Building Innovations ’ joint free slab on grade system is an innovative approach to the detailing and construction of slabs on grade which results in substantial savings in construction time, cost and maintenance.
Joint free slabs are similar in detail to the traditional stiffened raft slab with integral edge and internal thickenings, except that they incorporate a crack inducer grid which enables them to be extended to potentially limitless areas.
The crack inducer grid is assembled from extruded plastic conduits and injection-moulded plastic connectors. The grid is placed on the ground and the connectors double as reinforcement bar chairs.
The crack inducer grid is similar in effect to a grid of saw cuts installed in the underside of the slab at the earliest possible opportunity – as the concrete is being placed. As such the grid has the maximum possible effectiveness in both initiating and distributing shrinkage cracks throughout the length and breadth of any joint free slab.
In comparison with traditional slabs on grade, there is a reduction in the reinforcement required and all traditional isolation joints together with all formed and sawn control joints are eliminated.
The long term shrinkage cracks induced in joint free slabs on grade are sufficiently fine to have no detrimental effect on vinyl tiles, ceramic tiles, carpet, epoxy toppings and terrazzo toppings provided they are installed in accordance with the Buillding Innovations’ specification.
Australia’s first large-scale commercial use of joint free slab technology has been carried out at the Mount Sheridan retail development in Cairns, where there was an intricate pattern of ceramic tiles runnning almost 90m through the specialty mall area.
Why use the system?
Reduced construction time. Joint free slabs can be placed in large continuous pours. It has been found that 1500 to 2000sq m pours can be readily placed and finished in a single pour on a single day without the need for special logistics. On small retail projects with a total floor area of 3000 to 4000sq m, it is possible to reduce overall construction time by as much as three weeks.
Reduced construction cost of slabs. Construction cost for the slabs is reduced primarily due to the elimination of sand blinding, the elimination of all control joints, the possible reduction in slab thickness and reinforcement, elimination of all compressible filler boards and strips, the simplified placing of reinforcement and a reduction in concrete pump hire. The cost of the crack inducer grid is generally paid for with just the deletion of the control joints.
Reduced construction cost of finishes. Reduction in the cost of finishes is primarily due to the elimination of all brass and stainless steel cover strips. These typically cost $50 to $130 per linear metre for supply and fix, and if they installed over all control joints, the cost savings from this alone couldbe at least $30 to $50/sq m.
Lower maintenance costs and reduced risk. Brass and stainless steel cover strips are a high maintenance item in retail projects such as supermarkets. The cost of the maintenance is substantial and disruptive to operations, and the hazard presented by failed cover strips to both shoppers and staff is of great concern to retailers. With joint free slabs there are no cover strips and the problem is eliminated.
Better appearance. Control joints and cover strips disrupt the continuity of the floor finishes and cause a lot of concern to when they are not located with the set-out of aisles and shelving in mind. With joint free slabs there are no cover strips, therefore the pattern and continuity of the floor finishes is uninterrupted.
Greater versatility. Control joints in traditional slab on grade retail floors are often set out to suit the merchandising layout, however this effort is futile if there are subsequent changes.Joint free slabs provide the maximum versatility in these circumstances as there are no joints reflected in the finishes.