Essential Chemicals

01 Jul 2011 Editorial Team

Construction chemicals find use across the spectrum of construction projects, discovers Charu Bahri.

Here's an unassailable fact: construction chemicals have become essential for any construction project, irrespective of the kind of infrastructure being established or whether the project pertains to a new or repair job. In the case of new construction, construction chemicals account for a fraction of the cost of construction and help extend the life of the constructed structure or surface. As Sanjay Bahadur, Global CEO, Pidilite Industries Ltd, says, "Modern constructions are incomplete without construction chemicals, which account for about 1 to 2 per cent of total project costs."

Here, we profile the key role played by construction chemicals in different kinds of projects.

CASE STUDY: NANOTECHNOLOGY FOR WATERPROOFED ROADS

Infrastructure: A 700 m stretch on the water-logged and black cotton soil area of Bharthana-Bharthali rural road from NH 8 road km 0/0 to 3.5 km in Vadodara district was constructed by Simandhar Construction. The 700 m road starts from Bharthana village and ends towards the existing Bharthana-Bharthali road.
Project: The Gujarat government proposed the use and study of Zycosoil nanotechnology to protect the road against damage owing to black cotton soil and water ingress to Panchayat (R&B) and Gujarat Engineering Research Institute (GERI), Vadodara. They conducted the experimental project under the supervision of GERI. Stanley Consultants India was the third-party inspection agency that determined the efficacy of the application.
Solution: Terrasil nanotechnology is a 100 per cent organo silicon-based, water soluble, reactive soil modifier and forms a clear solution with water. It is spray-applied on compacted soil to make a waterproof soil layer and form a breathable membrane on in-situ soil. The technology addresses critical water ingress/capillary rise issues of sub-surfaces and resolves issues such as loss in strength, expansion of soil in wet conditions, water absorption through earthen shoulders and sides and utilisation of in-situ soil.
Methodology: Rolling, watering and compacting (to achieve 95 per cent field density at optimum moisture content) were carried out on the existing soil surface before laying the first layer of the embankment of the stipulated thickness. Waterproofing was done in two cycles using the spray-dry-spray technique. The compacted black cotton soil layer was waterproofed using 1 kg of Zycosoil DG diluted in 400 litre water (1:400) and sprayed at 3 l/sq m (1.5 l/sq m + 1.5 l/sq m, twice). Then, the first layer of the embankment was laid. Both the intermediate and top layers of soil were waterproofed using 1 kg of Terrasil diluted in 800 litre water (1:800) and sprayed at 2 l/sq m (1 l/sq m + 1 l/sq m, twice). Drop test and capillary rise tests were conducted to confirm that the treated soil surface is dry and waterproofed. Terrasil nanotechnology was used with medium setting cationic bitumen emulsion in prime coat for improved wetting, penetration, bonding of asphalt to aggregates and quick setting water-resistant prime coat. Zycosoil nanotechnology was mixed in hot asphalt binder to eliminate de-bonding of asphalt aggregates and improve strength of mix. The asphalt composition was laid on BUSG as a carpet and seal coat layer. According to Dr Ajay Ranka, CEO, Zydex, "Road construction with new, 100 per cent organo-silane nanotechnology prevents stripping of asphalt in flexible pavements and resolves water-related loss and failures like rutting, fatigue ing or disintegration (potholing). Zycosoil exemplifies new-generation green technologies aimed at resolving long pending issues of pavements."

CASE STUDY: Quick Fix Long-Lasting Airport Repair Jobs

Infrastructure: Mumbai International Airport Pvt Ltd (MIAL), Sahar, Andheri (E), Maharashtra.
Project: Airport authorities had tried repairing surface s, full depth s and potholes in the concrete pavement using conventional repair products like different epoxies, cementatious products and bitumen. But, these processes were time-consuming and short-lived, necessitating frequent shutdowns of the taxiways, aprons and bays. Besides, they increased maintenance costs, both in terms of money and man days owing to frequent repairs. MIAL also faced major problems in the alteration of the surface level of the nose-wheel area of bays because of heavy tonnage of the taxi nose (weighing over 150 tonne).
Solution: Choksey Chemicals proposed to use Delpatch elastomeric concrete to repair and rehabilitate the full depth s, potholes and nose-wheel areas. Delpatch is an excellent patching material, and easy to use to retrofit airport runways with lighting. Most importantly, Delpatch is self-levelling, adheres well to concrete and steel and resists impact under cold conditions as well as commonly-used chemicals. As it gains extreme high-compressive strength after curing, it does not change by level or volume nor does it have any shrinkage problem. Surfaces repaired with DelpatchTM can accept traffic in as little as one hour after the final pour when installed in normal working conditions. Water curing is not required. The solution also lasts for more than 10 years. Although it is elastomeric, such concrete does not melt or alter the surface level like bitumen, making it ideal and inexpensive for surface levelling at the nose-wheel area of the bay. Otherwise, replacement with normal concrete takes a minimum of seven to nine days for water curing and 28 days for full strength. Normal concrete costs Rs 1 lakh to Rs 1.5 lakh per panel and causes a minimum loss of Rs 5 lakh per day. According to Virendra Pratap Singh, Assistant Manager - Sales Infra Projects, Choksey Chemicals, "MIAL benefited from being able to release traffic in about one hour of performing repair jobs with Delpatch, thus minimising expensive downtime. The high load bearing capacity of Delpatch handles the weight of 777s and heavy truck traffic."

CASE STUDY: WATERPROOF COATINGS FOR BUILDING SURFACES

Infrastructure: The Indian Institute of Technology, Guwahati (IIT-G), is one of the premier institutes of engineering, science and technology in the northeastern region of the country.
Project: An expansion project of the institute involved the construction of 10 student hostel blocks in the first phase, which was completed in January 2011. Each block has five levels (G+4). Since the annual rainfall in the northeast averages 1,600 mm, the civil department desired to give the exterior wall of the buildings a durable waterproof coating that had to last for at least five years.
Solution: The team was considering various other weatherproof and water-resistant paints when Dr Fixit's Technical Wing proposed using the UV-resistant and long-life Dr Fixit Raincoat to the Dean of Institute of Internal Works at IIT-G. The contractor, Bright Construction of Guwahati, was advised to go ahead with Dr Fixit's solution.
Method: Dr Fixit's solution first involved surveying the exterior surface of the newly constructed hostel for s. The surface was then prepared by removing loose material and
Dr Fixit Primeseal applied as an exterior primer. Subsequently, two coats of Dr Fixit Raincoat were applied (by brush, roller or spray) at five to six-hour intervals to ensure the desired film thickness build-up. The product was used as intended, without being diluted. According to Sanjay Bahadur, Global CEO, Pidilite Industries Ltd, "Premium exterior paints can enhance a building's look but not protect it from the monsoon. Dr Fixit Raincoat is an elastomeric (with high elasticity to withstand the stress caused by thermal expansion and contraction) waterproof coating with a dry film thickness (DFT) of 110-120 microns, which is twice the thickness of other premium exterior paints available in the market. Its higher film thickness also helps bridge s and renders surfaces more resistant to ing as it covers hairline s (up to 0.5 mm) effectively. Hence, the product prevents the ingress of rainwater inside the walls and protects them from wind-driven monsoon rains." The client is satisfied with the solution provided. It has served the purpose of protecting the walls from rain, besides enhancing the structure's aesthetic appeal. Chinos colour was used for the main structure, while the borders were done in sand dune.

CASE STUDY: TREATED CORRODED WATER PIPELINES

Infrastructure: The Upper Vaitarna, Vaitarna, Tansa East and West are four water mains supplying water to the city of Mumbai. Together, these water trunk mains transport about
1,600 mld of water from the Modak Sagar and Tanda Dam. The Upper Vaitarna is the oldest of these mains, commissioned in 1925. It is also the largest, with a diameter of 2,750 mm. The Vaitarna main with a diameter of 2,400 mm was commissioned in 1954. The Tansa East and West mains each have a diameter of 1,800 mm and date back to 1971. All of these mains were fabricated from mild steel plates with a shell thickness of 12-16 mm.
Project: In 2009, the office of the Deputy Hydraulic Engineer (Operation), Municipal Corporation of Greater Mumbai (MCGM), Water Works Yard, took up a project to treat and protect the surface of these pipelines. The pipelines were in a severe state of distress owing to corrosion. Most pipeline failures occur as a result of corrosion, which erodes and reduces the thickness of walls. Because of the continuous flow of water under high pressure, this weakening of the pipe walls eventually leads to failure of the water mains. Ruptured water mains would compromise the water supply to the metropolis of Mumbai.
Solution: A team of civil and structural engineers from Sunanda Chemicals' Concrete Materials Consultancy Division (CMCD) conducted site visits, provided an analysis of the damage and finally proposed the treatment system to the MCGM. Sunanda's CMCD has been working in a consulting role providing expert and timely advice to the MCGM and other government bodies for three decades. The division also offers consultancy services on concrete and materials to architects, builders and contractors. Sunanda Chemicals supplied chemicals for the anti-corrosive treatment of the 2,400 mm diameter, mild steel Vaitarna main in the Gundavali-Kasheli section falling outside the city division. Phase I covered a length of 1.5 km.
Method: The treatment started with the removal of rust using Rusticide, a single-component, sulphate and chloride-free liquid. Subsequently, two protective coats of a cementitious polymeric, highly alkaline, elastomeric coating of Polyalk FP mixed with cement were applied to protect the pipeline from further corrosion and passivate the steel. Sunanda also ensured conformance to the associated codal provisions, BS 5896-1980 and IS2074/1962, which list the performance criteria for construction chemicals used in rust removal and steel passivation and IS 9077-1979 (reaffirmed) Appendix B.CI.5.3.3 that outlines the application procedure. According to Ishita Manjrekar, Senior Associate, Sunanda Speciality Coatings Pvt Ltd, "Codes and standards are in place to ensure a basic level of performance and quality of construction. In India, most construction materials including construction chemicals adhere to the IS code. Globally, however, the BS (British Standard), ASTM (American Society for Testing and Materials) and DIN (Deutsches Institut für Normung) standards are widely used and accepted. Consequently, in order to keep pace with global development, Sunanda's products conform to relevant international standards as well, in addition to the IS code."

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