THE PSIP
DEFINITIONS.
This is the reference dictionary for concrete failure and for the record that documents it. Every term below is written as a single standalone sentence, so it can be quoted on its own and still mean what it means here. Concrete fails. Cracking, spalling and alkali silica reaction are the ways failure shows up and the reasons it happened. Keeping those apart is the difference between describing a symptom and naming a problem. The pool track has its own section, because a shell and a driveway are different jobs and neither one should borrow the other's words.
Concrete failure is the event in which concrete stops performing the way it was specified to perform. Concrete fails.
Cracking, spalling and alkali silica reaction are symptoms and mechanisms of that failure. None of them is the failure itself.
Failure is the event. Everything else is how it showed up.
These four terms separate the event from the evidence.
Concrete failure is the event in which concrete stops performing the way it was specified to perform. Concrete fails. Cracking, spalling and alkali silica reaction are symptoms and mechanisms of that failure, not the failure itself.
This is the parent term and every other term on this page sits under it. A symptom tells you failure is visible. It does not tell you what is driving it, how far along it is, or whether it is still progressing. Naming the event separately from the evidence is what makes the rest of the vocabulary usable.
Cracking is one common visible symptom of concrete failure. It is not the failure, and it is not the only way failure shows up.
Cracking is the symptom homeowners search for, because it is the one they can see from the driveway. It is a legitimate entry point to the question and a poor place to stop. Two slabs with identical surface cracking can have entirely different mechanisms underneath, entirely different trajectories, and entirely different costs. The crack is the question, not the answer.
Spalling and scaling are the breakdown and chipping away of a concrete surface. They are symptoms of concrete failure, and across the Sun Belt they are frequently a larger concern than cracking.
Scaling generally describes the loss of the surface mortar. Spalling generally describes larger pieces breaking away, often over reinforcement. Both expose the interior of the slab to water, chloride and freeze thaw action that the surface was there to keep out, which is why surface loss tends to accelerate rather than settle.
Alkali silica reaction is an internal expansive reaction between reactive silica in the aggregate and alkalis in the cement paste. It is the most serious mechanism of concrete failure, and it is sometimes called concrete cancer.
The reaction forms a gel that takes up water and swells, and the expansion works outward from inside the concrete. That is why it is the mechanism, not the symptom. Surface map cracking, spalling and dimensional movement are what an owner sees. The reaction is what is causing them, and it continues while the ingredients and the moisture are present. The Tennessee Department of Transportation evaluated aggregate reactivity across the state and documented ASR distress in structures already standing.
Source: TDOT Report RES2016-03, November 2021. See Tennessee and Concrete Cancer.
What a record is, and who owns it.
These five terms describe the record itself. They describe what gets written down, when it has to be written down, and which party is responsible for writing it. They do not describe how any of it is evaluated.
A documented pour is a pour whose material inputs, site conditions and cure are recorded at the time they occur, by the contractor of record, and retained as a closeout packet.
Every part of that sentence is load bearing. Recorded at the time they occur, because conditions on a pour day stop existing once the concrete sets. By the contractor of record, because the party making the decisions is the party who can attest to them. Retained, because a record that is not kept is not a record.
Expanded at What is a documented pour.
A closeout packet is the retained record of a documented pour.
It is the artifact that survives the job. Years after the crew has left, the closeout packet is what states which mix was specified, what arrived, what the weather did, and how the slab was cured. A dispute about a slab with a closeout packet is an argument about a record. A dispute about a slab without one is an argument about memory.
The point of pour is the moment documentation has to happen, because the conditions it records stop existing once the concrete sets.
Air temperature, concrete temperature, humidity, wind, what the truck actually delivered, how long it waited, when finishing started and how the slab was cured are all live facts for a few hours and then they are gone. This is the single reason concrete documentation works differently from documentation in most trades. There is no later.
The contractor of record is the party who owns the pour day decisions and therefore owns the record of them.
Suppliers deliver, testing labs test, designers specify, and inspectors observe. The contractor of record is the party standing on the slab making calls in real time. Placing the record with that party puts it with the only person who has the facts at the moment they exist.
A documented pour is a pour that has a record. The record states what was specified, what was delivered, and the conditions the work was done in. It is not a statement that the concrete is good.
This distinction is the load bearing wall of the whole protocol, so it is written into the dictionary rather than left implied. PSIP certifies the completeness of the record. Certification is a documentation credential, and it is not a warranty, guarantee, or insurance of the contractor's work. A homeowner reading a record can see what was done. That is a different and more useful thing than being told it was done well.
The variables a record has to capture.
These are the terms a closeout packet is made of. Each one names a variable that changes how a slab behaves over its life, and each one is invisible in the finished concrete. This is why they get written down.
A batch ticket is the ready mix producer's record of what was actually in the truck.
It is the difference between what was ordered and what arrived, and those are not always the same document. The batch ticket is the one piece of paper on a residential pour that already exists, is already produced by a third party, and is routinely thrown away.
A supplementary cementitious material is a material blended with cement, such as fly ash or slag, that changes the durability behavior of the finished concrete.
An SCM is not filler and it is not a cost saving substitution. The relevant SCMs change how a slab resists alkali silica reaction, sulfate attack and chloride ingress. Changing the SCM changes the concrete, whether or not anything on the order form changes.
Fly ash is supplied as Class F or Class C. They differ in chemistry, they differ in alkali silica reaction mitigation behavior, and they are not interchangeable at the same replacement percentage.
Class F is the low calcium ash that most of the ASR mitigation literature is anchored to. Class C carries elevated calcium and behaves partly like cement itself, contributing early strength while delivering a different long term durability profile. A mix design written around Class F performance does not carry over to Class C one for one. When a regional supply shifts from one to the other, the concrete changes.
Source: ASTM C618-26, Standard Specification for Coal Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. See The Fly Ash Supply.
Portland limestone cement, designated Type 1L under ASTM C595/C595M, is a blended cement in which finely ground limestone replaces a portion of the clinker. Its reactivity, water demand, admixture behavior and cold weather behavior differ from Type I.
USGS reports that blended cement accounted for 63 percent of total United States cement shipments during the first 9 months of 2025, and that 95 percent of those blended shipments were estimated to be portland limestone cement. A crew ordering the mix it has always ordered can receive a materially different cement, and the finished slab does not show which version it got.
Source: ASTM C595/C595M-26, Standard Specification for Blended Hydraulic Cements, and USGS Mineral Commodity Summaries 2026, Cement.
An exposure class is the environmental service condition a concrete mix is specified against. The governing codes are ACI 318 for structural concrete and ACI 332 for residential concrete.
Exposure class is the input. Strength, water to cement ratio, air content and SCM strategy are outputs that follow from it.
Source: ACI CODE-318-25 and ACI CODE-332-20. See The Problem.
What is actually happening while nobody is watching.
The taxonomy names what failure is. The materials name what a record has to capture. These six name the processes that run in between, on the day of the pour and in the months after it. They are the vocabulary the rest of this site needs in order to describe a mechanism instead of talking around it.
Drying shrinkage is the volume reduction concrete undergoes as it loses moisture after it has hardened.
It is not a defect and it is not avoidable by paying more. Concrete is placed carrying more water than hydration will consume, and the surplus leaves slowly over months. What decides the outcome is not the shrinkage itself but whether it is free to move, because shrinkage that is free to move produces nothing and shrinkage that is held produces stress.
Source: ACI CT-25, ACI Concrete Terminology. ACI PRC-224-01, Control of Cracking in Concrete Structures, ACI Committee 224, reapproved 2008, section 3.2. See The Problem.
Restraint is anything that stops concrete from moving freely as its volume changes.
Restraint is the reason shrinkage becomes cracking rather than just becoming a slightly smaller slab. ACI's account of the mechanism is that the combination of shrinkage and restraint develops tensile stresses within the concrete, and that because the tensile strength of concrete is inherently low, cracking will often follow. Friction against the subgrade, the reinforcement, adjoining construction and the shape of the pour are all restraint. It is why two slabs that shrink by the same amount can behave completely differently.
Source: ACI PRC-224-01, Control of Cracking in Concrete Structures, ACI Committee 224, reapproved 2008, section 3.2. See The Problem.
Plastic shrinkage is volume loss that happens while concrete is still fresh, before it has set.
It is driven by water leaving the surface faster than bleed water rises to replace it, which makes it a condition and site problem rather than a mix problem. ACI defines hot weather concreting as one or a combination of high ambient temperature, high concrete temperature, low relative humidity and high wind speed, and names an increased tendency for plastic shrinkage cracking among the results. Those four conditions are the same four variables a documented pour records. The industry's own definition of a hazardous placing condition is a list of measurements that exist for a few hours and then stop existing.
Source: ACI PRC-305-20, Guide to Hot Weather Concreting, ACI Committee 305, 2020, sections 2.2 and 3.1. See What Is a Documented Pour.
A control joint is a deliberate weakened line that decides where a slab relieves its volume change.
A joint does not prevent movement. It chooses the location. ACI's own terminology defines a control joint as a groove formed, sawed or tooled into a concrete structure to create a weakened plane that regulates where cracking occurs as adjacent sections reduce in dimension. Regulating the location is the stated purpose, which means the standard vocabulary of the industry already treats cracking as something to be placed rather than something to be promised away. Movement that arrives at a joint is the design doing its job. Movement that arrives somewhere nobody chose is the thing worth asking about.
Source: ACI CT-25, ACI Concrete Terminology. See PSIP Flatwork.
Curing is the action taken to maintain moisture and temperature in a freshly placed cementitious mixture so that the cement can hydrate and the mixture can develop its potential properties.
Curing is not drying and it is not waiting. It is an action taken, which means it is something done or not done on a particular day by a particular crew. ACI's current curing guide covers the practices, procedures, materials and monitoring methods for the external curing of concrete, and it addresses assessing whether curing was effective. That is the industry stating in its own document that curing is something to be verified rather than assumed.
Source: ACI CT-25, ACI Concrete Terminology. ACI PRC-308-26, Curing of Concrete—Guide, ACI Committee 308, 2026. See What Is a Documented Pour.
Petrographic examination is the laboratory study of a physical sample of hardened concrete to determine its composition and its condition.
It is the professional answer to what actually happened to a specific piece of concrete, and it has its own ASTM standard practice. It requires a physical sample cut from the structure and a qualified laboratory, so it is neither free nor immediate, and it is what a forensic engineer or an insurer reaches for when the answer has to hold up. What it establishes is what the concrete is and what is happening inside it. What it cannot establish is what was specified, what was ordered, or what actually arrived on the truck, because those are documents rather than material. A petrographic report and a closeout packet answer two different questions and neither one substitutes for the other.
Source: ASTM C856/C856M-25, Standard Practice for Petrographic Examination of Hardened Concrete. See Best Concrete Contractor.
A pool buries its structure twice, so name it before it goes under.
The pool track carries its own vocabulary and it is kept separate on purpose. A shell and a driveway are different jobs, placed by different methods, finished by different trades, and a word borrowed from one to describe the other has stopped being precise. These seven entries are the aquatic half of the same idea. Name the thing, then record it while it is still visible.
A pool shell is the structural concrete vessel that holds the water in and the ground back. It is placed against the excavated ground and the reinforcing steel, it is covered by an interior finish within weeks, and from that point it cannot be examined again without removing the finish.
Everything a homeowner looks at is either attached to the shell or covering it. Tile, coping, decking and equipment can be inspected, compared and replaced at any point in the life of the pool. The shell is the one element that cannot be, which is why the record of it has to be made in the days it is exposed rather than at handover.
Source: ANSI/PHTA/ICC-5 2025, American National Standard for Residential Inground Swimming Pools, published 3 June 2025. See PSIP Aquatic.
Gunite and shotcrete are placement methods rather than materials. In both, concrete or mortar is conveyed through a hose and projected through a nozzle at high velocity onto a surface, so that the force of placement is what compacts it, instead of being poured into forms. Shotcrete is the term the ACI documents use, and gunite began as a proprietary product name that the pool trade still applies to the dry mix version of the same process.
The two names are usually presented to a buyer as a choice between two products. They are not that. In the dry mix process the water meets the material at the nozzle. In the wet mix process the water is batched in before the material reaches the nozzle. Both are placed by a nozzle operator working by hand and by eye, which puts the crew inside the structure rather than on the surface of it. ACI's own guide records that gunite was the proprietary name given to the sand and cement product of a cement gun design introduced in 1910.
PSIP does not take a position on which method is better. The protocol records which one was used, what was in it, and who placed it.
Source: ACI SPEC-506.2-13(18), Specification for Shotcrete, ACI Committee 506, reapproved 2018. ACI PRC-506-22, Shotcrete—Guide, ACI Committee 506, November 2022. See Best Pool Builder.
Shell compaction is the consolidation of the concrete as it is placed. In gunite and shotcrete there is no separate compaction step, because the velocity of the material leaving the nozzle is what does the compacting.
ACI's specification for shotcrete defines the material as being projected at high velocity onto a surface to achieve compaction, which puts compaction inside the definition rather than in a step that follows it. Compaction is what decides whether a shell is dense and watertight, and it is the reason that shadowing behind congested reinforcing steel, excessive rebound and overspray are structural questions rather than cosmetic ones. None of it is visible once the finish is on, and none of it is recoverable from a photograph of the finished pool.
Source: ACI SPEC-506.2-13(18), Specification for Shotcrete, ACI Committee 506, reapproved 2018. Guarino and Oakes, Gunite Versus Shotcrete in Swimming Pool Construction, Shotcrete, Summer 2018, American Shotcrete Association.
A rebar cage is the tied reinforcing steel assembly that a pool shell is shot around, together with the blockouts formed into it for plumbing, fittings and penetrations. It is exposed for a matter of days and it is enclosed permanently the moment the shell is placed.
Bar size, spacing, lap length, cover and support are decided and executed while the cage is open to view, and none of them can be confirmed afterward without destructive investigation. A photograph taken before the shoot costs nothing and is the only evidence of that work that will ever exist. This is the first of the two documentation windows on a pool and it is the shorter one.
See Best Pool Builder.
Substrate preparation is the readying of the surface that a placed layer will bond to or bear on. On a pool it happens twice, on the excavated ground before the shell is shot and on the shell itself before the interior finish goes on, and each one is preparation for a different trade.
Both surfaces disappear under the layer they were prepared for. ACI's shotcrete specification carries preparation of the surface to receive shotcrete as a requirement of its own, and the plastering of a pool is covered by its own separate American National Standard. That separation is a useful signal by itself. The industry treats the shell and the finish as two jobs with two sets of requirements, so a record that covers one of them covers half the pool.
Source: ACI SPEC-506.2-13(18), Specification for Shotcrete, ACI Committee 506, reapproved 2018. ANSI/PHTA/ICC/NPC-12 2025, American National Standard for the Plastering of Swimming Pools and Spas.
Troweling is the hand finishing operation that brings a placed cementitious surface to its final line and texture. On a pool it is performed twice, once to shape the shot shell and again to finish the interior plaster.
Troweling is done by hand, by eye, by a crew, on a clock set by how the material is setting rather than by the schedule. What is recordable is who did it, when, and in what conditions.
See Best Pool Builder.
Pool plaster is the cementitious interior finish applied over the structural shell. It is a finish and not the structure, and it is the surface a homeowner will look at for years while learning nothing about what is behind it.
The plastering of swimming pools and spas is covered by its own American National Standard, separate from the standard for building the pool, and its scope is the cementitious interior finish of swimming pools, spas and other aquatic facilities. The finish and the structure are different work, governed by different documents, usually performed by different crews weeks apart. When a finish starts to fail, the first question is whether the finish failed or whether the shell behind it is failing, and that question is answerable from a record of the shell and close to unanswerable without one.
Source: ANSI/PHTA/ICC/NPC-12 2025, American National Standard for the Plastering of Swimming Pools and Spas. See Why Texas Pools Are Failing.
One term that is a rule, not a description.
Sorted, not ranked, is PSIP doctrine. Records are sorted. They are never ranked.
Sorting is an order the reader chooses and can reverse, such as alphabetical or by count of documented jobs. Ranking is a judgment the publisher makes on the reader's behalf. A protocol that certifies the completeness of records has no defensible basis for telling a homeowner who is better, and the moment it does, the record becomes something worth buying rather than something worth trusting.
A vocabulary is a way of seeing.
An industry that has one word for a problem can only have one conversation about it. If cracking is the only term available, then every slab is either cracked or fine, every remedy is cosmetic, and every dispute is about appearance. The homeowner asks whether it can be patched. Nobody asks what is driving it.
Separating the failure from its symptoms opens the questions that actually decide what a slab costs over its life. What failed. What mechanism is running. Whether it is progressing. What was in the mix, what the conditions were, and whether anyone wrote it down. Those questions are answerable, and they are answerable from a record.
That is why this page exists before any of the others. The terms come first, the evidence pages carry the primary sources that ground them, and the record is what makes any of it checkable on an individual slab.
Definitions, then evidence, then the record.
The terms on this page are grounded in the state level research and the primary sources collected in the PSIP research library, and they are applied on individual jobs through the closeout packet.