Cement-bonded composite boards with arhar stalks

A study was carried out to explore the possibility of making cement-bonded composite building products using arhar stalks. The water extractive of arhar stalks is slightly acidic, pH value around 6.5. It was found that the extractive adversely affect the cement hydration and strength development processes. The increase in setting time varied from 25 to 130% when extractive content was from 0.5 to 2% by weight of cement. 28-day compressive strength reduced by 13 to 20% at 1–2% concentration of extractive powder. Further, studies showed that these effects could be overcome by adopting suitable measures like cold water extraction and/or by use of an accelerator. A dose of 2% calcium chloride, by weight of cement, could offset the effect of 1% concentration of arhar extractive. The cement bonded composites were prepared by varying the flakes content from 0 to 32%, by weight, in the flakes–cement mix using a casting pressure of 3 MPa and demoulding time up to 10 h. The results showed that cement composites with bending strength >9.0 MPa and internal bond strength >0.6 MPa could be made using arhar stalks as a reinforcing material. The strength properties of arhar stalks–cement composites were found to satisfy the minimum requirements of International Standard, ISO:8335-1987.