Modification of cement-based materials with nanoparticles

Abstract

a b s t r a c tThis is a summary paper on the work being done at the Center for Advanced Cement-Based Materials at Northwestern University on the modification of cement-based materials with nanoparticles, specifically nanoclays, calcium carbonate nanoparticles, and nanosilica. The rheological properties of clay-modified cement-based materials are investigated to understand the influence of nanoclays on thixotropy. The influence of the method of dispersion of calcium carbonate nanoparticles on rate of hydration, setting, and compressive strength are evaluated. And an in-depth study on the mechanisms underlying the influence of nanosilica on the compressive strength gain of fly ash-cement systems is discussed. The motivation behind these studies is that with proper processing techniques and fundamental understanding of the mechanisms underlying the effect of the nanoparticles, they can be used to enhance the fresh-state and hardened properties of cement-based materials for various applications. Nanoclays can increase the green strength of self-consolidating concrete for reduced formwork pressure and slipform paving. Calcium carbonate nanoparticles and nanosilica can offset the negative effects of fly ash on early-age properties to facilitate the development of a more environmentally friendly, high-volume fly ash concrete.

Influence of selected activating methods on hydration processes of mixtures containing high and very high amount of fly ash

“…This material is fine-grained and may cause deterioration of fluidity; however, this effect may be compensated by spherical grains of fly ash [87,88]. Accelerating action of small amount of silica fume on early hydration of high volume fly ash mixture may be manifested in changes of shape of heat release curve while improvement in pozzolanic activity by reduction in Ca(OH) 2 basing on TG/ DTG results.…”

“…Very fine grains of nanosilica act as nucleation centres for precipitating products; thus, hydration of cement is accelerated [87,89]. Interfacial transition zone is improved and compressive strength of final material is enhanced as a result of action of this additive despite its small amount used [87,92,95]. However, it should be indicated that very fine particles of nanosilica tend to agglomerate.…”

“…In general, small amount of nanoparticles, such as nano-Fe 2 O 3 , nano-CaCO 3 , nano-SiO 2 , can improve compressive strength of cement as well as microstructure of hardened matrix on condition that nanoparticles are well dispersed [87,92]. Exemplary literature reports concerning influence of nanoparticles on high volume fly ash mixtures are presented in Table 1.…”

“…Kawashima et al [87] revealed, basing on thermogravimetric results, that addition of nanosilica into blended cement containing 40% of fly ash causes rapid consumption of Ca(OH) 2 during early days of hydration resulting in increasing early strength gain. This effect of strength enhancing is gradually decreased over time.…”

Carbonic nanoparticles and C-S-H insertion into cementitious nanocomposite

“…Furthermore, the isolated insertion of NTCP-OX as the nanocomposite T2 (insertion of 0.2% of NTCPM-OX) presented tensile strength 13% higher than the control material, which can be explained by the fact that materials such as NTC exhibit high tensile strength and when well distributed in the matrix results in a nanoscale reinforcement [19,20], according to figure 9, preventing the appearance of the first cracks, which results in the increase of tensile strength. …”