Micro-filler Effect Research Articles

Physical properties of high-performance concrete with admixtures exposed to a medium temperature range 20°C to 50°C

This paper discusses two physical properties, namely, compressive strength and modulus of elasticity of high-performance concrete made with four types of concrete mixes exposed to temperatures within the range 20°C to 50°C under three types of curing methods. The results showed that the compressive strength of concrete incorporating mineral admixtures practically reached above 100 MPa from the age of 7 days. The highest levels of strength and modulus of elasticity were produced by silica fume (SF) concrete under water and wrapped curing at temperature of 35°C. This indicates that the high pozzolanic reactivity and microfiller effect of SF at medium temperature has modified the open channels at the transition zone in SF concrete. The medium temperature environment associated with proper curing has played an important role in the hydration process that produced the hardened concrete with higher strength and elasticity.

The influence of medium temperature environments on the water permeability of high performance mortar

In this study, the durability of normal portland cement mortar and silica fume mortar are characterized by measuring the water permeability under four different types of curing temperatures. It is observed that the water permeability of normal portland cement mortar increases as temperature increases up to 75°C. However, the water permeability of silica fume mortar decreases as the temperature increases. This indicates that the high pozzolanic reaction and microfiller effect of silica fume at medium temperature has modified the open channels at the transition zone of silica fume mortar, making it much denser and stronger and leading to a fine and discontinuous pore structure.

Statistical modelling of the microfiller effect on the rheology of composite cement pastes

Experiments were designed based on a so-called uniform-precision factorial plan to investigate the effect of limestone microfiller replacement of cement on the rheological properties of low w/c ratio super plasticized cement pastes. Cement pastes of different w/b ratios and incorporating various proportions of limestone powder and/or silica fume were assessed in terms of the saturation dosage of super plasticizer using a modified Marsh cone flow time. At a constant flow time, the different cement pastes were further characterized using a coaxial cylinder viscometer, a mini slump test and an induced bleeding test. The flow of mortars corresponding to the various cement pastes were also investigated, and the different rheological tests were compared. The statistical approach used highlighted the micro filler effect on the various rheological characteristics of cement paste, and permitted its modelling over the selected experimental domain.

The influence of microfillers on enhancement of concrete strength

The research presented in this paper was intended to clarify the nature of concrete strengthening in the presence of silica fume. For this purpose, compressive strength development of high strength concrete and its paste-matrix was investigated. Carbon black was introduced as an alternative microfiller to silica fume. The results indicated that carbon black was effective in modifying the basic concrete-matrix strength relationship to an extent similar to that obtained by silica fume. It is suggested that the mechanism by which silica fume affects the concrete behaviour is of a physical origin and is based on microfiller effect, prior to its action as a pozzolanic material. The microfiller effect is of greater significance to strength enhancement.