EFFECTS OF CHEMICAL ADDITIVE CONCENTRATIONS ON STRENGTH AND SORPTION OF CEMENT-BONDED BOARD

The influence of chemical additive concentration on the strength and sorption properties of cement-bonded boards (CBBs) produced from Nauclea diderrichii wood flakes was investigated. CBBs were made at three chemical additive concentrations: 1, 2 and 3% calcium chloride by weight of cement; three nominal board densities: 950, 1150 and 1250 kg m and two cement-wood ratios: 1.5:1 and 2.5:1 (weight to weight basis). The modulus of rupture (MOR) and modulus of elasticity (MOE) values increased with increased chemical additive concentration. However, increase in chemical additive concentration caused reduction in water absorption (WA) and thickness swelling (TS) after 24-hours of water soaking. MOR and MOE increased while WA and TS decreased with increase in board density and cement-wood ratio. All the CBBs produced in this study meet British standard requirements for the flexural MOE property and TS performance in the presence of water. However, only the CBBs produced using chemical additive concentrations of 2 and 3% at both 1.5:1 and 2.5:1 of cement-wood ratio satisfy the British requirement. Pengaruh bahan tambah kimia terhadap kekuatan dan sifat erapan papan ikatan simen (CBB) yang dihasilkan daripada kepingan kayu Nauclea diderrichii diselidik. CBB dihasilkan pada tiga kepekatan bahan tambah kimia: 1%, 2% dan 3% kalsium klorida mengikut berat simen; tiga ketumpatan papan: 950 kg m-3, 1150 kg m-3 dan 1250 kg m-3; dan dua nisbah simen-kayu: 1.5:1 dan 2.5:1 (nisbah berat kepada berat). Modulus kepecahan (MOR) dan modulus keanjalan (MOE) meningkat apabila kepekatan bahan tambah kimia meningkat. Bagaimanapun, peningkatan kepekatan bahan tambah kimia mengakibatkan penurunan penyerapan air (WA) dan pengampulan tebal (TS) selepas 24 jam direndam dalam air. MOR dan MOE meningkat apabila ketumpatan papan serta nisbah simen-kayu meningkat tetapi WA dan TS menurun. Semua CBB yang dihasilkan dalam kajian ini mematuhi standard British untuk sifat MOE lenturan dan prestasi TS dalam kehadiran air. Namun, hanya CBB yang dihasilkan dengan menggunakan kepekatan bahan tambah kimia 2% dan 3% pada nisbah simen-kayu 1.5:1 serta 2.5:1 mematuhi standard British tersebut.