Treatment with nano-silica and bacteria to restore the reduced bond strength between concrete and repair mortar caused by aggressive removal techniques

Purpose This paper aims to inspect the effect of indirect elevated temperature on the mechanical performance of nano silica concrete (NSC). The effect on both compressive and bond strengths is studied. Pre- and post-exposure to elevated temperature ranges of 200 to 600°C is examined. A range covered by three percentages of 1.5, 3 and 4.5 per cent nano silica (NS) in concrete mixes is tested. Design/methodology/approach Pre-exposure mechanical tests (normal conditions – room temperature), using 3 per cent NS in the concrete mix, led to the highest increase in both compressive and bond strengths (43 per cent and 38.5 per cent, respectively), compared to the control mix without NS (based on 28-day results). It is worth noticing that adding NS to the concrete mixes does not have a significant effect on improving early-age strength. Besides, permeability tests are performed on NSC with different NS ratios. NS improved the concrete permeability for all tested percentages of NS. The maximum reduction is accompanied by the maximum percentage used (4.5 per cent NS in the NSC mix), reducing permeability to half the value of the concrete mix without NS. As for post-exposure to elevated-temperature mechanical tests, NSC with 1.5 per cent NS exhibited the lowest loss in strength owing to indirect heat exposure of 600°C; the residual compressive and bond strengths are 73 per cent and 35 per cent, respectively. Findings The dispersion technique of NS has a key role in NSC-distinguished mechanical performance with NSC having lower NS percentages. NS significantly improved bond strength. NS has a remarkable effect on elevated temperature endurance. The bond strength of NSC exposed to elevated temperatures suffered faster deterioration than compressive strength of the exposed NSC. Research limitations/implications A special scale factor needs to be investigated for the NSC. Originality/value Although a lot of effort is placed in evaluating the benefits of using nano materials in structural concrete, this paper presents one of the first outcomes of the thermal effects on concrete mixes with NS as a partial cement replacement.

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Coupled effects of hydrophilic nano silica oxide and anatase nano titanium oxide on strengths of oilwell cement

Tanzania Journal of Science ◽

10.4314/tjs.v47i2.13 ◽

2021 ◽

Vol 47 (2) ◽

pp. 568-582

Author(s):

Petro E Mabeyo ◽

Jun Gu

Keyword(s):

Compressive Strength ◽

Bond Strength ◽

Shear Bond Strength ◽

Binary Systems ◽

Supplementary Cementitious Materials ◽

Nano Silica ◽

Nano Tio2 ◽

Nano Sio2 ◽

Zonal Isolation ◽

Cement Sheath

The life of oil wells depends on the stability of cement sheath and bond strength with the formation and casing. Extreme subsurface conditions cause substantial stresses on the cement sheath resulting in a serious impact on well integrity. The recommended API cement for oilwell fails to provide the required durability of the cemented well due to such conditions. Supplementary cementitious materials such as nanoparticles are added to improve the cement for long-lasting zonal isolation. In this study, the compressive and shear bond strengths of oilwell cement containing nano-SiO2 and nano-TiO2 were studied at 80 °C for 3, 7, 14, and 28 days of hydration. The XRD, TG, and DSC were used for the analysis of cement hydration products. The results revealed that both nano-SiO2 and nano-TiO2 increased strength evolution. A ternary system made with 2% nano-SiO2 and 2% nano-TiO2 improved compressive strength by 22.6 and 48.4%, while the shear bond strength increased by 110.6 and 55% at age of 3 days and 28 days, respectively, compared to their corresponding binary systems. Therefore, these results remark the potential of replacing an appropriate proportion of oilwell cement with coupled nano-SiO2 and nano-TiO2 to ensure cement sheath structure durability in the annular and long-lasting zonal isolation. Keywords: Nano-silica, nano-titanium, compressive strength, shear bond strength, oilwell cement

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Influence of Nano-silica and Polypropylene Fibers on Bond Strength of Reinforcement and Structural Lightweight Concrete

International Journal of Engineering ◽

10.5829/idosi.ije.2014.27.02b.10 ◽

2013 ◽

Vol 27 (2 (B)) ◽

Cited By ~ 1

Author(s):

S. H. Hashemi

Keyword(s):

Bond Strength ◽

Lightweight Concrete ◽

Polypropylene Fibers ◽

Nano Silica

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Study on the Bond and Anti-Abrasion Performance of Repair Materials for Hydraulic Concrete

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.426-427.403 ◽

2010 ◽

Vol 426-427 ◽

pp. 403-408 ◽

Cited By ~ 2

Author(s):

Chao Hua Jiang ◽

T.J. McCarthy ◽

D. Chen ◽

Q.Q. Dong

Keyword(s):

Bond Strength ◽

Basalt Fiber ◽

High Strength ◽

Sem Analysis ◽

Tensile Bond Strength ◽

Repair Mortar ◽

Hydraulic Concrete ◽

Repair Materials ◽

Bond Interface ◽

Direct Tensile

The bond and anti-abrasion performance of repair materials are the key factors for successful repair of hydraulic concrete. Acrylic acid emulsion (AAE) mortar, silica fume (SF) mortar, high strength (HS) mortar, polypropylene (PP) fiber mortar and basalt fiber (BF) mortar were prepared and their direct tensile bond strength, splitting tensile bond strength, abrasion resistance and SEM analysis of bond interface are studied in this paper. The results show that the highest direct tensile bond strength was recorded for fiber mortar. But compared to homogenous specimen’s tensile strength, AAE mortar showed the highest direct tensile bond strength. The anti-abrasion properties of repair mortars were tested with decreasing performance recorded in the following order: PP fiber mortar, SF mortar, BF mortar, HS mortar and AAE mortar. Compared with the HS mortar without fiber, the wear rate of PP fiber mortar was decreased by 29.2 % and the anti-abrasion strength was increased by 37.7%. This shows that adding fiber can greatly improve the anti-abrasion property. SEM analysis showed that addition of PP fiber and BF into repair mortar did not change the type of hydrates. The interface of AAE mortar was level and dense. The bond interface of SF mortar was uniform without big porosity. Addition of super plasticizer, the bond interface of HS mortar presented a large quantity of fibrous the CSH gel and less porosity which could improve the mortar bond effect effectively.

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