HOW TO
PREVENT
ASR.
This page reports what ASTM and ACI publish about reducing the risk of alkali silica reaction, in their names. PSIP does not choose the mix, set a number or rank a material. A PSIP record holds the batch ticket as photographed on the day, and the PSIP certificate, once it issues, attests that the record is complete.
The mitigation decisions for alkali silica reaction are made when the mix is specified, before placement, and the record of those decisions is made on the day of the pour.
Concrete fails. ASR is the mechanism, cracking and spalling are symptoms of it. Every term on this page is defined once, as a standalone sentence, in the PSIP definitions, and the record that holds what was specified, and the batch ticket as photographed, is the documented pour.
WHAT THE STANDARDS
DESCRIBE.
WHAT THE RECORD HOLDS.
Per ASTM C1778, the Standard Guide for Reducing the Risk of Deleterious Alkali-Aggregate Reaction in Concrete, ASR can be reliably prevented by eliminating any one of its three required conditions: reactive silica, sufficient alkalis, or moisture above 80% RH. ACI PRC-221.1-98, the American Concrete Institute's Report on Alkali-Aggregate Reactivity, describes the same three conditions. The measures ASTM C1778 describes include fly ash, slag cement and other supplementary cementitious materials (SCMs). Which one a job uses, if any, is a mix design decision, and PSIP does not make it. In a PSIP record, what the batch ticket showed on the day is on file either way.
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. Type 1L is portland limestone cement, a blended cement in which finely ground limestone replaces a portion of the clinker. Its reactivity, water demand, admixture behaviour and cold weather behaviour differ from Type I.
Fly ash is a byproduct of burning coal for electricity. 2.6 GW of coal capacity retired in 2025, per EIA. Fly ash used in concrete rose from 11.9 million tons in 2023 to 14.6 million tons in 2024 (American Coal Ash Association, 2024 Production and Use Survey, released 4 December 2025).
SUPPLEMENTARY
CEMENTITIOUS MATERIALS
A supplementary cementitious material is not filler and it is not a cost saving substitution. Each material below is listed under the specification that covers it, where there is one. PSIP does not recommend a material. Not a class, not a replacement level, not a brand. Those are mix design decisions that belong to the people specifying concrete for the site and its exposure.
Fly ash is supplied as Class F or Class C. ASTM C618 separates them by calcium oxide: 18 percent or less for Class F, more than 18 percent for Class C. The two 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.
A multi-analytical study confirmed that addition of Class F fly ash to reactive mortar systems resulted in generation of significantly fewer ASR products compared to control systems. Raman spectroscopic analysis revealed aluminate monomer formation at aggregate crack interfaces, confirming that fly ash introduces an additional mitigation mechanism beyond simple alkali dilution, aluminate-bearing reaction products compete with ASR gel formation sites.
Many tickets do not name the class, so the contractor adds what he knows in the notes.
ASTM C618 covers raw or calcined natural pozzolan as Class N. Calcined clay, calcined shale and volcanic pozzolan all qualify as Class N pozzolans per ASTM C618.
Ground granulated blast furnace slag, specified under ASTM C989/C989M.
Colloidal nano silica is a manufactured admixture, batched at the plant. PSIP makes no claim about what it does in concrete.
ASTM C150/C150M designates cement with less than 0.60% Na₂O equivalent as low-alkali cement. Per ASTM C1778, low-alkali cement alone is considered an insufficient mitigation strategy for highly reactive aggregate combinations. Where the ticket does not show the cement type, the contractor can add it in his notes.
A label tells you what the maker chose to print on it. A concrete batch ticket is the producer's own record of the load, printed at the plant. Tickets vary, and many do not list everything in the load. A PSIP record holds a photograph of the ticket for every delivery, as printed, and anything more the contractor knows about the load is recorded as his own statement. If your contractor cannot produce the ticket, the plant that batched the load may hold its own copy.
WHAT EACH OPTION IS,
AND WHAT THE PHOTOGRAPH SHOWS.
| Material | What It Is | On the Batch Ticket |
|---|---|---|
| Class F Fly Ash | Low calcium coal combustion byproduct, specified under ASTM C618 Class F | The photograph shows it when the ticket lists it |
| Class C Fly Ash | Higher calcium coal combustion byproduct, specified under ASTM C618 Class C; not interchangeable with Class F at the same replacement percentage | The photograph shows it when the ticket lists it |
| Natural Pozzolan (Class N) | Calcined clay, shale or volcanic material, specified under ASTM C618 Class N | The photograph shows it when the ticket lists it |
| Slag Cement (GGBFS) | Ground granulated blast furnace slag, specified under ASTM C989/C989M | The photograph shows it when the ticket lists it |
| Colloidal Nano Silica Admixture | A manufactured admixture, batched at the plant | The photograph shows it when the ticket lists it, or the contractor's notes name it |
| Low-Alkali Cement Only | ASTM C1778 treats low-alkali cement alone as insufficient for highly reactive aggregate combinations | The photograph shows the cement type when the ticket lists it |
| No SCM | The mix carries no supplementary cementitious material. | The ticket shows no SCM, and the photograph shows it |
KNOWING ISN'T ENOUGH.
WRITING IT DOWN IS.
A verbal assurance about a mix design is not a record. "We always use good material" is not an answer. A batch ticket is an answer.
PSIP's protocol adds one layer to the chemistry: documentation. Under the protocol, the batch ticket for every delivery is photographed, and the photograph records what the ticket shows, including whether an SCM is listed. On a pool, the shell thickness is recorded at each point measured, and any post cure treatment is recorded by type. The PSIP certificate goes to the property owner once it issues.
This is not bureaucracy. A builder with no batch ticket and no record made at the time is answering with memory instead of evidence.
WHAT THE RECORD HOLDS: The batch ticket as photographed at delivery, with its SCM line as printed, or blank. Anything the builder adds goes in the notes as his own statement, beside the photograph, never in place of it.
THE CHEMISTRY
AND THE PAPER.
PSIP KEEPS THE PAPER.
The contractor builds it. The building department enforces the code. PSIP keeps the record. The contractors and homeowners who have the record are the ones who can show what the batch ticket said.
THREE THINGS A
PSIP RECORD HOLDS
WHAT PSIP
GIVES YOU
THE ASR QUESTION,
ANSWERED IN WRITING.
ASTM C1778 describes the mitigation options. A PSIP record holds a photograph of the batch ticket, so what the ticket shows about the mix is on file, and anything the contractor adds is recorded as his own statement. The institutional architecture is published on the PSIP Independence Standard; the protocol's technical governance passes to the Technical Advisory Council once it is seated, and no seat is filled yet.