Effect of Electric Heat Tracing Pre-Curing Condition on Critical Strength of Concrete

Abstract

Abstract: Electric heat tracing pre-curing is a simple and efficient method to ensure the curing temperature and strength development of ready-mixed concrete in cold weather. The research analyzed the effects of pre-curing temperature and aging on the compressive strength of a high slump C30 normal concrete. Tests of 7 d constant negative temperature (-5 ℃, -10 ℃, -15 ℃) once-freezing to standard curing pretreatment test were reported. According to the definition of critical strength, the reasonable critical strength values and pre-curing time under the electric heat tracing pre-curing treatment were acquired. The results show that concretes pre-cured by electric heat tracing subjected to high temperatures attain higher compressive strengths than concretes subjected to normal temperature. Nevertheless, the pre-curing temperature should be controlled at 30 ℃, because the rate of strength development and R_-7+28 (compressive strength of negative temperature curing for 7 d and then standard curing for 28 d) are reduced at higher pre-curing temperatures. When the pre-curing temperature is 30 ℃ and the hardening temperature is not lower than -15 ℃, the pre-curing time is between 36 h and 48 h. Under the hardening condition of constant negative temperature (-5 ℃, -10 ℃, -15 ℃), the critical strength of concrete pre-cured with electric heat tracing is in the range of 6.6 MPa to 17.8 MPa, which is 22.0% to 59.3% of the standard value for the compressive strength of concrete cubes. This paper aims to compare the influence of electric heat tracing pre-curing treatment on the mechanical properties of common concrete and to guide the relevant engineering applications.

Key words: electric heat tracing, ready-mixed concrete, critical strength, compressive strength, pre-curing temperature, pre-curing time, constant negative temperature

CLC Number:

TU528.1

LIU Zhongyang, FU Shuai, MA Guowei, WANG Shan, LI Bingyang, YANG Han, CUI Xiujun, ZHANG Zhou. Effect of Electric Heat Tracing Pre-Curing Condition on Critical Strength of Concrete[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2022, 41(6): 1990-1997.

References

[1] 朱卫中,赖晓峰,李莉.混凝土抗冻临界强度取值研究与实践[J].低温建筑技术,1995,17(4):35-38.
ZHU W Z, LAI X F, LI L. Consideration and practice of the some concepts for frost-resisting critical strenth of concrete[J]. Low Temperature Architecture Technology, 1995, 17(4): 35-38 (in Chinese).
[2] 朱卫中,尚晓林.冬施中混凝土抗冻临界强度若干概念的理解与实践[J].施工技术,1995,24(10):30-33.
ZHU W Z, SHANG X L. Understanding and practice of several concepts of concrete frost resistance critical strength in winter construction[J]. Construction Technology, 1995, 24(10): 30-33 (in Chinese).
[3] 刘润清,刘军,刘宇,等.受冻环境对低温混凝土抗冻临界强度的影响[J].辽宁工程技术大学学报(自然科学版),2011,30(1):92-95.
LIU R Q, LIU J, LIU Y, et al. Study on anti-frozen critical strength of low-temperature concrete under different cold environments[J]. Journal of Liaoning Technical University (Natural Science), 2011, 30(1): 92-95 (in Chinese).
[4] 杨英姿,王政,高小建,等.负温混凝土的受冻临界强度及其耐久性[J].武汉理工大学学报,2009,31(2):37-41.
YANG Y Z, WANG Z, GAO X J, et al. Critical compressive strength of concrete at subzero temperature and its durability[J]. Journal of Wuhan University of Technology, 2009, 31(2): 37-41 (in Chinese).
[5] 中华人民共和国住房和城乡建设部.建筑工程冬期施工规程:JGJ/T 104—2011[S].北京:中国建筑工业出版社,2011.
Ministry of Housing and Urban-Rural Development, PRC. Construction regulation of building engineering in winter: JGJ/T 104—2011[S]. Beijing: China Architecture and Architecture Press, 2011 (in Chinese).
[6] 于海洋.受冻混凝土的早期变形及冻害机理分析[D].哈尔滨:哈尔滨工业大学,2016.
YU H Y. The early-age deformation and frost damage of concrete under sub-zero temperature[D]. Harbin: Harbin Institute of Technology, 2016 (in Chinese).
[7] 孟跃朋.冬施现浇混凝土的电伴热养护法技术研究[D].北京:北京交通大学,2016.
MENG Y P. The research of the curing technology using electric heat tracing of the cast-in-situ concrete in winter[D]. Beijing: Beijing Jiaotong University, 2016 (in Chinese).
[8] 倪锋.波罗的海明珠项目冬期混凝土内置电加热回路养护法的应用[J].建筑施工,2010,32(7):687-689.
NI F. Curing method of internally installed and circulated electrical heating applied to concrete construction in winter season for Baltic pearl project[J]. Building Construction, 2010, 32(7): 687-689 (in Chinese).
[9] LEE G C, HAN M C, BAEK D H, et al. Effect of heat curing methods on the temperature history and strength development of slab concrete for nuclear power plant structures in cold climates[J]. Nuclear Engineering and Technology, 2012, 44(5): 523-534.
[10] 严小卫,刘昌永.严寒地区大体积混凝土在不同保温措施下温度及强度发展研究[J].混凝土,2020(7):135-140+144.
YAN X W, LIU C Y. Development of temperature and strength for mass concrete under different insulation measures when constructed in severe cold area[J]. Concrete, 2020(7): 135-140+144 (in Chinese).
[11] 中华人民共和国住房和城乡建设部.普通混凝土配合比设计规程:JGJ 55—2011[S].北京:中国建筑工业出版社,2011.
Ministry of Housing and Urban-Rural Development, PRC. General concrete proportion design specification: JGJ 55—2011[S]. Beijing: China Architecture and Architecture Press, 2011 (in Chinese).
[12] 中华人民共和国住房和城乡建设部,国家市场监督管理总局.混凝土物理力学性能试验方法标准:GB/T 50081—2019[S].北京:中国建筑工业出版社,2019.
Ministry of Housing and Urban-Rural Development, PRC, State Administration for Market Regulation. Standard of test method for physical and mechanical properties of concrete: GB/T 50081—2019[S]. Beijing: China Architecture and Architecture Press, 2019 (in Chinese).
[13] 刘宇.负温混凝土抗冻临界强度与微观结构的研究[D].沈阳:沈阳建筑大学,2011.
LIU Y. Research on the anti-freeze critical strength and microstructure of negative temperature concrete[D]. Shenyang: Shenyang Jianzhu University, 2011 (in Chinese).
[14] 谭克锋,刘涛.早期高温养护对混凝土抗压强度的影响[J].建筑材料学报,2006,9(4):473-476.
TAN K F, LIU T. Effect of high temperature curing on compressive strength of concrete[J]. Journal of Building Materials, 2006, 9(4): 473-476 (in Chinese).
[15] KIM J K, HAN S H, SONG Y C. Effect of temperature and aging on the mechanical properties of concrete: part I. Experimental results[J]. Cement and Concrete Research, 2002, 32(7): 1087-1094.
[16] KIM T, RENS K L. Concrete maturity method using variable temperature curing for normal and high-strength concrete. I: experimental study[J]. Journal of Materials in Civil Engineering, 2008, 20(12): 727-734.
[17] KIM J K, MOON Y H, EO S H. Compressive strength development of concrete with different curing time and temperature[J]. Cement and Concrete Research, 1998, 28(12): 1761-1773.
[18] 钟翔,李北星.温度匹配养护对大掺量矿物掺合料混凝土抗压强度及早期水化性能的影响[J].硅酸盐通报,2019,38(10):3080-3086.
ZHONG X, LI B X. Effect of temperature match curing on compressive strength and early hydration properties of concrete with high volume of mineral admixture[J]. Bulletin of the Chinese Ceramic Society, 2019, 38(10): 3080-3086 (in Chinese).
[19] 阎培渝,王强.变温条件下粉煤灰对混凝土抗压强度的影响[J].混凝土,2008(3):1-3.
YAN P Y, WANG Q. Influence of fly ash on the compressive strength of concrete under temperature match curing conditions[J]. Concrete, 2008(3): 1-3 (in Chinese).
[20] 崔正龙,张雪虹,唐博.不同养护环境对粉煤灰混凝土强度及碳化性能的影响[J].硅酸盐通报,2019,38(1):65-69+76.
CUI Z L, ZHANG X H, TANG B. Effect of different curing environments on strength and carbonation of fly ash concrete[J]. Bulletin of the Chinese Ceramic Society, 2019, 38(1): 65-69+76 (in Chinese).