The Effect Of Paper Sludge On The Properties Of Cement-based Calcium Silicate Board And Insulation Mortar

Paper sludge generated from the industrial wastewater belongs to solid waste and it is one of the largest pollution sources in paper industry,which can be divided into paper sludge with and without fiber.The addition of paper sludge can improve the thoughness,mechanical performance and thermal conductivity of calcium silicate board?CSB?and insulation mortar.It can reduce the content of wood fiber and cement,and then decrease the cost.This paper primary investigated the effect of paper sludge on the properties of CSB and insulation mortar.The mainly research content as following:?1?The Ca/Si ratio on the formation of tobermorite is investigated in CSB;?2?The preparation technology on the formation of tobermorite is discussed in CSB;?3?The effect of paper sludge on the properties of CSB is studied and its appropriate addition is achieved according to response surface methodology;?4?The effect of three admixtures on the properties of insulation mortar is analyzed using response surface methodology and their appropriate addition is achieved;?5?The effects of different kind of paper sludge on the mechanical strength and insulation property of insulation mortar are investigatd.Some experimental results are concluded as following.?1?Tobermorite is the main hydration product in CSB and has the significant influence on the properties of CSB.It achieved the highest generation amount of tobermorite according to the analysis of XRD and DSC when the Ca/Si ratio,autoclaved curing time and temperature were 1.15¹.60,4h⁸h and 190?¹95?,respectively.Meanwhile,tobermorite was difficult to form under low Ca/Si ratio and it can transform from CSH to C₃SH under high Ca/Si ratio;The Porosity and mechanical analysis of specimens after compression molding presents the flexural strength increases to its maximum value when molding pressure reaches 40 MPa.High curing temperature can accelerate the reaction of Ca?OH?₂ and SiO₂;C₅S₆Hn will generate when the curing time is short and tobermorite can transform to xonolite when the curing time is long.From the results of mechanical strength,the optimal cement content was 72%?Ca/Si ratio reached 1.22?and flexural strength is 16.1MPa;The optimal autoclaved curing temperature was 190? and the flexural strength reached 15.7MPa;The optimal autoclaved curing time was 6h and the flexural strength reached 14.4MPa.?2?According to the properties of CSB added de-ink paper sludge?DIPS?and ecological paper sludge?EIPS?,it can ensure that the optimal addition of DIPS was 5%⁷.5% and the flexural strength was 16.7MPa ¹6.9MPa,it can increase about 19.3²0.7% compared with 0% specimen.The optimal addition of EIPS was 5%¹0% and the flexural strength was 15.0MPa ¹5.5MPa,it can increase about 7.1¹0.7% compared with 0% specimen.The porosity and physical properties of CSB with paper sludge ash?PSA?and alkali recovery paper sludge?ARPS?presents that the optimal addition of PSA is 30% and the flexural strength reached the maximum value was 17.8MPa,it can increase about 27.1% compared with 0% specimen,the porosity was lowest,only has 11.7%;the optimal addition of ARPS is 15% and the flexural strength reached the maximum value was 17.1MPa,it can increase about 22.1% compared with 0% specimen,the porosity was lowest,only has 11.9%.?3?RSM can analyze clearly the properties of CSB added the mixture of PSA and ARPS and adopt the model of cubic function,showing the optimal range is 12²0% and 6%¹2%,respectively.?4?Base on of quadratic model,the influence of mixtures on the insulation mortar was investigated.The optimal compound addition range of hydroxypropyl methyl cellulose ether,water reducing agent and air-entraining agent in insulation mortar was 0.5%⁰.55%,0.5%⁰.55% and 0.25%⁰.28% using response surface methodology.?5?Due to the different fiber content in paper sludge,it has different effect on the properties of insulation mortar.Paper sludge with high fiber content presents the good properties in the addition range of 2.5%⁷.5%.In addition,paper sludge with low fiber content can only improve the properties of insulation mortar slightly in the addition range of 2.5%⁵%.?6?The particle size of ARPS is far lower than that of cement.So,the addition of ARPS can improve the strength and water resistance of insulation mortar and decrease the thermal conductivity significantly.The optimal addition of ARPS is in the range of 20%⁴0%.The component of PSA is CaSO₄ and Ca₂Al₂SiO₇,it can improve the thermal conductivity and water absorption in insulation mortar,the optimal addition was 20%³0%.