Secrete of maintaining existing buildings.

Micro-concrete pump to place high strength grout into inaccessible areas:

Micro-concrete pump to place Micro-concrete high strength self flowing grout

Preamble:

Struct-Mast Engineers and their team of engineers has innovated, conceptualized, designed, fabricated, assembled the Micro-concrete pump to place high strength cementitious grout into forms to offer apt solutions to puzzling problems in pumping. This apparatus and is intended to do the continuous pumping and placement of self-flowing high strength cementitious grout into restrained area. 

The assembly is mounted on a fixed or mobile frame. There is a continuous pumping of the self-flowing grout which is supplied to an intake port of a screw-type, positive-displacement pump and discharged from this through a conduit pipe to placement site into forms on a continuous basis.

Struct-Mast Engineers are using this pump successfully to cater the needs of their client to restore the RCC structures.  We have intentions to develop this pump on large scale and have a desire to set up a marketing set up including awarding dealership.

Actual users and dealers who are interested in the pump may contact us on structmast@yahoo.co.in or call Mr. Jayant Sheth on + 91 9820291968 or Mr. Chintan Sheth on + 91 9820857365 or to call our office + 91 22 23452248 for better deal.

Consulting engineers, Consulting Architects, prospective Clients and research scholars also may contact us how to specify the pump in their special conditions of contract to achieve good quality works to place high strength micro-concrete grout which will receive prompt attention from us.

History:

Struct-Mast Engineers during their tenure as specialist contractors had come across difficult turns to place high strength grout in to inaccessible areas like soffit of the slab, other concrete structures surrounded by facilities like piping in refineries, power plants, cement companies, other major industrial plants, deep seated marine structures surrounded by sea water through out the service life and many more similar situation wherein the conventional repairs are carried out hand applied applications with lot many limitations and major being strength development and durability.  To keep up our goal to achieve best results for the beloved clients and to place rendering as specified by the consulting engineer and the consulting architects, our innovative engineers conceptualised the pump into realities to keep space with the modern technology which has developed self flowing, self compacted and high strength micro-concrete.

Application in the Field:

The self-flowing self-compacted high strength cementitious grouts have many applications in the repair sector, new construction, tunnel lining etc. of civil engineering, empty pipe filling, soil stabilization / cavities filling in geo-technical works, such as for filling gap between base plate and concrete pedestals, filling micro-concrete in to beams and column locations where reinforcement is found congested and concrete cannot flow, between existing prepared surface of damaged concrete and shuttering location to strengthen and repair RCC members, abandoned pipelines locations and other large voids in the earth, and for grouting of tunnel liners and similar structures. These grout is mixed into the mixers as ready to mix micro-concrete. Because of the high-strength along with other properties like self-flowing, cohesive mix, the cement grout which achieves strength in relatively shorter period compared to normal cement concrete and being non-shrink type the damaged structures retains the strength as desired and the structure is expected to perform which otherwise would have been under risk of not performing under service load. This results in great cost savings, especially when structures are critical structures. Other advantages of the high-strength grout is because it is fluid and non-shrinking, the need for contact grouting or bonding coat is eliminated.

Advantage of the pump:

• Although other grout namely application of in geotechnical field of civil engineering cement is modified with fly ash or bentonite and the grout is highly advantageous material for grouting, backfilling, void filling, and so forth, its success in many of these applications has been limited to a significant degree by the manner in which it is conventionally prepared and subsequently pumped with the pump which will not segregate the individual constituents namely sand, cement, fine aggregates and other additives and or ad-mixture due to every cross section of grout remains same as it is existing.
• The conventional batch-process approach and grouting under gravity or using other centrifugal type of pumps exhibits certain inherent inefficiencies and disadvantages, especially when it comes to large fill jobs. 
• It may be possible to prepare batches of cement grout which are big enough to complete relatively small grouting jobs, this is simply not feasible in the case of larger jobs, such as the filling of abandoned pipelines, which may call for large quantities in terms of several cubic meter of grout. Obviously, the repeated starting and stopping of pumping which is involved in a batch process introduces a strong element of inefficiency on such projects, especially being that large crews of workers may be left standing idle between the placing of each batch. This enhances the costs.
• The need to mix up separate batches of grout and pump these individually invariably leads to quality control difficulties. Apart from mix variations which occur inevitably from batch-to-batch, the batch-type processes are inherently incapable of permitting adjustment of the quality of the grout as it is being pumped.  
• Though the cohesive structure of the fluid grout is very stable, and will withstand high pressures without loss of integrity, significant passage of time may cause segregation due to friction between the grout and the piping or surface in contact with flowing grout through which it is pumped. These friction losses are somewhat unpredictable, and naturally become more serious as pumping distances increase. The inability of the batch-type processes to adjust the quality of the grout to compensate for observed friction losses means that an entire batch of grout may be placed at the placement location with the constituent structure being significantly deteriorated due to friction loss, resulting in a severe decrease in the volumetric yield of the batch.
• Another serious problem which has been encountered with such conventional grouting systems, particularly when filling abandoned pipelines and other elongate voids or placing grout underneath large span slabs for restoration purpose, stems from their inability to deliver the grout continuously at a high volume rate over sustained periods. As was noted above, the cohesive structure of the grout is very stable so long as there is free liquid along with evenly distributed constituents of the grout in the mixture, and so this can be pumped at relatively high pressures. However, once hydration of the grout proceeds to the point where it takes an initial set, the cohesive structure ceases to exist and is replaced by hard and harsher mortar which is maintained only by the cement paste which surrounds it; if this is subjected to external pressure, as by the pumping of additional grout adjacent to or on top of the first, the hard / harsher mortar structure will collapse very easily, resulting in a severe segregation of the cementitious mortar and blocking / choking of the paths as good as loss of volumetric yield. In simple words, it is very difficult to avoid this when using a batch-type process, since the process is slow by its own very nature and placement will periodically halt while another batch is being prepared, and the grout will continue to set during these pauses; the pumps and related equipment which are conventionally employed in these processes are not suited to high placement rates.
• At times due to head existing between pump location and grout placement, there is back pressure causing choking of pumping grout at the delivery point causing frequent closure of the operations and one cannot deliver quality works.  This problem has been resolved in our apparatus and it’s system by proving hopper which hold the grout and contains the back pressure as well as maintaining inclination of the screw and complete assembly.

All above problems has rendered the conventional techniques facing lots of limitations and the pump innovated has an edge.  

Pumping of Micro-concrete for ceiling of a residential flat.

Micro-concrete pump.

Placing of Micro-concrete by pumping - Ceiling of stadium roof.

Our mission:

1.  To successfully develop, produce and sell high quality micro-concrete pump and pumping systems and contributing to a better quality of life in healthier environment.
2.   To strive to become world class leading pump manufacturer to offer our Clients user's friendly, reliable, efficient, saves on wastage of material and sustainable product.

Strengthening of Roof slab

The RCC roof of Tennis court & Badminton court of Malabar Hill club - Strengthening measures

Soffit of roof

Roof top

Abstract:

The roof covering badminton court and tennis court seating arrangement was found in total distressed condition when concrete was exposed.  The engineer decided to repair, strengthen and restore roof at once without any delay.  Requirement from the Client was to allow the local tournaments to proceeds unhindered.  Why repairs have been undertaken?

• Restore or improve structural integrity 
• Improve appearance 
• Improve durability 
• Improve functional performance 
• Provide water-tightness

M/S. Struct-Mast Engineers a leader in the repair industries was selected for the restoration and strengthening works who successfully accomplished the work without any untoward incident in most safest manner and complying to standards and in time completion without hindering the local tournament to the best satisfaction of the Client. 

Sliding moving platform

Struct-Mast Engineers had put in action innovated sliding moving platform which proved a great tool to deliver the durable work in most safest manner with quality as envisaged by the Consulting Engineer for large span roof structures.  

History:

The club was constructed about sixty years back.  The roof of the slab to give shelter to tennis court and badminton court was constructed out of RCC and both the roof needed severe repairs.  Struct-Mast Engineers was awarded the work to repair both the roofs and both the roof are balancing cantilever type roof.  

The carbonation of concrete caused the cracking of concrete due to corrosion of rebars embedded in concrete was the reason to allow ingress of water into the roof structure which further aggravated serious corrosion of cantilever beams forming main load bearing members.  The engineer diagnosed condition of deterioration of steel reinforcing bars and concrete carbonation as severe and advised to repair the roof without any delay.  Expert engineers of Struct-Mast realised that the conventional tubular scaffold if put in action will have lot of limitations due to geometry of seating arrangement and cantilever roof beams.

Compulsions:

• The Club wanted to use the seating arrangements for both the court as internal tournament was being held and could not afford to cancel the tournament for children.
• The Club did not want any incident and wanted to repair the roof structures in safest manner.
• The Consulting engineer had diagnosed the roof structures as critical and needed repairs to begin the repairs without any delay.
• The location is such that the club is surrounded by elites and if any work involving noise will attract wrath from neighboring building. 
• To Curb noise and dust pollution only could help in smoother way to repairs.

Roof Structure:

The roof structure is self balancing cantilever beams with slab supported on beams.  These roof structure is sheltering seating arrangement on either side for badminton court and tennis court.  The repairs of this roof requires a blend of skills from the leading service provider.  The cantilever beams were restored first in sequential orders.

Road map to achieve formidable repairs:

The roof slab and beams repairs were undertaken with following ultimate goal which was divided into various tasks.

• Health and safety of all personnel;    
• Minimum degradation of environment;                    
• Zero accidents project and goal of zero incidents;        
• Achieve in time completion;                      
• Lasting repairs in demanding conditions;                    
• Proactive planning and force majeure. 

The first step was to evaluate current condition of existing concrete.  A review of structural design, details, structural instrumentation data, visual inspection were assessed by the expert engineer.

The second step was to relate data obtained from above to mechanism that causes the damage / deterioration. The competent person related observations to cause of damage. In compliance to the assessment for corrosion initiation phase more proactive maintenance program was worked out and in corrosion propagation phase more detailed repairs strategy was worked out.  

Access system for ceiling repairs

The classified damages were assessed as: 

•   Surface repair - removal and replacement of deteriorated concrete.
•     Strengthening - strengthen or enhance capacity of a structural member.
•   Stabilization - halting unwanted condition like cracking or settlement
•    Water-proofing - stops fluid from entering or exiting concrete structure.
•     Protection- protect concrete from aggressive environment 

The surface damage is superficial damage mainly due to shrinkage crack /cob web crack  seen on surface and are not more than 1.5 mm deep and widths are less than 0.1 mm.   

For ceiling sliding platform was used for an access which proved very beneficial to obtain the quality repairs and progress as very fast.  

Varying degree of damage observed in ceiling

 The entire ceiling was tapped and loose laminated concrete was removed till carbonation.  For deeper degree of damage the micro-concrete was placed in to form works using specially innovated micro-concrete pump which proved very beneficial to achieve good quality works and faster progress.  All anti-corrosive treatment was applied to rebars and on need base the steel was replaced when found corroded more than 15%.   

Micro-concrete pump used to place grout underneath ceiling

•      Minor 

Crack width < 0.1 mm observed on roof slab

crack widths are narrow and are found in the range of ≥ 0.1mm & < 0.3 mm damage defined as the damage restricted within cover concrete portion of the structure.   Isolated cracks are seen and spalling of concrete is not more than 30mm. depth.  No rebar are found corroded.  It is important to restore concrete cover in order to prevent rebar from eventually exposed to corrosion.  The GI weld-mesh of 100 X 100 mm placed with 10 Gz. and connected with 8mm diameter shear connector anchored with epoxy compounds. The area is uniformly leveled with 30 mm thick concrete screed with a acrylic polymer bond coat to restore bond strength between existing parent concrete and screed mortar overlay.

Moderate damage

•     Moderate damage 

consists of concrete cracks and wider de-lamination exposing reinforcing steel.  The reduction in cross section of rebar are not more than 5%. There is no immediate effect on the structural capacity. Although cracks and exposed reinforcement can reduce structure life due to corrosion and freeze thaw action.  The cracks widths are medium and in the range of ≥ 0.3 mm and < 1.0 mm.  The repair work should commence within one to six months or simultaneously with the major repairs works. The restoration of existing concrete surface was proceeded with Polymer modified mortar upto 25 mm thickness.

Shear connectors.

•     Severe damage 

wherein crack widths are >1mm, the exposed rebar are found corroded.  The damage to rebar along with loss of significant cross section and possible lateral misalignment due to distortion calls for urgent attention to primary structure as negligence can cause problem. The reduction in cross section of rebar are not more than 15%.     The crack widths are wider than ≥ 1.0 mm.  The corroded bars have been replaced with 10 mm diameter bars with anchorage derived as lapped bars. The entire surface was restored with high strength micro-concrete.  Shear connectors were introduced to have better compatibility between existing concrete materail and rendered surface.

Shuttering for beams

•    Potentially hazardous damage 

wherein damages are wide spread and cracks are wider than 3mm.  Main bars are found necked / reduced cross section more than 15%.  Excessive deflection of the load bearing member of cantilever beams.  The concrete was removed till found carbonated.  The steel bars were replaced with steel bars as per actual.  Concrete was restored with micro-concrete layer as thick as 50 mm with addition of anchor shear connectors. To enlarge the beam sections shuttering was prepared and micro-concrete was poured which reduced time to strengthen the existing beam and strengthened  the beam.

    The photographs below shows the finished surface of ceiling as well as the roof structures.

Finished repair system of first half

Finished surface of ceiling and columns supporting roof.

Finished surface of cantilever beams over roof.

Conclusion:

• In the entire repair process the sliding platform could help in finding cause and effect of the damages to the stadium structures with ease.
• Application of rendering could be accomplished smooth and quicker there by reducing the cost and imrpove durability.
• The main problem in strengthening anticipated was to achieve the desired ‘compatibility’ and a ‘continuity’ in the structural behavior between the original material structure and the new material/ repaired structure.  
• Visual survey subsequently conducted by competent person could ascertain sound repairs.  No leakage through roof slab or joints was observed during the progress of complete monsoon period.
• NDT tests conducted over the repaired structures like UPV test, half cell techniques showed improved results.

Sustainable means of restorations of structures

STRUCT-MAST ENGINEERS

A push in right direction for your project is our forte

Sustainability  O  Development  O  Innovation

Innovative remedial methods 

Rational repair strategies

Creative engineering solution

ISO 9001:2007 & OHSAS 18001:2008 certified company. CRISIL rated company

Struct-Mast Engineers have mastered major repairs & restoration of all types of R.C.C. structure & steel structure from 1986 onward  which are found distressed or BIS recommends to strengthen to improve performance objective of the structures. Types of structures include are marine structures, bridges, residential buildings, machine foundations, overhead reservoirs. We have taken a lead in mitigating Co2 generation and offered concrete solutions to comply to sustainable means of restorations.

Industrious professionals all the time

Competence to achieve results for demanding tasks of repairs to industrial or residential structures of importance on land or under water by adopting sustainable practices at all stages of repair activities. 

Brief steps how Struct-Mast Engineers achieve sustainable means: 

Struct-Mast Engineers is far more convinced that refurbishing, strengthening and retrofitting of existing building has potentials of reducing carbon footprint.  Continuous evaluation and findings motivates Struct-Mast Engineers to concentrate on perpetual improvement in technology followed by good maintenance & followed by repair work helps to minimise energy wastage and living discomfort, but also increases the durability and longevity of a building’s fabric, yielding further long-term benefits in terms of the retention of embodied / capital carbon. Retrofit and refurbishment is also a carbon-generating activity in itself and its impact should be considered in relation to the total lifespan (whole life) of a building.  Still Struct-Mast Engineers maintains that executed maintenance and repair should be the first option sought in making existing buildings sustainable.  Further to above, well-designed and executed refurbishment and retrofit work comes with added benefits, not least the ‘sense of place’ that is maintained for the people who live, work in, or use the buildings otherwise. Here we describe below an holistic approach to retrofit and refurbishment concerning sustainability,  

Planning, design & specifications.

Repairs to Jaslok Hospital - a multi storey building. 

Shear connectors & protective coats to rrebars.

Sliding platform do not allow dust to fly

•     Plan out how the building can be improvised to become thermally and with natural light more efficient and sustainable. Plan your scaffolding which allows natural light and air movements while repair works are in progress.  The correct specification of scaffold reduces noise and dust pollution, reduces risks, enhances safe use for which Struct-Mast Engineers have designed and used moving suspended / sliding platform or sturdy "H" frame with intermediate platforms is a first step to achieve sustainable repair job. 
•    Specify lasting repairs and compatible method statement which supports durability of repaired structures.  The workmanship which is a vital component for achieving durable repairs is achieved next to perfection when suspended moving scaffold is used.  Lasting  concrete repairs lies in bonding the new material to the old material, use of acrylic bonding coat enhances bond between rendering surface and substrate, use of shear connectors or pins.  Protection to Reinforcement bars is also a vital step in the direction of lasting repairs. Apt selection of rendering material is the last link to achieve lasting repairs.  
•     Specify eco-friendly material namely cement + fly ash + super plasticizers.  

     Material conservations & selections. 

• Use of high performance concrete, fibres to reduce shrinkage, use of cement substitute products, use of alternative pipes for plumbing and drainage, use of durable paints, anti-carbonation coatings, use of composite material etc. are some of the measures Struct-Mast Engineers have successfully employed and used with commendable expertise.  The use of such material discourages over consumption of cement, steel and other precious material and uses industrial wastage otherwise would have created the dumping problems.

Use of dismantled / recycled material. 

Struct-Mast Engineers encourages use of industrail recycled material or waste materail in building construction as an alternative to virgin building material, building products by using industrial byproducts.  To list them few are coal combustion products, foundry waste, and slags, construction demolition products say brickbats and wastage of tiles for waterproofing of terraces etc. and these material has chemical and physical proerties that make them valuable resource.

Brickbats used for waterproofing

 Energy conservation & innovations

Recycling of industrial material is a rational effort to conserve energy and other resources  and reducing green hose gas emissions by managing material most efficiently thereby conserving natural resources and decreasing energy use.  

Innovations has made industrial byproducts use in the building construction more compatible has helped for environmental beneficial as it replaces non-renewable virgin material there by reduced energy consumption and pollution associated with these activities, saves land fill space.  Innovations has helped in usage of industrial waste more economical which reduces cost of construction for builders.  

Otherwise also using recycled material proves economical as it reduces cost of hauling and disposal.  At times material like coal bottom ash proves lighter than the virgin material is used as bedding material for green roof as it is lighter than any other virgin material. Tier shreds provides effective drainage around foundation compared to virgin gravel material obtained from river and puts less pressure on foundation. Green sustainable building is the practice of creating and using healthier and more resource-efficient methods of construction, renovation, operation, maintenance, and demolition.  Use of geo-synthetics and rock anchors have reduced pressure on retaining walls thereby calling for walls using less steel and concrete for the pressure being exerted on walls thereby reducing cost of construction and saving on steel and cement.

Other applications of using recycled material are: 

Roofs when covered with plants it reduces storm runoff. 

Furniture made with plastic lumber and containing fly ash

Building facade constructed out of cement substitute material.

Compound / side walks can be constructed out of recycled aggregates and recycled asphalt material. 

Ceiling tiles constructed out of recycled gypsum boards and use of fly ash.

Air cooled blast furnace slag is used to produce mineral wool for insulation. 

Rock anchors calls for saving in cost of  retaining wall

Everything of above you get them all under  single roof  !!!!

Conclusion:

The striking advantages of refurbishing & retrofitting are:

• The refurbishing will render the building more sustainable for existing use or intended use.
• Rendering buildings more energy efficient which reduces carbon emissions greater sustainable use of embodied-carbon investment (capital carbon).
• The word of caution is it proves at times costly and inconvenient. 

Some salient features of Suspended moving platform for high rise buildings.

Suspended platform - High rise building

Salient features:

• Suspended platform is very safe and ease with which it can be erected in the building.
• Suspended from terrace using out riggers with factor of safety 2.50.
• Assembled in shorter lengths as per requirement of building facade.
• Designed as per OSHA and relevant BIS standards for construction load handling. 
• Fuel, oil and power consumption zero.
• Debris and material handling from platform leading to reduce dust & noise pollution. 
• User's friendly, workman achieved is next to perfection.
• Economical in use, low maintenance cost, supports sustainable activities.
• Repeated usage, no blockage of light and air, railing and toe provided in the deck.
• Can be operated in fair seasons.  We have achieved zero accident and no incident.
• Any adult person of any gender and / or of any age can use with most comfort.

Services provided by Struct-Mast Engineers

Innovative approach