The Study On The Application Of Waste Slurry From Stone Processing In Cement Mortar

The stone processing process produces 20%³0%waste slurry,with a stone output of350 million square meters in 2015,30 million tons of waste slurry is produced every year.At present,the treatment of stone waste slurry is mostly took to the landfill,which has a great impact on the environment and restricts the development of the stone industry.How to solve the problem has become the key to the sustainable development of the stone industry.In this paper,the marble waste slurry and granite stone slurry from stone processing factory which located in the Yunfu City,Guangdong Province are taken as research objects,and carried out the application research of stone waste slurry in cement mortar.The main research contents and results are as follows:1.The waste slurry is dried and ground,then tested and analyzed the basic performance.The results show:The main chemistry of marble powder is CaCO₃,the mineral composition is calcite,the main chemistry of granite powder is SiO₂ and Al₂O₃,the mineral composition is quartz,feldspar and mica;the mid grain diameter of marble powder is 8.7μm,and the mid grain diameter of granite powder is 13.8μm,so the marble powder particles are more granular than the granite powder.2.The effect of stone powder on rheological properties and hydration characteristics of cement was studied.（1）The rheological curve of the cement paste afeter mixed with stone powder still belongs to the Bingham model,but with the increase of the amount of stone powder,the yield stress,plastic viscosity and thixotropy were increased.Compared with the two kinds of stone powder,the granite powder had a far greater impact.The changes of rheological parameter was more significant;the cement paste mixed with stone powder after placement for a certain time has greater yield stress and plastic viscosity than the fresh,and then gradually increases with hydration time.The effect of marble powder was greater than granite powder.（2）The stone powder did not change the cement hydration process,but the different stone powder had changed the length of each hydration’s stage.The marble powder shortens the hydration induction and acceleration period,and increases the heat release rate and hydration heat,while the granite powder extended hydration induction and acceleration period,reduce the heat release rate and hydration heat.3.The effect of stone powder on the cement mortar’s performance was studied by comparison with fly ash and limestone.（1）The effect of cement mortar’s consistence,setting time and water retentivity shows that the internal stone powder increased the consistence.The marble powder is similar to fly ash,which had less effect on the consistency than granite powder and limestone powder.The influence of marble powder and limestone powder on the setting time is consistent,which significantly shortens the setting time,and the setting time decreases with the increase of stone powder;and the effect of granite powder and fly ash on the setting time is small,but delayed the setting time;the effect of internal and externally mixed stone powder on the water retention is similar,and it increases with the increase of marble,granite and limestone powder.But the water retention capacity first increases and then decreases with the increase of fly ash.（2）The effect on cement mortar’s strength shows:the effect of marble,granite and limestone powder on the early strength is similar,and it increases first and then decreases with the increase of stone powder,while the strength gradually decreases with the increase of the amount of fly ash.The 28d’s strength decreases with the increase of marble and limestone powder,and increases with the increase of granite powder.It increases first and then decreases with the increase of fly ash;the marble and granite powder are mixed,the strength of cement mortar increased significantly at each period.（3）The effect on the pore structure and anti-penetrability of mortar shows:doped marble powder increased the 28d’s average pore size,water absorption and true porosity;while the doped granite powder reduced the 28d’s average pore size,water absorption and true porosity,The porosity increased firstly and then increased.Mixed marble and granite powders reduced the average pore size,water absorption and true porosity,and improved the anti-penetrability of the cement mortar.（4）The effect on the volume stability of cement mortar shows:the effect of doped marble,limestone powder and fly ash on the dry shrinkage is similar,and it increases first and then increases with the increase of powder.With the amount of grantie increased,the dry shrinkage is gradually reduced.When the marble and granite powder are mixed,the dry shrinkage of the cement mortar is obviously reduced.（5）The effect on the durability of cement mortar shows:the effect of doped marble powder on the sulfate resistance of cement mortar is similar to limestone powder,that coefficient of resist corrosion decreases with the increase of powders,but doped granite powder and fly ash can increased coefficient of resist corrosion.In the process of sulfate attack,the mass loss of each proportioning mortar is consistent,and both negative growth first and then positive growth.4.The application of stone powder in thin-layer dry powder mortar was studied.Taking M5 mortar as the object,through the orthogonal test,the basic mix ratio that meets the requirements of the standard"pre-mixed mortar"（GB/T25181-2010）is obtained.On this basis,the effects of stone powder on various properties were systematically studied.The results showed that:1)the addition of stone powder reduced the amount of cellulose ether but water retentivity retention to meet the requirements;2)stone powder can inhibit the shrinkage deformation,with the amount of granite powder increased,the shrinkage value gradually decreased,with the increase of marble powder,shrinkage value first and then increased,and the overall value was still lower than the baseline group;3)Within the range of the test,the stone powder reduced the thin layer-mortar 14d bonding strength,but still higher than 0.3MPa;4)granite powder increased the 28d compressive strength,while the marble powder reduced the 28d compressive strength,but the addition of stone powder is 30%can still meet more than 5MPa strength requirements.