A persistent set of troubles plagues construction contractors across civil infrastructure, bridge and municipal engineering projects, including accumulated construction slurry, concrete bleeding and cracking, excessive pollutant discharge from construction wastewater, and poor water retention of mortar. As a water-soluble high-molecular polymer manufactured in China, polyacrylamide (abbreviated as PAM) features four core properties: flocculation, thickening, water retention and adhesion. It serves as a cost-effective, stable-performance multi-functional chemical additive for construction, with wide applications covering construction wastewater treatment, concrete admixtures, underwater pile foundation construction, dry-mix mortar production, tailings and sand-gravel recovery, and more. Combining practical on-site construction practices, this paper provides a comprehensive overview of the functions, type selection criteria and operational guidelines of domestically produced polyacrylamide for global construction industries.
1. Classification of Polyacrylamide & Targeted Selection for Construction Applications
Polyacrylamide falls into three categories: anionic, nonionic and cationic. Each construction scenario requires a specific grade; mismatched models readily lead to caking, efficacy loss and compromised performance.
- Anionic Polyacrylamide (APAM, molecular weight: 12–19 million)
The most widely adopted grade in construction. Its molecular chains contain abundant hydrophilic groups, delivering outstanding flocculation, thickening and water retention capacity. Suitable for construction slurry dewatering, sand washing wastewater treatment, concrete water retention and thickening, anti-dispersion for underwater pile foundations, as well as water retention and solidification of subgrade soil.
- Nonionic Polyacrylamide (NPAM)
Low molecular charge and moderate viscosity. Primarily applied to repair mortars, thin-layer self-leveling compounds and low-alkali special building materials, as it rarely reacts with calcium ions contained in cement.
- Cationic Polyacrylamide (CPAM)
Rarely incorporated into concrete and mortar systems. Mainly used for dewatering biochemical construction sludge and septic tank sludge on construction sites; direct blending into cement slurry is not recommended.
2. Application of Polyacrylamide in Key Construction Scenarios
2.1 Concrete Admixtures: Mitigating Bleeding, Segregation and Drying Shrinkage Cracking
Ready-mix concrete, pumpable concrete and underwater cast concrete are prone to aggregate settlement, surface bleeding and microcracks formed during subsequent curing. A small dosage of anionic polyacrylamide forms a reticulated structure within the cement slurry to trap free water and stabilize the workability of mortar.
- Core functions: Reduce slurry leakage and stratification, inhibit drying shrinkage cracks, and improve concrete impermeability;
- Dosage specification: Added at 0.005%–0.02% by total cement mass. Overdosage causes excessive slurry viscosity and drastically increases pumping resistance;
- Matching products: Anti-dispersion admixtures for underwater concrete, water-retaining thickeners for ready-mix concrete, special admixtures for precast components.
2.2 Pile Foundation & Underwater Engineering: Core Raw Material for Non-Dispersible Underwater Concrete
For underwater bridge pile foundations, river cofferdams and underwater repair works, conventional concrete collapses and loses cement upon contact with water, resulting in severely reduced structural strength. Anti-dispersion agents compounded with high-molecular-weight anionic polyacrylamide rapidly form high-viscosity networks when exposed to water, ensuring concrete remains non-stratified and non-dispersible after submergence and securing the structural strength of underwater works.
2.3 Dry-Mix Mortar & Repair Putty: Thickening & Water Retention for Improved Workability
A small amount of nonionic polyacrylamide blended into wall repair mortar, self-leveling floor compounds and waterproof putty extends the open time of mortars, prevents cracking and powdering in thin-layer construction, enhances inter-particle adhesion of raw powders, and delivers smooth workability without premature water loss and solidification.
2.4 Construction Wastewater Treatment: Rapid Sedimentation of Sand-Washing Slurry & Foundation Pit Mud
Construction activities generate massive volumes of sand-washing wastewater and foundation pit slurry with high suspended solid concentrations; direct discharge causes environmental pollution. Dosing anionic polyacrylamide into slurry water quickly adsorbs fine sand and gravel particles to form dense flocs, enabling fast solid-liquid separation. The clarified water can be recycled for on-site concrete mixing, while dewatered sludge facilitates filter pressing and off-site transportation, substantially cutting wastewater treatment costs.
2.5 Subgrade & Soil Stabilization: Moisture Retention & Dust Suppression for Earthworks
In road subgrade and backfilling projects, diluted polyacrylamide solution sprayed onto subgrade soil locks soil moisture to suppress dust, boosts soil cohesion, mitigates soil erosion induced by rainwater washing, and simplifies subgrade curing procedures.
3. Standard Operating Procedures for Polyacrylamide On-Site Construction Use
- Dilution formulation: Prepare aqueous solutions with clean tap water at a mass concentration of 0.1%–0.3%;
- Agitation control: Stir at low speed for 30–90 minutes until fully dissolved without white gel agglomerates. High-shear stirring is prohibited as it breaks molecular chains;
- Feeding method: Never add dry powder directly into mixers. Dissolve powder into aqueous solution in advance and introduce it together with mixing water;
- Storage requirements: Store dry powder in cool, dry environments. Prepared aqueous solutions shall be consumed within 24 hours to avoid viscosity degradation.
4. Common Misoperations on Construction Sites
- Arbitrary over-dosing: Excessive polyacrylamide leads to overly viscous concrete that blocks pumping pipelines and lowers compressive strength;
- Dissolution in hard water or wastewater: Calcium and magnesium ions in water disrupt polymer molecular structures and drastically weaken flocculation and water retention performance;
- Blending cationic PAM into concrete: Cement slurry contains high concentrations of calcium ions, which instantly trigger severe flocculation and caking of cationic polyacrylamide, rendering it completely ineffective;
- Long-term storage of aqueous solutions: Solutions stored for more than 48 hours experience continuous viscosity loss and fail to meet construction performance standards.
5. Conclusion
Domestically manufactured Chinese polyacrylamide is far more than a single-purpose water purification chemical; it acts as a multi-functional additive running through the full construction workflow. From preliminary earthwork and subgrade treatment, underwater pile foundation construction, mid-stage concrete and mortar batching, to on-site slurry and wastewater treatment, selecting the corresponding polyacrylamide grade rationally optimizes construction quality, eliminates bleeding and cracking defects, realizes wastewater recycling and reduces overall construction costs. Pre-construction lab trials are recommended with local sand, gravel and water samples to determine the optimal dosage and maximize polyacrylamide performance.