بررسي رفتار هيدروليكي و مكانيكي بتن پارچه‌اي خود ترميم شونده با استفاده از نانو لوله¬هاي كربني (CNTs) به منظور پوشش كانال‌هاي آبياري

In the context of global water scarcity, particularly in arid an‎d semi-arid regions such as Iran, optimal water resource management has become a strategic priority. Water conveyance canals, as the main arteries for agricultural, industrial, an‎d potable water supply, lose significant volumes of water annually due to seepage through traditional concrete linings an‎d wall deterioration. Consequently, developing durable, impermeable, an‎d resistant concrete linings capable of enhancing hydraulic efficiency an‎d reducing maintenance costs has become a technical an‎d economic imperative. This research aimed to design an‎d fabricate an intelligent cementitious composite for use in canal linings. To this end, a combined macro- an‎d nano-scale technological approach was employed. A three-dimensional spacer fabric was incorporated as a macro-scale reinforcement, an‎d multi-walled carbon nanotubes (MWCNTs) were added as a nano-scale reinforcement to the cementitious matrix. Additionally, the comparative effect of microsilica (Micro Sililca) on the mechanical properties of textile concrete was investigated. Specimens were prepared in two main groups: conventional concrete (Series C) an‎d textile concrete (Series TC), with thicknesses of 10 mm an‎d 60 mm. Various weight percentages of MWCNTs an‎d Micro Sililca (0.5%, 1%, an‎d 2%) were added using dry an‎d wet mixing methods. Control specimens without additives were also fabricated as a baseline. A comprehensive experimental eva‎luation was conducted at curing ages of 7 an‎d 28 days, encompassing: mechanical tests (flexural strength, modulus of elasticity, toughness, an‎d fracture toughness), hydraulic tests (determination of permeability coefficient), durability tests (immersion in magnesium sulfate solution for up to 90 days an‎d freeze-thaw cycles up to 300 cycles), an‎d microstructural studies (scanning electron microscopy, energy-dispersive X-ray spectroscopy, an‎d porosity analysis). The findings indicated that the optimal MWCNT content was 0.5 wt% for conventional concrete (specimen CNT10_1) an‎d 1 wt% for textile concrete (specimens TCNT10_2 an‎d TCNT60_2). At these optimal levels, the 28-day flexural strength increased by 24%, 65%, an‎d 24%, respectively, compared to the control specimens (C10_0, TC10-0, an‎d TCNT60_2). Although microsilica also improved flexural strength (up to 13% improvement in specimens containing 2% Micro Sililca), the performance of MWCNTs at lower dosages was superior in terms of strength an‎d toughness enhancement. Adding MWCNTs beyond the optimal percentage led to a reduction in strength due to agglomeration an‎d poor dispersion. These three optimal compositions also led the way in other mechanical properties. The optimized specimens reduced hydraulic permeability by up to 31% an‎d 35% in Series TC an‎d C, respectively. In the sulfate environment, the degradation rate was significantly lower in Series TC compared to Series C. Freeze-thaw cycles also demonstrated the superiority of Series TC specimens, particularly at the optimal MWCNT concentration. Microstructural analyses confirmed complete interfacial transition zone integrity an‎d uniform dispersion of nanotubes. To investigate the nano-scale mechanisms responsible for these improvements, advanced characterization techniques including FESEM imaging, BET surface area analysis, an‎d EDS mapping were employed. These techniques verified the uniform distribution of nanotubes, reduction in porosity, an‎d formation of bridging networks within the matrix at the optimal state.

محمد شايان نژاد , مهدي حجازي

جهانگير عابدي كوپائي , منوچهر حيدرپوراسفرجاني

الهام فاضل , محمد شيخ زاده , مسعود نوشادي