Throughout the history of post-tensioned (PT) concrete, progress has been driven by engineers who understand both the technical and constructability sides of design. The challenge of Restraint to Shortening (RTS) has long been one of those persistent problems — and for decades, pour strips have been the standard solution. But pour strips bring their own complications and compromises, from wide leave-outs and backshoring to schedule delays and coordination headaches.
Years ago, our firm (Reigstad Engineers) faced a project that required a pour strip alternative — PTI classified the option as an Embedded Release Device — that promised to eliminate the wide leave-out and backshoring on the project. The concept offered a potential schedule savings of about a month. However, as we evaluated it, the limitations became clear. While it allowed for temporary volume change, the system was not an ACI-permitted rebar splice. It relied on brittle mechanisms to transfer forces rather than the ductile yielding provided by rebar in a lap splice. Once the device was “locked,” a hinge or discontinuity remained in the slab — unable to effectively transfer tension forces, only shear. In short, it attempted to replace a pour strip but failed to replicate its structural performance.
A true pour strip, on the other hand, forms a continuous slab that transfers both tension and shear across the joint. Its ACI-permitted lap splice satisfies the structural integrity provisions that ensure ductility and redundancy in the structure. Understanding this, we could not approve the substitution. But it did raise an important question: Is there another way?
I commend the original inventors for pushing the industry forward — because their attempt ultimately inspired another breakthrough. Dr. Gordon Reigstad recognized the potential and developed a rebar coupler-based solution that solved the same problems while fully meeting ACI code requirements. That innovation was PS=Ø (Pour Strip Zero).
With over 40 years in PT design and restoration, Dr. Reigstad applied deep technical insight to create a mechanical rebar splice that replaces the traditional pour strip — maintaining structural continuity while allowing temporary movement. The result is a system that creates self-supporting slabs, eliminates backshoring, and transforms the wide pour strip into a narrow, manageable joint.
PS=Ø advances proven rebar coupler technologies that have been used for decades. One end of the coupler receives a threaded bar; the other holds a Continuation Bar inserted into a grout-filled sleeve. While ungrouted, it allows for temporary movement in two horizontal directions — just like a pour strip or temporary joint release. Once grouted, it forms a full-tension ACI 318 Type 1 and Type 2 mechanical splice. The system is ICC-approved and proudly made in the USA.
Like the innovators before him, Dr. Reigstad moved the industry forward by combining sound engineering with practical constructability — taking what worked, refining it, and applying it in a new way.
Eliminating Compromise in Quality, Schedule, and Safety
The PS=Ø system delivers what traditional pour strips never could — high-quality concrete without compromise.
In conventional PT construction, pour strips sit squarely on the critical path. This often forces a trade-off between quality and schedule, as engineers and contractors negotiate how long a leave-out can remain open before project timelines are affected. The result is an all-too-common compromise: pour early to stay on schedule or delay the project to achieve better long-term performance.
PS=Ø changes that dynamic entirely. By eliminating the wide leave-out and removing the need for backshoring, the pour strip is no longer tied to the critical path. The system can remain ungrouted for extended periods — often 3, 6, 9 months or more — allowing the structure to move, shrink, and stabilize naturally before final connection — all without delaying other trades or construction progress.
This flexibility unlocks better performance, faster schedules, and safer jobsites. Crews can move freely without the hazards and obstructions of backshoring or large leave-outs with exposed rebar. On PS=Ø projects, extended ungrouted durations have become the norm. Once design and construction teams experience a project without the coordination challenges and risks of traditional pour strips, they recognize the benefit of leaving the system ungrouted as long as possible. In short, PS=Ø removes the conflict between quality, schedule, and safety — allowing all three to advance together. Zero Compromise.
Practical Applications of PS=Ø
The PS=Ø system is engineered for flexibility — applicable across a range of post-tensioned and reinforced concrete details where restraint to shortening (RTS) is most problematic. From elevated slabs to subterranean structures, the system creates temporary release while maintaining code-compliant continuity.
Slab Relief Joint
A PS=Ø Slab Relief Joint is the most common application on elevated PT slabs. Either side of the joint can be poured first, and the first slab can be stressed from either edge. Before the second pour, a continuation bar is inserted into the grouted sleeve of the PS=Ø coupler — the only element crossing the joint.
Positioned near the slab’s inflection point, the joint allows full formwork release without backshoring, using only typical reshoring for the next pour. As the slabs shorten, a narrow joint forms instead of a wide pour strip. The result is a self-supporting floor that keeps the site open and accessible, improving productivity for other trades and simplifying coordination.
Slab Relief Joint with Temporary PT Stressing Strip
When internal slab stressing is required, a temporary stressing strip can be incorporated. After stressing, the strip can be poured back immediately, forming a typical PS=Ø Slab Relief Joint. This detail is especially useful where exterior slab edges are inaccessible — such as in subterranean or podium conditions — allowing all slabs to be stressed efficiently and safely.
Because of this capability, PS=Ø often enables engineers to convert reinforced concrete (RC) designs to more economical PT systems, even in below-grade environments. By eliminating wide leave-outs and simplifying stressing, PS=Ø opens the door for PT use where it was previously avoided due to constructability concerns.
Beam Relief Joint
PS=Ø couplers can also be used in PT or RC beams, providing a clean and practical way to relieve restraint. When required, a temporary stressing strip can be integrated in the same manner as with slab joints. This gives engineers and contractors more flexibility in both design and sequencing.
Slab Relief Joint at Wall
Restraint is often greatest at the base of structures, particularly where slabs tie into stiff shear walls or basement walls. In these locations, PS=Ø Slab Relief Joints at Walls allow the slab to temporarily move away from the wall during shortening. This reduces cracking, eliminates unnecessary reinforcement, and enables the use of PT slabs in areas that previously defaulted to RC systems due to RTS concerns.
By temporarily releasing basement walls and integrating stressing strips, PS=Ø has reintroduced PT efficiency and economy into subterranean construction — improving long-term durability and reducing owner maintenance costs.
Slab Relief Joint at Top of Wall
For podium structures where slabs rest on top of walls, PS=Ø provides a simplified detail that allows temporary movement in all directions — without the need for traditional release mechanisms or leave-outs. The result is a clean, continuous surface that keeps trades working while the slab undergoes its natural volume change.
Vertical Wall Relief Joint
Even when slabs are released horizontally, restraint can still develop where vertical walls are locked into the system. The Vertical Wall Relief Joint addresses this by allowing the wall and slab to move together during shortening. Increasingly, engineers are pairing vertical wall relief joints with slab relief joints for complete release across both planes — a holistic solution to restraint-induced cracking in subterranean or high-restraint conditions.
Real World Results. Zero Compromise.
Encore Lot 12 in Florida was a high-density, fast-moving project with extremely limited laydown space, leaving little room for inefficiencies. The construction team turned to PS=Ø to streamline the build, maintain schedule, and deliver high-quality concrete — all without compromising safety or performance. By eliminating wide pour strips and the need for backshoring, PS=Ø allowed the slabs to undergo natural volume changes while staying on schedule. The system created self-supporting slabs, cleared space for other trades, and reduced the risk of cracking — resulting in a cleaner, more efficient jobsite.
Blake Dorr, Project Engineer at PCL, noted: “On a tight site like Encore Lot 12, PS=Ø helped us clear space fast. It provides cleaner connections, less cracking risk, and a better finish — all while letting the concrete move naturally without schedule delays. It’s a smart system that makes things faster, safer, and easier overall.”
For Encore Lot 12, PS=Ø was more than a structural solution — it was a practical advantage on a complex site, enabling the team to build faster, safer, and with confidence in the finished product.
Let’s get to work.
PS=Ø isn’t just a solution — it’s a way to build faster, safer, and with higher-quality results. Whether you’re tackling tight urban sites, complex projects, or subterranean slabs, PS=Ø gives you control, eliminates compromise, and keeps your projects moving. Learn how PS=Ø can transform your next project — contact us today to explore the system and see it in action.