The Research On Several Engineering Performance Of Calcium Silicate Board/Fiber Reinforced Foamed Concrete Sandwich Panel

With the rapid development of China's economy,environmental problems become more serious,waste of resources and low energy efficiency can be found everywhere.In the proportion of China's energy consumption,buildings' energy consumption accounts for about one-third.An important way to reduce buildings' energy consumption is to develop and use new walls with good thermal insulation performance.On the other hand,much more attention is paid to the development of assembly-style housing.In this paper,sandwich panels are prepared by direct casting method using foamed concrete as the core material and the calcium silicate board as the panel.Aiming at the problems such as large shrinkage,low compressive strength and insufficient thermal performance research of calcium silicate board/foamed concrete sandwich panel,this paper mainly studies several engineering properties,namely,shrinkage performance,compressive performance and thermal insulation performance.The research content and results are as follows:?1?Study on drying shrinkage performance of calcium silicate board/foamed concrete sandwich panel.Using polypropylene fibers and polyvinyl alcohol fibers to reduce the shrinkage of sandwich panel.The results show that,polypropylene fiber and polyvinyl alcohol fiber can effectively reduce the shrinkage of foamed concrete sandwich panel.When the polypropylene fiber content is 3kg/m3,60 days dry shrinkage of sandwich panel decreased by 34.3%.When the polyvinyl alcohol fiber content is 3kg/m3,28 days dry shrinkage of the sandwich panel decreased by 40.1%.The effect of polyvinyl alcohol fiber on shrinkage is more pronounced than that of polypropylene fiber.The adhesion between the polypropylene fibers/polyvinyl alcohol fibers and the hardened slurry is tight.The fiber can effectively transfer and consume the stress and energy during the shrinkage of the foamed concrete.The shrinkage of sandwich panel on different position during the shrinkage process is not the same.The drying shrinkage value of the central part of the sandwich panel is greater than the dry shrinkage value of the ends.When fiber content is 1kg/m3,the drying shrinkage in the end was about 37.8% smaller than the drying shrinkage in the middle.With the increase of the quantity of fiber,the difference gradually decreases.When the amount of fiber is 3kg/m3,the difference between the middle and end of sandwich panel is reduced to 9.3%.The drying shrinkage of the top/bottom part of the sandwich panel is slightly larger than that of the center,but the drying shrinkage in the ends of sandwich panel are not much different betwent each other.It is proved that the incorporation of fiber can reduce the shrinkage stress of the sandwich panel,and reduce the stress value of each part of the sandwich panel.?2?Study on compressive performance of calcium silicate board/foamed concrete sandwich panel.When no fiber incorporation,the compressive strength of sandwich panel is about 25.00% higher than that of the foamed concrete,and the compression toughness index is increased by about 8.80%.When the fiber content is 2kg/m3,compressive strength of sandwich panel is 76.08% higher than that of the fiberless sandwich panel,and tcompressive toughness index is increased by 30.03%.The compressive strength of foamed concrete sandwich panel is closely related to its dry density.The compressive strength of sandwich panel with dry density of 600kg/m3 is 90.27% higher than the compressive strength of 400kg/m3.The compression toughness index of the sandwich panel increases with the dry density.The typical measured stressstrain curve can be divided into four stages: elastic stage,stress hardening stage,stress softening stage and failure stage.The stress-strain curve system is established by the different equations of the compressive stress-strain curve with different fiber content.The ascending section adopts the cubic polynomial,and the descending section is the rationale formula.The ascending section result is Y=0.11X+2.35X²-1.46X³(0??3?1?,the descending section result with fiber is Y=1/?k₁?X-1?^k₂+1??X?1?,the descending section result with no fiber is Y=0.31+0.01X+?0.68?/X²?X?1?,Replace 20% cement with fly ash,emulsion powder 1.5%²%,xanthan gum 0⁰.1% to optimize the performance of foamed concrete and sandwich panel.The results show that the compressive strength and compression toughness index of the foameded concrete and the sandwich wall with fiber addition are higher than those of mineral admixtures and admixtures addition.From the point of view of cost and sandwich panel performance,select fiber to improve the compression performance of the sandwich panel firstly.?3?Study on thermal insulation performance of calcium silicate board/foamed concrete sandwich panel.Using time lag and decrement factor to evaluate the thermal insulation performance of foamed concrete and sandwich panel.The ?s and ?r of the foamed concrete with dry density of 500kg/m3 and 700kg/m3 are 9.17 min.After turning it to sandwich panel,the ?s and ?r are 18.33 min of sandwich panels with dry density of 500kg/m3 and 700kg/m3,which is twice as large as the delay time of foamed concrete.At the same time,decrement factor is correspondingly increased.Sandwich panels have better thermal insulation properties.With the increase of dry density,sandwich panels' ?_r and ?_s decreases.?_r and ?_s of sandwich panel with dry density of 300kg/m3 are 5.70 and 5.79,respectively.When dry density is 700kg/m3,the decrement factor ?_r and ?_s reduce to 4.84 and 5.27.As the thickness increases,the decrement factor of sandwich panel ?_r and ?_s also increase.Decrement factor ?_r and ?_s of sandwich panel with thickness of 70 mm are 6.77 and 7.06,respectively.When the thickness is 30 mm,decrement factor ?_r and ?_s are 3.98 and 4.37 only.The thermal insulation performance of foamed concrete and sandwich panel was simulated by ANSYS Workbench 15.0,and the internal temperature distribution cloud and isotherm distribution of foamed concrete and sandwich panel were obtained.The results show that the decrease of dry density and the increase of thickness are beneficial to improve the internal temperature distribution of foamed concrete and sandwich panel.As the dry density of the foamed concrete and sandwich wall increases,the isotherm move to low temperature place in different degrees.The performance of foamed concrete sandwich panel can effectively reduce building energy consumption and the amount of building materials used.It has great significance of promoting wall materials to the direction of high-performance,and improving building wall insulation and building energy efficiency in China.