CBGM Wind Turbine Grout Construction Guide

Correct construction is essential for wind turbine foundation grouting. Even high-performance grout can fail to deliver the expected result if the base surface is not prepared properly, water dosage is not controlled, placement is interrupted, or curing is ignored.

This guide summarizes the recommended site procedure for CBGM wind turbine grout used in base plate grouting, anchor bolt grouting and foundation secondary grouting.

1. Material Storage and Site Protection

Store wind turbine grout in a dry, ventilated indoor area. Keep the material away from rain, moisture, freezing and direct sunlight. On site, the grout bags should be protected with shade or light-colored cover sheets to reduce heat absorption before mixing.

During transport from the warehouse to the construction area, protect the material from direct sun and water exposure. Do not use damp or caked material.

2. Water Quality and Water Dosage

Use clean tap water or potable water. Do not use water containing oil, acid, alkali or organic impurities. Water dosage must be measured accurately with an electronic scale. Do not use rough volume marks, spring scales or visual estimation.

For CBGM-130 projects, a typical water dosage may be around 2.5 kg per 25 kg bag, but the final dosage must follow the latest product technical data sheet and project approval. Extra water is not allowed during construction because it can reduce strength, cause segregation and increase cracking risk.

3. Tools and Equipment

Before grouting, prepare the required tools and equipment:

• Mortar mixer or suitable grout mixer

• Water tank and clean water supply

• Electronic scale for water measurement

• Metal buckets or transport containers

• Formwork and sealing materials

• Plastic film, wet geotextile, burlap or curing cloth

• Grout pusher or guide strip

• Thermometer for weather and material temperature control

• Flow test device when site flowability testing is required

4. Base Surface Preparation

Remove laitance, dust, loose concrete, oil, wax, mud and other contaminants from the concrete foundation surface. The base should be sound, clean and slightly roughened to improve contact with the grout.

Pre-wet the concrete surface before grouting. For normal conditions, wet the surface sufficiently before placement and remove standing water before grouting begins. In hot weather, pre-wetting should be planned earlier to prevent rapid water loss from the grout.

5. Mixing Procedure

Place the mixer as close as possible to the grouting area. Long transportation after mixing should be avoided because it may cause loss of flow, segregation or delayed placement.

Add the measured water and grout powder according to the recommended mixing sequence. Mix until the material becomes uniform and free of lumps. The mixing time should be adjusted according to mixer efficiency. Avoid excessive mixing time because it may increase material temperature and reduce workability.

If steel fiber is supplied separately, first mix the grout powder and water evenly. Then add the steel fiber slowly and continue mixing until the fibers are uniformly dispersed in the grout.

6. Formwork Installation

Formwork must be firm, stable and fully sealed. It should be able to resist the side pressure generated by the fluid grout. All joints and gaps must be sealed before grouting to prevent leakage.

For wind turbine base plate grouting, the formwork height should be higher than the underside of the base plate to provide enough grout head pressure. Use non-absorbent or low-absorbent formwork materials where possible.

7. Grouting Method

Grouting should be carried out continuously from one side until the grout flows out from the opposite side. This one-side grouting method helps push trapped air out and improves full-contact filling under the base plate.

Do not grout from two opposite sides at the same time. This may trap air inside the grout layer and create voids. During placement, vibration is strictly prohibited. If assistance is needed, use a grout pusher only along the bottom and in the flow direction.

For large-volume grouting, organize mixing, transport and placement in advance. Each placement should be completed within the planned working time.

8. Curing

After grouting, immediately cover the exposed grout surface with plastic film and wet curing materials. This prevents rapid water evaporation, surface skinning and early shrinkage cracking.

After the grout has hardened and the surface temperature becomes close to the ambient temperature, continue wet curing. Keep the grout moist for at least 7 days unless the latest product technical data sheet specifies another method.

Avoid vibration or loading near the freshly placed grout within the early hardening period. If formwork removal is required, follow the approved project schedule and avoid early removal.

9. Cold-Weather Grouting Notes

When the average daily temperature is low, winter construction measures should be used. Preheat the foundation surface if required, remove standing water and protect the grout immediately after placement with plastic film and insulation materials.

Do not water-cure under negative-temperature conditions. If the ambient temperature is below the minimum construction temperature or faster strength development is required, artificial heating or an insulated shelter may be needed.

10. Hot-Weather Grouting Notes

In hot weather, avoid construction under direct sunlight whenever possible. Morning or evening grouting is preferred. Before grouting, protect the foundation, formwork, equipment and material from excessive heating.

Rapid surface drying can cause shrinkage cracks. After placement, cover the grout surface immediately and keep it moist during curing.

11. Common Problems and Prevention

Segregation or Layering

Common causes include excessive water, poor mixing and long-distance transportation after mixing. Measure water accurately, follow the recommended mixing method and keep the mixing station close to the work area.

Cracking After Grouting

Cracking may be related to early formwork removal, vibration, rapid drying, poor curing or a large temperature difference between the grout surface and the internal grout. Use proper insulation, avoid cold-water curing during high hydration heat, and maintain wet curing after the temperature becomes stable.

Voids Under the Base Plate

Voids may result from trapped air, insufficient grout head, poor sealing or interrupted placement. Use one-side continuous grouting and make sure the grout flows out from the opposite side.

Technical Support

For project-specific guidance, send ZRETE your foundation drawings, grout thickness, construction temperature, required strength, selected CBGM grade and placement method. Our technical team can help review the grouting plan and recommend suitable site control measures.