3.2. Internal bonding and impact strength
Theinternalbondstrengthoftheboardswasfoundtobeamaximum when wood content was 30%. Further addition of wood increases volume of strands and reduces volume of matrix causing
lower bond strength. Also, as the wood content in the mix is increased, a greater number of wood-to-wood bonds are formed. The increase in wood-to-wood bonds reduces the interfacial area of contact between the wood and the cement matrix, and hence diminishes the potential of a given wood to be able to bond with the matrix. Variation of impact strength with increasing ratio of wood/cement and CaCl2 content is also shown in Fig. 1b. It can be observed thataslongasthewoodcontentofboardsincreased,higherimpact strength were obtained. Increase in the wood content significantly improvedtheimpactstrengthoftheboards.Theimpactstrengthof boards containing wood strands was 40–51% higher than control (neat cement). Interfacial interaction between wood particles and cement matrix plays a major role in determining the crack initiation process. An optimum interaction between the wood and the cement is essential for having good impact strength. As mentioned earlier, all mechanical properties, particularly internalbondingandimpactstrengthoftheboards,weremarkedly improved when the CaCl2 content was increased from 3 to 7%