An Experimental Study on the Durability Properties of Foam Concrete with Addition of Natural Fibers

Abstract

Fibers are usually used in concrete to control cracking due to plastic shrinkage and due to drying shrinkage. They also reduce the permeability of concrete and thus reduce bleeding of water. Some types of fibers produce greater impact, abrasion, and shatter resistance in concrete. Generally fibers do not increase the flexural strength of concrete, and so cannot replace moment–resisting or structural steel reinforcement. Indeed, some fibers actually reduce the strength of concrete. The amount of fibers added to a concrete mix is expressed as a percentage of the total volume of the composite (concrete and fibers), termed "volume fraction" (Vf). Vf typically ranges from 0.1 to 3%. The aspect ratio (l/d) is calculated by dividing fiber length (l) by its diameter (d). Fibers with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the fiber's modulus of elasticity is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increasing the aspect ratio of the fiber usually segments the flexural strength and toughness of the matrix. However, fibers that are too long tend to "ball" in the mix and create workability problems. The inclusion of fiber reinforcement in concrete, mortar and cement paste can enhance many of the engineering properties of the basic materials, Such as fracture toughness, flexural toughness, flexural strength and resistance to fatigue, impact, thermal shock and spalling. Foamed concrete has become most commercial material in construction industry. People in industries came out with the new mix design of foamed concrete to meet the specification and the requirement needed, this is because foamed concrete has the possibility as alternative of lightweight concrete for producing intermediate strength capabilities with excellent thermal insulation, freeze-thaw resistance, high impact resistance and good shock absorption. It is known to employ foam in concrete to improve its use characteristics; however, it is difficult to provide and maintain correct ratios of foam producing agent in water supplied to the dry concrete mix, and correct ratios of foam to concrete, particularly at the job site, and it is found that such ratios can and do vary greatly at different job sites whereby the quality, pumpability, extrudability, and finishing characteristics of the concrete vary and suffer. There is need for simple, low-cost, and effective apparatus and method to provide required quality control of the ratios referred to and enable production of high quality concrete, in terms of pumpability, extrudability weight control, insulative and fire proofing capability, as well as other desirable qualities.