How to Steam Cure GRC Components in Low-Temperature Environments? Qinglong GRC Special Technology for Winter Low-Temperature Curing

In winter, when ambient temperatures fall below 5°C, the production of GRC components faces enormous challenges. Conventional natural curing essentially comes to a standstill, and steam curing becomes a necessity. However, steam curing at low temperatures is not simply a matter of raising the temperature; it requires a refined set of methods to address the special challenges of "low-temperature start-up, large temperature-difference control, condensation prevention, and freeze-damage prevention." Drawing on many years of winter production experience in the severe cold regions of northern China, Qinglong GRC has developed a mature and reliable low-temperature steam curing technology system.

In the production of GRC components for supporting facilities at a Harbin Ice and Snow World, workshop temperatures dropped as low as -10°C. Qinglong activated its winter production contingency plan: first, raw materials (sand and cement) were moved into a heated warehouse 24 hours in advance to preheat them to above 5°C, and mixing water was heated to 40°C. Warm-air heaters kept the molding workshop above 10°C. Components were cured in their molds, covered with insulating blankets, and demolded only after reaching a strength of 5 MPa or more before entering the curing kiln. The kiln adopted a "step-wise heating" regime: a slow 4-hour preheating from room temperature to 20°C, followed by heating at the normal rate up to the constant curing temperature. With these measures, components meeting performance standards were successfully produced under severe cold conditions. Testing showed that both their early and later-age strengths were identical to those of products made in normal-temperature seasons.

Preheating and Insulation of the Production Environment

Curing starts at the production stage. All raw materials, molds, and equipment should be moved into an insulated workshop (≥10°C) for preheating before production. Mixing water may be heated to 30-50°C but should not exceed 60°C to prevent false setting of the cement. The mixing plant and delivery pipelines should be insulated. The molding workshop must be kept enclosed and maintained at above-freezing temperatures using hot-air heaters and similar equipment.

Pre-curing in Molds and Critical Strength Control

After molding, components must not be demolded immediately. Plastic film and insulating quilts should be placed over the molds, and pre-curing in the molds should be carried out under above-freezing workshop conditions. The goal of this stage is for the components to acquire the "critical strength" needed to withstand demolding operations and thermal stress, generally requiring a compressive strength of ≥5 MPa. Before critical strength is reached, demolding and moving are strictly prohibited.

The Curing Kiln's "Slow Start, Gradual Heating and Cooling" Regime

This is the core of low-temperature curing. When components enter the kiln, the temperature inside the kiln should be close to the workshop temperature. Heating is divided into two stages: in the first stage, the kiln temperature is raised at an extremely slow rate of ≤5°C/hour from a low temperature (e.g., 0°C) to 15-20°C; the purpose of this stage is to preheat the components uniformly throughout and eliminate the temperature difference between the interior and exterior. In the second stage, the temperature is raised at the normal rate (10-15°C/hour) to the set constant curing temperature (usually 40°C). The constant-temperature period may be extended by 10%-20%. The cooling stage must be strictly rate-controlled (≤10°C/hour), and when components leave the kiln, the temperature difference between their surface and the outdoors should not exceed 20°C; otherwise, a transition through a buffer room is required.

Anti-Condensation and Drying Measures

When cold components enter the hot, humid curing kiln, condensation easily forms on their surfaces, causing water spots or uneven strength. Before entering the kiln, the component surfaces can be briefly preheated with low-temperature hot air. After curing is complete, thorough hot-air drying must be carried out, reducing the moisture content of the components to a safe level before they leave the kiln, to prevent them from freezing immediately in the low-temperature environment.

Whole-Process Temperature Monitoring and Recording

Low-temperature curing requires whole-process temperature monitoring. Thermocouples should be placed inside the components (especially at thick, massive sections) and on their surfaces to monitor the temperature difference between the core and the surface in real time, keeping it within 20°C. All temperature and humidity data are recorded automatically, producing traceable curing curves as part of the quality archive.

Steam curing in low-temperature environments is a severe test of a manufacturer's technical and management capabilities. Through environmental control, process adjustments, and whole-process monitoring, Qinglong GRC's winter production system ensures that GRC products with stable performance and reliable quality can be produced even under severe cold conditions, meeting the year-round, uninterrupted construction needs of projects everywhere.