few years , two major changes have taken place in the cement and construction industry in India. Firstly, the emphasis of construction industry has shifted from   high – strength to high – performance concrete . The realisation has come on account of the fact that nearly 65 % of the total cement sales in the country presently go towards the repairs of old structures , most of which are built with OPC . Secondly, the mineral admixtures, namely the fly ash (FA) and the blast furnace slag (BFS), are being increasingly used to improve the long term strength and the durability characteristics of cement and concrete. The need to build durable structures is felt not only from the point of view of economy , but also for the conservation of resources , energy and environment . The present study reviews the provisions of the Indian Standard, IS 456 – 2000, towards building  durable structures. To know the details, click here.

                     Concrete is used as a material to build varieties of structures under different surrounding conditions. Here are some guidelines to select appropriate cement or binding material for concrete used for different structural applications, click here.

  USING  CONSTRUCTION  CHEMICALS  EFFECTIVELY

         The construction chemicals or the chemical admixtures are the ingredients in concrete, other than Portland cement, mineral admixtures, aggregate and water. They are added to concrete immediately before or during mixing. The addition of chemical admixtures modifies the properties of concrete, both in fresh and hardened state. The experience shows that proper addition of chemical admixtures improves the strength and durability of concrete. To get more information on the subject, click here

Suppliers of construction chemicals in India

 SLAG CEMENT FOR DURABLE STRUCTURES

                The experience gained in the laboratory as well as field trials, all over the world, shows that the addition of ground granulated blast furnace slag (ggbs) to cement and concrete improves durability of structures. The durability of structure is its resistance towards the internal or external deleterious agents causing deterioration of concrete on account of corrosion, sulphate attack, carbonation, alkali-silica reaction and freeze and thaw cycles. To know how ggbs improves the durability of structures, click here

 BACTERIAL CONCRETE

The bacterial concrete makes use of calcite precipitation by bacteria. The phenomenon is called microbiologically induced calcite precipitation (MICP). It is a self-healing concrete. It is used to bridge the microcracks in concrete to improve durability and strength of structures.

 View article on bacterial Concrete

SHRINKAGE COMPENSATING CONCRETE

Shrinkage compensating concrete can be produced using expansive cements or expansive constituents. 

The expansive cement, also known as sulfoaluminate cement or modified Portland cement, comes in the category of hydraulic cements that expand slightly during the early hardening period after setting. They meet the requirements of ASTM     C 845 in which the group of expansive cement varieties is designated as Type E-1. Expansive cement is used to make shrinkage-compensating concrete that is used to (a) compensate for volume decrease due to drying shrinkage, (b) induce tensile stress in reinforcement and (c) improve dimensional stability of post-tensioned concrete structures. One of the major advantages of using expansive cement is in the control and reduction of drying-shrinkage cracks. In recent years, shrinkage-compensating concrete has been of particular interest in bridge deck construction, where crack development must be minimized. It is also used to minimize cracks in the concrete slabs and structures.

View article on Shrinkage Compensating Concrete 

CEMENT GRINDING AIDS

The cement grinding aids are the additional materials (gas, liquid or solid), admixed in small amounts during the cement grinding process, which can significantly improve the grinding efficiency, reduce energy consumption, without compromising the performance of the cement. Some commonly used cement grinding aids are triethanolamine (TEA), mono- and diethylene glycols (DEG), oleic acid, sodium oleate, sulphite waste liquor and dodecylbenzene sulphonic acid sodium lignosulphonate (from paper industry).

 View article on cement grinding aids

 GREEN BUILDINGS

Green buildings are buildings that are environmentally responsible, profitable and healthy places to live and work (USGBC).

 View an article on green buildings

 Eco-Towns

Four sites have been approved by the UK government for the construction of low-carbon eco-towns. They will serve as a platform from which to pioneer and launch the energy-efficient design and infrastructure necessary for lower carbon emissions.

From 2016 all new residential buildings are to be built to zero-carbon specifications as part of plans to reduce the quarter of all UK emissions that come from housing. More than a quarter of CO2 emissions come from houses.

Read an article on eco-towns

Processing rice husks for use in concrete could lead to a boom in green construction. Rice husks form small cases around edible kernels of rice and are rich in silicon dioxide (SiO2), an essential ingredient in concrete. Scientists have recognized the potential value of rice husks as a building material for decades, but past attempts to burn it produced an ash highly contaminated with carbon, not useful as a cement substitute.The RHA can be effectively used to cut the concrete's carbon footprint.

Read an article on RHA

BANDRA – WORLI SEA LINK (INDIA):

A MARVEL OF ARCHITECTURE & ENGINEERING

Bandra Worli Sea Link Project has been one of the most highly appreciated projects of all the transport studies done for the metropolitan region. The sea link consists of approach viaducts and two aesthetically pleasing cable-stayed bridges. The link, which is 5.86 km long, 8-lane freeway connecting Worli and Bandra, will serve the purpose of providing an additional fast moving outlet from the South Mumbai to the Western Suburbs and thereby providing much needed relief to the congested Mahim Causeway. Widely noticed by the media , it is an architectural marvel . However some Mumbaikars have a viewpoint, know that ?.

Read the technical article on Bandra-Worli Sea Link

 Fact file on recycled concrete

Recycling concrete reduces natural resource exploitation and associated transportation costs and reduces wastes going to landfill. However, it has little impact on reducing greenhouse gas emissions. Twice as much concrete is used in construction around the world than the total of all other building materials, including wood, steel, plastic and aluminum.

 Read some facts about the recycled concrete

Green concrete roof

A green or vegetated roof provides the function of a conventional roof, while allowing plants to grow on the surface. A vegetated roof includes water proofing, a drainage system, filter layer, a lightweight growing medium and plants. Concrete is the structural system of choice for vegetated roofs because it provides a continuous load-bearing surface for the potentially moist growing medium and plants.

Read the full article