Comparison of lightweight and normal-weight aggregate concrete

In this experimental study, lightweight aggregate concrete (LWAC) and normal-weight aggregate concrete (NWAC) were compared within the contexts of the size of calcium hydroxide (CH) crystals in interfacial transition zone (ITZ), compressive strength, and oven-dry density. Six LWAC and NWAC mixtures were prepared for this study. Thirty-six images obtained from Scanning Electron Microscope (SEM) were used to determine the size of CH crystals in ITZ of LWAC and NWAC. Eighteen test specimens (three for each of the six LWAC and NWAC mixtures) were prepared in 150x300 mm sizes and in the form of cylinders for the compressive strength tests and also eighteen test specimens in 100x100x100 mm sizes and in the form of cubes for the oven-dry density tests. It was determined that the size of CH crystals in ITZ of LWAC is 8.43% less than (on average), compressive strength of LWAC is 39.09% more than (on average), and oven-dry density of LWAC is 10.97% less than (on average) the NWAC’s that has the same volumetric proportions of ingredients. The findings of this study show that lightweight aggregate that has high particle density, angular shape, rough surface texture, and a structure that enables chemical reaction with CH crystals will be beneficial for the ITZ microstructure and properties of concrete. It is considered that these properties should be taken into consideration in the selection of lightweight aggregate for structural concrete production.