Performance Evaluation of Cementless Composites with Alkali-Sulfate Activator for Field Application

Traditional cement production contributes significantly to global CO2 emissions. Alkali-activated composites (AAC) have been proposed as an alternative to ordinary Portland cement (OPC). However, the field application potential of AAC remains unclear. While prior research has shown that AAC can form hydration products similar to OPC, the acid resistance and environmental benefits of AAC have not been fully evaluated. This gap motivated the current study to assess the mechanical and chemical performance of AAC in real-world conditions. The study also aimed to quantify the global warming potential (GWP) of AAC compared to OPC. No prior work had resolved the exact binder weight ranges for optimal AAC performance. This uncertainty drove the investigation into AAC's viability for field use. The need to compare AAC and OPC in terms of acid resistance and CO2 emissions is critical for sustainable construction practices. This paper addresses these questions by analyzing AAC's performance under controlled conditions.

The study aimed to evaluate the performance of alkali-activated composites (AAC) with an alkali-sulfate activator for field application. Specifically, the researchers sought to compare the mechanical strength, acid resistance, and environmental impact of AAC with ordinary Portland cement (OPC). The goal was to determine whether AAC could serve as a viable alternative to OPC in real-world construction. By analyzing the hydration products and binder weight requirements, the study aimed to assess AAC's suitability for practical use. The researchers also wanted to quantify the global warming potential (GWP) of AAC compared to OPC. This investigation was motivated by the need to reduce CO2 emissions in construction materials. The study focused on binder weight ranges that meet target geltime requirements. The findings could inform decisions about adopting AAC in construction projects.

The study used a combination of mechanical testing, microstructural analysis, and environmental impact assessment. Researchers prepared alkali-activated composites (AAC) with an alkali-sulfate activator and compared them to ordinary Portland cement (OPC). They measured homogel strength at 7 days of age by increasing binder weight by 100 kg/m³. Matrix microstructures were analyzed using hydration product identification techniques. Acid resistance was tested in HCl and H₂SO₄ solutions. Global warming potential (GWP) was calculated based on binder weight ranges. The study also estimated binder weight ranges that satisfy target geltime (20–50 s). This approach allowed the researchers to evaluate AAC's performance in controlled and simulated field conditions. The analysis combined both qualitative and quantitative methods to assess AAC's viability.

The homogel strength of ordinary Portland cement (OPC) increased by 0.9 MPa at 7 days when binder weight increased by 100 kg/m³. Alkali-activated composites (AAC) showed a larger increase of 5.0 MPa under the same conditions. Microstructural analysis revealed that AAC formed calcium silicate hydrates (C-S-H) and ettringite, similar to OPC hydration products. Acid resistance tests showed that AAC mass change in HCl and H₂SO₄ solutions ranged from 36.1% to 88.0%, lower than OPC. This suggests superior acid resistance in AAC. The binder weight range for OPC satisfying target geltime (20–50 s) was 180.1–471.1 kg/m³. For AAC, the range was 261.2–469.9 kg/m³. Global warming potential (GWP) for OPC ranged from 102.3 to 257.3 kg CO₂ eq/m³. For AAC, GWP ranged from 72.9 to 126.0 kg CO₂ eq/m³. These results indicate that AAC could reduce CO₂ emissions compared to OPC.

The study concluded that alkali-activated composites (AAC) with an alkali-sulfate activator offer mechanical and chemical performance comparable to ordinary Portland cement (OPC). The formation of calcium silicate hydrates (C-S-H) and ettringite in AAC suggests similar hydration mechanisms to OPC. The acid resistance of AAC was found to be superior, with lower mass change in acidic solutions. The binder weight ranges for AAC satisfying target geltime were comparable to OPC. Global warming potential (GWP) for AAC was consistently lower than OPC across all binder weight ranges. These findings suggest that AAC could reduce CO₂ emissions in construction applications. The study supports the use of AAC as a viable alternative to OPC in field applications. The authors propose that further research could explore the long-term durability of AAC in real-world conditions.