Improvement of Core-Shell Lightweight Aggregate by Modifying the Cement-EPS Interface.

The compatibility between cement matrices and expanded polystyrene (EPS) remains a challenge in lightweight aggregate design. Prior research has shown that poor interfacial bonding can reduce mechanical performance and durability. While some studies have explored polymer additives, the specific effects on hydration and interface density remain unclear. This gap motivated an investigation into how different interfacial agents influence cement-EPS compatibility. No prior work had resolved the combined impact of inorganic and organic additives on interface properties. Understanding these effects is essential for optimizing lightweight aggregate performance. The need for durable, lightweight construction materials drives this research. Current methods often fail to fully address hydration delays and interface roughness. This study aims to clarify these unresolved factors.

This study aimed to evaluate how various interfacial agents affect the compatibility between cement and EPS in core-shell lightweight aggregates (CSLA). The goal was to improve mechanical and durability properties by modifying the interface. The specific problem addressed is the poor interfacial bonding that limits aggregate performance. The motivation stems from the need for stronger, more durable lightweight construction materials. The study focused on sodium silicate, PVA emulsion, VAE emulsion, acrylic acid, and acetic acid. These agents were selected to assess their impact on interface density and hydration. The researchers propose that interface modification can enhance CSLA properties. This work seeks to provide insights into optimal agent selection.

The study used scanning electron microscopy (SEM) to analyze the density of the cement-EPS interface. Heat of hydration and induction resistivity were measured to assess the impact of interfacial agents on cement hydration. The macroscopic properties of CSLA were evaluated using the 'leak-white' rate, drop resistance, and numerical crushing strength. Sodium silicate, PVA emulsion, VAE emulsion, acrylic acid, and acetic acid were tested as interfacial agents. Each agent was applied to EPS surfaces before cement mixing. Interface characteristics were compared across treatment groups. SEM imaging provided detailed structural insights. The hydration process was monitored to determine delays caused by agents.

Sodium silicate was found to densify the interface by forming hydration products on the EPS surface. Organic acids increased surface roughness and allowed hydration products to grow in micropores. Both inorganic and organic agents delayed cement hydration. The 'leak-white' rate and drop resistance improved with sodium silicate and VAE emulsion. VAE emulsion and sodium silicate combination achieved a crushing resistance of 5.7 MPa. This represents a 46% increase compared to the reference group. The interface properties were comprehensively evaluated using multiple metrics. These findings suggest that interface modification significantly enhances CSLA performance.

The authors propose that sodium silicate and VAE emulsion improve interface properties by densifying and roughening the EPS surface. The combination of these agents achieved the highest crushing resistance of 5.7 MPa. The study suggests that interface modification can significantly enhance CSLA performance. The findings indicate that hydration delays are a common effect of interfacial agents. The 'leak-white' rate and drop resistance metrics support the effectiveness of the agents. The authors suggest that interface properties are critical for aggregate durability. They propose that further work is needed to optimize agent combinations. The study highlights the importance of interface modification in lightweight aggregate design.