Cold-weather concreting applies when the air temperature has fallen to, or is expected to fall below, 4 °C (40 °F) during the protection period, which is how ACI 306R-16 defines cold weather.
Cold matters because fresh concrete freezes below about -4 °C (25 °F), and NRMCA CIP 27 reports that the strength loss from early freezing can exceed 50 %. ACI 306R-16 sets 3.5 MPa (500 psi) as the strength concrete needs before it can survive a single freeze. The producer reaches that strength sooner through the mix, with accelerating admixtures, Type III cement, more cement and fewer slow-reacting SCMs, all of them concrete additives or binder choices that change hydration in the cold.
The contractor then holds the concrete at 13, 10, 7 or 5 °C (55, 50, 45 or 40 °F), depending on the least section dimension, for 3 days (2 days with an accelerator, Type III cement or 59 kg/m³ (100 lb/yd³) of extra cement) under ACI SPEC-306.1-90. Calcium chloride stays at or below 2 % by mass of cementing material, and EN 934-2:2009+A1:2012 Table 7 requires a hardening accelerator to deliver at least 130 % of control strength at 5 °C (41 °F) and 48 h. In-place strength is proven by the maturity method or in-place tests, not by field-cured cylinders, and a US winter surcharge of $6.5 to $9.2 per m³ ($5 to $7 per yd³) or more was reported in September 2026.
Each value is traced to its source: standards and codes to their issuing body, product values to the data sheet named with them, prices to the dated source beside them (methodology and fact-checking).
The table below lists the attributes that define cold-weather concreting and the document behind each value.
| Attribute | Value |
|---|---|
| Names | cold-weather concreting, cold-weather concrete, winter concreting |
| Definition (ACI 306R-16) | air temperature has fallen to, or is expected to fall below, 4 °C (40 °F) during the protection period |
| Older specification wording (ACI SPEC-306.1-90) | more than 3 successive days with an average daily outdoor temperature below 4 °C (40 °F) |
| Fresh concrete freezes | below about -4 °C (25 °F) (NRMCA CIP 27) |
| Frost threshold | 3.5 MPa (500 psi) before a single freeze (ACI 306R-16 section 3.1) |
| Minimum concrete temperature | 13 / 10 / 7 / 5 °C (55 / 50 / 45 / 40 °F) by least section dimension (ACI SPEC-301-20 section 4.2.2.5(a)) |
| Protection period | 3 days; 2 days with Type III cement, an ASTM C494 accelerating admixture or 59 kg/m³ (100 lb/yd³) of additional cement (ACI SPEC-306.1-90 section 3.4.4) |
| Verification | in-place testing or the maturity method; field-cured cylinders inappropriate (ACI 306R-16 section 8.2) |
| Not the same as | placement below freezing with antifreeze and cold-weather admixtures (ASTM C1622/C1622M-24) |
What Is Cold-Weather Concreting?#
Cold-weather concreting begins when the air temperature has fallen to, or is expected to fall below, 4 °C (40 °F) during the protection period (ACI 306R-16), the trigger for every mix and protection measure below. The older ACI SPEC-306.1-90 wording is different: it counts more than 3 successive days with an average daily outdoor temperature below 4 °C (40 °F), and the period stops counting when the temperature is above 10 °C (50 °F) for more than half of any 24 h. ACI 306R-16 is sold as ACI PRC-306-16 (24 pages), was adopted and published in September 2016 and supersedes ACI 306R-10. ACI SPEC-306.1-90, reapproved in 2002 (5 pages), remains the current ACI cold-weather specification.
Cold-weather concreting is weather practice rather than a material. Its mix side uses the same accelerators, cements and SCMs that define high-early-strength mixes, which is why it sits among the special concretes of this site rather than under one admixture.
Can you pour concrete in winter?#
Yes: concrete is placed in winter when the mix and the protection keep it above the minimum temperature for its section until it reaches 3.5 MPa (500 psi). ACI SPEC-301-20 section 4.2.2.5(a) sets that minimum at 13 °C (55 °F) for sections below 305 mm (12 in) and 5 °C (40 °F) above 1,829 mm (72 in). ACI SPEC-306.1-90 section 3.4.4 then fixes the protection period at 3 days, or 2 days with Type III cement, an ASTM C494 accelerator or 59 kg/m³ (100 lb/yd³) of extra cement. Protection ends on proven strength, and ACI 306R-16 section 8.2 calls for in-place testing or the maturity method to prove it.
What early freezing does to fresh concrete#
Fresh concrete freezes below about -4 °C (25 °F), and its strength loss can exceed 50 % (NRMCA CIP 27). ACI 306R-16 section 3.1, after Powers (1962), sets 3.5 MPa (500 psi) as the strength that protects concrete against a single freeze, and most mixtures reach it within 48 h at 10 °C (50 °F), in the guide's own words. NRMCA CIP 27 sets a higher bar of 24.1 MPa (3,500 psi) before air-entrained concrete faces repeated freeze-thaw cycles.
The time to reach either threshold grows as the concrete cools. NRMCA CIP 27 states that a drop of 10 °C (20 °F) in concrete temperature roughly doubles setting time, so a mix stays plastic, and vulnerable to frost, about twice as long at 10 °C (50 °F) as at 20 °C (68 °F).
Which Accelerators and SCMs Change a Cold-Weather Mix?#
Three mix levers speed strength gain in cold weather: an accelerating admixture, Type III cement or more cement, and a lower share of fly ash or slag cement, while an accelerator does not stop concrete from freezing (NRMCA CIP 27). In the US an accelerator is classified as ASTM C494/C494M-24 Type C (accelerating) or Type E (water-reducing and accelerating); in Europe EN 934-2:2009+A1:2012 separates set accelerators from hardening accelerators. ACI PRC-212.3-16 Table 1.2 lists the accelerating materials as calcium chloride, triethanolamine, sodium thiocyanate, sodium or calcium formate, sodium or calcium nitrite, calcium nitrate, aluminates and silicates, and chapter 19 of the same report covers very cold weather. The search for a concrete accelerator for cold weather leads to the full family of accelerating admixtures.
The table below compares the cold-weather levers by class or standard, the limit that applies and the effect in the cold.
| Lever | Class or standard | Basis or limit | Cold-weather effect |
|---|---|---|---|
| Calcium chloride (calcium chloride in concrete) | ASTM D98-15(2021), Type S solid, Type L liquid | at most 2 % by mass of cementing material (NRMCA CIP 27); water-soluble chloride limits of ACI CODE-318-25 Table 19.3.2.1, see chloride ingress and rebar corrosion | accelerates set and early strength; not permitted in sulfate class S2 (ACI CODE-318-25) |
| Non-chloride accelerators (non-chloride accelerators, calcium nitrate as a concrete accelerator) | ASTM C494/C494M-24 Type C or E; ACI PRC-212.3-16 Table 1.2 | dose per product data sheet | accelerates without adding chloride |
| Hardening accelerator | EN 934-2:2009+A1:2012 Table 7 | at least 130 % of control strength at 5 °C (41 °F) and 48 h | faster early strength in the cold |
| Set accelerator | EN 934-2:2009+A1:2012 Table 6 | initial set at 5 °C (41 °F) at most 60 % of control | offsets the slower setting time of concrete, which roughly doubles per 10 °C (20 °F) drop |
| Type III cement or extra cement | ACI SPEC-306.1-90 section 3.4.4 | 59 kg/m³ (100 lb/yd³) of additional cement | shortens protection from 3 days to 2 |
| Air-entraining admixtures | ASTM C260/C260M-24 | air content per exposure class | protects against freeze-thaw damage once 24.1 MPa (3,500 psi) is reached |
| Fly ash in concrete, slag cement (GGBS) | FHWA; Slag Cement Association | pozzolanic reaction reduced below 4.4 °C (40 °F); slag sets later below 29 °C (85 °F) | slower early strength; lower share speeds strength gain |
Doses convert to batch quantities with the admixture dosage calculator.
Calcium chloride: the 2 % ceiling and code restrictions#
Calcium chloride is dosed at most 2 % by mass of cementing material (NRMCA CIP 27). The material itself is specified by ASTM D98-15(2021), an active standard with two types: Type S solid and Type L liquid.
Worked example (calculated from the NRMCA CIP 27 ceiling): a mix with 350 kg/m³ (590 lb/yd³) of cementitious material allows at most 7.0 kg/m³ (11.8 lb/yd³) of calcium chloride. The arithmetic is 350 × 0.02 = 7.0 kg/m³.
The building code limits chloride in the concrete rather than the admixture dose. ACI CODE-318-25 Table 19.3.2.1, as reproduced in NRMCA 2PE004-26, caps water-soluble chloride at 0.06 % by mass of cementitious materials for prestressed concrete in exposure classes C0, C1 and C2, and at 0.15 % for nonprestressed concrete in class C2. The same table does not permit calcium chloride admixtures in sulfate exposure class S2. The dose, the corrosion risk and the safety data of calcium chloride in concrete are covered on the substance page.
Type C and E admixtures and the European strength tables#
ASTM C494/C494M-24 classes cold-weather accelerators as Type C (accelerating) or Type E (water-reducing and accelerating), two of the standard's eight types, A to G and S. Type E combines the water reduction of a Type A with acceleration, so one product lowers the water-cementitious ratio and speeds setting at the same dose.
EN 934-2:2009+A1:2012 adds a cold test. Its Table 7 requires a hardening accelerating admixture to reach at least 120 % of control compressive strength at 20 °C (68 °F) and 24 h, at least 90 % at 28 days and at least 130 % at 5 °C (41 °F) and 48 h, with air content at most 2 % by volume above the control. Table 6 requires a set accelerating admixture to give an initial set of at least 30 min at 20 °C (68 °F) and at most 60 % of the control's initial set at 5 °C (41 °F), with 28-day strength at least 80 % of control and 90-day strength at least the test mix's 28-day value. Both tables include a test at 5 °C (41 °F), which makes them the European proof of cold-weather performance.
Why accelerators are not antifreeze#
Accelerating admixtures do not prevent freezing (NRMCA CIP 27). At permitted doses calcium chloride lowers the freezing point of the mix water only a few degrees, so accelerated concrete still needs the section temperatures and protection described below. Placement into concrete that falls below freezing is a different product class: ASTM C1622/C1622M-24 covers cold-weather admixture systems for concrete as low as -5.0 °C (23.0 °F) immediately after placement until initial set. Those systems, their qualification and their limits belong to antifreeze and cold-weather admixtures.
How SCMs slow down in the cold#
FHWA reports that pozzolanic reactions are significantly reduced below 4.4 °C (40 °F). The Slag Cement Association reports that slag cement concrete sets later below 29 °C (85 °F). A cold-weather mix therefore lowers the share of fly ash or slag cement where durability allows, or accepts a longer protection period.
How Is a Cold-Weather Concrete Mix Proportioned?#
A cold-weather concrete mix gains strength faster through Type III cement, a higher cement content, a lower water-cementitious ratio, fewer SCMs where durability allows and the lowest practical slump (NRMCA CIP 27). ACI SPEC-306.1-90 section 3.4.4 rewards two of these levers directly: 59 kg/m³ (100 lb/yd³) of additional cement, Type III cement or an ASTM C494 accelerating admixture shortens the protection period from 3 days to 2.
The table below sets out what each proportioning lever changes and the document that supports it.
| Lever | What it changes | Source |
|---|---|---|
| Type III cement and more cement | faster strength gain and more internal heat of hydration; the same route as high-early-strength concrete | NRMCA CIP 27; ACI SPEC-306.1-90 section 3.4.4 (59 kg/m³ (100 lb/yd³)) |
| Lower w/cm | higher early strength; class F2 caps the water-cement ratio at 0.45 with f'c at least 31.0 MPa (4,500 psi) | ACI CODE-318-25 Table 19.3.2.1 (NRMCA 2PE004-26) |
| Fewer SCMs | less slow-reacting binder below 4.4 °C (40 °F) (fly ash) and 29 °C (85 °F) (slag set) | NRMCA CIP 27; FHWA; Slag Cement Association |
| Accelerating admixture | faster set and early strength; protection 2 days instead of 3 | ACI SPEC-306.1-90 section 3.4.4; NRMCA CIP 27 (calcium chloride at most 2 %) |
| Worked dose | 350 kg/m³ (590 lb/yd³) of cementitious material allows at most 7.0 kg/m³ (11.8 lb/yd³) of calcium chloride | calculated from NRMCA CIP 27 |
General proportioning is covered under concrete mix design.
Members that will be saturated and face freeze-thaw cycles in service also need the durability limits of exposure class F2 in ACI CODE-318-25 Table 19.3.2.1: w/cm at most 0.45 and f'c at least 31.0 MPa (4,500 psi). The cold-weather levers adjust an existing mix designed for strength, exposure and workability.
What Concrete Temperatures Do ACI and EN Documents Set?#
ACI SPEC-301-20 section 4.2.2.5(a) sets minimum concrete temperatures of 13, 10, 7 and 5 °C (55, 50, 45 and 40 °F) for least section dimensions below 305 mm, 305 to 914 mm, 914 to 1,829 mm and above. ACI SPEC-306.1-90 Table 3.2.1 lists the same four values as the minimum concrete temperature as placed and maintained during protection. The temperature of each load is measured on delivery with the other fresh concrete tests.
The table below gives the minimum temperature and the allowed drop after protection for each section size.
| Least section dimension | Minimum as placed and maintained | Maximum gradual drop in 24 h after protection |
|---|---|---|
| below 305 mm (12 in) | 13 °C (55 °F) | 28 °C (50 °F) |
| 305 to 914 mm (12 to 36 in) | 10 °C (50 °F) | 22 °C (40 °F) |
| 914 to 1,829 mm (36 to 72 in) | 7 °C (45 °F) | 17 °C (30 °F) |
| above 1,829 mm (72 in) | 5 °C (40 °F) | 11 °C (20 °F) |
ACI SPEC-301-20 4.2.2.5(a) and ACI SPEC-306.1-90 Table 3.2.1; placed concrete not more than 11 °C (20 °F) above the minimum.
Minimum temperature by section thickness#
The minimum concrete temperature rises as the section gets thinner, from 5 °C (40 °F) above 1,829 mm (72 in) to 13 °C (55 °F) below 305 mm (12 in). A thin slab or wall has more surface per unit of volume and loses its heat of hydration faster, while a thick footing holds its own heat. ACI 306R-16 section 8.10 explains why the floor matters: its models treat hydration as negligible below 5 °C (40 °F) and freezing damage as possible below 0 °C (32 °F), both conservative assumptions.
Upper limit and the allowed drop after protection#
Placed concrete should not be more than 11 °C (20 °F) above its section minimum (ACI SPEC-301-20 section 4.2.2.5(a)). A hotter mix widens the gap between the concrete and the cold air. When protection ends, ACI SPEC-306.1-90 Table 3.2.1 limits the gradual temperature drop in the first 24 h to 28, 22, 17 and 11 °C (50, 40, 30 and 20 °F) for the four section sizes, from the thinnest to the thickest. Thick sections get the smallest allowed drop.
European practice and the Greenland national annex#
EN 934-2:2009+A1:2012 tests set and hardening accelerators at 5 °C (41 °F), the European admixture route to cold-weather performance of the mix. Execution rules for concreting in frost sit in EN 13670 and its national annexes rather than in one European temperature table.
The Greenland national annex, EN 13670 GL NA:2025 section 8.5(18) and (19), requires a placing temperature of at least +10 °C (50 °F) when casting in frost and special measures when the air stays below -10 °C (14 °F) for 2 days or more. The concrete itself is specified to EN 206-1:2026, approved by CEN on 2026-01-19, dated March 2026 and superseding EN 206:2013+A2:2021, with national withdrawal of conflicting standards by September 2026. Exposure classes, admixture rules and the transition are covered under EN 206 concrete specification.
How Long Must Fresh Concrete Be Protected from Freezing?#
Fresh concrete must be protected from freezing until it reaches 3.5 MPa (500 psi) (ACI 306R-16 section 3.1), and ACI SPEC-306.1-90 section 3.4.4 sets the minimum protection period at 3 days. The period drops to 2 days with Type III cement, an ASTM C494 accelerating admixture or 59 kg/m³ (100 lb/yd³) of additional cement.
The 3.5 MPa threshold protects against a single freeze, not against a winter of cycles. NRMCA CIP 27 calls for 24.1 MPa (3,500 psi) before air-entrained concrete faces repeated freeze-thaw cycles, so an element exposed to cycling soon after protection ends needs more strength than the specification period alone delivers.
Protection period and the degree-hour deficiency rule#
When concrete temperatures fall short of the minimum without freezing, ACI SPEC-306.1-90 section 3.4.6 extends protection until twice the deficiency in degree-hours is made up.
Worked example (calculated from ACI SPEC-306.1-90 section 3.4.6): concrete held 3 °C below its minimum for 10 h has a deficiency of 30 °C·h (54 °F·h), so protection continues until 60 °C·h (108 °F·h) is made up. The inputs are a shortfall of 3 °C (5.4 °F) and a duration of 10 h; the factor of two comes from the specification.
Removing protection without thermal cracking#
Protection comes off gradually: ACI SPEC-306.1-90 Table 3.2.1 limits the temperature drop in the first 24 h after protection to 28, 22, 17 or 11 °C (50, 40, 30 or 20 °F) by section size. NRMCA CIP 27 adds the reason: a difference of more than about 20 °C (35 °F) between surface and core risks cracking. Sections above 1,829 mm (72 in) carry the tightest drop limit, 11 °C (20 °F), and their thermal control belongs to mass concrete thermal control.
How Is In-Place Strength Verified in Cold Weather?#
ACI 306R-16 section 8.2 calls field-cured cylinders inappropriate in cold weather and points to in-place testing or the maturity method instead. ACI 306R-16 section 8.10 sets the modeling assumptions behind those calculations: hydration is treated as negligible below 5 °C (40 °F), and freezing damage as possible below 0 °C (32 °F), both conservative.
The maturity method (ASTM C1074)#
ASTM C1074-19e1, the active edition with revision work item WK97581 open, estimates in-place strength from the concrete's temperature history in four steps. The steps are listed below.
- Establish the strength-maturity relationship for the mix that will be placed.
- Record the concrete temperature in the element from placement onward.
- Compute the temperature-time factor M = Σ(T - To)Δt, with the Nurse-Saul datum To traditionally taken as -10 °C (14 °F) (Carino and Lew, NIST, 2001).
- Check the estimate with validation cylinders and build a new strength-maturity relationship when they differ by more than 10 % (ACI 306R-16).
Carino and Lew (NIST, 2001) report activation energies of 30 to 64 kJ/mol at w/c 0.45 and 31 to 56 kJ/mol at w/c 0.60, so the temperature sensitivity of a mix depends on its composition and each mix gets its own strength-maturity relationship.
Which Standards and Guides Govern Cold-Weather Concreting?#
Cold-weather concreting is specified in the US through ACI SPEC-306.1-90 and ACI SPEC-301-20 with ACI 306R-16 as the guide, and in Europe through EN 13670 and its national annexes. ASTM C494/C494M-24 and EN 934-2:2009+A1:2012 classify the accelerating admixtures on both sides. India's cold-weather concreting code is IS 7861 (Part 2):1981.
The table below lists each document by region with its edition and its role in cold-weather work.
| Region | Document (edition, status) | Role |
|---|---|---|
| US | ACI 306R-16 (sold as ACI PRC-306-16, 24 pages, September 2016; supersedes ACI 306R-10) | guide: definition, frost threshold, verification |
| US | ACI SPEC-306.1-90 (reapproved 2002, 5 pages) | specification: temperature table, protection period, deficiency rule |
| US | ACI SPEC-301-20 section 4.2.2.5 | minimum concrete temperature by section; hot-weather limit |
| US | ASTM C494/C494M-24, active (ASTM C494 chemical admixtures types) | Types C and E accelerators |
| US | ASTM D98-15(2021), active | calcium chloride, Types S and L |
| US | ASTM C1622/C1622M-24, active (antifreeze and cold-weather admixtures) | cold-weather admixture systems down to -5.0 °C (23.0 °F) |
| US | ASTM C1074-19e1, active (revision WK97581 open) | maturity method |
| US | ACI PRC-212.3-16 (ACI 212.3R-16 report on chemical admixtures) | Table 1.2 accelerating materials; chapter 19 very cold weather |
| EU | EN 934-2:2009+A1:2012 (EN 934-2 admixture requirements) | Table 6 set and Table 7 hardening accelerators tested at 5 °C (41 °F) |
| EU (Greenland) | EN 13670 GL NA:2025 | placing at least +10 °C (50 °F) when casting in frost |
| EU | EN 206-1:2026 (EN 206 concrete specification) | concrete specification; supersedes EN 206:2013+A2:2021 |
| IN | IS 7861 (Part 2):1981 | cold-weather concreting code; values not reproduced (no verified current text) |
How to specify cold-weather concrete#
A cold-weather specification fixes six items, from the section temperature to the removal rule. The six items are listed below.
- Section minimum: 13, 10, 7 or 5 °C (55, 50, 45 or 40 °F) by least dimension (ACI SPEC-301-20 section 4.2.2.5(a)).
- Upper limit: placed concrete no more than 11 °C (20 °F) above the minimum.
- Protection period: 3 days, or 2 days with Type III cement, an ASTM C494 accelerator or 59 kg/m³ (100 lb/yd³) of extra cement, plus the degree-hour deficiency rule (ACI SPEC-306.1-90 sections 3.4.4 and 3.4.6).
- Accelerator class and chloride limit: ASTM C494/C494M-24 Type C or E, or EN 934-2:2009+A1:2012 Table 6 or 7, with ACI CODE-318-25 water-soluble chloride limits of 0.06 % (prestressed) and 0.15 % (nonprestressed, C2) by mass of cementitious materials.
- Verification: the maturity method (ASTM C1074-19e1) or in-place tests, never field-cured cylinders alone (ACI 306R-16 section 8.2).
- Removal: the 24 h drop limits of ACI SPEC-306.1-90 Table 3.2.1.
What Drives the Cost of Cold-Weather Concreting?#
Cold-weather concrete costs more through heated water and materials, accelerating admixtures, protection and the testing that proves strength. A September 2026 US consumer cost guide reports winter surcharges of $6.5 to $9.2 per m³ ($5 to $7 per yd³) or more. One Houston producer's published winter heating fee, dated February 2025, is $6.5 to $19.6 per m³ ($5 to $15 per yd³). Both are dated public records; a project price depends on the four factors listed below.
- Heated water and materials: the plant-side winter program of admixtures in ready-mix concrete, sized to deliver the section minimum.
- Accelerating admixtures: the dose of a Type C or E product or of calcium chloride within the 2 % ceiling.
- Protection: enclosures, insulation and heat for 3 days, or 2 with an accelerator, plus any deficiency time.
- Verification: maturity sensors and calibration or in-place tests on the element.
How Does Cold-Weather Practice Differ from Hot-Weather and Below-Freezing Placement?#
Cold-weather practice protects early strength from freezing, while hot-weather practice limits concrete temperature to 35 °C (95 °F) as delivered (ACI SPEC-301-20 section 4.2.2.5(b)). Both rest on the same ACI specification clause, and the hot side has its own guide, ACI 305R-20 (sold as ACI PRC-305-20, 28 pages). Curing methods and curing materials for cold weather are construction-chemical topics outside this page. Retarders, cooling and the hot-weather limits are covered under hot-weather concreting.
Placement into concrete that falls below freezing is not cold-weather concreting in the ACI 306R-16 sense: it relies on cold-weather admixture systems qualified to ASTM C1622/C1622M-24, down to -5.0 °C (23.0 °F) after placement. Fast-track mixes that need early strength for schedule rather than for frost belong to high-early-strength concrete.
Cold-weather concreting FAQs#
How cold is too cold to pour concrete?#
ACI documents tie placement to the concrete temperature rather than to one air temperature: 5 to 13 °C (40 to 55 °F) by section (ACI SPEC-301-20 section 4.2.2.5(a)). Fresh concrete itself freezes below about -4 °C (25 °F) (NRMCA CIP 27), so the mix and protection must keep it well above that point.
Will fresh concrete freeze at -2.8 °C (27 °F)?#
Fresh concrete freezes below about -4 °C (25 °F) (NRMCA CIP 27), so -2.8 °C (27 °F) is just above that point. ACI 306R-16 section 8.10 still models freezing damage below 0 °C (32 °F), so unprotected concrete under 3.5 MPa (500 psi) is at risk at that temperature.
Can concrete be poured if it freezes at night?#
Yes, when protection holds the concrete at its section minimum until it reaches 3.5 MPa (500 psi) and for at least 3 days. ACI SPEC-306.1-90 section 3.4.4 shortens that period to 2 days with Type III cement, an ASTM C494 accelerator or 59 kg/m³ (100 lb/yd³) of extra cement.
Does calcium chloride lower the freezing point?#
At permitted doses calcium chloride lowers the freezing point only a few degrees (NRMCA CIP 27). It accelerates setting and early strength within its 2 % ceiling by mass of cementing material, but it does not protect concrete from freezing.