FUNDAMENTAL ACTIONS OF AIR-ENTRAINING AGENTS

THE FORMATION AND RETENTION OF AIR BUBBLES IN CEMENT PASTES CONTAINING SURFACE-ACTIVE AGENTS, DEPEND GENERALLY ON TWO MAJOR FACTORS: (1) AFTER ANY PRECIPITATION OR ADSORPTION, THE RESIDUAL CONCENTRATION OF THE SURFACE-ACTIVE AGENT IN THE MIXING WATER OF A PASTE MUST BE SUFFICIENT TO GENERATE AIR BUBBLES. (2) THE SURFACE-ACTIVE AGENT SHOULD BE ADSORBED ON THE CEMENT PARTICLES MAKING THEM HYDROPHOBIC SO THAT AIR BUBBLES MAY ADHERE TO THEM. THE CONDITIONS GOVERNING THE FORMATION OF STABLE AIR-ENTRAINED MORTARS AND CONCRETES BY MEANS OF SURFACE-ACTIVE AGENTS ARE SIMILAR TO THOSE FOR CEMENT PASTES. HOWEVER, UNDER SOME CONDITIONS, THE AGGREGATE INFLUENCES THE AIR-ENTRAINMENT PROCESSES BY ENTRAPPING AND RETAINING AIR BUBBLES IN THE INTERSTICES BETWEEN AGGREGATE PARTICLES. THE VISCOSITIES AND BLEEDING PROPERTIES OF AIR-ENTRAINED CEMENT PASTES ARE AFFECTED BY BOTH THE PRESENCE OF AIR BUBBLES AND THE TYPE OF ADSORPTION OF THE SURFACE-ACTIVE AGENT ON CEMENT. ALTHOUGH THE IMPROVEMENT IN WORKABILITY OF MORTARS AND CONCRETES PRODUCED BY AIR-ENTRAINMENT, IS DUE LARGELY TO THE PRESENCE OF AIR BUBBLES, THE HYDROPHOBIC ADSORPTION OF SURFACE-ACTIVE AGENTS CAN INFLUENCE SUCH PROPERTIES AS COHESIVENESS AND RESISTANCE TO SEGREGATION. THE SPECIFIC SURFACE AREAS OF ENTRAINED BUBBLES IN CEMENT PASTES DEPEND TO A LARGE EXTENT ON THE TYPE OF SURFACE-ACTIVE AGENT USED AND THE EFFICIENCY OF MIXING. /CRIC/FESR/RRL/A/

• Supplemental Notes:
  • to Pic Iii, REPORT III/4, PP 5-23, 6 FIG, 3 TAB, 12 REF
• Authors:
  • BRUERE, G M
• Conference:
  • Intl Symp Admix Mortar & Concr /Belg/
• Publication Date: 1967

Subject/Index Terms

• TRT Terms: Adsorption; Aggregates; Air entraining agents; Cement; Cohesion; Hydrophobic properties; Pastes; Surface phenomena
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00212947
• Record Type: Publication
• Source Agency: Road Research Laboratory /UK
• Files: TRIS
• Created Date: Jun 22 1970 12:00AM