Improving the bond strength of concrete to reinforcement by adding methylcellulose to concrete

The use of methylcellulose (0.4 to 0.8 percent by weight of cement) as an admixture in cement paste or concrete was found to increase the shear bond strength with steel reinforcing bar, steel fiber or carbon fiber to values attained by using latex (20 percent by weight of cement) as an admixture, even though latex was used in a much larger quantity than methylcellulose. The bond strength increased with increasing methylcellulose amount. The contact electrical resistivity between cement and fiber or between concrete and reinforcing bar was increased by latex addition, but not changed by methylcellulose addition. The combined use of silica fume (15 percent by weight of cement) and methylcellulose (0.4 percent by weight of cement) as admixtures was found to give concrete that exhibited high bond strength to steel reinforcing bar, in addition to previously reported high tensile modulus, tensile ductility, flexural strength and flexural toughness; the bond strength attained was higher than that attained by using either silica fume or methylcellulose as admixture. Latex in combination with silica fume did not work due to low workability. Methylcellulose in combination with silica fume was effective due to silica fume increasing the matrix modulus and methylcellulose promoting adhesion.