Special concretes are concretes whose placement, strength, density, heat, carbon or self-repair requirement is met by a designed system of admixtures, SCMs and fibers rather than by a conventional mix. Which type does an element need, and which admixtures make it work?
Each of these special types of concrete, also searched as types of special concrete, is one application of concrete additives.
Each type has one defining value from a named document: 550 to 850 mm (21.7 to 33.5 in) of slump flow for SCC (EN 206-9:2010), 55 MPa (8,000 psi) for high-strength concrete (ACI CT-25), 120 MPa (17,000 psi) for UHPC (ASTM C1856/C1856M-24) and 15 to 35 % voids for pervious concrete (ACI PRC-522-23). Mix ranges run from w/cm 0.18 in a non-proprietary UHPC study mix to 0.37 to 0.43 in fast-track paving, and ACI SPEC-301-20 caps concrete temperature at 35 °C (95 °F) as delivered.
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).
What Is a Special Concrete?#
A special concrete is a concrete defined by a placement or performance requirement that a conventional mix cannot meet and that a designed system of admixtures, SCMs and fibers makes possible.
Four requirements show the range: flowing into congested formwork without vibration, exceeding 120 MPa (17,000 psi), draining water through 15 to 35 % voids, and keeping a thick section below 70 °C (158 °F), above which delayed ettringite formation (DEF) can occur (PCA EB547).
Special concrete vs conventional concrete#
Conventional concrete is specified by strength and slump, while a special concrete adds a defining property with its own test and limit.
ACI CT-25 draws the line in its definitions. Self-compacting concrete spreads into place, fills the formwork and encapsulates the reinforcement without mechanical consolidation. High-performance concrete meets special combinations of performance and uniformity requirements that cannot always be achieved routinely with conventional constituents (ACI CT-25).
Six defining bases: placement, strength, density, heat, carbon and function#
Special concretes fall into six groups by the property that defines them, listed below.
- Placement: self-compacting concrete, shotcrete, pervious concrete, 3D printing concrete.
- Strength and performance: high-strength, high-performance, UHPC, high-early-strength concrete, flowable fill.
- Density: cellular concrete.
- Heat: mass concrete.
- Carbon: low-carbon concrete, geopolymer concrete.
- Function: self-healing concrete.
Hot- and cold-weather concreting are practices applied to any of these concretes, not types.
How Do Admixture Systems Make Special Concretes Work?#
Each special concrete works through a system with separate jobs: a high-range water reducer for flow at low w/cm, a stabilizer or extra powder against segregation, set control for timing, and an SCM or fiber for the hardened property. ACI CT-25 defines a chemical admixture as a liquid or dispersible powder used as an ingredient in a cementitious mixture to improve its economy or properties, so SCMs and fibers are not admixtures in the ACI sense.
Table 1 compares the core admixtures and materials of each group and the job each does in the mix.
| Group | Core admixtures and materials | Job in the mix | Read more |
|---|---|---|---|
| Placement (SCC, shotcrete, pervious, 3D printing) | high-range water reducer; viscosity-modifying admixture; set accelerator at the nozzle; retarder for working time | flow without segregation; early stiffening; working time | superplasticizers (high-range water reducers); viscosity-modifying admixtures |
| Strength and performance (high-strength, HPC, UHPC, high-early-strength) | ASTM C494 Type F or G high-range water reducer; silica fume; steel fibers; accelerator | low w/cm; dense paste; tensile capacity; early strength | accelerating admixtures; supplementary cementitious materials |
| Density (cellular) | foaming agent to ASTM C869/C869M-24 | stable macro-air voids | foaming agents for concrete |
| Heat (mass) | Class F fly ash, slag cement; retarders (little effect on peak temperature) | lower heat of hydration | set-retarding admixtures |
| Carbon (low-carbon, geopolymer) | water reducers; high SCM levels; alkali activators | less clinker per m³ | none |
| Function (self-healing) | bacterial healing agents; no ASTM, EN or IS product specification found (October 2026) | crack sealing | fiber-reinforced concrete (fibers also serve the placement and strength rows) |
| Weather practice (hot, cold) | retarders; accelerators; air-entraining admixture where freezing occurs | timing and frost protection | air-entraining admixtures |
Flow without segregation: dispersants and stabilizers#
A high-range water reducer gives flow at a low water/powder ratio, and 380 to 600 kg/m³ (640 to 1,011 lb/yd³) of powder or a viscosity-modifying admixture gives stability (European Guidelines 2005). The Guidelines set the water/powder ratio of self-compacting concrete at 0.85 to 1.10 by volume.
High-strength mixes push the dispersant further: NRMCA CIP 33 places w/cm at 0.23 to 0.35 with higher-than-typical doses of ASTM C494 Type F or G admixtures. UHPC goes below w/cm 0.25 with a high share of discontinuous fibers (FHWA).
Set control in both directions: accelerating and retarding systems#
Special concretes use accelerators where strength must arrive within hours and retarders where working time is too short. The NJDOT fast-track mix (FHWA-NJ-2001-015) carried accelerator at 2,086 mL/100 kg (32 fl oz/cwt) of cement and reached its target strength in 6 to 9 h under insulated covers. In pervious concrete, PCA EB302 puts working time at about 1 h, which retarders or hydration stabilizers extend by up to 1.5 h.
Printing needs both directions: Roussel (2018) shows that 1 m of purely thixotropic build-up cannot be printed faster than about 1 h 40 min without hydration control. Accelerators, including calcium chloride, do not prevent freezing (NRMCA CIP 27).
SCMs, fibers and foam inside special mixes#
SCMs carry the heat and carbon groups, fibers carry the tensile capacity of UHPC, and preformed foam sets the density of cellular concrete. PCA EB547 places Class F fly ash at 35 to 50 % of cementitious materials in mass placements, cutting heat of hydration by about 50 %, and slag cement at 50 to 75 %.
UHPC carries at least 2 % fibers by volume in the PCI-UHPC definition (Tadros, 2021). Cellular concrete takes its voids from a foaming agent conforming to ASTM C869/C869M-24 and tested by ASTM C796/C796M-25.
Defining Values and Classes of Special Concrete Types#
Every special concrete has one defining value set by a named document, from the EN 206-9:2010 slump-flow classes for SCC to the 8.3 MPa (1,200 psi) ceiling for flowable fill in ACI PRC-229R-13(22). Table 2 labels each value type.
| # | Type | Basis | Defining value (document, edition) | Value type |
|---|---|---|---|---|
| 1 | Self-compacting concrete | placement | SF1 550 to 650 mm, SF2 660 to 750 mm, SF3 760 to 850 mm (EN 206-9:2010 Table 1) | standard |
| 2 | Shotcrete | placement | concrete placed by high-velocity pneumatic projection from a nozzle, dry-mix or wet-mix (ACI PRC-506-22) | guide |
| 3 | Pervious concrete | placement | 15 to 35 % voids, pores 2 to 8 mm (0.08 to 0.32 in), 2.8 to 28 MPa (400 to 4,000 psi) (ACI PRC-522-23) | guide |
| 4 | 3D printing concrete | placement | qualification under ISO/ASTM 52939:2023; ACI Committee 564 had no published document in October 2026 | standard |
| 5 | High-strength concrete | strength | 55 MPa (8,000 psi) or more (ACI CT-25, ACI 363) | definition |
| 6 | High-performance concrete | performance | ACI CT-25 definition; strength grades G1 41 to 55 MPa (6 to 8 ksi) to G4 97 MPa (14 ksi) or more (1996 FHWA performance grades) | definition; agency grades |
| 7 | UHPC | strength | at least 120 MPa (17,000 psi) (ASTM C1856/C1856M-24 scope); at least 150 MPa (22,000 psi) (ACI CT-25) | standard; definition |
| 8 | High-early-strength concrete | early strength | opening flexural strength 1.0 MPa (145 psi) for sawing, 2.1 MPa (300 psi) for traffic (NESMEA 2008) | study |
| 9 | Flowable fill (CLSM) | strength ceiling | 8.3 MPa (1,200 psi) or less, most uses 2.1 MPa (300 psi) or less (ACI PRC-229R-13(22)) | guide |
| 10 | Cellular concrete | density | oven-dry density 800 kg/m³ (50 lb/ft³) or less (ACI PRC-523.1-06) | guide |
| 11 | Mass concrete | heat | ACI PRC-207.1-21; DEF can occur above 70 °C (158 °F) (PCA EB547) | guide |
| 12 | Low-carbon concrete | carbon | cast-in-place scope above 17 MPa (2,500 psi) up to 55 MPa (8,000 psi) (ACI CODE-323-24) | code |
| 13 | Geopolymer concrete | carbon | BSI Flex 350 v2.0 (September 2024); performance route ASTM C1157/C1157M-25 | standard |
| 14 | Self-healing concrete | function | 0.46 mm (0.018 in) healed vs 0.18 mm (0.0071 in) control after 100 days (Wiktor and Jonkers 2011) | study |
| 15 | Hot-weather concreting | practice | 35 °C (95 °F) maximum as delivered (ACI SPEC-301-20 4.2.2.5(b)) | specification |
| 16 | Cold-weather concreting | practice | air at or expected below 4 °C (40 °F) during the protection period (ACI 306R-16) | guide |
Strength and performance thresholds that are often confused#
High-strength concrete starts at 55 MPa (8,000 psi) in ACI CT-25, and high strength alone does not make a concrete high-performance (FHWA). The 1996 FHWA performance grades for high-performance concrete run from G1 at 41 to 55 MPa (6 to 8 ksi) to G4 at 97 MPa (14 ksi) or more, so 41 MPa (6 ksi) is the lower bound of grade G1, not the ACI high-strength threshold.
UHPC has four thresholds that are not identical: at least 120 MPa (17,000 psi) in ASTM C1856/C1856M-24, at least 150 MPa (22,000 psi) in ACI CT-25, above 150 MPa (21.7 ksi) with post-cracking tensile strength above 5 MPa (0.72 ksi) for FHWA, and f'c of 120.7 MPa (17.5 ksi) or more in AASHTO LRFDUHP-1 (2024).
Mix Ranges and Admixture Doses Across Special Concretes#
Special concretes span w/cm from 0.18 in a non-proprietary UHPC study mix to 0.37 to 0.43 in high-early-strength paving, with admixture doses stated per 100 kg (cwt) of cementitious material. Table 3 gives guide and study values with their basis; none is a product value or a standard requirement.
| Type | w/cm | Binder or cementitious | Admixture dose (basis) | Value type, source |
|---|---|---|---|---|
| Self-compacting | water/powder 0.85 to 1.10 by volume | powder 380 to 600 kg/m³ (640 to 1,011 lb/yd³) | high-range water reducer plus viscosity-modifying admixture or extra powder | guide, European Guidelines 2005 |
| High-strength | 0.23 to 0.35 | 400 to 600 kg/m³ (700 to 1,000 lb/yd³) | ASTM C494 Type F or G at higher-than-typical doses | guide, NRMCA CIP 33 |
| UHPC | 0.18 | 1,127 kg/m³ (1,900 lb/yd³) cement plus silica fume | high-range water reducer 1,098 mL/100 kg (16.84 fl oz/cwt) of cementitious material; steel fibers 78.3 kg/m³ (132 lb/yd³) | study, TDOT RES2024-04 mix NS1-SF |
| Pervious | 0.27 to 0.34 | 270 to 415 kg/m³ (450 to 700 lb/yd³) | retarder or hydration stabilizer; air entrainer in freeze-thaw exposure | guide, FHWA-HIF-13-006 (2012) |
| High-early-strength | 0.365 | Type I cement 474 kg/m³ (799 lb/yd³) | superplasticizer 1,043 mL/100 kg (16 fl oz/cwt), accelerator 2,086 mL/100 kg (32 fl oz/cwt), air entrainer 82 mL/100 kg (1.25 fl oz/cwt) of cement | study, FHWA-NJ-2001-015 |
| Mass | not set here | Class F fly ash 35 to 50 % or slag 50 to 75 % of cementitious materials by mass | retarders have little effect on peak temperature | guide, PCA EB547 |
| Low-carbon | not set here | SCM about 30 % where early strength matters, up to 70 % in footings and walls tested at 56 or 90 days | a 12 % water reduction removes about 42 kg/m³ (70 lb/yd³) of cement | guide, NRMCA 2022 |
| Geopolymer | activator-based | low-calcium fly ash precursor | activator solution 0.3 to 0.4 of fly ash by mass | study, Curtin GC1 |
Conversions: 1 fl oz/cwt = 65.2 mL/100 kg; 1 lb/yd³ = 0.5933 kg/m³. How w/cm drives strength and durability is covered under w/cm and mix design.
The worked example below, calculated from the TDOT NS1-SF study mix, turns a dose per 100 kg into a batch quantity.
- Cementitious content (input): 1,710 lb/yd³ of cement plus 190 lb/yd³ of silica fume = 1,900 lb/yd³, or 1,127 kg/m³.
- Dose (input): 1,098 mL/100 kg, so 11.27 × 1,098 = 12,374 mL, about 12.4 L of high-range water reducer per m³ (19 cwt × 16.84 = 320 fl oz per yd³).
- Water (input): 342 lb/yd³, so 342 / 1,900 = w/cm 0.18.
Final doses come from trial batches with the project's materials.
Selecting a Special Concrete by Application and Climate#
The element, the exposure and the weather select the special concrete: congested elements point to SCC, sprayed linings to shotcrete, drainable pavements to pervious concrete and thick sections to a low-heat mass mix. Weather practice is added on top of the chosen mix.
Table 4 matches the governing requirement of an element to a special concrete or practice.
| Requirement | Special concrete or practice | Read more |
|---|---|---|
| congested reinforcement, no vibration | self-compacting concrete | none |
| sprayed linings | shotcrete | none |
| stormwater infiltration | pervious concrete | none |
| thick sections | mass concrete | none |
| fast opening to traffic | high-early-strength concrete | none |
| trench and void backfill | flowable fill | none |
| freezing, chloride and sulfate exposure | any type, by durability class | concrete durability |
| delivery above 35 °C (95 °F) | hot-weather practice | none |
| protection below 4 °C (40 °F) | cold-weather practice | none |
Placement-driven choices: congested forms, sprayed linings and drainable paving#
Self-compacting concrete suits congested and vibration-free elements, shotcrete suits sprayed linings, and pervious concrete suits pavements that must drain. The European Guidelines (2005) assign class SF2 to walls and columns and SF3 to congested vertical work. ACI PRC-506-22 treats shotcrete as a placement method covering both dry-mix and wet-mix.
Pervious concrete is used where a pavement passes stormwater into a drainable base, at 81 to 730 L/min/m² (2 to 18 gal/min/ft²) (FHWA-HIF-13-006, 2012). Flowable fill below 0.7 MPa (100 psi) long term stays excavatable with hand tools (ACI PRC-229R-13(22)).
Temperature-driven practice: heat, frost and thick sections#
Temperature drives three choices: hot-weather practice above 35 °C (95 °F) as delivered, cold-weather practice below 4 °C (40 °F), and a low-heat mass mix in thick sections. ACI SPEC-301-20 4.2.2.5(b) sets the 35 °C (95 °F) maximum, higher where proven locally or by preconstruction testing.
ACI 306R-16 defines cold weather as air that has fallen to, or is expected to fall below, 4 °C (40 °F) during the protection period, and asks for 3.5 MPa (500 psi) before a single freeze. In thick sections, retarders have little effect on peak temperature (PCA EB547).
Carbon-driven choices: SCMs, alkali activators and GWP benchmarks#
Carbon-driven choices are measured against a benchmark: the NRMCA industry-wide EPD v4 (EPD-IES-0034276, 2026-10-09) puts a 27.6 MPa (4,000 psi) mix without SCM at 330.17 kg CO2e/m³ (252.4 per yd³) for stages A1 to A3. With 50 % slag, the same EPD gives 216.12 kg CO2e/m³ (165.2 per yd³).
A 12 % water reduction removes about 42 kg/m³ (70 lb/yd³) of cement and about 10 % of carbon at 27.6 MPa (4,000 psi) (NRMCA, 2022). ACI CODE-323-24, the Low-Carbon Concrete Code, covers cast-in-place concrete above 17 MPa (2,500 psi) up to 55 MPa (8,000 psi).
Which Standards Govern Special Concretes?#
Special concretes are governed in two layers: product standards for the admixtures, such as ASTM C494/C494M-24 and EN 934-2:2009+A1:2012, and concrete-level documents per type, such as ACI PRC-237-07 for SCC. ASTM C494/C494M-24 covers eight types, A to G and S, and EN 934-2 is harmonised under CPR 305/2011. EN 206-1:2026 (CEN approval 2026-01-19) supersedes EN 206:2013+A2:2021 and gives SCC guidance in Annex D.
India specifies admixtures through IS 9103:1999, the Indian specification for concrete admixtures with five types, reaffirmed 2018 with two amendments (BIS).
Table 5 sets the governing documents by region and role.
| Region | Documents | Role | Read more |
|---|---|---|---|
| US | ASTM C494/C494M-24 | admixture types A to G and S | ASTM C494 |
| EU | EN 934-2:2009+A1:2012 | admixture conformity | EN 934-2 |
| EU | EN 206-1:2026 | concrete specification | EN 206 |
| India | IS 9103:1999 | admixture specification, five types | IS 9103 |
| EU / US | EN 206-9:2010; ACI PRC-237-07 (reapproved 2019); ASTM C1611/C1611M-21 | SCC | none |
| US / EU | ACI PRC-506-22; EN 14487-1:2022; EN 934-5:2007 | shotcrete | none |
| US | ACI PRC-522-23; ASTM C1701/C1701M-17a(2023), C1688/C1688M-26, C1754/C1754M-25 | pervious concrete | none |
| US | ASTM C1856/C1856M-24; AASHTO LRFDUHP-1 | UHPC | none |
| US | ACI PRC-229R-13(22); ACI PRC-523.1-06, PRC-523.3-14; ASTM C869/C869M-24, C796/C796M-25 | flowable fill, cellular concrete | none |
| US | ACI PRC-207.1-21 | mass concrete | none |
| US | ACI CODE-323-24 | low-carbon concrete code | none |
| UK / US | BSI Flex 350 v2.0; ASTM C1157/C1157M-25 | alkali-activated binders | none |
| International | ISO/ASTM 52939:2023 | 3D printing qualification | none |
| US | ACI 305R-20; ACI SPEC-301-20; ACI 306R-16 | weather practice | none |
Withdrawn and superseded documents that specifications still cite#
Five groups of special-concrete documents are withdrawn or superseded, listed below with their status.
- ASTM C1747: pervious concrete abrasion method, withdrawn 2022.
- ASTM shotcrete standards: C1141/C1141M withdrawn 2024, C1436 in 2022, C1480/C1480M in 2021, C1385/C1385M in 2026.
- ACI 506R-16: superseded by ACI PRC-506-22 in November 2022.
- PAS 8820:2016: withdrawn on 2024-11-26; BSI Flex 350 v2.0 (September 2024) covers alkali-activated binders.
- 15 to 25 % pervious voids: the older ACI 522R-10 range cited by FHWA in 2012, now 15 to 35 % in ACI PRC-522-23.
Complete Table of Special Concrete Types#
Table 6 lists 14 special concretes and 2 weather practices, each with the admixture system that defines it in one line.
| # | Special concrete | Admixture system in one line |
|---|---|---|
| 1 | self-compacting concrete (SCC) | high-range water reducer plus viscosity-modifying admixture or powder |
| 2 | high-performance concrete (HPC) | high-range water reducer, silica fume, fly ash, slag |
| 3 | high-strength concrete mixes | Type F or G high-range water reducer at w/cm 0.23 to 0.35, silica fume |
| 4 | ultra-high-performance concrete (UHPC) | high-range water reducer, silica fume, at least 2 % fibers by volume |
| 5 | pervious concrete | retarder or hydration stabilizer, air entrainer |
| 6 | shotcrete mixes | accelerator, fibers |
| 7 | mass concrete thermal control | Class F fly ash, slag cement |
| 8 | cellular concrete | foaming agent |
| 9 | flowable fill (CLSM) | low cement, fly ash |
| 10 | low-carbon concrete | water reducers, high SCM levels |
| 11 | geopolymer and alkali-activated concrete | alkali activators |
| 12 | 3D printing concrete | viscosity-modifying admixture, set-on-demand accelerator |
| 13 | high-early-strength concrete | accelerator, superplasticizer |
| 14 | self-healing concrete | bacterial healing agents |
| 15 | hot-weather concreting | retarders, cooling |
| 16 | cold-weather concreting | accelerators, protection |
A request for mix design, trial batching or testing names the special concrete type, the element, the exposure class and the volume in m³ (yd³).
What Falls Outside Special Concrete Mix Systems?#
A special concrete here is a batch that a producer designs and doses, so cement types sold as products, finished concrete products and repair methods sit outside it. Shotcrete as a repair method and repair mortars are outside the scope of this page. Finished concrete products, such as cellular blocks, are not covered here.
Are special cements the same as special concretes?#
No: a special cement is a binder product, while a special concrete is a complete mix whose admixture and SCM system is designed for one requirement. Special cements, such as rapid-hardening or sulfate-resisting cements sold as cement products, are not covered here.
Does a special concrete need different fresh tests?#
Yes for SCC and pervious concrete: SCC is accepted by slump flow under ASTM C1611/C1611M-21 instead of slump, and pervious concrete by fresh density and voids under ASTM C1688/C1688M-26. UHPC adds a flow of 200 to 250 mm (8 to 10 in) on a modified flow table within the scope of ASTM C1856/C1856M-24. The methods sit with the other fresh concrete tests.
Do special concretes cost more than conventional concrete?#
Yes in the dated public cost records for pervious, UHPC, low-carbon and self-healing concrete, from a few dollars per cubic meter to 5 to 10 times the price of normal concrete. Pervious concrete costs 15 to 25 % more than conventional concrete (FHWA, 2012). Non-proprietary UHPC costs USD 747 to 837 per m³ (USD 571 to 640 per yd³), material only, at April 2025 prices, 5 to 10 times normal concrete (TDOT RES2024-04). Low-carbon mixes carry a USD 2.6 to 26.2 per m³ (USD 2 to 20 per yd³) premium (Massachusetts supplier 2022, RMI 2022-06-27). Self-healing concrete costs EUR 85 to 100 per m³ (EUR 65 to 76 per yd³) against EUR 80 (EUR 61 per yd³) for conventional concrete (MPI Bremen, May 2015).