Properties of the Base Raw Material
1. Base liquor characteristics: solids content, water reduction rate, slump retention capability, and initial adsorption vs. sustained-release properties;
Molecular weight, charge density, and functional group type (ether-type vs. ester-type; high slump retention vs. high water reduction);
Base liquor sensitivity: sensitivity to cement type, temperature, and silt/clay content in aggregates.
2. Compatibility of compounded additives: defoamers, air-entraining agents, retarders (sodium gluconate, sodium citrate, sucrose, phosphates, etc.), slump-keeping agents, thickeners, clay-tolerance agents, accelerators, etc.
Key focus: Preventing flocculation, phase separation, precipitation, or loss of efficacy among additives (e.g., certain organic retarders are prone to incompatibility with specific defoamers).
Cementitious Material System (Critical Variables)
1. Cement types: Ordinary Portland cement, slag cement, fly ash cement, and calcium aluminate cement; cement C₃A content, gypsum type (dihydrate/anhydrite), and alkali content;
2. Supplementary cementitious materials (SCMs): Fly ash (Grade I/II, carbon content), ground granulated blast-furnace slag (GGBS), silica fume, and limestone powder;
3. Total content and proportions of cementitious materials; risk of fluctuations between different cement batches.
Aggregate Conditions
1. Content of silt, clay lumps, and stone powder; clay type (montmorillonite is the most detrimental, as it significantly adsorbs polycarboxylate superplasticizers—the mix design must consider the addition of clay-mitigating agents);
2. Aggregate gradation, particle shape (flakiness and elongation), water absorption, and sand fineness modulus;
3. Fluctuations in aggregate moisture content (affecting the effective water-binder ratio on-site).
Concrete Design Specifications and Construction Requirements
1. Target performance: initial spread/slump, slump retention duration (1h/2h), and assessment of segregation or bleeding risks;
2. Strength grade, water-binder ratio, pumping distance, and application type (e.g., underwater placement, self-compacting concrete, or precast elements); 3. Setting time requirements: short setting times for precast elements; extended retardation for mass concrete and long-distance pumping;
4. Air content control: stable air content required for road concrete and frost-resistant concrete;
5. Architectural (fair-faced) concrete: low bubble content required; strict balance between air entrainment and defoaming.
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