This paper reports the influence of raw and sonicated cellulose nanocrystals (CNCs) on the microstructure of cement paste. A novel centrifugation method is designed to measure the concentrations of the adsorbed CNCs (aCNCs) on the cement surface, and the free CNCs (fCNCs) which are mobile in water. It is found that, the majority of the CNCs (>94%) are aCNCs. More importantly, sonication does not significantly reduce the amount of aCNCs (reduction of less than 2%). We surmise that, after sonication, the aCNCs are primarily dispersed over the cement surface, instead of becoming fCNCs via sonication. Isothermal calorimetry and energy-dispersive X-ray spectroscopy (EDX) results support this theory. The water desorption tests show that the total porosities of cement pastes with raw and sonicated CNCs are 14.8% and 14.4%, which showed a reduction from 16% for the plain cement paste. The porosity reduction is a result of an increase in the degree of hydration. The advantage of sonicated CNCs is they are dispersed, avoiding therefore agglomerates that can lead to pores, voids, and air entrapment. The nanoindentation results show that the reduced indentation modulus on the interfacial regions between cement particles and the low density CSH is increased when CNCs are used.

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Patients with chronic kidney disease (CKD) have an increased risk of fracture. Raloxifene is a mild anti-resorptive agent that reduces fracture risk in the general population. Here we assessed the impact of raloxifene on the skeletal properties of animals with progressive CKD. Male Cy/+ rats that develop autosomal dominant cystic kidney disease were treated with either vehicle or raloxifene for five weeks. They were assessed for changes in mineral metabolism and skeletal parameters (microCT, histology, whole bone mechanics, and material properties). Their normal littermates served as controls. Animals with CKD had significantly higher parathyroid hormone levels compared to normal controls as well as inferior structural and mechanical skeletal properties. Raloxifene treatment resulted in lower bone remodeling rates and higher cancellous bone volume in the rats with CKD. While it had little effect on cortical bone geometry it resulted in higher energy to fracture and modulus of toughness values than vehicle-treated rats with CKD, achieving levels equivalent to normal controls. Animals treated with raloxifene had superior tissue-level mechanical properties as assessed by nanoindentation and higher collagen D-periodic spacing as assessed by atomic force microscopy. Thus, raloxifene can positively impact whole bone mechanical properties in CKD through its impact on skeletal material properties.

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