Search

To achieve specific construction requirements, such as the desired strength and flowability, the proportion of ultra-high performance concrete (UHPC) constituents must be carefully balanced. However, traditional concrete mixture design requires comprehensive trial-and-error experiments, which are cumbersome and costly. The requirements and objectives of a project may be contradictory, rendering the experimental design much more difficult. Therefore, to optimize the mixing ratio of UHPC, particle swarm optimization (PSO) was used to perform multi-objective optimization of the mechanical and flow properties of UHPC. The premise of comprehensive consideration of compressive strength and fluidity was given based on the Pareto optimality theory. The optimal ratio was validated through a combination of the macroscopic force phenomenon and microscopic mechanism. The findings show that the generated PSO algorithm model can simulate and analyze the complete relationship among all functional UHPC components, compressive strength, and fluidity and thus demonstrates its quite high accuracy and efficiency. The macro-micro test results indicate that the optimized UHPC ratio based on the PSO algorithm satisfies the best compressive strength and fluidity. The PSO algorithm can identify the direction for the optimization of the combination of UHPC multiple performance ratios. [ABSTRACT FROM AUTHOR]

• The lime mud accelerated the hydration of fly ash and increased the strength of foamed concrete. • Replacing cement with high volume lime mud and fly ash could improve the dry-wet resistance and freeze–thaw resistance, as well as reduce the drying shrinkage of foamed concrete. • The air voids structure of foamed concrete was closely related to the lime mud-fly ash dosage and wet density. • All prepared foamed concrete containing high volume lime mud-fly ash was suitable for use in pavement engineering. This paper aims to study the drying shrinkage, durability and microstructure of foamed concrete containing high volume lime mud (LM) and fly ash (FA). The effects of wet density (600 kg/m3, 700 kg/m3, 800 kg/m3 and 900 kg/m3) and LM-FA dosage (0 wt%, 50 wt%, 60 wt%, 70 wt% and 80 wt%) on flowability, compressive strength, drying shrinkage, dry-wet resistance, freeze–thaw resistance, and microstructures were investigated. X-ray diffractometer (XRD) and thermo gravimetric (TG) were used to study the hydration products. Environmental scanning electron microscopy (ESEM) and image analysis method were combined to analyze the characteristics of air voids, including aspect ratio, average pore diameter, and size distribution. The results show that wet density and LM-FA dosage had significant on foamed concrete properties. When the wet density increased or LM-FA dosage decreased, the compressive strength and the drying shrinkage increased. The compressive strength ranged from 1.31 to 2.52 MPa. The drying shrinkage was between 0.34% and 0.44%. For all specimens, after 30 freeze–thaw or 50 dry-wet cycles, the compressive strength was still higher than the specification required strength of 0.8 MPa. For air voids, the equivalent diameter, ranging from 149 μm to 202 μm, and the volume of pores larger than 200 μm decreased as the wet density and LM-FA dosage increased. However, the aspect ratio was between 1.15 and 1.20 for all specimens. TG and XDR results show that the lime mud accelerated the hydration of FA. [ABSTRACT FROM AUTHOR]