Ready-mix concrete · Bali
Concrete grades K-225 to K-350: which one for which job
In Bali concrete is ordered by its K grade. This page explains what the number means, how it relates to fc′ on an engineer's drawing, which grade is typical for each part of a villa — and what to say when you order.
Updated 2026-10-03
K and fc′: two ways to write strength
K is the compressive strength of a 15 cm cube at 28 days, in kg/cm² (the older Indonesian PBI system). fc′ is the strength of a cylinder in MPa, used in SNI 2847 and on most engineers' drawings. The two are not the same test: a quick conversion is fc′ ≈ K/10 × 0.83, so K-300 is roughly fc′ 25 MPa.
| Grade (K) | fc′ ≈ MPa | Typical use |
|---|---|---|
| K-175 | 14.5 | Lean concrete under footings, blinding, kerbs, non-load-bearing fill |
| K-225 | 18.7 | Ground floors of houses, footpaths, light foundations, boundary wall footings |
| K-250 | 20.8 | Slabs, sloof, columns and beams of one- and two-storey houses |
| K-300 | 24.9 | Structural frame of villas (2–3 storeys), suspended slabs, retaining walls, driveways for trucks |
| K-350 | 29.1 | Swimming-pool shells, water tanks, basements, cantilevers, heavily loaded elements |
| K-400 and above | 33.2+ | Precast, long spans, special structures — by engineer's specification |
Using a grade higher than the drawing does not make a structure safer by itself, but it does cost more; using a lower one is a defect. Order the grade that is written — if the drawing only shows fc′, give us that number.
Slump: how wet the mix should be
Slump is measured by filling a 30 cm cone and seeing how far the concrete settles when the cone is lifted. For normal placing with vibrators slump 10 ± 2 cm is typical; for pumped concrete 12 ± 2 cm. A wetter mix is easier to place but weaker — never add water at the site. If you need a more fluid mix, ask for a plasticiser in the recipe instead.
Fly-ash and non-fly-ash concrete
Many plants in Bali offer fly-ash (FA) and non-fly-ash (NFA) mixes. FA concrete uses part fly-ash in place of cement: it is cheaper, flows better and gains strength more slowly in the first days. NFA sets faster, which helps when formwork has to be stripped quickly. The 28-day strength is the same grade either way — ask which one you are being quoted.
Not sure which grade? Send the drawing or a photo — we will tell you
Get a quote on WhatsAppWhat to tell the plant when you order
- Grade (K or fc′) and slump — or the element you are pouring, so we can suggest.
- Volume in m³ (use the calculator) and whether it is one pour or several.
- Pumped or placed directly — the mix is designed differently.
- Admixtures: waterproofing for pools and tanks, retarder for hot days and long drives.
- Date, start time and the access to the site.
Questions we get
Which grade for a swimming pool?
Pool shells in Bali are usually K-300 to K-350 with a waterproofing admixture, poured in as few joints as possible. Follow the structural engineer's specification.
K-250 or K-300 for a villa slab?
Ground-bearing slabs of a single-storey house are often K-250; suspended floors and the frame of a two- or three-storey villa are usually K-300. The drawing decides — ask the engineer if it only shows fc′.
Can we add water on site to make it easier to pour?
No. Water added after batching lowers the strength and increases cracking. Order the right slump or a plasticiser instead; the driver cannot add water on your behalf.
How long until I can walk on the slab or strip formwork?
Concrete can usually be walked on after 24–48 hours in Bali's climate. Stripping side forms, props and beams follows the engineer's schedule; design strength is reached at 28 days. Keep the surface wet for the first week — curing matters as much as the grade.
Do you test the concrete?
Ask for a slump test at the site and test cubes for each pour; results at 7 and 28 days show whether the grade was reached. We will tell you exactly what is included in your quote.
What does "Jayamix" mean?
Jayamix is a brand name of another producer that is often used in Bali as a general word for ready-mix concrete. AVC produces its own concrete at our plant; you order it by grade — K or fc′ — not by brand.