INFLUENCE OF AIR ENTRAINING AGENTS ON WORKABILITY OF FRESH HIGH PERFORMANCE CONCRETE

Air entrainment is essential for the durability of high performance concrete (HPC) exposed to freeze - thaw conditions. Air entrainment effect is accomplished by the use of air entraining agents (AE). Addition of AE may significantly change workability of fresh HPC. In order to adjust workability of air entrained HPC, the knowledge on how AE influences the rheological properties of fresh HPC is necessary. The results of the research on the influence of AE on rheological properties of concrete mixes with different cement - superplasticizer (SP) systems, also in presence of fly ash (FA), are presented and discussed in the paper. The effect of AE was studied using Two Point Workability Test (TPWT) made on the modified standard mortars, which can be considered as model of HPC. The obtained results prove that rheological properties of air entrained fresh HPC depend on: properties of cement and SP, dosage of AE, presence of FA, and compatibility of the AE with the cement - SP - FA system. Discussion about the results covers: mechanism of AE action and consequences of AE addition for HPC workability. It is concluded that basic relationships presented in the paper of AE influence on the rheological parameters of fresh HPC can be applied to adjust workability of air entrained HPC. However, due to the variety of AE agents, the influence of given AE on workability of HPC should be experimentally verified. TPWT made on the model mortars is a simple and rapid method to evaluate the influence that admixtures and additives have on fresh concrete.

• INTRODUCTION

• EXPERIMENTAL

• TEST RESULTS AND DISCUSSION

• CONCLUSIONS

• REFERENCES