The quality and performance of concrete is improved by the introduction of multi-walled nanotubes (MWCNTs). However, some research has shown negligible improvement. This paper investigates the effect of sonicated water and sonicated water plus MWCNTs on the properties of Portland cement concrete and paste. Changes are expected in the areas of compressive strength, load versus displacement, absorption, void space (ASTM C642) ratio, and microstructure. Deionized water (DI), sonicated deionized water (SDI), and sonicated deionized water with 0.01% MWCNTs concentration (SDI + MWCNTs) were used in preparing three batches. Compressive strength was improved by 18% for samples made with SDI and 21% SDI + MWCNTs in comparison with samples made with DI water. The load versus displacement, absorption, and permeable void ratio were improved for SDI and SDI + MWCNT samples. Results revealed the main effects are related to the sonication of water rather than incorporation of untreated MWCNTs. The scanning electron microscopy observations showed that cement paste samples made with SDI and SDI + MWCNT water have the same distinctive microstructure with more ettringite needles than paste samples made with deionized water. The hypothesis explaining those effects is that the sonication process produces a salt-calcium peroxide (CaO2), which enhances the early mechanical and microstructural properties of Portland cement.
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- Cement hydration
- Multi-walled carbon nanotubes (CNTs)
- Portland cement mechanical properties
- Sonicated water
- Sonication effect