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    Alkali-Activated Mortar for Tunnel-Lining Structure Repair

    Source: Journal of Materials in Civil Engineering:;2019:;Volume ( 031 ):;issue: 010
    Author:
    Rui Chen
    ,
    Hongpeng Lai
    ,
    Da Cui
    ,
    Yue Zhu
    DOI: 10.1061/(ASCE)MT.1943-5533.0002857
    Publisher: American Society of Civil Engineers
    Abstract: With the aging of tunnel structures, rehabilitation and repair has become an increasingly important part of tunnel maintenance. This paper investigates the use of alkali-activated mortar for tunnel-lining structure repair. First, the effects of NaOH concentration and ordinary portland cement (OPC) content on the fresh and hardened states of alkali-activated repair mortar (ARM) were studied by investigating its setting time and compressive strength. Second, the bond strength of ARM made from the optimum mix proportion was compared with that of cement repair mortar (CRM) using a self-design tunnel-lining-crack-treatment platform (TLCTP). Finally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were undertaken to study the morphology, mineral composition, and hydration products of ARM and CRM. It is found that the setting times of ARM are greatly shortened and its compressive strength is noticeably increased with increasing OPC content. Increasing the NaOH concentration from 10 to 12 M induces decrease in setting times and increase in compressive strength of ARM, but further increasing NaOH concentration to 14 M results in a slight increase in setting times and decrease in the compressive strength of ARM. Bond strength test results show that ARM made from an optimum mix proportion exhibits a bond strength superior to that of CRM in dry curing conditions. Although the presence of water has a negative effect on bond strength, ARM still shows better bond strength than CRM. XRD characterization indicates that ARM consists of sodium aluminosilicate hydrate (NASH) gel and calcium silicate hydrate (CSH) gel that are responsible for increasing its strength. SEM characterization reveals that ARM has a dense structure with voids filled with cementing agents, whereas the CRM shows a rough structure with small cracks and unfilled pores. The dense microstructure benefits the reduction in crack propagation and water absorption, leading to high compressive and bond strengths.
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      Alkali-Activated Mortar for Tunnel-Lining Structure Repair

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4259500
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    contributor authorRui Chen
    contributor authorHongpeng Lai
    contributor authorDa Cui
    contributor authorYue Zhu
    date accessioned2019-09-18T10:37:23Z
    date available2019-09-18T10:37:23Z
    date issued2019
    identifier other%28ASCE%29MT.1943-5533.0002857.pdf
    identifier urihttp://yetl.yabesh.ir/yetl1/handle/yetl/4259500
    description abstractWith the aging of tunnel structures, rehabilitation and repair has become an increasingly important part of tunnel maintenance. This paper investigates the use of alkali-activated mortar for tunnel-lining structure repair. First, the effects of NaOH concentration and ordinary portland cement (OPC) content on the fresh and hardened states of alkali-activated repair mortar (ARM) were studied by investigating its setting time and compressive strength. Second, the bond strength of ARM made from the optimum mix proportion was compared with that of cement repair mortar (CRM) using a self-design tunnel-lining-crack-treatment platform (TLCTP). Finally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were undertaken to study the morphology, mineral composition, and hydration products of ARM and CRM. It is found that the setting times of ARM are greatly shortened and its compressive strength is noticeably increased with increasing OPC content. Increasing the NaOH concentration from 10 to 12 M induces decrease in setting times and increase in compressive strength of ARM, but further increasing NaOH concentration to 14 M results in a slight increase in setting times and decrease in the compressive strength of ARM. Bond strength test results show that ARM made from an optimum mix proportion exhibits a bond strength superior to that of CRM in dry curing conditions. Although the presence of water has a negative effect on bond strength, ARM still shows better bond strength than CRM. XRD characterization indicates that ARM consists of sodium aluminosilicate hydrate (NASH) gel and calcium silicate hydrate (CSH) gel that are responsible for increasing its strength. SEM characterization reveals that ARM has a dense structure with voids filled with cementing agents, whereas the CRM shows a rough structure with small cracks and unfilled pores. The dense microstructure benefits the reduction in crack propagation and water absorption, leading to high compressive and bond strengths.
    publisherAmerican Society of Civil Engineers
    titleAlkali-Activated Mortar for Tunnel-Lining Structure Repair
    typeJournal Paper
    journal volume31
    journal issue10
    journal titleJournal of Materials in Civil Engineering
    identifier doi10.1061/(ASCE)MT.1943-5533.0002857
    page04019217
    treeJournal of Materials in Civil Engineering:;2019:;Volume ( 031 ):;issue: 010
    contenttypeFulltext
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