Concrete Repair Mortars

Fosroc Renderoc S

Single component structural grade polymer modified concrete reinstatement mortar.


Renderoc GP is a general purpose concrete reinstatement mortar which can be used as a render as well as for all types of patch repairs. Renderoc GP is alkaline in nature and will protect embedded steel reinforcement. The mortar is suitable where superior resistance is required to chlorides and carbon dioxide.


  • Can be applied by the dry spray process for fast, exceptionally high-build repairs with enhanced characteristics
  • Low permeability provides good protection against carbon dioxide and chlorides
  • Excellent bond to the concrete substrate
  • Shrinkage compensated
  • Pre-bagged to overcome site-batched variations — only the site addition of clean water required
  • Contains no chloride admixtures
  • Renderoc Galvashield XP compatible

Standards compliance:

Renderoc GP has been approved by the British Board of Agrément, Certificate No. 98/3461


Renderoc GP is supplied as a ready to use blend of dry powders which requires only the site addition of clean water to produce a highly consistent, medium-weight repair mortar for general purpose use. The material is based on Portland cement, graded aggregates, special fillers and chemical additives to provide a mortar with good handling characteristics, while minimising water demand.

The product exhibits excellent thermal compatibility with concrete and good water repellent properties. The low water requirement ensures fast strength gain and long-term durability. Renderoc GP is designed for vertical, overhead or horizontal use. It can be applied up to 20 mm thickness in sections overhead and 30 mm thickness in vertical sections. Up to 100 mm thickness can be achieved in small pockets or by the use of formwork. In horizontal locations, Renderoc GP can be applied up to 100 mm thickness. Thicker sections can be built up in layers. The material should not be applied at less than 10 mm thickness. Thicknesses greater than 20 mm overhead and 30 mm vertically in large areas can be achieved by spray application. Consult the local Fosroc office for further information.


The following results were obtained at a water : powder ratio of 0.18 and temperature of 20°C.

Test method Typical result:

  • Compressive strength - (BS 1881 Pt 116 — dry cure): 9 N/mm2 @ 1 day 28 N/mm2 @ 28 days
  • Flexural strength (BS 6319 Pt 3: 1983): 7.0 N/mm2 @ 28 days
  • Water absorption ISAT (BS 1881 Pt 5: 1970) — 10 minutes: 0.18 ml/m2/sec 2 hours: < 0.06 ml/m2/sec
  • Chloride diffusion (Taywood Method): 4 x 10–10 cm2/sec
  • Carbon dioxide barrier — Equivalent thickness of concrete to Renderoc GP @ 10 mm (Taywood Method): 220 mm
  • Equivalent thickness of air to Renderoc GP @ 10 mm (Taywood Method): 60 metres
  • Coefficient of thermal expansion: 7 to 12 x 10–6/°C

Setting time (BS 5075) —

Initial set:
3 hours, 30 minutes

Final set:
4 hours

Fire rating:
(BS 476 Pt 6: 1968 and BS 476 Pt 7: 1971): Class 0

Fresh wet density:
Approximately 1850 kg/m3 dependent on actual consistency used

Chemical resistance:
The low permeability of Renderoc GP severely retards chemical attack in aggressive environments. The cured mortar is resistant to acid gases, chloride ions, oxygen and water


Renderoc GP should not be used when the temperature is below 5°C and falling. Do not mix part bags. The product should not be exposed to moving water during application.

Exposure to heavy rainfall prior to the final set may result in surface scour. If any doubts arise concerning temperature or substrate conditions, consult the local Fosroc office.


Store in unopened bags in cool dry internal conditions. The product has a shelf life of 12 months from the date of manufacture if kept in dry storage in the original, unopened bags.

If stored at high temperatures and/or high humidity, the shelf life may be reduced to less than 6 months.


Health and safety:
For further information refer to appropriate Product Safety Data Sheet.

Renderoc GP is non-flammable.
For further information, refer to the Product Safety Data Sheet.
Nitoprime Zincrich Plus and Fosroc Solvent 102: are flammable. Keep away from sources of ignition. No Smoking. In the event of fire, extinguish with CO2 or foam.
Do not use a water jet.

Flash points:
Nitoprime Zincrich Plus: 41°C
Fosroc Solvent 102 33°

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