Strength and shrinkage properties of alkali-activated slag concrete placed into a large column

摘要

The properties of alkali-activated slag concrete(AASC) are generally determined on small-scale laboratory-produced prisms or cylinders. This investigation reports the insitu strength and in situ strain results from measurements on an800×800×1200-mm column composed of AASC produced at aconcrete plant. The results are contrasted with those of columnsmade with ordinary portland cement (OPC) and blended cement(50% OPC + 50% slag) designated as GB50/50. For this type ofAASC, the workability improved from the time of production tothe time of concrete placement and minimal slump loss occurredover 2 hours (in contrast with OPC). The rate of in situtemperature development was similar to GB50/50, and slowerthan OPC; however, the maximum temperature differencebetween the interior and the exterior was considerably less thanOPC and GB50/50. The in situ strength was identical to OPC andsuperior to GB50/50 at 28 and 91 days. Embedded strain gaugesshow small initial in situ expansion within the centre of thecolumn followed by a rapid rate of tensile strain growth up to 14days. At 91 days the differential strain between the centre of thecolumn and the corner was sufficient to crack OPC concrete;however, the AASC column remained uncracked. Possibleexplanations for this behaviour could be due to a greater tensilestrain capacity of AASC than OPC concrete caused by greatercreep and lower elastic modulus and higher tensile strength of AASC.