The Impact of Superplasticizer Chemical Structure on Reactive Powder Concrete Properties

Area of Science:

• Materials Science
• Civil Engineering
• Chemical Engineering

Background:

• Achieving adequate flowability in reactive powder concrete (RPC) is challenging due to low water/binder ratios.
• Polycarboxylate superplasticizers (SPs) and modified mixing procedures offer potential solutions for improving RPC workability.

Purpose of the Study:

• To investigate the impact of two different polycarboxylate superplasticizers (SPs) and mixing procedures on the fresh and hardened properties of reactive powder concrete (RPC).
• To elucidate the role of SP chemical structure in influencing RPC mix characteristics and performance.

Main Methods:

• Systematic experimental studies including physicochemical and spectroscopic tests.
• Molecular modelling to understand superplasticizer-particle interactions.
• Comparative analysis of three-stage versus four-stage mixing procedures.

Main Results:

• Superplasticizers with a higher density of carboxylate salt groups (-COO- Me+) enhanced RPC mix fluidity and deaeration.
• Improved fluidity and deaeration correlated with reduced porosity and increased compressive strength in hardened RPC.
• Transitioning from a three-stage to a four-stage mixing procedure boosted both RPC mix flowability and strength.
• Neither SP chemical structure nor mixing procedure significantly altered cement hydration rates.

Conclusions:

• The chemical architecture of polycarboxylate superplasticizers is critical for optimizing reactive powder concrete flowability, deaeration, and mechanical properties.
• Modifying the mixing sequence provides an effective strategy to enhance RPC performance.
• These findings offer valuable insights for both fundamental materials science and the practical design of cementitious composites in construction.