Concrete Mix Design and Application
Cement
No need to seal before or during direction of work changes. Use water-cured cement with pH > 7 without substitutes. Chloride content should follow arid class 0.81.250.25 (0.40.33) without clay particles. Floating soft, sulfur, and chloride exposure should be within limits. Use CEM I, IIa, IIb (blue). Fineness should be 6 MnC for rolled types, and III’s, IV’s with 0-10 M or limestone I, II0’s and 15 MC I, II’s. V2/P/6 Coef = v1 + d3 .. d3 + y = 100Rd / D.
Water
Use water with a pH between 5 and 7, and hardness between 20 and 40. Perform additive tests before work, avoiding air-entraining chlorides. Maximum particle size: 20-300 microns in 0.5-2%. Address lamination and fragmentation. Use water-holding and anti-freeze admixtures. Controlled addition of shrinkage-reducing admixtures is recommended.
Aggregates
Use 10 hp (cl) 35 HS-C2S, with many superior special properties. Ensure consistency and cooling to resist arid conditions and water deprivation. Apply in three 300mm layers: dry, plastic, and soft. Maintain fluidity (margin). Curing should be initiated in two phases: fluid-plastic and final. Homogenization is crucial for different spill heights or transportation. Target density: 2.2 g/cm3. Hardened density: 2.5 (2.8-2). Compactness: P = 1-C. Permeability depends on the aggregate-cement ratio (0.5). Measure fine aggregate penetration at various pressures (over half).
Shrinkage and Compression
Shrinkage is related to volume and cement content, especially in thin sections (0.35 mass armed .2). Compression strength (fck) should be verified through trials. Calculation of all factors is essential, with a safety margin of -5%. Resistance is calculated using fcd and fck coefficients. Limit state design should be employed. Conversion of 15×30 piece trials is orientative. 28-day strength is typically used. Flexural strength (fxl/d1xd2) and concrete compressive strength (fcf) are important parameters.
Reinforcement and Durability
For mass less than 20, use 25mm reinforcement. Flexion should be less than 10. Maximum cement content: 400. Wear resistance is improved with longer curing and less water, along with surface treatment. Durability against external agents, repeated loads, or shock loads is crucial. Reinforcement corrosion should be considered based on the environment: I (interior), IIa (high humidity), IIb (chloride corrosion without marine influence), IIIa (chlorides within 5km of coast), IIIb and IIIc (tidal zones with non-marine chloride), IV (marine environment). Hormone durability is categorized as Qa (weak chemical attack), Qb (medium, sea), Qc (strong). Frost resistance without salt fluxes (F) and salt erosion (E) are also important.
Reinforcement Recommendations
Use 8D reinforcement if possible, otherwise, use 1.25D. Consult tables for nominal resistance (Rnom) and deflection separators. Coated reinforcement should be greater than 50mm with appropriate cover. Separate formwork and reinforcement. Protective coverings are essential. Temperature increases up to 5-106º can cause expansion and strength loss.
Concrete Mix and Placement
Consider temperature (HM, HA, HP), resistance characteristics, consistency (SPBF), and size (D). Mix proportions should be adjusted for the most unfavorable environment. Typical mix: 1 cement, 1.5 water, and 2-3 aggregate. Central mixing is preferred for quality control. Store, dose, mix, and transport concrete carefully. Dry or plastic concrete should be vibrated. Soft and fluid concrete is suitable for formwork. Maintain temperature between 5 and 40ºC during placement. Independent control of materials and execution is necessary. Stamped receipts are not required. Curing duration: 3, 2, and 1 month. Use appropriate water and aggregates. Control other additive content and loss on ignition.
Testing and Quality Control
If tested strength (fest) is greater than design strength (fck), it is acceptable. If fest is less than 90% of fck, recalculate and perform additional tests. Ultrasonic hammer testing can provide complementary information. Actual resistance should be determined for each batch under the same conditions as the work. Lightweight concrete (0.3-1.8 density) can be used with non-resistant aggregates and minimal porosity for frost resistance and capillary structure. Cellular concrete (with bubbles, without fines) is suitable for heavy radioactive areas and can achieve densities up to 2.8 when reinforced with fibers or staples. High-strength concrete (HAR) can exceed 550 MPa with CEM I 52.5, using gunite or semi-dry methods. Consistency should be tested with a penetration test (3 samples maximum). Maximum penetration: <50mm for surfaces, <65mm for other areas. Prior resistance should be between 30-40 (without references above). Lab testing should include 2 samples per mix. Resistance should be >130% fck. Control mix proportions (1+2-3) to achieve target fck. Reduced testing (100x100mm cubes) can be used with 2 samples. Statistical rounding is important. For lots larger than 500m2, test 100 flexural and surface elements. Seal double with a minimum of 3 samples. For fck>25, use 2 batches; for fck between 25-30, use 4 batches; for fck>35, use >6 batches. If n<6, use kn.X1 for fest. If n>6, use fest=(2X1+X2../m-1). Xm