Fractal dimension of concrete incorporating silica fume and its correlations to pore structure, strength and permeability

Utilization of low-quality desulfurized ash from semi-dry flue gas desulfurization by mixing with hemihydrate gypsum

Performance and ITZ of pervious concrete modified by vinyl acetate and ethylene copolymer dispersible powder

Comparison of Mercury Intrusion Porosimetry and multi-scale X-ray CT on characterizing the microstructure of heat-treated cement mortar

The development of Expanded Polystyrene (EPS) concrete involves two major concerns: (a) poor strength resulting in the EPS concrete unsuitable for structural applications, and (b) segregation of the ultra-light weight of EPS during mixing (EPS is approximately 100 times lighter than concrete). Though EPS displays high insulation (thermal conductivity ≈ 0.04 W/m-K), these issues limit its usage in concrete. This study aims to develop a lightweight-EPS cement composite (LECC) having enhanced insulating capacity as well as satisfactory compressive strength for structural applications. To mitigate the deteriorating effect of EPS on strength, the LECC is developed using the base material of ultra-high performance concrete (UHPC). EPS beads of 3–5 mm diameter are mixed in UHPC in five proportions by volume of 0, 16, 25, 36, 45% and the resulting composites are tested for mechanical and thermal properties. Microstructural characterization is performed using micro-computed tomography (μCT). The choice of the UHPC ingredients proportion is found successful in achieving a balance between an optimum viscosity and satisfactory workability for uniform dispersion of EPS, confirmed by the flow values and μCT results. McLachlan's general effective media approximation, based on percolation theory, is used to homogenize the composite and estimate its thermal conductivity with satisfactory accuracy. The LECC thus developed displays a strength 45 MPa with a corresponding density of 1677 kg/m3 and thermal conductivity of 0.58 W/m-K.

Lightweight structural cement composites with expanded polystyrene (EPS) for enhanced thermal insulation

Thermally insulating lightweight cement-based composites incorporating glass beads and nano-silica aerogels for sustainably energy-saving buildings

Anti-water-penetration techniques are important to raise the durability of cement-based materials (CBMs). Here the water penetration resistances of cement mortars with ethylene-vinyl acetate copolymer (EVA) and styrene butadiene rubber (SBR) were in-situ and non-destructively probed by micro-focus X-ray computed tomography (μ-XCT). Caesium Chloride (CsCl) was mixed in water to enhance the contrast gradients of μ-XCT images. SEM and EDS tests were provided to assess the mortar microstructure changes induced by water penetration. Results show that the CsCl enhancement helps trace the water penetration fronts, while exerting minor influences on the water penetration kinetics. The polymers can greatly raise the resistance against the water penetration into the cement mortars. The pore blocking induced by the formation of polymer films on the surfaces of cement grains and aggregates may account for the enhanced water-penetration resistance. The findings of this work provide a new method to track the water penetration in CBMs by μ-XCT and deepen the knowledge in the anti-water mechanisms of polymer-modified cement materials.

In-situ assessment of the water-penetration resistance of polymer modified cement mortars by μ-XCT, SEM and EDS

Mercury intrusion porosimetry (MIP) is a vital method for assessing the pore structure of cement-based porous materials (CBPMs), but its applicability remains to be clarified Herein we employed X-ray computed tomography (X-CT) to trace the entrapped mercury in two hardened cement pastes (HCPs) after MIP tests to reassess the method for pore structure characterization Four different maximum pressures were employed in the MIP tests Results show that the maximum intrusion pressure had no significant influences on the threshold pore sizes, but impacted the mean pore sizes that were linked to the pore intervals X-CT can measure the mercury drops entrapped in macro pores A pore model with the pore structure of thick chamber connected with thin throats was proposed to associate the links between the MIP and X-CT data The combined uses of MIP and X-CT provide new insights in better understanding MIP results and the possibility for quantitative pore structure characterization of CBPMs

Reassessment of mercury intrusion porosimetry for characterizing the pore structure of cement-based porous materials by monitoring the mercury entrapments with X-ray computed tomography

Yu Peng

Papers

Thermally insulating lightweight cement-based composites incorporating glass beads and nano-silica aerogels for sustainably energy-saving buildings

In-situ assessment of the water-penetration resistance of polymer modified cement mortars by μ-XCT, SEM and EDS

Reassessment of mercury intrusion porosimetry for characterizing the pore structure of cement-based porous materials by monitoring the mercury entrapments with X-ray computed tomography

Retardation effect of elevated temperature on the setting of calcium sulfoaluminate cement clinker

The influence of Si/Al ratio on sulfate durability of metakaolin-based geopolymer