CHU Ruizhi;YAN Yaoqi;YANG Wei;LUO Weidong;REN Wanxing;MENG Xianliang;

• 1:Institute of Chemical Technology
• 2:China University of Mining and Technology
• 3:Guizhou Panjiang Coal and Electricity Group Technology Research Institute Co.
• 4:Ltd.

Abstract：

The fluidity of fly ash-based shotcrete material plays a very important role in practical engineering applications. In order to explore the regulation mechanism of water reducing agent on the fluidity of fly ash-based slurry, the effects of different water reducing agent dosage on slurry flow performance were compared through the characteristics of reducing water rate, fluidity, setting time, slurry viscosity and shear stress, and the best water reducing agent and dosage were selected. The change law of hydration process and time of flyash-based slurry by polycarboxylate acid superplasticizer(PCE)was emphatically explored by using hydration heat analyzer, X-ray diffraction and scanning electron microscope and the hydration mechanism of shotcrete materials with PCE was proposed. The results show that PCE has the most obvious improvement on flow performance of fly ash base slurry. When the saturated content is 0.6%, the water reduction rate can reach 29.3%, the fluidity extends from 113 mm to 351 mm, the initial setting time is extended from 32 min to 149 min, and the final setting time is extended from 42 min to 182 min, with a significant delayed setting phenomenon. In the early hydration process, The adsorption of PCE can inhibit the dissolution of C_3A, hinder the growth of ettringite(AFt) and change its crystal form. At the same time, the complexation of PCE can combine with Ca~(2+ ) to form complex, affecting the formation of Ca(OH)_2, delaying the enrichment of Ca~(2+) and prolonging the induction period of cement hydration. The hydration of C_3S is also inhibited, which reduce the number of C-S-H nucleation and the second hydration exothermic peak. In the middle and late stages of hydration, the inhibition effect of PCE fails and the mechanical strength of the material increases gradually. PCE can only delay the early hydration process, but has no effect on the middle and late hydration process.

Key Words： polycarboxylate acid superplasticizer;hydration process;shotcrete materials;induction period;fluidity

Abstract:

Keywords:

Foundation: 贵州省科技支撑计划资助项目([2020]2Y029)

Authors: CHU Ruizhi;YAN Yaoqi;YANG Wei;LUO Weidong;REN Wanxing;MENG Xianliang;

DOI: 10.13226/j.issn.1006-6772.21122401

References：

• [1] YAO Z T,JI X S,SARKER P K,et al.A comprehensive review on the applications of coal fly ash[J].Earth-Science Reviews,2015,141:105-121.
• [2] KOUKOUZAS N K,ZENG R,PERDIKATSIS V,et al.Mineral-ogy and geochemistry of Greek and Chinese coal fly ash[J].Fuel,2006,85(16):2301-2309.
• [3] BHATT A,PRIYADARSHINI S,ACHARATH Mohanakrishnan A,et al.Physical,chemical,and geotechnical properties of coal fly ash:A global review[J].Case Studies in Construction Materials,2019,11:e00263.
• [4] BAGHERI A,ZANGANEH H,ALIZADEH H,et al.Comparing the performance of fine fly ash and silica fume in enhancing the properties of concretes containing fly ash[J].Construction and Building Materials,2013,47:1402-1408.
• [5] WON J P,HWANG U J,KIM C K,et al.Mechanical performa-nce of shotcrete made with a high-strength cement-based mineral accelerator[J].Construction and Building Materials,2013,49:175-183.
• [6] A?TCIN P C.The durability characteristics of high performance co-ncrete:A review[J].Cement and Concrete Composites,2003,25(4):409-420.
• [7] SAHMARAN M,YURTSEVEN A,YAMAN I O.Workability of hybrid fiber reinforced self-compacting concrete[J].Building and Environment,2005,40(12):1672-1677.
• [8] ZHANG C,HOU Z Y,CHEN C,et al.Design of 3D printable concrete based on the relationship between flowability of cement paste and optimum aggregate content[J].Cement & Concrete Composites,2019,104.
• [9] HAN S,YAN P Y,KONG X M.Study on the compatibility of cement-superplasticizer system based on the amount of free solution[J].Science China-Technological Sciences,2011,54(1):183-189.
• [10] MAARUP C,HJULER K,DAM-JOHANSEN K.High temperature cement raw meal flowability[J].Powder Technology,2014,253:686-690.
• [11] WU W D,MATALKAH F,SOROUSHIAN P,et al.Influence of admixtures on rheological properties and heat of hydration of alkali aluminosilicate cement[J].Advances in Cement Research,2017,29(9):397-403.
• [12] PALACIOS M,PUERTAS F,Bowen P,et al.Effect of PCs superplasticizers on the rheological properties and hydration process of slag blended cement pastes[J].Journal of Materials Science,2009,44(10):2714-2723.
• [13] DE MATOS P R,JIAO D W,ROBERTI F,et al.Rheological and hydration behaviour of cement pastes containing porcelain polishing residue and different water-reducing admixtures[J].Construction and Building Materials,2020,262:120850.1-120850.11.
• [14] YUN K K,CHOI P,YEON J H.Rheological characteristics of wet-mix shotcrete mixtures with crushed aggregates and mineral admixtures[J].Ksce Journal of Civil Engineering,2018,22(7):2469-2479.
• [15] YUN K K,CHOI S Y,YEON J H.Effects of admixtures on the rheological properties of high-performance wet-mix shotcrete mixtures[J].Construction and Building Materials,2015,78:194-202.
• [16] KONG X M,ZHANG Y R,HOU S S.Study on the rheological properties of Portland cement pastes with polycarboxylate superplasticizers[J].Rheologica Acta,2013,52(7):707-718.
• [17] SHUI Liangliang,SUN Zhenping,YANG Hajing,et al.Experimental evidence for a possible dispersion mechanism of polycarboxylate type superplasticisers[J].Advances in Cement Research,2016,28(5):287-297.
• [18] 李顺，余其俊，韦江雄.聚羧酸减水剂的分子结构对水泥水化过程的影响[J].硅酸盐学报，2012,40(4):613-619.LI Shun,YU Qijun,WEI Jiangxiong.Effect of molecular structure of polycarboxylate water reducers on hydration of cement[J].Journal of the Chinese Ceramic Society,2012,40(4):613-619.
• [19] 王国建，魏敬亮.混凝土高效减水剂及其作用机理研究进展[J].建筑材料学报，2004,7(2):188-193.WANG Guojian,WEI Jingliang.Development of study on working mechanisms of high range water-reducers[J].Journal of Building Materials,2004,7(2):188-193.
• [20] 马保国，谭洪波，董荣珍，等.聚羧酸减水剂缓凝机理的研究[J].长江科学院院报，2008,25(6):93-95.MA Baoguo,TAN Hongbo,DONG Rongzhen,et al.Retarding mechanism of polycarboxylic acid type water-reducing agent[J].Journal of Yangtze River Scientific Research Institute,2008,25(6):93-95.
• [21] NAVARRETE I,KURAMA Y,ESCALONA N,et al.Effect of supplementary cementitious materials on viscosity of cement-based pastes[J].Cement and Concrete Research,2022,151:DOI:10.1016/j.cemconres.2021.106635.
• [22] SCRIVENER K L,JUILLAND P,MONTEIRO P J M.Advances in understanding hydration of Portland cement[J].Cement and Concrete Research,2015,78:38-56.
• [23] 孔祥明，卢子臣，张朝阳.水泥水化机理及聚合物外加剂对水泥水化影响的研究进展[J].硅酸盐学报，2017,45(2):274-281.KONG Xiangming,LU Zichen,ZHANG Chaoyang.Recent development on understanding cement hydration mechanism and effects of chemical admixtures on cement hydration[J].Journal of the Chinese Ceramic Society,2017,45(2):274-281.
• [24] SCRIVENER K L,NONAT A.Hydration of cementitious materials,present and future[J].Cement and Concrete Research,2011,41(7):651-665.
• [25] CHEUNG J,JEKNAVORIAN A,ROBERTS L,et al.Impact of admixtures on the hydraton kinetics of Portland cement[J].Cement and Concrete Research,2011,41(12):1289-1309.
• [26] 王培铭，丰曙霞，刘贤萍.水泥水化程度研究方法及其进展[J].建筑材料学报，2005(6):646-652.WANG Peiming,FENG Shuxia,LIU Xianping.Research approaches of cement hydration degree and their development[J].Journal of Building Materials,2005(6):646-652.
• [27] SOWOIDNICH T,RACHOWSKI T,R??LER C,et al.Calcium complexation and cluster formation as principal modes of action of polymers used as superplasticizer in cement systems[J].Cement and Concrete Research,2015,73:42-50.
• [28] 董红娟，王博，张金山，等.粉煤灰基复合胶凝喷浆材料的强度及水化机理[J].硅酸盐通报，2020,39(10):3293-3297.DONG Hongjuan,WANG Bo,ZHANG Jinshan,et al.Strength and hydration mechanism of fly ash-based composite cementitious shotcrete material[J].Bulletin of the Chinese Ceramic Society,2020,39(10):3293-3297.