About Fosroc Conplast RP264

Fosroc Conplast RP264 is a chloride-free water-reducing and retarding admixture based on selected lignosulphonate materials. It is supplied as a dark brown liquid that instantly disperses in water and is added to concrete to improve the effectiveness of the mixing water and to provide controlled retardation of the initial cement hydration.

Important correction: Conplast RP264 is NOT a shrinkage-reducing admixture (SRA). It is a retarding, water-reducing admixture in the ASTM C494 Type B (retarding) and Type D (water-reducing and retarding) classes. Its function is to disperse the fine particles in the mix so that less water is needed for a given workability, while simultaneously delaying the onset of cement hydration to extend the period during which the concrete remains placeable and workable.

For Space Arc Engineering customers across Delhi NCR and Pan-India, Conplast RP264 is most valuable in ready-mixed concrete (RMC) operations where concrete must survive long transit and pumping times, and in hot-weather concreting where rapid stiffening and premature setting are a constant risk. By combining water reduction with controlled set retardation, it helps maintain workability of ready-mixed concrete, supports lower water-cement ratios and is well suited to low-cohesion mixes. As an authorised Fosroc distributor and applicator, Space Arc Engineering supplies Conplast RP264 alongside the wider Conplast admixture range, with technical support on dosage trials and mix design.

The technical insight

Conplast RP264 works through two combined actions, and neither involves the surface-tension mechanism of a shrinkage-reducing admixture. First, the lignosulphonate molecules adsorb onto and disperse the fine cement particles, breaking up flocs and freeing trapped water; this dispersion improves the effectiveness of the mixing water and allows the same workability to be achieved at a reduced water content. Second, the same chemistry delays the initial hydration of the cement, producing controlled retardation that extends the working and placing window. Because the product is chloride-free (nil chloride to BS 5075 / BS:EN 934), it is suitable for reinforced and prestressed concrete where chloride-induced corrosion must be avoided. At normal dosages it entrains less than 2% additional air, so it does not behave as an air-entraining agent. The cementitious content used for dosage calculation includes supplementary materials such as PFA, GGBFS or microsilica.

Where it is used

• Ready-mixed concrete requiring extended workability over long transit and pumping distances
• Hot-weather concreting where extended working time and delayed set are needed
• Reducing water-cement ratio at constant workability to improve concrete quality
• Low-cohesion concrete mixes that benefit from improved fine-particle dispersion
• Mass and structural concrete pours where controlled retardation reduces the risk of cold joints
• Concrete using supplementary cementitious materials (PFA, GGBFS, microsilica)

Key advantages

• Chloride-free (nil chloride content), suitable for reinforced and prestressed concrete
• Reduces water demand for a given workability, allowing lower water-cement ratios
• Controlled retardation extends working time and helps maintain workability of ready-mixed concrete
• Particularly effective in hot-weather concreting and long-haul RMC placements
• Instantly disperses in water for easy, uniform batching
• Adds less than 2% additional entrained air at normal dosages
• Compatible with PFA, GGBFS and microsilica blended cements
• Complies with BS 5075, BS:EN 934-2 and ASTM C494 Type B and Type D

Limitations & considerations

• It is a retarding water-reducing admixture, not a shrinkage-reducing admixture (SRA) and not a high-range superplasticiser (PCE or SNF type)
• Optimum dosage must be established by site trial; over-dosage can cause excessive retardation
• Must be added to the mixing water or wet mix, never to dry cement
• Set retardation is influenced by ambient temperature, cement type and mix design, so behaviour should be verified on the actual mix
• Should be protected from freezing; the product freezes at approximately -4 deg C
• For very high water reduction or flowing concrete, a dedicated superplasticiser may be more appropriate

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Conplast RP264

Conplast RP264 sits in the water-reducing and retarding (ASTM C494 Type B/D) segment of the Fosroc Conplast admixture range, distinct from plasticisers and high-range superplasticisers. Within the Conplast family it is the lignosulphonate-based retarding choice, complementing normal water reducers and superplasticisers used where higher water reduction or flow is needed. Comparable lignosulphonate-based retarding water reducers in the Indian market include BASF MasterPozzolith / Pozzolith (now MBCC/Master Builders Solutions), Sika Plastiment, and Chryso retarding admixtures. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering positions Conplast RP264 for ready-mixed and hot-weather concrete where extended workability and controlled set, rather than shrinkage reduction, are the objective.

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