Apollo Proton Therapy and Cancer Care Hospital project is a distinctive project emerging first in South Asia and is famed for its magnificent structure. The project comprises of three main buildings; Proton therapy building, Hospital building and the Service building. Apart from these three blocks there is RMU building, OSR area, etc. The Proton therapy block consists of one basement, the ground floor and first floor together makes the Proton therapy block (treatment block) and nine floors above the Proton therapy block, comes the MLCPs (Multi Level Car Parking). In Hospital building, there are two basements, ground floor and nine floors above, while the Service building consists of one basement, ground floor and two floors above it.
Proton Therapy Building & LINAC:
The structure for Proton therapy block is built in a way that it resists radiation, as high radioactive waves are about to be developed by the equipments erected for the Proton therapy’s functioning. We call the structure, massive because the thickness of elements like the walls, the rafts and the slabs varies from about 1.6m to 4.6m. Also LINAC in Hospital building has mass concreting with the thickness of its elements ranging from 1.4 m to 2.4 m. Elements with such huge thicknesses were casted with Temperature controlled concrete to prevent the occurrence of cracks. The special concreting techniques which were adopted for casting these elements are;
Temperature controlled concrete (RESOURCES):
Proton therapy was successfully casted with Temperature controlled concrete, of total quantity 9180 cum (excluding LINAC) during the period of March’16 to December’16. The number of workmen deployed to accomplish this was 1040 man-days (mason/helper), 9000 man-days (carpenter/helper), 12500 man-days (fitters) with 50 numbers of pours in various elements say raft, wall & slab in Gantry 2 & 3, FBTR, Cyclotron, PSR, BTS & ESS. Concrete procured from 3 different RMC’s (Lafarge, ACC & RMC India) and concrete was placed with boom placers, pumps with capacities 1800 HP, in each of the major pours, 5 numbers of vibrators and 10 numbers of needles of 40 mm and 60 mm diameter were used. 5000 Rmt. of HDPE pipe of diameter 100 mm were embedded in the concrete for MEP works.
A major achievement was made by placing a concrete quantity of 1000 cum for Cyclotron slab in a single pour with 2 RMC’s (Lafarge & RMC India) and 4 pumps within 10 hours. LINAC was also successfully casted with temperature controlled concrete, of total quantity 1026 cum.
Special insulated formwork arrangement was used to prevent the structure from getting exposed to the atmosphere. Concrete surface was insulated by keeping PUF foam fixed as insulation panel at the sides as formwork shutters and top of concrete surface was covered with polythene sheet with a layer of sand, so that the temperature variation between inside and outside can be reduced.
Formwork plywood of 12 mm thickness was used and thermocol was sandwiched between two plywoods and was used in the sides of the structure. 40 mm thick High density thermocol (25 kg/m) of size 1000 x 500 mm was used. Silver wood runner piece of 40 x 40 mm size @ 500 mm spacing placed to resist the thermocol and maintained the uniform form board shutters. To avoid restrained cracks wooden reaper was placed at every 1.2 m interval to the mass Gantry /FBTR / Cyclotron wall.
De-shuttering of wall was done only when the internal peak temperature is reduced to 40 deg. Celsius, so that variation of temperature between the core temperature and ambient temperature was less than 19 deg. celsius.
Quality Control Techniques:
Concrete Design Mix:
Concrete grade of M 30 was used. 400 kg cementitious material was used where; 200 kg of GGBS (Ground Granulated Blast Furnace Slag) and 200 kg of OPC 53 grade cement were used. The concrete was temperature controlled by preparing the concrete with 60% of ice flakes (crushed ice) and 40% of ice water having a temperature of 3-4 deg. celsius, thus bringing down the temperature of the concrete to around 25 deg. celsius and with a slump of 125 mm +/- 25 mm before the placing of the concrete. The GGBS was used to maintain a low temperature of the concrete while its production and also to control the heat of hydration.
Control of Concrete Production:
Before commencing of main concrete works, a few mockups were done in M/s. Lafarge, M/s. ACC and M/s. RMC concrete production plants to analyze the behavior of temperature controlled concrete. M/s. Lafarge is around 4 kms away from the site, M/s. ACC and M/s. RMC plants are around 25 kms away from the site. During the production of concrete the following precautions were taken to control the temperature of the concrete;
- The raw materials were made moist by sprinkling water before mixing of concrete to reduce the temperature of the concrete.
- The transit miller- mixer drums were covered with Hessain cloth to maintain the temperature of the concrete during the transportation of the concrete from plant to the site.
- To maintain the temperature of the concrete, 60% of ice flakes (crushed ice) and 40% of ice water having a temperature of 3-4 deg. was mixed with concrete.
- The temperature of the concrete at the plant was brought to 17 deg. +/- 1 deg. celsius having a slump of 160 mm, so that the temperature and the slump of concrete is maintained until the concrete is brought to the site and the temperature of the concrete before placing was 25 deg. and the slump was 125 mm +/- 25 mm.
Construction joint was provided as per the drawing. Hy-rib sheets were provided at the junction of construction joint (vertical) and to receive the concrete without the need for surface preparation or as per GFC standard drawings. To avoid radiation leak provide stepped construction joints wherever possible. In a few places, MS plate of 300mm wide 6mm thick was provided in all construction joints which come above ground level. MS plate was embedded 150mm on either sides of the joint or provided stepped construction joints wherever possible, or provided the shear key of size 100 mm deep and 1/3rd width of wall thickness.
Concrete Placing Sequence:
As soon as the concrete arrives at site the dispatch slip was checked for required mix and grade of concrete and receiving time was recorded. It was ensured that the concrete was placed as earliest as possible.
Before placing of concrete, every transit miller arriving at site was checked for required temperature and slump, by L&T QC team and AHEL (Client).
The concrete produced was sampled and checked periodically to analyze quality of concrete being produced. Frequency of sampling of concrete for each grade was done as per the ITP requirements.
A continuous supply and placement of concrete was maintained throughout the pouring sequence to avoid any possibility of cold joint formation.
Concrete was poured in successive layers as per pour plan in its final position to avoid segregation due to re-handling. Concrete was placed carefully to avoid displacement of side shutter and reinforcement.
Concrete was laid with concrete pumps as per construction program or site condition. The resources were deployed in such a way that the planned rate of pour of concrete was reasonably achieved.
The receiving hopper of the pumps was provided with hydraulically/electrically operated remixing blades, to keep the concrete agitated continuously and maintain consistency and uniformity.
Concrete was thoroughly compacted and fully worked around the reinforcement, around embedded fixtures and into corners of the formwork. Concrete was compacted using mechanical vibrators.
Different method of curing was adopted unlike water bunding curing technique. Since the structure was said to be insulated, the top surface could not be kept exposed to the atmosphere, hence curing compound was applied on to the top surface and was covered with plastic sheet of 1 mm thickness. Over which a layer of thermocol was placed and another layer of tarpaulin sheets were placed covering the thermocol layer.
Temperature observations were done in the concrete by using thermocouples as per GFC drawing. The placing of thermocouples in a raft/wall was done in the following manner;
- Thermocouples are fixed to a rebar.
- At the centre point to the thickness of the raft/wall, three thermocouples are placed with its monitoring pins placed at the top, middle and bottom points of the wall.
- The top point and the bottom point is be 200mm below and above the level of casting respectively and the middle point is at the centre to the entire depth of the level of casting.
- In case of wall thermocouples of one number are placed in left side and right side of the wall, with its pin positioned at the centre, lying parallel to the centre point of the thermocouple placed at the middle of the wall. The left side and right side thermocouple readings are taken as east and west reading for Location-A and north and south readings for Location-B.
- While in case of raft the thermocouples of the sides are not provided.
With these techniques we have successfully completed, the construction of Proton therapy structures with temperature controlled concrete of quantity 9180 cum from M/s. Lafarge, M/s. ACC & M/s. RMC and LINAC concrete of quantity 1026 cum from M/s. Lafarge & M/s. ACC concrete plants with good co-ordination among L&T EDRC team, IBA team, AHEL team and Concrete technology cell.
Contractor : L&T Construction, B&F IC
Client : Apollo Hospitals Enterprises Ltd. (AHEL)
The project won Innovative Application of Special Concrete Award 2018 which was given by ICI Bengaluru Center and