Ready-mix versus site-mix concrete: cost, quality and logistics

Cost per cubic metre

Ready-mix concrete from a regional batching plant typically prices at a ten to fifteen percent premium over the cost of site-mix on the same nominal mix design at the same project location. The premium covers the plant overhead, the transit-mixer freight, the admixture content needed to maintain workability over transit time and the larger margin required by the ready-mix supplier. On a small house with concrete demand under fifty cubic metres total, the absolute rupee saving from site-mix is modest and is often consumed by the labour cost of operating a small mixer, the spillage and the inconsistency of small batches.

On a large pour over a hundred cubic metres in a single shift, ready-mix is almost always cheaper per cubic metre after accounting for the labour, the mixer-fuel cost, the cement waste and the sand-and-aggregate handling at site. The crossover point is typically around twenty cubic metres for small pours and drops to ten cubic metres for high-rise floor slabs where pumping is required regardless of the batching choice.

Quality control

The single largest difference between ready-mix and site-mix is repeatability of the mix. A batching plant uses weight batching of cement, aggregate and water to within plus or minus two percent, with admixture dosage to within plus or minus three percent, and produces a documented batch slip for every load. A site mixer using volume batching with site labour produces variability of plus or minus ten to fifteen percent on cement and water content from one batch to the next, which translates to a strength variation of fifteen to twenty percent on twenty-eight-day cube tests. For structural elements where strength matters, ready-mix is the lower-risk choice.

Slump retention is the second axis. A ready-mix supplier dosing a retarder and a polycarboxylate superplasticiser can deliver a 100-millimetre slump concrete that retains workability for ninety minutes from batching, which is required for transit, pumping and placement. A site-mix without admixtures loses slump within thirty minutes, which makes pumping problematic and finishing inconsistent.

Logistics

Ready-mix is delivered in transit mixers of typically six or eight cubic metres capacity, with a placement rate matching the supply rate. A continuous pour of two hundred cubic metres requires a mixer to be on site every twenty to thirty minutes for a full shift, which in turn requires the supplier to be within a transit time of ninety minutes from the plant under IS 4926. Around Bengaluru, Tumakuru and the immediate periphery, the ninety-minute rule is generally satisfiable; on remote sites in interior Karnataka, Tamil Nadu hill stations or coastal Kerala beyond the supplier reach, ready-mix is simply not available and site-mix is the only option.

Site access constraints affect both options. Transit mixers are typically nine metres long and require a clear approach; narrow lanes and low gates rule them out. Site mixers come in sizes from a small one-bag mixer to a ten-cubic-metre pan mixer, and can be set up almost anywhere with power and water. For projects with constrained access, a portable concrete pump combined with site-mix is sometimes the only viable arrangement.

Statutory and contractual testing

Both ready-mix and site-mix are subject to compressive strength testing under IS 456 Clause 15 with cube tests at seven and twenty-eight days. The ready-mix supplier provides cubes from each batch as part of the contract; the site-mix project must arrange its own sampling, casting and laboratory submission. For institutional projects with formal quality plans, the documentation discipline of ready-mix is a significant advantage. For residential projects, the same testing can be done with site-mix but it requires deliberate planning rather than emerging by default.

Default recommendations

For a single house under fifty cubic metres total concrete, site-mix is the practical default if the contractor is reliable and the labour is competent, with the option of switching to ready-mix for the largest single pour such as a ground-floor slab. For a residential apartment block above three floors, ready-mix should be the default for slabs and main columns, with site-mix reserved for small footings and isolated patches. For any commercial or institutional building, ready-mix should be the default for all structural concrete.

Related reading

The category page on cement and binders carries the grade-selection table that feeds either ready-mix or site-mix. The technical article on concrete curing covers the post-pour discipline that determines whether the strength gain matches the mix design. The article on cement grades is the natural prerequisite read.

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