Classification and treatment measures for temperature cracks in mass concrete

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Core treatment principles: surface sealing for leakage prevention → deep grouting for reinforcement → structural strengthening across the entire structure plus leakage prevention reconstruction. First, stop cracks and stabilize temperatures; then carry out repairs and reinforcements; finally, implement long-term monitoring, with emphasis on durability, load-bearing capacity, and leakage prevention as the three key aspects. Analysis of Crack Resistance Techniques for Mass Concrete in Water Conservancy Projects – Water Conservancy Construction – Zhulong Water Conservancy Project Forum. Crack issues are addressed in a hierarchical manner, starting with minor cracks, followed by surface cracks, deep cracks, and through-cracks; attention is given to structural safety, impermeability, and durability, with testing and assessment carried out first before targeted treatment is applied. I. Preliminary general procedures (to be carried out on all cracks first): Comprehensive inspection: measuring the width, depth, length, direction of the cracks, determining whether they are interconnected, and checking for water seepage, in order to assess the level of risk ； Clean the joint surface: Remove loose debris, oil stains, and impurities; dry it out / ensure no standing water is present ； Eliminate the causes: Investigate any remaining temperature differences, contraction, water cooling, and insulation defects; first stabilize the temperature field to prevent further expansion of cracks. II. Fine cracks (δ≤0.1mm, h≤30cm): Characteristics – Surface-level hair-like cracks; no water seepage, and they do not affect strength or waterproofing. Treatment measures: Grinding, sealing, maintenance, monitoring. Process: Surface grinding and cleaning → High-pressure air blowout to remove dust ； Applying cement-based penetrating crystalline material / Flexible epoxy thin-layer sealing ； Enhance the moisture and heat retention of the surface layer to improve its durability, resistance to carbonation, and resistance to weathering ； For subsequent monitoring, deep grouting is not required. III. Surface cracks (δ≤0.2mm, h≤1m): Hazards: Affect frost resistance, weathering resistance, and durability; prone to inducing deeper cracks. ① Crack sealing method: Cut V/U-shaped grooves along the cracks and clean them thoroughly ； Dry joint: Filled with epoxy mortar / polymer cement mortar ； Wet/micro-seepage cracks: Repaired using a fast-setting sealant specific for hydraulic applications, combined with flexible waterproof mortar. ②Overall surface protection: For large-scale surface cracks, apply elastic waterproof coating throughout the area, as well as an anti-corrosion and leak-proof protective layer ； Enhance external insulation to reduce the temperature difference between the inside and outside, thereby preventing cracks from spreading deeper. IV. Deep cracks (δ≤0.4mm, h=1～5m, h＜1/3 of the dam block width, L＞2m): Hazards include reduced structural integrity, local stress concentration, and a risk of water seepage. ① Chemical grouting at low pressure and low speed is used; grouting holes and vent holes are installed, with holes drilled along the joints and at diagonal angles arranged in a staggered pattern ； Use low-viscosity epoxy grouting materials or polyurethane grouting materials; pouring can be carried out under controlled pressure to fill deep cracks and restore bond strength ； ②Surface sealing: First, seal the cracks to prevent grout from leaking out ； By combining internal water flow regulation and optimizing the temperature gradient within the dam, residual temperature stresses are reduced ； After maintenance, recheck the density and use core drilling to assess the grouting effectiveness. V. Through-cracks (running from the foundation upward and throughout the entire structure; pose the greatest threat by affecting strength and waterproofing). Comprehensive reinforcement measures include high-pressure consolidation grouting at deep levels + contact grouting, along with filling of gaps to block water infiltration pathways ； If necessary, reinforce with steel bars / prestressed anchor cables / driven rebar to restore the overall structural system ； Special anti-seepage treatment: installation of anti-seepage curtains and water-stop structures to enhance the dam’s anti-seepage integrity ； Review of structural zoning to verify dam stability, stress, and temperature control parameters; weight reduction, reinforcement, and optimized zoning for temperature control may be undertaken if necessary ； Long-term online temperature + deformation monitoring to dynamically assess crack stability. VI. Special condition treatment: Active cracks due to seepage – first seal them, then carry out structural reinforcement grouting, and finally seal the surface ； Sudden temperature drops cause new cracks: immediately enhance surface insulation, suspend water supply during cooling, and slow down the rate of temperature reduction. Temperature-related cracks at the junction between old and new concrete: roughen the interface, clean it, apply an interface agent, and carry out reinforcement grouting to prevent further cracking due to temperature differences between the old and new concrete. VII. Acceptance and Post-construction Management: After repairs are completed, maintain moisture and heat to reach the designed age ； Core drilling, water pressure testing, and ultrasonic testing to assess density and integrity ； Establish a long-term monitoring record for cracks (width, opening degree, seepage rate, ambient temperature), and conduct regular remeasurements for early warning purposes.