The Sustainable Housing Complex for ACC

Sometimes, even the biggest giants surprise you.

ACC, one of India's super brands and the oldest cement company had set a mandate of going green. Over the last years substantial changes from their composition of cement, to the manufacturing process, and even the way they built their own corporate office were initiated. The mantra in their plants was non-polluting and the greater production of pozzolonic cement. For their buildings were set the goals to achieve the highest standards of green building practices.

Along these lines, ACC had initiated the process of building their entire residential campus for their staff colony of their cement grinding plant at Kudithini, in Bellary, Karnataka, as a sustainable campus. M/s Ashok B Lall Architects, ABLA, from Delhi were roped in as the main Architects for this project. Mr Lall's office went about putting together the remaining team for the project (services consultants, energy consultants, LEED/GRIHA certifcation consultants, Landscape consultants, and last but not the least, the Construction Management Consultants. That is where we (IGH) came in.

As construction management consultants, we had the task of enabling, coordinating and managing the various outcomes of the various consultants. To boot, our programme was by our design, carried out as 'Sustainable Construction Management Consultancy'. By this definition, we took up cudgels on the behalf of the architects to ensure that the entire development, its building construction systems and methods employed would be resource efficient and therefore occupy a low ecological footprint.

The ACC Greens Village, as it was later named, occupied the western section of the larger 240 odd acre campus of the Kudithini cement grinding plant. Area for this campus was demarcated and occupied about 50 acres in all. Going beyond the mandate of designing and building residential quarters and some amenities (amounting to some 83,000 sft), this Village of sorts also incorporated into the brief

• a huge afforestation programme,
• food sustainability- which saw the development of a sizable farm, a cattle shed (for milk) and a fish pond
• rainwater management, harvesting and recharge,
• energy sustainability which saw the incorporation of biomass gassification infrastructure, supplement by woody biomass from the afforestation programme, and a bio-methanisation unit supplement by the dung from the cattle shed.

Our engagement on this project can be highlighted in these following sections:

Development of a prototype structure

The first part of our involvement as a member of this team saw the suggestion of building a prototype structure that would embody all the construction systems envisaged and also serve as a benchmark of quality for the remaining construction to follow. This would also have ensured that all obstacles and hiccups (design or execution) would be limited to just this structure, with smooth sailing on the larger project.

An alternative to RCC slabs

Mr Lall's office had designed some exquisite buildings that were based on solar passive design principles and were based on an innovate thermal management of the interior spaces through cooling tubes, insulation and aided hydration for those hotter months. Essentially, the building type can be described as being sandwiched between cooling tubes to the east and west, and verandahs to the north and south. The cooling tubes had a wind scoop from the northwest and an exhaust side towards the southeast. The verandahs had openable insulated screens that would remain shut during the hotter months (trapping air which would retard any heat exchange) and be kept open for the more cooler months.

One feature designed originally by the ABLA was to pass cool air from the cooling tubes through the slabs of the building, therefore resulting in a deeper RCC slab and with PVC pipes as passages to this air. We suggested an alternative- a pre-cast system, which involved the placing of semi cast latticed RCC rafters and hollow pre-cast blocks that were cast to fit the needed profile. This system involved the usage of lesser concrete than the RCC slab originally suggested, and also meant the reduction in the usage of steel in the slab. One added advantage was the doing away of any shuttering for the in-situ pouring of concrete. Another was quality control. After scrutiny of the system and a visit to a vendor's site, the architects were convinced and the system was chosen.

The rafters were latticed t-beams, and were semi-cast (2 inches of the base was cast first) on the ground and cured. They were then lifted and set in place, using nothing more than a team of four (these rafters were limited to maximum spans of 4 metres). Props are placed at 1.5 metre intervals of each rafter to ensure that no buckling or cracking occurs during construction. The pre-cast filler blocks were made using a custom template on an egg-laying type block making machine. Once cured, they would be lifted into place and set on the protruding flanges of the t-beam. Above this, a grid using welded mesh is placed to cater for any upward thrust. Apart from that in the rafters, this is the only steel in this kind of slab. Concrete is then poured over this to create a layer of 1.5-2 inches above the pre-cast blocks.

As a total, this building used about 1.4 kg per sq ft of steel.... A saving of about 40% steel when compared to a conventionally built structure. (this is in spite of the extra steel used in the RCC tie bands as seismic area construction, and in the precast slabs used to cover the cooling tubes).

Finalising a resource sensitive block

Bellary has predominantly black cotton soil, so the architects had originally opted for a site-cast concrete block for the masonry. I remember having pursued a more resource efficient block from the get go.... We collected soil samples and tested them in Bangalore (including at the IISc Civil Engineering Department). We got mixed results. Then a eureka moment... the Kudithin cement plant had been procuring hundreds of tons of GGBS (ground slag) from the nearby Jindal steel plant. GGBS is a by product of the steel manufacturing process. This was used in the cement that the plant manufactured... and was a pozzolonic material. We checked this out as a substitute at the IISc lab and found that we got incredible strengths even at a high 40% GGBS constitution of the block (the remaining being quarry dust and cement).

The block manufacturing was initiated at site using manual presses, which resulted in the manufacture of over 800-1000 blocks per day. These blocks were designed as 200 thk blocks and were to meet a density requirement of about 2.0 kg/cm3 to ensure a requisite thermal mass design to meet the thermal dynamics of this design. While the contractor employed for the construction of the prototype building was very experienced in soil block making and other alternative construction technologies, we encouraged and roped in three other vendors in block making using the GGBS mix. They would come in handy for the block making for the main project. Despite the expensive procurement rate for the GGBS, we were able to make these blocks more economical than the originally envisaged site made concrete blocks.
An interesting anecdote is that ACC, which had originally initiated building several kilometres of boundary wall around and within their campus with concrete blocks, shifted to using these GGBS blocks.... as it also made financial sense. A big impact of the interventions of the entire team of architects and engineers.
Another impact of building use these site made GGBS blocks, were that we could control quality and due to the good consistency of these blocks, we could afford to leave the walls exposed. Of course this meant that we had to opt for some surface pointing to secure them from any untoward seepage. Being grey, this did mean that an interesting enough aesthetic had to be developed to avoid getting a dull appearance..

Reclaimed timber

At IGH we had been keen to push earlier thresholds of using alternatives for regular timber for doors and windows. The small scale merchants of old timber doors and windows in various parts of Bangalore had always intrigued us and showed promise if only we could use this wonderful resource at a larger scale. These merchants are small time operators and mainly cater to smaller requirements.

The properties of such a timber source is that it can be used as is, if the door/window component is in good shape, or has to be re-sized, planed and finished to suit the new design. The wooden members bear the scars of nails and pegs, that would have been removed in the resizing exercise. Care has to be taken to develop an aesthetic that incorporates these blemishes and scars (which add character to the wood), or, to mask them appropriately. A big benefit of the exercise is that wood can be considered as super treated wood due to both the more thorough treatment processes followed back in the day, and due to the natural conditioning of this wood over the years. Chances of deflection are extremely rare in the use of such wood. Another important aspect to consider while using such wood is that since these merchants don't segregate the wood based on wood type (neem, mathi, teak, sal, etc) the raw material is a mixture. The most one can do (with ease) is to ensure that each door component, is made from one wood. One can tone, or, paint over to bring an element of congruity over a much larger usage.

Most of this wood is sourced from areas that are seeing great urban renewal.... mostly smaller towns of Karnataka. The primary source is a demolition contractor who then re-sells these wooden components to these reused timber merchants.

ABLA was thrilled to have this value addition. The challenge was to find sections that were as wide as the designed double shuttered windows.... we just about managed to get a guarantee of the sections of that width for the entire project. We prepared a list of reused timber merchants and ensured that we could manage scale by using a group of vendors, instead of depending on just one. Eventually, the architects chose to paint these windows and doors with a colour scheme inspired by how rural homes around Bellary always articulated their doors/windows in resplendent colours. 

A lower energy floor

Bellary is situated at the border of central Karnataka and Anantpur in Andhra Pradesh. It is a dry arid belt, and is close to some repositories of granite (in Karnataka) and some slates (from AP). Originally, a granite was considered for all the flooring, but after discussions it was felt that we could achieve a further lower embodied energy footprint by opting for a pigmented cement floor. The logic was that since cement mortar forms the base of all stone floors, we could achieve this by simply eliminating the stone above, and rendering the cement floor well.

The challenge, however, was to get good skills to make these floors. We chose to go for an ochre coloured oxide floor, which would create a nice contrast to the grey surfaces of the GGBS blocks.

We went through a number of mixes of cement and different yellow oxides, and finally settled on the use of white cement instead of grey, and a minimum thickness of 3 mm of this mixture. This brought out the colour of the floor, and avoided the revealing of the lower grey cement base due to the additional thickness of this coat.

It had been common practise to use glass or brass strips in these concrete floors (also seen in cast in-situ mosaic floors) to control expansion cracks. This was not appealing to the design team, so an interesting, but more labour intensive method of laying this pigmented floor was chosen. The floor areas were divided into a 1m x 1m grid of panels. Alternate panels were cast first, and once set, the remaining panels were cast. Yes, this did take a bit more time than casting this floor in one shot, but it also meant that chances of large size cracks would be limited as one could consider the casts as limited to a smaller size, and therefore leading to a controlled expansion and contraction... leading to lesser cracking. Apart from a vibrant aesthetic and being a more resource efficient alternative, this also saved the client money as a pigmented cement floor costs much less than a stone floor.

Oh... those high energy industrialised tiles (vitrified, ceramic, etc) were not even an option!!

Bamboo engineered wood replacing plywood

As per the thermal management design of this building type, adjustable screens were provided in the verandahs. The purpose of these screens was to provide an adjustable thermal barrier when needed. These screens were panels that were built around a metal frame. The core layer was insulation and it was clad with plywood and a thin veneer on either side. To reduce the usage of conventional wood (plywood being a contributing factor) we proposed the usage of Bamboo mat board, BMB, as a replacement to the plywood. BMB is an engineered product that is a glued laminate of several bamboo mats. As BMB was attractive by itself, one did not require the use of a veneer over this. BMB is akin to marine grade ply and some manufacturers make versions that are external grade, with a protective UV resistant coat. Bamboo being a renewable resource (it is actually a fast growing grass and not a wood), is the ideal resource for the manufacture of woody boards, sheets, etc. An aside- bamboo is said to sequester more carbon than most woods.
There are a number of manufacturers of such Bamboo Enginnered products in the country, but there are differences in quality. (incidentally, there are is a Bamboo Mat Corrugated Sheet, BMCS, alternative to corrugated tin sheets.

A non-toxic anti-termite method

Sustainability or not, whether we withdraw water from the ground of not, the usage of any toxic substance for any activity is a strict NO. Anti-termite solutions are injected in great amounts into and around the excavation works during the start of construction, and we were concerned about such mindless injection of toxins into the soil. An alternative neem-based solution that we had been using for many years was employed to overcome this. The application method is pretty much the same,.. the difference being that the vendor who promoted this product would readily take a swig of this solution to drive home the point that it was harmless to humans, and not a poison.

Apart from these main interventions, there were many other significant but often overlooked options that were put in use in the construction of this building. For example-

• the usage of quarry dust instead of sand in plastering, mortar and concrete..... which is mostly dredged (illegally) from riverine systems
• the architects designed an attractive masonry railing, which used thinner GGBS blocks between bands of kadappa (a slate) and bethamchella (a smooth limestone).... reducing the usage of steel.
• the architects, along with the structural consultant, designed an interesting box trench foundation, specially for the black cotton soil of this region. Essentially, it was a lean concrete mix using large stone aggregate that was filled into this trench and allowed to cure. It was simple to execute and saved us many man-days, and did not need any reinforcement.

In parallel, while the mock-up building came up, other works related to the rest of the main project had been initiated. While the usual large scale vendor finalisation and tendering processes unfurled, another interesting story involving bamboo is worth covering.

As part of the campus, the architects had developed an interesting club building. The form was dramatic, with a gently angled roof protruding from two sides and held over slender built-up columns. The span of the building roof was 120ft x 80 ft. This roof was originally designed as a series of steel trusses (curiously designed to have an inverted arc like profile as it's bottom section) supporting a galvalum sheet roofing. There was also an interesting heat management process designed by the incorporation of a 'silver ceil' insulating fabric stretched across below this truss, ensuring that whatever heat is gained by the roof, is not transferred to the large hall below. The architects had designed this interesting mechanism to manage the venting of this roof.

While we could not but be appreciative of this design, we felt that we could try an alternative to those steel trusses. We proposed the use of bamboo trusses, and even roped in a specialised agency, WonderGrass, to back this. It was decided that a prototype of this truss would be developed in full scale and tested. Apart from this the prototype for the roof structures of three utility buildings (housing the barn, cowshed and gassifier) was also proposed. We worked with ABLA and WonderGrass to finalise this truss design and the prototype development was initiated. As a result we have managed to assemble and erect an 80 ft long truss... a testimony to the structural properties of bamboo and an elegant alternative to steel.

The ACC Greens Village is significant as it highlights innovate use of cement, apart from other building materials & systems, in creating a low ecological footprint built environment. It was also a momentous occasion for ACC, having achieved a significant milestone towards its agenda in promoting sustainability. Here's to the rest of the project.
Click here for more pics of the project.