Effect of sand, fly ash and limestone powder on preplaced aggregate concrete mechanical properties and reinforced beam shear capacity

Abstract

A laboratory investigation on the effect of sand, fly ash, and limestone powder on mechanical properties of preplaced aggregate concrete (PAC) and shear strength of reinforced PAC beams without stirrups was conducted. Sand, fly ash and limestone powder is varied in each mixture to show their effects on the mechanical and structural strength properties of PAC. Ten reinforced PAC beams were cast, with PAC compressive strength ranging from 9.7MPa to 35.8MPa. From the same mix proportions, PAC slab members were cast to show an example application of PAC in the precast concrete industry. Beams were load tested in a four-point loading configuration with shear span to depth ratio (a/d) of 2.5, while slabs were loaded in equal 1/3 points. Load bearing performances of beams were evaluated based on load at first flexural cracking and ultimate shear load capacity. It was found that sand reduces workability of PAC grouts, but could be compensated by adding fly ash, while no significant fresh property effects were observed when cement was replaced with limestone powder. PAC mechanical strength had been shown to decrease as more cement was replaced with limestone powder. Modulus of rupture and ultimate shear strength of PAC beam members without stirrups can be designed using ACI 318-14 provisions. Finite element simulation using Vector2 can predict the ultimate shear strength of beam members. PAC example application through PAC slab members has shown similar performance at a lower concrete cost.