It has become a major challenge to select right techniques, materials, and procedures for the repair and restoration of floors. The key here is timely evaluation and selection of experts for execution. We have focused on Floor Rehabilitation and Restoration of Danisco – DuPont Project done by Experiva Engineering. We have discussed herewith the design specification, planning, selection of material, selection of equipment, sequence of placements and curing.
Floor requirement by client for rehabilitation, reinstallation and restoration
The client had enlisted a basic requirement which was to be complied with the deadline. The requirements included-
- As the factory was running, and production was in process, where they wanted to rehabilitate their floor, that to be in a very stipulated time frame.
- Dismantling of existing Epoxy and Screed over slab on grade floor.
- Client Requirement was FM2: Forklift and automated MHE has to move on defined in racks and some of free movement areas.
- Basic foremost requirement was floor should on service. Time duration 20 days, area 4000sqft.
Execution process for floor rehabilitation and restoration
The execution once started required strategic sequence specification order for the execution of the work, the order followed were-
- DESIGN AND SPECIFICATION
- SELECTION OF MATERIAL
- SELECTION OF EQUIPMENTS
- PLACEMENT OF MATERIALS METHODOLOGY
- CURING OF HSSGM
- CUTTING OF CONSTRUCTION JOINT (a/b<1.02)
- PLACEMENT OF PU FLOORING
Design and specification
Performance of a floor depends on design principal specification and techniques used in its construction, where the floor should remain serviceable assuming plant maintenance and no gross misuse or overloading.
Floor must be able to carry the required static point loads, uniformly distributed loads and dynamic loads without unacceptable deflection cracking settlement or damage to joints.
Joint layouts should take into account the location of racking legs or mezzanine floor columns. Joint should be robust in both design and construction. Joints and reinforcement should be detailed to minimize the risk of cracking.
The floor should have suitable surface regularity, and must have some suitable abrasion, chemical and slip resistance, with hygiene and antimicrobial property.
We followed floor designing from TR 34 3rd edition, ACI360 01 10, ACI 302, BS8204, ACI 548 1R 09, ACI 224 1R-93. At the design stage we shared every details for the system to the client and consultant for HSSGM (High Strength Structural grade mortar) and Synthetic floor details, like –
- High early final setting time for the proposed system
- Compressive strength
- Tensile strength
- Flexural strength
- Curing period
For Reinforcement we used structural fiber, also provided all the required details of Macro Synthetic Fiber. Designed followed by ACI 360 R-10 and calculator given by Euclid, whereas fiber provides equivalent strengths to WWM and rebar provided.
We also provided joint layout, and set out the expected number and performance of the joints at HSSGM and PU flooring.
Successful floors are the result of an integrated and detailed planning process that addresses the needs of the user in a readily understandable way. To play our part in this process, we shared total knowledge of process, advantages and limitations of our techniques. By Understanding the time limits we planned with Manpower, machine, electricity, water, shear anchors and our resources so that everything should be optimized.
Selection of material
The selection of material was decided as per the project requirement. We needed materials that would fit in with our vision for the project we used the following ones-
High strength structural grade mortar: VERSASPEED: VERSASPEED is a versatile, single-component, rapid-setting repair mortar for horizontal, and form and pour repair projects. Requiring only the addition of water, VERSASPEED is a low shrinkage, high early strength material that is easy to use with an accelerated set time for fast turn-around projects.
TUF STRAND SF: TUF-STRAND SF is a patented polypropylene/polyethylene macro synthetic fiber successfully used to replace steel fibers, welded wire mesh and conventional reinforcing bars in a wide variety of applications. TUF-STRAND SF fibers comply with ASTM C1116, Standard Specification for Fiber Reinforced Concrete, and are specifically designed to provide equivalent tensile and bending resistance to conventional reinforcement requirements.
LOWFRESH MF: Flowfresh MF is a chemical resistant, antimicrobial, polyurethane resin floor system with smooth matt coloured finish. Flowfresh MF incorporates Polygiene® – a performance based antimicrobial additive which inhibits the growth of bacteria, fungi, moulds and mildew. Ideal for dry or semi-wet processing zones such as food or pharmaceutical packaging zones .
Selection of equipments
There were requirements for various types of equipments, the selected ones are-
- INDUSTRIAL VACUUM CLEANER
- AUTO LEVEL
- LAZER LEVEL
- CONCRETE PAN MIXTURE
- VIBRATAM (MAGIC SCREED)
- BULL FLOATER
- CUTTER MACHINE
- POLYTHENE SHEETS AND POLYBAGS
- GRINDING MACHINE
- MIXING MACHINE
Sequence of placements
We followed a standardised sequence of placements so that the final curing could be as per the best quality. The sequence adopted were-
Concrete surface preparation
Each repair material needs a particular type of surface preparation but generally the concrete surface must not be too smooth, too rough, or too irregular.
Concrete surface preparation for specially such kinds of repairs require special attention and provide long term performance, as need to have proper bonding with the proposed High strength structural grade mortar, where as for repairing there are various methods here we have opted Mechanical preparation.
Mechanical Preparation (opted CSP level-10 as per ICRI guideline No. 03732 and ICRI guideline No.310.02)
In this act of process, we removed the total layer of screed/PCC of 50mm and to take out we used our Hilti T800 concrete breaker, First cleaned the surface manually and then mechanically followed by high pressure water jetting of Bosch.
Fixing of shear anchors
According to us all the shear anchors nowadays are becoming a prominent method to structural connections via mechanically, and it is economical and safe. So the advancement of designed member load can be rest completely. As per ACI 318-11 and EN 1504. Here the prepared concrete surface fixed with shear anchors using HYSD bars of 6mm diameter on the concrete substrate with 1Mtr C/C. For convenience and ease of application, it is ideal to have the ‘L / T’, Here we have used L type shear anchor with web length of 20mm and flange length of 50mm, where inserted 30mm in concrete with the help of hammer drill machine.
Fixing of channels
We fix the panel dividers (as mentioned in the drawing) in longitudinal positions where dividing strips of aluminum panel layout are corrected in line and level so that to take HSSGM in alternative panels. The panel’s size was 4.3MTRX13MTR. Top of the strip matched with required slope and – 4mm down to finished floor level. Strip fixing we did with the mortar, that to be one day before placement of High strength structural grade mortar.
The prepared concrete surface shall be saturated with clean potable water at least 2 hours prior to application of repair material, and it is an integral part of the repair systems and essential part to develop bond line as well as bond to the HSSGM. Well, it is essential because to block the pinholes or porosity, to avoid air bubbles in later stages on the cured top surface.
Here in this case we did priming with rich polymer modified slurry with SBR Latex confirming to ASTM C 1059-86, where consumption @ 20 % by weight of cement. For a bond coat of SBR Latex we mixed in a ratio of 1: 1 ratio (1 part SBR Latex mixed with 1 part cement by volume). Compressive strength in 7 days as per ASTM C109, 40MPA, Tensile strength in 7 days as per ASTM C190, 48 MPA.
Placement of high strength structural grade mortar with macro synthetic fiber
Fiber Reinforced High Strength Structural Grade Mortar (FRHSSGM), it can be defined as a composite material consisting of latex and micro silica modified cementitious mortar and discontinuous, discrete, uniformly dispersed suitable fibers. Here on FRHSSGM, we added 4.4kg of structural grade fiber to control plastic shrinkage cracking and drying shrinkage cracking if any. Where as added designed fiber will also lower down the possibility of permeability. Here the modulus of elasticity of the fibre is higher than the matrix (Base Concrete floor and FRHSSGM), so that helps to carry the load by increasing the tensile strength of the material.
The primed concrete substrate shall be poured with FHSSGM and 25% of 6mm down pea gravel aggregate. It was easy to use and installed with standard equipment as discussed. It bonds tenaciously to properly prepared concrete.
The FRHSSGM is prepared by mixing the powder with water at the designed water powder ratio. Initially we add 80% of the water in the pan mixture and then slowly add the powder component and finally added remaining amount of water and continue mixing for 2 minutes till lump free paste consistency is achieved.
The mixed FRHSSGM shall be used within its workable time and no further addition of water for workability is allowed. The mixed FRHSSGM poured in divided strips and the top finished with steel trowel to make it in line with required – 4mm floor detailing.
Cutting of control and construction joints (A/B<1.02)
We provided the construction joints, control joints, as per the detail submitted where we cut 30% of the thickness to restrict the cracks, with in 48hr as per TR34 3rd edition and ACI224, we saw cut 4mmX15mm. Left the grooves for filling with PU, during the installation of synthetic floor.
We cured finished FOR HSSGM cured for a minimum period of 1days with water and later on covered with LDPE sheet for rest 3days.
Laying of PU flooring (BS8204, FeRFA,)
Polyurethane can be applied to any fresh concrete or any cement screed surfaces with +/-5% moisture, that to be provided with vapour barrier below. The substrates should be adequately thick, sound and strong enough to meet service requirements. As an example – industrial floors in factories, warehouses and commercial facilities are recommended to have a compressive strength of at least 25Mpa and a pull-off cohesive strength of at least 1.5Mpa
On 4the day, we have prepared the substrate with the help of SURIE POLEX scrifier with integral vacuum collector for dust and waste which give more precise, controlled and almost dust free working, where as Scarification works by using steel cutters mounted in rows with several rows around the perimeter of a rotating drum help to achieve desired CSP, here we achieved CSP Level 3, for the application of 4mm PU as performance and durability will depend very much on the bond line.
Provided shear keys for PU flooring within 75 mm of all ‘free edges’ these may be cast into the surface or cut subsequently. As the PU floor has a tendency of curling, so by providing these keys we provide more anchorage to the top 4mm thick layer, Moreover also help to minimize any floor problem from beneath, if occurred to its own area. Here we have provided 8mmX8mm grooves which is just double the thickness of the floor, and the trend of laying synthetic flooring. These shear keys (or micro control joints) which normally we provide in between control and construction joints and; 2mX2m.
After cutting off shear keys and cleaning, we did scratch coats of the same material with 1mm-1.5mm to block the pores from the substrate which may lead to surface defects such as pinholes or blister, where scratch coat helps in facilitating application engineering and gives a more accurate and finished surface. Here during the application, we follow all the guidelines of the manufacturer for pre and post mixing handling and well practically mixing of material and retention period after mixing, will purely depend on the climatic condition, here we got 20-25min of time as the surrounding was close to 20 degree Celsius temperature.
After 24hours, we did top coat, where material was spread and maintained the thickness with notch steel trowel, supported by spike roller, where the role of spike roller is to release entrapped air and to assist in flow followed by proper spreading with uniform distribution of material. After application, we restricted the movement for 3 days.