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Thick rafts, dams, bridge piers and large foundations heat up as the cement hydrates and can crack, and big pours risk cold joints. A retarding superplasticiser or set retarder spreads the heat release and keeps each layer workable until the next one arrives.
General guidance based on the manufacturer data sheets. Site conditions differ: confirm the system with MCT before you start. Where we do not name a product, ask us and we will confirm the right one.
The engineer sets the pour sequence, layer thickness and temperature controls. Fix the admixture dosage by trial for the real haul time and placing rate (Sikament RB 850 PK p.2).
Sikament RB 850 PK, RB 858 PK and RB 918 are listed for mass concrete pours, with reduced thermal peaks and longer workability (Sikament RB 850 PK p.1; Sikament RB 858 PK p.1; Sikament RB 918 p.1). Starting dosage is 0.8–2.0 L per 100 kg cementitious material for RB 850 PK (p.2) and 400–1200 ml for RB 918 (p.2).
Microsilica concrete Mass concrete pours Ready mixed concrete Long-distance transport Pumped concrete Casting in hot climates To obtain Reduced thermal peaks High workability for longer periods Lower pumping pressure Delayed setting with longer workability … (TDS p.1)
Primary Uses Microslica concrete Mass Concrete Ready Mix Concrete Long-distance Concrete Pumped concrete Casting in hot climate To Obtain Reduced thermal peaks High workability for longer periods Lower pumping pressure Delayed setting for longer workability… (TDS p.1)
Ready mixed concrete Long hauls Pumped concrete Concrete containing Granulated Slag/ Pozzolans Mass concrete pours Hot weather concreting (TDS p.1)
Sika Plastiretard TM 100 C2 WR PK delays and spreads the heat release to reduce thermal stress, and lets work resume after several hours of interruption if the surface is protected from drying (p.1). Dose 0.2–2 % of cement (p.2). Sika Retarder-47 PK gives strong retardation for long hauls (p.1) at 0.2–2.0 % (p.1). Sika Plastiment-250 PK suits areas where large volumes are placed at one time (p.1).
Concreting in Hot Weather Plastiretard provides an effective set-retarding action that prevents a sudden rise in concrete temperature during setting. Its use becomes particularly essential: When ambient temperatures are high, In large-mass concreting works such as dams and other massive structure… (TDS p.1)
Sika® Plastiment®-250 PK is used as a general purpose admixture where the placing conditions for high quality concrete are more demanding elevated temperatures such as: Fair faced concrete, Pumped concrete, Ready mix concrete, Areas where large volumes must be placed at one time, High mechanical … (TDS p.1)
The right product here depends on your site. We confirm it before naming it.
Sika AER PK is used for dams, reservoirs and mass concrete structures (p.1) at 0.03–0.15 % of cement, set by air-meter trials (p.2). Air lowers strength; compensate with a plasticiser (p.2).
Sika® AER PK is used to produce easily workable and dureable concrete for: Roads, Runways and Taxiways, Aprons and hard Standings, Dams and Reservoirs, Mass Concrete Structure. (TDS p.1)
Add the admixture with the mixing water; the effect is higher if it goes in after 50–70 % of the water. Do not add it to dry aggregate or cement (Sikament RB 850 PK p.2). Never pre-mix admixtures in one tank: Sika Retarder-47 PK can form solids with some admixtures and block pumps and pipes (p.2).
Cure as early as possible (Sika Retarder-47 PK p.2). If a retarder is overdosed, keep the concrete moist during the extended set (Sika Plastiment-250 PK p.2).
A starting point for a site proposal. Quantities, prices and the final specification follow a site visit or photos.
| Step | Product | Pack | Source |
|---|---|---|---|
| 2. Use a retarding superplasticiser | Sikament RB 850 PK | 05 ltr jerry can | TDS p.1 · June 2025, Version 04.03 |
| 2. Use a retarding superplasticiser | Sikament RB 858 PK | 05 ltr jerry can | TDS p.1 · June 2025, Version 03.01 |
| 2. Use a retarding superplasticiser | Sikament RB 918 | 05 ltr jerry can 20 ltr plastic can 235 ltr drum 1000 ltr IBC Bulk supply in tanker is… | TDS p.1 · June 2025, Version 03.01 |
| 3. Add a set retarder for very large or interrupted pours | Sika Plastiretard TM 100 C2 WR PK | 05 ltr jerry can | TDS p.1 · August 2026, Version 01.01 |
| 3. Add a set retarder for very large or interrupted pours | Sika Plastiment-250 PK | 20 ltr plastic can 200 ltr drum | TDS p.1 · March 2026, Version 02.01 |
| 4. Dams and exposed mass concrete: air entrainment | Sika AER PK | 05 ltr jerry can | TDS p.1 · June 2025, Version 02.01 |
Yes, if it is properly compacted and cured. Plastiretard improves mechanical strength development (Sika Plastiretard TM 100 C2 WR PK p.1), and Sikament RB 850 PK is used to obtain higher ultimate strengths (p.1).
Plastiretard lets concreting resume after several hours of interruption, provided the surface was protected against drying (Sika Plastiretard TM 100 C2 WR PK p.1). The engineer decides whether a construction joint is needed.
It reduces the risk by delaying and spreading the heat release (Sika Plastiretard TM 100 C2 WR PK p.1). Pour sequence, insulation and curing still matter. Ask us: it depends on site conditions.
Ask us: it depends on site conditions. Sika Retarder-47 PK is used at 0.2–2.0 % of cement (p.1), set by laboratory trials (p.2).
Steps and product facts are taken from the manufacturer data sheets (page cited). Products are named only where the data sheet confirms the use; quantities follow a site visit or photos. General guidance: check the data sheet or ask us before you start.