Study on the Mechanical Performance of Carbon Nanotube-modified Concrete with Partial Fly Ash Cement Replacement

The growing demand for concrete with enhanced mechanical and durability properties has led to increased research focused on improving concrete. This enhancement is achieved through various additives and replacements in cement-based composites. Carbon Nanotube (CNT)-reinforced concrete has emerged as a recent area of research in the construction sector. This study explores the effects of incorporating higher levels of carbon nanotubes, beyond previous studies, to evaluate their influence on the strength properties of concrete. Additionally, 20% of the total cement volume was replaced with fly ash to reduce cement consumption. The research focused on three key properties: compressive strength, flexural strength, and tensile strength, all of which are critical for concrete performance. Previous studies incorporated CNT levels ranging from 0.025% to 0.075% (with a 0.025% increase in cement weight), while the current research used increased CNT levels of 0.1% and 0.125%. Three specimens were cast for each of the four mix types: the Control Concrete (CC) mix of M30 grade, a concrete mix with 20% fly ash replacing cement (CF), a mix with 20% fly ash and 0.1% CNT (CNT 0.1), and a mix with 20% fly ash and 0.125% CNT (CNT 0.125). For the tests on compressive and split tensile strength, 12 cubes (150 mm side) for each test were casted totally 24 specimens and 12-cylinder specimens (150 mm diametre and 300 mm height) were casted for cylinder compressive strength test. Additionally, 12 prism specimens were casted for flexural strength analysis, making a total of 48 specimens for this study. In order to ensure proper dispersion of carbon nanotubes within the concrete, a surface treatment process was used involving Polycarboxylate Ether (PCE) additive and magnetic stirring.