Study On Preparation Of Shale Ceramsite And Properties Of High Strength Sub-light Concrete

Light weight and high strength are the significant characteristics of sublight concrete.In the application of long-span structure,the constructs with light weight can obviously enhance the capacity of load,reduce the ratio of reinforcement of designing as well as building precast concrete,decrease the amount of digging as well as construction,and save the cost of construction and maintenance.In this study,the shale obtained in Sichuan province was used to prepare the artificial ceramsite,which was also applied to prepare the sublight concrete.It not only solved the managing problems of manpower and material resources caused by waste shale in stacking and storage,but also reduces the pollution problems such as fugitive dust caused by waste shale to the environment.Both sintered and expanded ceramsite were prepared by the optimization of sintering schedule and mix proportions in this study.In addition,the technologies of XRF,XRD,SEM,TG-DSC were used to investigate the influence of sintering schedule and additives on the bulk density,single particle strength,and water absorption of the ceramsites.The sublight shale-ceramsite concretes of class LC30 and LC50 stipulated by national standard were successfully manufactured by the substitution of macadam by expanded ceramsites as the coarse aggregate and the optimization of parameters of expanded ceramsite dosage,water to binder ratio,and additives.The carbonation,sulphate resistance,heat conductivity coefficient of sublight shale ceramsite concrete and conventional concrete were compared,and the LC30 and LC50sublight concretes with excellent durability,heat insulation,and dry bulk density of 1950～2300 kg/m³ were obtained.Both sublight concretes were conducive to the harmonious development between economy,environment,and society,and the investigation of this thesis provided the experimental basis and references for the application of this concrete in the field of high-rise buildings,bridge construction,and prefabricated buildings.Main conclusions can be obtained as follows:（1）The pure An Yue shale was suitable to prepare the sintered ceramsite（P_K<3.5）with the performance of low water absorption and high strength.When the sintering temperature was 1100-1130℃,the ceramsite density is high,its apparent density is greater than 2200 kg/m³,the water absorption rate is less than 1%,and the single particle strength is higher than 25 MPa.In addition,shortening the sintering time from 30 min to 10 min helps to reduce the bulk density of ceramsite,maintain its high strength and low water absorption.The shale containing10 wt%Z inorganic silicate mineral additive was preheated at 500°C for 20 min,and sintered at 1130°C for 20 min,the apparent density was 1705 kg/m³,and the water absorption rate was1705 kg/m³.0.2%,light-weight and high-strength shale ceramsite with a single particle strength of 15.8 MPa.（2）The pure De Yang shale was used to prepared the burning expanded ceramsite（10>P_K>3.5）.When the proportions of De Yang shale,clay,and M-intumescient additive were30:60:10,the ceramsite prepared by sintering has good swellability.The sintering temperature was increased from room temperature to 400°C at 10°C/min,kept for 20 min,and then continued to heat up to 1130°C for 20 min.The obtained swelled ceramsite had an expansion ratio of 1.25 and an apparent density of 1896 kg/m³,The water absorption rate is 8.2%.The ceramsite raw pellets dried at 105°C were directly preheated at 400°C for 20 min,and then calcined at 1130°C for 10min.The expansion ratio was 1.58,the apparent density was 1020kg/m³,and the water absorption rate was 8.4%.of light intumescent shale ceramsite（LESC）.（3）When the proportion of substitution of macadam by LESC achevied by more than20%,LC30 secondary light concrete dry apparent density decreases with the increase of ceramsite substitution rate,but all meet the requirements of secondary light concrete density（1950～2300 kg/m³）.When the replacement rate of ceramsite is 80%,the content of polypropylene methyl cellulose（HMPC）is 4‰,the water-binder ratio is 0.46,and the content of water reducing agent is 2.5%,the slump of the prepared LC30 light concrete is 165 mm,dry apparent density 2012 kg/m³,28 d compressive strength 39.8 MPa,28 d flexural strength3.9 MPa.（4）Different from LC30,the dry bulk density of LC50 decreased with the increasing of ceramsite when the ratio of substitution of macadam by LESC achevied by more than 40%.However,Its density still meets the standards of sub-light concrete.When the ceramsite replacement rate is 60%,the cellulose content is 4‰,the water-binder ratio is 0.32（0.33）,and the water reducing agent content is 1.5%（1.4%）,the LC50 slump is 200 mm,and the dry surface is 200 mm.The apparent density is 2210 kg/m³,the 28 d compressive strength is 64.7MPa,and the 28 d flexural strength is 6.8 MPa.（5）The carbonization resistance,sulfate erosion resistance and thermal insulation performance of sub-light concrete are better than those of ordinary ordinary concrete.C30-T0and C30-T80H4-3 have 28d carbonization depths of 10 mm and 5.8 mm,30d compressive strength corrosion coefficients of 75%and 95%,and thermal conductivity of 0.51 w/（m·k）and0.23 w/（m·k）,respectively.The incorporation of ceramic particles,on the one hand,fills the larger pores inside the concrete,the structure is more dense,and the total porosity is reduced from 19.04%to 10.89%,which effectively reduces the erosion of CO₂,H₂O and SO₄^2-on the concrete.On the other hand,due to the internal curing effect of ceramic concrete,the secondary hydration reaction of cement or fly ash is promoted,so that the performance of the surface transition zone is enhanced,and the ion erosion is hindered,so that the resistance to sulfate erosion and carbonization is enhanced.The ceramic particles contain more pores and the thermal conductivity is low,so that the sub-light concrete has good thermal insulation performance.