Improvement of mechanical properties of Oil well cement by incorporate Nano-CaCO3 prepared from eggshell waste

The objectives of this work were to prepare, characterize the CaCO3 nanoparticles as admixture derived from eggshell waste to improve the mechanical properties and performance of oil well cement (OWC) and to evaluate the interactions regarding the cement-admixture compatibility. The results suggest to use the combination of ultrafine grinding (ball milling) and heating treatment. The evaluation of the effectiveness of the addition of eggshell nanoparticles (ESNP) on the mechanical properties (compressive strength) of OWC was also an important objective. The high purity of eggshell powder was milled for 5–30 h to prepare ESNP with an average particle size of 40 nm after 25 h. The physico-chemical properties of the ESNP were characterized by different techniques including particle size analyzer (PSA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) methods. The ESPN was added in three different percentages to the OWC (2%, 6% and 10% as partial replacement of cement) and a w/c of 0.44. It was also revealed that the best percentage of ESNP addition not only resulted in much denser microstructure in OWC but also changed the formation of hydration products through presence of CaCO3 nanoparticles, which increased the rate of reaction of tricalcium aluminate (C3A) to form a carboaluminate complex. In this way the rate of hydration increased, the total hydration products increased and consequently the strength as well. Hence the addition of ESNP contributed to the improvement of early-age compressive strength, microstructure and durability properties of cement. According to the results, it was found that the optimal addition of ESNP to OWC is 6%.