Conditions for the Preparation of Self-Compacting Lightweight Concrete with Hollow Microspheres

Producing self-compacting concrete with lightweight aggregates is a difficult task. Mixtures with a high content of expanded aggregate tend to separate. It is possible to evaluate the possibility of producing self-compacting lightweight concrete with low average density. This work presents the results of a study of self-compacting lightweight concrete on hollow microspheres. The ability of a lightweight concrete mixture on hollow microspheres with low density (ρ = 1450 ± 25 kg/m³) to self-compact has been established. The closeness in the values of the spreading diameter before and after shaking on the table D_sp,1 → D_sp,2 confirms this. The dependences (regression equations) of mobility, coefficients of the Ostwald-Weil equation, and density and strength on the W/C ratio and plasticizer concentration for lightweight concrete with a volume content of hollow microspheres of 46.4% have been established. The limits for homogeneity of lightweight concrete mixtures on hollow microspheres are W/C ≤ 0.6 and C_Pl ≤ 1.0%. The dispersion of quartz sand (varying the S_p/S_f ratio) in an amount of 8.7% in the composition of lightweight concrete does not have a significant effect on the self-compaction criterion and physical and mechanical properties. Changes in the physical and mechanical properties of lightweight concrete on hollow microspheres in the selected range of varying the W/C ratio and plasticizer concentration are in the following ranges: ρ = 1403-1485 kg/m³, R_fl = 3.34-5.90 MPa, R_com = 29.6-45.7 MPa. The presence of delamination at W/C ≥ 0.6 does not allow one to correctly establish the influence of variable factors.