Ramming mass is a dry, granular monolithic refractory that is compacted in place, by ramming or vibration, to form a seamless lining; in induction furnaces it comes as acid silica, neutral alumina-magnesia or basic magnesia masses. A silica mass holds at least 98.5 % SiO2 as a class range and sinters on the first melt with 0.2 to 1.5 % boron compounds (Sengupta, IntechOpen book chapter, 2022).
In Indian trade, the bare term "ramming mass" is the name under which the silica mass for melting iron is sold. US practice calls the clay-, phosphate- or carbon-bonded mixes for arc furnace hearths, ladles and runners "ramming mixes", and ASTM C673-97(2022) classifies the fireclay and high-alumina ones. Both belong to the unshaped branch of refractory materials.
The class follows the slag and the metal: silica for cast and ductile iron, neutral or basic for mild, manganese and stainless steel. One Indian producer leaflet gives its neutral mass 86 ± 2 % Al2O3 with 12 ± 1 % MgO as typical values. Buyers trade the product under HS heading 3816, and 2026 city listings in India asked INR 3,500 to 5,000 per tonne in Raipur.
Every value names its standard and edition, the product data sheet or the dated source it comes from; see our methodology and fact-checking process.
The table below summarizes ramming mass as a product class.
| Attribute | Value |
|---|---|
| Definition | Unshaped refractory placed by compaction; ISO 1927-1:2012 lists "ramming materials" as a product type (clause 4) |
| Classes | Acid (silica), neutral (alumina-magnesia, spinel-forming), basic (magnesia) |
| Placement | Dry, rammed or vibrated between coil and former |
| Bond | Boron sintering aid (silica); in-situ spinel (neutral); magnesia sintered in place (basic) |
| Main use | Coreless induction furnaces |
| Key standards | ISO 1927-1:2012; ASTM C673-97(2022) |
| HS heading | 3816 |
What Is Ramming Mass?#
A ramming mass is the monolithic refractory placed by compaction rather than by casting or spraying: ISO 1927-1:2012 lists ramming materials as one of the unshaped product types in clause 4, next to castables, gunning and jointing materials. The meaning of the term is therefore the placement method, not one chemistry. ISO 1927-1:2012 was last confirmed on 2023-09-04 and replaced ISO 1927:1984.
The same standard then classifies each product by chemical type in clause 5 (alumina-silica, basic, special, carbon-containing), by main raw material and classification temperature in clause 6, and by designation in clause 7. ISO 1927 has 8 parts, from classification and sampling to physical properties and pre-formed shapes. Ramming mass sits beside castables, gunning mixes and mortars among the monolithic refractories.
Silica, Neutral and Basic Classes by Slag Character#
There are three classes of induction furnace ramming mass, named by the slag they tolerate: acid (silica), neutral (alumina-magnesia, spinel-forming) and basic (magnesia). The class decides which metal a lining can hold.
ISO 836:2001 defines the three slag terms. An acid refractory (term 002) contains a substantial amount of silica and reacts with basic refractories, basic slags and alkali; silica ramming mass is a typical acid product. A neutral refractory (term 089) has no appreciable reaction with acid or basic refractories, slags or fluxes. A basic refractory (term 009) may react with acid refractories, acid slags or alumina, and its components include magnesia, calcium oxide, chromite and spinel.
The classes work as a slag-compatibility rule: an acid lining meets an acid slag, a basic lining a basic slag, and a neutral lining sits between them. The rule in full, with bricks and castables, is set out under acid, basic and neutral refractories compared.
The table below compares the three classes by ISO 836:2001 term, main oxide and service.
| Class | ISO 836:2001 term (number) | Main oxide | Metal and slag | Page |
|---|---|---|---|---|
| Acid | acid refractory (002) | SiO2 | cast and ductile iron, acid slag | this page |
| Neutral | neutral refractory (089) | Al2O3 with MgO (spinel) | steels, both slag types | this page |
| Basic | basic refractory (009) | MgO | mild, manganese and stainless steel, basic slag | refractory magnesia |
The ISO 836:2001 terms describe slag behavior; ISO 1927-1:2012 classifies the product by chemistry.
Ramming Materials in ISO 1927 and ASTM C673 Terms#
Standards name the product type, not the induction furnace grade: ISO 1927-1:2012 covers ramming materials as a type, and ASTM C673-97(2022) classifies fireclay and high-alumina plastic refractories and ramming mixes. The ASTM edition replaced C673-97(2018), withdrawn on 2022-09-29.
ASTM C673 governs the clay- and phosphate-bonded mixes that US and EU practice uses for arc furnace hearths, ladles and runners. Silica, neutral and basic induction masses are bought on producer data sheets, which state chemistry, grading and boron content, so the buyer compares one data sheet with another.
Regional and Trade Names: Ramming Mix, Stampfmasse and Dry Vibratable#
One product travels under five names, and one trade name means the opposite placement. The five regional names are listed below.
- India: ramming mass, premix ramming mass, and acidic, neutral or basic ramming mass
- US: ramming mix and rammable
- US: dry vibratable (DVC) for induction furnaces
- Germany: Stampfmasse
- UK and EU: silica dry mix
Allied Mineral Products sells MINRO-SIL RAM 1001 as a silica-based dry vibratable for iron alloy working linings, despite the "RAM" in its name.
Ramming Mass Composition by Class#
A silica ramming mass is quartz or quartzite grain with at least 98.5 % SiO2 as a class range (Sengupta 2022), neutral masses combine alumina with magnesia, and basic masses build on magnesia. One named silica product, Adore ADRAM-IN, states at least 99 % SiO2 and below 0.05 % Fe2O3 on its data sheet.
The table below compares the main components by class, with the basis of each value.
| Class | Main components (mass %) | Basis | Raw-material page |
|---|---|---|---|
| Silica | SiO2 ≥ 98.5 % (quartzite or quartz) | class range, Sengupta 2022 (IntechOpen book chapter) | n/a |
| Silica, ADRAM-IN | SiO2 ≥ 99 %, Fe2O3 < 0.05 %; grain 0 to 4 or 0 to 6 mm (0 to 0.16 or 0 to 0.24 in) | typical value of ADRAM-IN, Adore data sheet | n/a |
| Neutral | Al2O3 86 ± 2 %, MgO 12 ± 1 %, SiO2 < 0.1 % | typical value of one Indian neutral ramming mass leaflet (2023) | magnesium aluminate spinel |
| Basic | fused magnesia 61 to 65 %, calcined magnesium dolomite 34 to 37 % | patent example CN111018497A, a formulation figure, not a class limit | refractory magnesia |
Grain grading matters next to chemistry: the same ADRAM-IN product comes in a 0 to 4 mm or a 0 to 6 mm range, and a wrong grading or boron level lets metal penetrate the lining. The basic example is a patent formulation, so it shows one way to combine fused magnesia with calcined magnesium dolomite rather than a limit any basic mass must meet. Each grain family, from quartzite to fused magnesia, is described among the refractory raw materials.
Which Binders and Sintering Aids Does a Ramming Mass Use?#
A silica ramming mass is installed dry and binder-free, and the bond forms only in the furnace, where a boron sintering aid turns the hot face into a dense sintered layer while the cold side stays loose. Neutral and basic masses need no boron: they bond by ceramic reaction, through spinel formation or magnesia sintering in place.
Boric Acid and Boron Oxide in Silica Premix#
Boric acid (CAS 10043-35-3) or boron oxide (CAS 1303-86-2) is the sintering aid of silica ramming mass, at 0.2 to 1.5 % boron compounds as a class range and 0.4 to 1.0 % for boron oxide (Sengupta 2022). The boron forms a borosilicate glass that sinters the quartz at the hot face. Three zones result across the wall: a sintered zone at the melt, a semi-sintered zone and a powder zone against the coil.
How much boron does a lining take? A higher furnace operating temperature takes less boron, and the boron oxide dose is about half the boric acid dose for the same sintering temperature (Sengupta 2022). Premix grades arrive with the boron already blended, so the buyer specifies the level on the order. Dosing by sintering temperature and the boron chemistry itself are covered under boric acid and boron oxide sintering aids.
In-Situ Spinel, Sintered Magnesia and Chemical Bonds#
Neutral masses bond by forming magnesium aluminate spinel in place, a reaction that expands the lining, so producers add pre-sintered spinel to limit the volume increase (Saikia et al., peer-reviewed paper, 2004). The expansion keeps the lining tight against the former, and the pre-sintered share sets how far it goes.
Basic masses rely on magnesia sintering in place. The US ramming mixes for arc furnaces, ladles and runners use clay, phosphate or carbon bonds instead; HarbisonWalker's EXCELERATE ABR PLUS, for example, is sold as a phosphate-bonded ramming mix. The two binder pages below cover these chemical bonds.
- phosphate binders for phosphate-bonded ramming mixes
- refractory additives and binders for every binder family
Ramming Mass Properties: Standard Requirements and Typical Values#
No standard on this page's sources sets a property requirement for silica, neutral or basic induction masses, so their data sheets carry typical values of one product, and only the ASTM C673 ramming mixes are classified by a standard. A value in the table below therefore describes its product, not the class.
The table below separates the standard basis from the typical values of named products.
| Property | Standard requirement | Typical value (product, basis) | ASTM / ISO method |
|---|---|---|---|
| Bulk density | n/a for induction masses | 2.2 g/cm³ (137 lb/ft³), ADRAM-IN, Adore data sheet; 2.90 g/cm³ (181 lb/ft³), one Indian neutral ramming mass leaflet | see apparent porosity and bulk density |
| Pyrometric cone equivalent | n/a | Orton cone 32 to 32 1/2, ADRAM-IN, Adore data sheet | ASTM C24-09(2022); ISO 528:1983; see pyrometric cone equivalent |
| Service temperature | n/a | 1800 °C (3,272 °F), one Indian neutral ramming mass leaflet | n/a |
| Grain range | n/a | 0 to 4 or 0 to 6 mm (0 to 0.16 or 0 to 0.24 in), ADRAM-IN, Adore data sheet | sieve analysis |
| Drying and firing linear change of ramming mixes | ASTM C673-97(2022) class basis | see the C673 classes | ASTM C179-14(2024); ISO 1927-6:2012 |
The two densities, 2.90 and 2.2 g/cm³, belong to two single products, a neutral leaflet and the Adore ADRAM-IN data sheet, so they compare those products and set no class boundary. The full set of methods is explained under properties of refractory materials.
Reading a Ramming Mass Data Sheet#
Six checks make two ramming mass data sheets comparable, whatever the brand. The six checks are listed below.
- Confirm the class (acid, neutral or basic) against the metal and the slag.
- Read the chemistry with its basis: SiO2, Fe2O3, Al2O3 and MgO in mass %.
- Compare the grain range and the grading curve.
- Ask whether boron is premixed and at what level.
- Note the PCE method and edition, ASTM C24-09(2022) or ISO 528:1983 (see ASTM C24 pyrometric cone equivalent).
- Check the shelf life and the bag size.
Which Standards Cover Ramming Mixes and Their Tests?#
Ramming mixes are classified by ASTM C673-97(2022) in the US and fall under ISO 1927-1:2012 as ramming materials, and their test specimens are pressed and dried under ASTM C1054-24 or, for basic mixes, ASTM C975-87(2020). C1054-24 replaced C1054-18, withdrawn on 2024-09-19.
The table below sets the ASTM and ISO methods side by side; methods in one row measure the same property, but their results are not interchangeable.
| Purpose | ASTM (edition) | ISO (edition) | Note |
|---|---|---|---|
| Classification | C673-97(2022), fireclay and high-alumina plastic refractories and ramming mixes | ISO 1927-1:2012, ramming materials (clause 4) | ISO 1927 monolithic refractory products |
| Specimen pressing and drying | C1054-24, plastic and ramming specimens classified per C673 | n/a | C1054-18 withdrawn 2024-09-19 |
| Basic ramming specimens | C975-87(2020), pressing | n/a | latest reapproval 2020 |
| Drying and firing linear change | C179-14(2024) | ISO 1927-6:2012 (physical properties) | results not interchangeable |
| Pyrometric cone equivalent | C24-09(2022), fireclay and high-alumina materials | ISO 528:1983 | C24 not for specification outside fireclay and high-alumina |
Linear change after drying and firing comes from ASTM C179-14(2024) on the US side and from ISO 1927-6:2012 on the ISO side, and the two results are not interchangeable, so a specification names one method. Parts 1 to 8 of the ISO series are compared under ISO 1927 monolithic refractory products.
Where Is Ramming Mass Used?#
Ramming mass lines coreless induction furnaces that melt iron and steel, and basic or high-alumina ramming mixes line arc furnace hearths and blast furnace runners and troughs. Silica is the lining for cast and ductile iron: it costs little, iron does not wet it, and its expansion closes cracks (Allied Mineral Products technical paper, 2017).
Neutral or basic masses line the furnaces that melt mild, manganese and stainless steel. A basic lining matches a basic slag, and a neutral lining resists both the thermal-shock cracking of basic linings and the slag erosion of silica.
Induction furnaces are built as coreless and channel types, and ramming mass lines the coreless crucible. Lining choice, life in heats and furnace-by-furnace practice are set out under induction furnace lining.
The table below maps each industry and zone to its class.
| Industry | Zone | Class and reason | Page |
|---|---|---|---|
| Foundry | coreless induction furnace | silica for cast and ductile iron (low cost, not wetted by iron) | see the induction page above |
| Steel induction melting | coreless induction furnace | neutral or basic for mild, manganese and stainless steel; Allied Minro-Mag RAM M20 is a basic working lining for furnaces under 1 t | see the induction page above |
| Steel | arc furnace hearth | basic ramming mass | electric arc furnace refractory lining |
| Ironmaking | blast furnace runners and troughs | trough ramming mass (C673 high-alumina, SiC-C) | blast furnace trough and runner castables; blast furnace refractory lining |
| Whole steel plant | all zones | ramming among the lining classes | refractories for iron and steel |
How Is Ramming Mass Installed and Sintered?#
A ramming mass reaches its data-sheet values only after it is compacted to full density between the coil and a steel former and sintered on the first melt. The bottom is rammed or vibrated first; the sidewall is then filled between coil and former and compacted with a 2- or 3-arm lining vibrator, as one neutral ramming mass leaflet describes and as silica practice repeats.
Silica sinters only at the hot face, so the powder zone behind it is intended, not a defect. Moisture is kept away from the coil during installation and first heat, because moisture damage to the coil insulation is one of the recorded failure modes of rammed linings.
Heat-up rates, holds, former practice and the first-melt procedure come from the producer and the lining procedure of each furnace. They are set out by furnace size under induction furnace sintering and lining practice.
- refractory installation methods compares ramming with casting, gunning and vibration
Why Do Rammed Linings Fail, and How Are They Checked?#
Rammed induction linings fail by metal penetration through cracks, and a wrong boron level or poor grading is the material-side cause of that penetration. Basic linings crack vertically under thermal shock, silica wears by slag erosion where steel slags reach it, and rammed linings also lose thickness at the slag line, bottom and sidewall.
The table below lists the failure modes by class with the check that finds each one.
| Failure | Class | Cause | Check |
|---|---|---|---|
| Metal penetration | silica | cracks; wrong boron level or grading | chemistry, grading, boron content (refractory failure modes) |
| Vertical thermal-shock cracks | basic | thermal cycling | visual inspection |
| Slag erosion and slag-line wear | silica with steel slags | slag chemistry | lining thickness |
| Bottom and sidewall erosion | rammed linings | wear in service | lining thickness |
| Overheating | silica | fused above 1700 °C (3,092 °F), statement of one neutral ramming mass leaflet | temperature record |
| Coil insulation damage | rammed linings | moisture | see the lining procedure (refractory inspection and quality control) |
Four material checks catch the causes before and after a campaign. A delivery is tested for chemistry (SiO2, Fe2O3, Al2O3, MgO), grain size distribution and the boric acid content of a premix. After tear-out, a post-mortem measures the thickness of the sintered, semi-sintered and powder zones.
Health and Safety: Quartz Dust and Boron Compounds#
The main hazard of silica ramming mass is respirable crystalline silica, regulated in US workplaces at 50 µg/m³ (8-h TWA) with an action level of 25 µg/m³ under 29 CFR 1910.1053, effective 2016-06-23. In the EU, the limit is 0.1 mg/m³ under Directive (EU) 2017/2398, transposition by 2020-01-17.
Quartz itself has no harmonized CLP entry, so its classification is product-specific and the supplier SDS decides. California lists "Silica, crystalline (airborne particles of respirable size)" under Proposition 65 for cancer since 1988-10-01, and IARC places crystalline silica in Group 1 (Monograph 100C, 2012).
The boron compounds carry a harmonized reproductive-toxicity classification, Repr. 1B, while the magnesia and alumina grains of neutral and basic masses have no Annex VI entry. The table below lists each substance with its rule and the instrument and date.
| Substance | Rule or classification | Instrument and date |
|---|---|---|
| Quartz (crystalline silica), CAS 14808-60-7 | No Annex VI entry; product-specific, see supplier SDS (ECHA C&L: no majority; not classified 27.5 %, H372 25.2 %, H373 18.8 %, H350 7.7 %) | CLP Regulation (EC) No 1272/2008 Annex VI and ECHA C&L, read 2026-10-27 |
| Respirable crystalline silica, US | PEL 50 µg/m³ 8-h TWA, action level 25 µg/m³ | 29 CFR 1910.1053, effective 2016-06-23 |
| Respirable crystalline silica, EU | 0.1 mg/m³ respirable fraction, 8-h TWA | Directive (EU) 2017/2398, transposition by 2020-01-17 |
| Crystalline silica, California | "Silica, crystalline (airborne particles of respirable size)", cancer | Proposition 65 list, listed 1988-10-01 |
| Crystalline silica (quartz, cristobalite), IARC | Group 1 | IARC Monograph 100C (2012) |
| Boric acid, CAS 10043-35-3, EC 233-139-2 | Harmonised CLP Annex VI: H360FD (index 005-007-00-2, Repr. 1B, Note 11) | CLP Annex VI as amended by ATP 20, in application since 2025-02-01 |
| Boric acid | REACH Candidate List (SVHC), toxic for reproduction | REACH Article 59, on the list since 2010-06-18 (ECHA list read 2026-10-27) |
| Boron oxide, CAS 1303-86-2, EC 215-125-8 | Harmonised CLP Annex VI: H360FD (index 005-008-00-8, Repr. 1B) | CLP Annex VI as amended by ATP 20, in application since 2025-02-01 |
| Magnesia grain, EC 215-171-9 | No Annex VI entry; not classified in 90.44 % of ECHA C&L notifications; see the supplier SDS | ECHA C&L, read 2026-10-27 |
| Alumina grain, EC 215-691-6 | No Annex VI entry; ECHA C&L notified: not classified (93.7 %) | ECHA C&L, read 2026-10-27 |
Exposure control and the boron rules for workers are covered on the two safety pages below.
- crystalline silica and cristobalite in refractories
- refractory health and safety
Ramming Mass Grades, Packaging, HS Code and Sourcing#
Ramming mass is traded under HS heading 3816 (refractory cements, mortars, concretes and similar compositions), and the US tariff gives dolomite ramming mix its own subheading, 3816.00.10. Every other ramming mass falls under 3816.00.20 (official US HTS, checked 2026-10-27).
A buyer specification names five points, listed below.
- Class and the metal it holds (silica, neutral or basic).
- Chemistry with its basis (SiO2, Fe2O3, Al2O3, MgO in mass %).
- Grain range and grading.
- Boron premixed or not, and its level.
- Shelf life and packing, as for the Indian grades described under refractories in India.
A request names the class, the quantity in tonnes and the delivery country, and brand questions go through the same data-sheet checks. Buying routes for each region are set out under refractory manufacturers and suppliers.
What Does Ramming Mass Cost?#
Ramming mass was listed at INR 4,200 to 6,000 per tonne in Coimbatore and INR 3,500 to 5,000 per tonne in Raipur on TradeIndia city listings in 2026, asking prices rather than contract prices. No dated contract price range is recorded for the class.
The table below gives the listing ranges per tonne and per short ton, followed by the factors that move a quote.
| Item | Range (per t; per short ton) | Region and date | Source type |
|---|---|---|---|
| Ramming mass listings | INR 4,200 to 6,000; INR 3,810 to 5,443 | India (Coimbatore), 2026 | directory listings (TradeIndia) |
| Ramming mass listings | INR 3,500 to 5,000; INR 3,175 to 4,536 | India (Raipur), 2026 | directory listings (TradeIndia) |
| Quote factor | class and grade (silica, neutral, basic) | n/a | quote factor |
| Quote factor | boron premix and its level | n/a | quote factor |
| Quote factor | raw-material origin | n/a | quote factor |
| Quote factor | quantity and packaging | n/a | quote factor |
| Quote factor | freight | n/a | quote factor |
| Quote factor | installation and sintering | n/a | quote factor |
Both city ranges are asking prices for one product type, not contract prices. Class and grade lead the quote factors, so a quote compares one class at a time.
Ramming Mass Compared With Dry Vibratables, Plastics and Castables#
A ramming mass and a dry vibratable mix are both installed dry between coil and former, and the line between them is placement by ramming or by vibration, not chemistry. US practice names the dry induction linings dry vibratables (DVC). The vibrated alternative is described under dry vibratable mixes.
A plastic refractory is rammed too, but it arrives moist and workable with a clay or phosphate bond. A castable is mixed with water and cast, so it needs a dry-out that a dry mass does not.
The table below compares ramming mass with its three alternatives and one related additive.
| Alternative | Placement | When it is used | Page |
|---|---|---|---|
| Dry vibratable mix | dry, vibrated | silica, alumina, spinel or magnesia induction linings | dry vibratable mixes |
| Plastic refractory | moist, rammed | clay- or phosphate-bonded linings and repairs | plastic refractories |
| Refractory castable | mixed with water and cast | cast linings and precast shapes | refractory castables |
| Boric acid sintering aid | an additive, not a mass | sinters silica ramming mass | see the boron section above |
Ramming Mass FAQs#
Does Neutral Ramming Mass Contain Boric Acid?#
No: neutral ramming masses are bonded by in-situ spinel and use no boric acid, which is a sintering aid for silica masses. Their bond forms as alumina and magnesia react in the furnace.
How Long Can Ramming Mass Be Stored?#
One neutral ramming mass leaflet states a storage life of at least 6 months in the original packing; the data sheet of each product sets its own. Shelf life belongs on the buyer's checklist for that reason.