Geopolymer Concrete with Lightweight Artificial Aggregates.

Area of Science:

• Materials Science
• Civil Engineering
• Concrete Technology

Background:

• Geopolymer concrete (GPC) offers a sustainable alternative to traditional Portland cement concrete.
• Lightweight artificial aggregates can reduce the density of GPC but may affect mechanical properties.
• Optimizing the composition of pozzolanic additives and activators is crucial for GPC performance.

Purpose of the Study:

• To determine the optimal physical and mechanical properties of geopolymer concrete (GPC) incorporating lightweight artificial aggregate.
• To investigate the influence of fly ash-slag (FA-S) mix proportions and sodium hydroxide (NaOH) molarity on GPC characteristics.
• To evaluate the effect of NaOH impregnation on the interfacial transition zone (ITZ) between aggregate and matrix.

Main Methods:

• Systematic variation of pozzolanic additive content (200-600 kg/m³), FA-S ratio (0-100%), and NaOH molarity (8-12 M).
• Impregnation of lightweight artificial aggregate with NaOH solution to enhance matrix adhesion.
• Assessment of compressive strength, water absorption, density, and thermal conductivity of geopolymer lightweight concrete (GLC).

Main Results:

• Optimal GLC properties were achieved with 400 kg/m³ of pozzolanic additives (50% FA-S, 50% FA) and 10 M NaOH.
• Increasing NaOH molarity from 8 M to 10 M significantly improved compressive strength (up to 54%).
• Higher pozzolanic additive content (400 kg/m³) reduced water absorption to 18%; highest thermal conductivity was 0.463 W/m·K.

Conclusions:

• The study identified optimal mix parameters for geopolymer lightweight concrete with enhanced mechanical and physical properties.
• NaOH impregnation effectively improved the interfacial transition zone (ITZ), leading to better aggregate-matrix bonding.
• Fly ash-slag mixes and controlled NaOH concentration are key factors in developing high-performance geopolymer lightweight concrete.