Construction glossary · Concrete and masonry
What is concrete admixture in construction?
A concrete admixture is a chemical added to the mix, beyond cement, water, and aggregate, to change how the concrete behaves: air entrainment for freeze thaw durability, accelerators for faster set in cold weather, retarders for hot weather, and plasticizers for flow without extra water. Admixtures are priced per cubic yard on top of the base mix, so the estimator needs to know which ones the spec and the season demand.
Updated June 2026 · Reviewed by the Ruh construction team
Admixture is a small share of the mix
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Book a walkthroughAdmixtures show up in two places: the concrete spec (03 30 00 and the mix design submittals) and the ready mix quote, where each one is a separate adder per cy. The common families are air entraining agents (required for exterior concrete in freeze thaw climates), water reducers and superplasticizers (flowable mixes, pumpability, high strength), accelerators (early strength for winter pours, with non chloride versions required around rebar), retarders (slowing set in summer heat or long truck cycles), and corrosion inhibitors and shrinkage reducers on demanding structures. The estimating mistakes are predictable: pricing every cy at the plain mix rate when the exterior concrete needs air and the winter pour needs accelerator, missing that the pump mix costs more than the tailgate mix, and ignoring that the engineer can reject calcium chloride accelerators near reinforcing, forcing the pricier non chloride product.
Admixtures are quantified by the cubic yards of the mixes that carry them, not measured separately on drawings. The estimator splits the concrete takeoff by mix design: footings at one strength, slabs at another, exterior flatwork with air entrainment, winter pours with accelerator. Each split carries its own price per cy from the supplier quote, with the admixture adders built in. Adders are quoted per cy, commonly a few dollars for air or standard water reducer and an illustrative $8 to $15 per cy for non chloride accelerator, but the live quote rules.
Worked example
A winter pour covers 120 cy of footings and 230 cy of slab on grade. The spec requires non chloride accelerator for any pour below 40 F, and the schedule puts both pours in January. Base mix is an illustrative $172 per cy. The supplier quotes the accelerator adder at an illustrative $12 per cy. Footings: 120 cy x $12 = $1,440. Slabs: 230 cy x $12 = $2,760. Total accelerator exposure: $1,440 + $2,760 = $4,200 on 350 cy, which simply does not exist in a summer bid of the same drawings. Carrying the adder moves the concrete material line from 350 x $172 = $60,200 to $64,400, about a 7 percent swing decided by the calendar, not the design.
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How Ruh handles concrete admixture
Ruh splits the concrete takeoff by element and mix design as it reads the structural sheets, so quantities arrive already separated into the buckets that carry different admixtures. It prices each bucket from the contractor's own price book, including the adders the contractor actually pays. The estimator confirms the seasonal assumptions, swaps mixes where needed, and signs off.
See concrete estimating softwareConcrete admixture: frequently asked questions
What are the most common concrete admixtures?+
Air entraining agents for freeze thaw exposure, water reducers and superplasticizers for workability and strength, accelerators for early set in cold weather, and retarders for hot weather. Larger projects add corrosion inhibitors, shrinkage reducers, and fibers. Most commercial pours carry at least one, and exterior concrete in cold climates almost always carries air.
Do admixtures change the price of concrete?+
Yes, every admixture is an adder on the per cy price from the ready mix supplier, from a dollar or two for air up to double digits per cy for non chloride accelerators or specialty products. The estimator's job is splitting the takeoff by mix so each cy carries the right adders rather than averaging everything at the plain mix price.
Why can't calcium chloride accelerator be used everywhere?+
Chloride attacks reinforcing steel, so specs commonly ban calcium chloride in reinforced concrete, post tensioned work, and anything with embedded metals. The substitute is a non chloride accelerator, which does the same scheduling job at a higher price per cy, and that difference belongs in any winter estimate.
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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.