The Study On The Production Technology And Properties Of Cement-based Fiberboard By Semi-dry Processing

Cement fiberboard is a kind of new building wall material, which the cement is the binder filled with fiber as reinforcing material. It combines the dual benefits of cement and timber, such as high strength, light weight, fire protection, sound proofing, and so on. It can be used for non-load bearing external wall panels, ceiling, activity rooms or other fields. As ideal construction material, the cement-based fiberboard has been applied quite common in foreign countries. However, our study about cement fiberboard has been recently started. It has not been used widely. In this study, the ordinary Portland cement was used as the cementations material, and the wood-pulp fiber, bamboo fiber and hot-mill fiber were used as reinforced material. The semi-dry process was applied to produce cement-based fiberboard, and then the physical properties of the composite boards and compared of various process factors on the physical and mechanical properties of fiberboard were analyzed, so as to obtain better production parameters. This study can provide reference data for the industrial production of cement fiberboard. At the end, the scanning electron microscopy was used to explore reinforced cement composite reinforcement mechanism. The results were as follows:1. Though the fiber morphological analysis, the fiber length range of wood-pulp fiber is 2.03~2.97mm, bamboo fiber is 1.08~2.60mm, hot-mill fiber is 1.01~1.98mm. Based on fiber classfication standard, the wood-pulp fibers are long fibers, bamboo fiber and hot-mill fiber are belonged to the middle length fibers.2. The total sugar contents of cold water extracts in the wood- pulp fiber, bamboo fiber and hot-mill fiber were 11.38mg/g,36.55mg/g,62.96mg/g.The holocellulose contents of wood-pulp fiber was 99.69%, the holocellulose contents of bamboo fiber and hot-mill fiber were 74.86% and 73.69%. The cold water extract, hot water extract, 1%NaOH extract from the wood-pulp fiber were 4.75%, 4.93%, 6.26%. The cold water extract, hot water extract,1%NaOH extract from the bamboo fiber were 7.16%,7.70%,12.63%.The cold water extract, hot water extract,1%NaOH extract from the hot-mill fiber were 8.85%,10.02% and 26.76%.3. Wood-pulp fiber and cement has better compatibility. It can be directly used for production of cement fiberboard. The bamboo fiber and hot-mill fiber both have blocking coagulation, in which the hot-mill fiber is the most serious. The chemical additives can accelerate the coagulation of cement hardening, slow the adverse effects on cement hydration from the extract and sugar in fiber. And with the increase in the amount of additives, the more obvious procoagulant effect will be. The use of Aluminum Sulfate as a coagulant, and the amount of 1% of the amount of cement is better for the preparation of the cement fiberboard.4. The semi-dry process can be used for the production of the fiber reinforced cement board. Wood cement ratio and water cement ratio both have a significant impact on the physical and mechanical properties of cement fiberboard. In this study, the better parameters for the board is: wood cement ratio of 0.22, water cement ratio of 0.42, the target density is 1.3g/cm~3, under these conditions, the MOR of board can up to 10~14MPa, the MOE can up to 3200~3900MPa, IB was 0.81~0.94MPa, 24h TS was 0.41%~1.26%, these data can up to the superior product requirements in Cement Particleboard (GB/T 24312-2009) .5. The chemical additives should be added while producing cement-based bamboo fiberboard. The semi-dry process can be used to suppress the bamboo fiber cement board. The physical and mechanical properties such as MOE, IB and 24hTS of the board could up to the requirements of GB / T 24312-2009 "cement particle board" and the JC / T 411-2007 "cement wood board". In this study, the MOR (which can up to 8.76MPa) can not yet reached the eligibility requirements, it should be further tested.6. In the better process parameters of preparing wood-pulp fiber reinforced cement board, to the incorporation of hot-mill fiber in the wood-pulp fiber can still produce the fiber reinforced cement board which could up to the standard requirements, in the premise of meeting the performance, the hot-mill fiber in the total fiber content can up to 30% of the largest share.7. Though the use of microscopes and scanning electron microscopy, the microstructure of the fiber reinforced cement composite board and fiber distribution in the matrix were observed. Cement hydration can form a large number of C-S-H gel. The fiber and cement-based materials mixed enough to form a network support system in the slurry, reducing the tension when the cement contraction and frozen, and then improve board structure and performance. 8. In this study, the actual density of the fiber reinforced cement composite boards is about 1.3g/cm~3, which belongs to lightweight board. It is possible to be applied for non-load bearing internal wall panels, ceiling, activity rooms and other fields.