Study On Preparation And Properties Of Light Bamboo-based Concrete Formwork

Concrete formwork is an indispensable construction tool in civil engineering,its use is huge while either transportation cost or proportion of labor is high.The construction industry at home and abroad has focused on the reform of template engineering.Light type of bamboo-based concrete formwork is becoming a trend.In this paper,phenolic resin impregnated paper,bamboo mat,chordwise bamboo curtain and radial bamboo curtain were used as the main raw material.Effects of processing gas,processing power,processing time and other factors by plasma modification on the mechanical strength of light bamboo-based concrete formwork were analysed.Effects of four kinds of slab structures(A,B,C and D)on the physical and mechanical properties of bamboo-based concrete formwork,such as density and static bending strength were also researched.The hot pressing process of light bamboo-base concrete formwork was optimized by response surface method.The contact angle measurement,infrared spectrum analysis of Fu Liye(FTIR),scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS)were used to characterize modification mechanism of oxygen cold plasma on bamboo during the process light bamboo-based concrete formwork.The results showed that:(1)There were significant influence of cold plasma processing gas and processing power on the static bending strength of bamboo-based concrete formwork but no one of processing time in the 60-120s range on them.The optimum parameters of cold plasma modification were as follows:processing gas was oxygen,processing power was 160W,processing time was 90s,and the static bending strength of light bamboo-based concrete formwork under this condition was 98.5MPa.(2)There were very significant influence of four different kinds structure(type A,type B,type C and type D)on the density,static bending strength,elastic modulus and internal bond strength of bamboo-based concrete formwork,but significant one on 24h water absorption thickness swelling rate.Compared with traditional bamboo-based concrete formwork with density of 0.85 g·cm-3,light bamboo-based concrete formwork(type D)slab was lightened efficiencily,which density was decreased by 27.06%,while its physical and mechanical properties could meet the requirements of forestry industry standard(LY/T 1574-2000).(3)Each hot pressing factor had strong interactive effects during the preparation process of light bamboo-based concrete formwork by oxygen cold plasma modification.Through optimizing the response surface model,the optimum hot pressing scheme was obtained as follows:the hot pressing pressure was 2.87MPa,hot pressing temperature was 131.04℃,hot pressing time was 1.20min·mm-1,bamboo water content was 10.57%.The relative error between actual value and predictive value by regression model was 1.02%,which showed that the regression equation had high fitting degree,the regression model was accurate and reliable.The physical and mechanical properties of light bamboo-based concrete formwork modified by oxygen plasma could meet the requirements of forestry industry standard(LY/T 1574-2000)while part of the performance of light bamboo-based concrete formwork could not meet the requirements without treated by oxygen plasma.It was necessary and efficiency for plasma modification to be used in the process of reducing the density of the formwork.(4)After oxygen plasma treatment,the equilibrium contact angle of bamboo outter surface,bamboo pulp surface and bamboo inner surface was reduced by 61.15%,43.59%,48.32%respectively.The surface wettability of bamboo towards phenolic resin adhesive could be obviously improved by oxygen plasma treatment.The bamboo must be treated in 6 days after oxygen plasma treatment because of its timeliness.FTIR analysis showed that after bamboo outter,bamboo pulb and bamboo inner were treated by oxygen plasma,the stretching vibration of hydroxyl(3433cm-1)and carbonyl(1246cm-1)in lignin increased obviously,and the carbonyl(1739cm-1)and ether(1048cm-1)bond stretching vibration of cellulose and hemicellulose were also enhanced.SEM analysis showed that the surface of bamboo was treated by high energy particles after oxygen plasma treatment,the wax layer on bamboo outter surface and the bamboo clothing on bamboo inner surface were obviously damaged,and bamboo was etched.XPS analysis showed that the contents of carbon and nitrogen in the surface of bamboo outter,bamboo pulb and bamboo inner decreased significantly,while the contents of O and O/C increased obviously,when they were treated by oxygen plasma.Oxygen cold plasma treatment could promote bamboo outter,bamboo pulb,bamboo inner surface producing large amounts of-OH,-C=O,-COOH and other oxygen-containing functional groups.