Preparation And Properties Of Light Portland Cement Particleboard

Cement particleboard is an inorganic wood-based panel made of cement as cementing material and wood,bamboo and other biomass materials as reinforcement materials.It mainly focuses on the research and development of exterior wall panels with a density of 1.2-1.4g/cm3.With excellent moisture-proof and waterproof,flame retardant and smoke suppression,green environmental performance.But the cement particleboard has the disadvantages of high density,high brittleness and weak resistance to deformation.For cement particleboard,light weight and high strength are a contradiction.How to prepare light weight Portland cement particleboard with high strength is an important challenge faced by researchers.Biomass material such as wood,bamboo contain more or less of Portland cement with the anticoagulating effect of water soluble sugar and carboxylic acids,these "anticoagulating" composition affects the phase of cement and biomass material eligibility,hinder or delay in the process of cement particle board forming Portland cement solidification,in turn,affects cement particle board,especially the strength of the low density of lightweight Portland cement particle board.In this paper,from improving the compatibility of poplar wood particleboard and Portland cement and toughening process of board,poplar wood particleboard and Portland cement as the main raw materials to prepare light poplar Portland cement particleboard,study the influence of coagulant,toughening agent on the properties of poplar Portland cement particleboard.The research conclusions are as follows:(1)The compatibility of poplar and Portland cement was studied by setting up four mixing systems of Portland cement+ water,Portland cement+water+ poplar wood+sodium silicate,and Portland cement+water+poplar wood+calcium chloride.The results showed that poplar wood inhibited the hydration of cement significantly.The main substances inhibiting the hydration reaction of Portland cement in poplar wood were formic acid,acetic acid and water-soluble polysaccharide.The "anticoagulation" effect of poplar wood mainly inhibited the hydration reaction of calcium silicate(C2S)and tricalcium silicate(C3S)in cement clinker through formic acid,acetic acid and water-soluble polysaccharide,and reduced the formation of hydration products such as calcium hydroxide(CH)and ettringite(Aft).The addition of sodium silicate(Na2SiO3)and calcium chloride(CaCl2)can weaken the"anticoagulation" effect,accelerate the hydration reaction of cement,and improve the suitability of poplar wood and cement,of which sodium silicate has the best effect.(2)Single factor test was conducted to study the effect of sodium silicate dosage on mechanical properties of cement particleboard with sodium silicate as coagulant.The results show that:Within the scope of the experiment,with the increase of content of sodium silicate,poplar wood with that of silicate cement eligibility,mainly manifested in sodium silicate of cement hydration reaction of promoting effect to strengthen,dicalcium silicate cement clinker in(C2S),tricalcium silicate(C3S)decreased,the content of hydration products hydrated calcium silicate gel(C-S-H),increased levels of cement matrix porosity is more compact,Poplar wood shavings are more tightly bonded with cement matrix.With the increase of sodium silicate content,the static bending strength,elastic modulus and internal bonding strength of cement particleboard increased,the expansion rate of 24h water absorption thickness decreased,the elastic modulus increased from 4.8mpa to 9.4mpa,and the elastic modulus increased from 1800.5MPa to 3412MPa.The internal bonding strength increased from 0.17MPa to 0.45MPa,and the expansion rate of 24h water absorption thickness decreased from 1.852%to 1.423%.Sodium silicate content in 3.5%cement quality has been in line with the national standard.(3)Light poplar wood Portland cement particleboard was prepared by single factor experiment with polyvinyl propylene(PVA)fiber as toughening modification,and the influence of PVA fiber addition amount on the properties of light Portland cement particleboard was investigated.The results show that the blending of PVA fiber with oil agent does not affect the suitability of cement and poplar wood and the subsequent hydration reaction of cement.Because of its high strength,high elastic modulus,high alkali resistance and excellent bonding with Portland cement hydration gel,PVA fiber can enhance the mechanical properties of cement particleboard.With the increase of the content of PVA fiber,the physical and mechanical properties of light Portland cement particleboard are improved obviously.When the content of PVA fiber reaches 1.5%,the board has the best mechanical properties,and the brittle failure of the board is transformed into ductile failure,and the toughness is the best.