Exploratory Investigation of Nanomaterials to Improve Strength and Permeability of Concrete

Concrete containing various supplementary cementitious materials (SCMs) such as silica fume, fly ash, and slag has improved properties. Nanomaterials, new SCMs with possible applications in concrete, have the smallest particle size (less than 100 nm). Nanomaterials are reactive because of the small size and large surface area of the particles, and they have great potential in improving concrete properties such as compressive strength and permeability. This study evaluates the use of a variety of nanomaterials in concrete compared with conventional concrete and concrete containing common SCMs. The potential benefits of using nanomaterials over other SCMs are high reactivity and cost-effectiveness; in addition, smaller amounts are necessary, resulting in less cement replacement. Concretes containing nanosilica and nanoclay were prepared in the laboratory. They were compared with concretes containing silica fume, fly ash, slag, or only portland cement. Specimens were tested for compressive strength and permeability. The microstructure of selected concretes with improved compressive strength and permeability was analyzed by using an atomic force microscope and nanoindenter to explain the improvements. The results of this study indicate that some of the nanomaterials tested have potential in concrete applications. The microstructure of the nanosilica concrete was denser and more uniform than the conventional concrete microstructure. In addition, the nanosilica had the largest improvement in both compressive strength and permeability among the nanomaterials tested.