This research aims to develop the gypsum refractory board mixed with corn leaf coir. The 5 ratios of gypsum plaster: corn leaf coir: tap water: sodium silicate are equal to 1: 0: 1: 0.03 1: 0.100: 1: 0.03 1: 0.150: 1: 0.03 1: 0.200: 1: 0.03 1: 0.250: 1: 0.03 และ 1: 0.300: 1: 0.03 by weighted. The gypsum refractory boards were produce by casting in normal temperature (30 – 35 degree of Celsius). The properties testing of gypsum refractory board mixed with corn leaf coir followed the TIS 219-2009 standard (gypsum plasterboard) included: breaking load nail pull resistance deflection water absorption density and thermal conductivity coefficient. From the results 1: 150: 1: 0.03 is the most suitable ratio of gypsum refractory board mixed with corn leaf coir. This developed gypsum refractory boards can reduce the quantity of corn leaf waste and get the good thermal insulation gypsum refractory board products.

Gypsum is a substance derived from nature and some synthesis. Its structure consists of calcium ion (Ca2+) sulphate ion (SO4 2-) and molecules of H2O. Its formula is CaSO4.2H2O. From this structure gypsum is used in agriculture as soil conditioners especially acid soil and saline soil. The calcium ion will replace aluminium ion (Al3+) in acid soil and sodium ion (Na+) in saline soil. It is effective to reduce acidity salinity compaction in soil and increase friable condition which is suitable for agriculture. Moreover calcium and sulphur are the secondary nutrients for plants. Therefore the application of gypsum as soil conditioners will reduce soil deterioration increase agricultural profits conserve of soil relieve problem of agricultural areas and maintain our agricultural sustainability