Quantitative Characterization of Effective Porosity in Cement-Based Composite Materials

2010 ◽  
Vol 163-167 ◽  
pp. 3174-3179
Author(s):  
Guo Wen Sun ◽  
Jin Yang Jiang ◽  
Yun Sheng Zhang ◽  
Cai Hui Wang
Keyword(s):  
Composite Materials ◽  
Cement Paste ◽  
Pore Diameter ◽  
Effective Porosity ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Pore Characteristics ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Second Peak

The method of the second intrusion mercury in MIP was used to investigate the pore characteristics of hardened cement paste with w/c ratio 0.23, 0.35 and 0.53, respectively, in order to research the quantitative relationship between transport properties and pore characteristics in cement-based composite materials. The results show the second intrusion mercury could well determine the effective pore structure parameters, and effective porosity accounts for 25% to 50% of total porosity in cement paste. At the same time, the existence of the first and second peak in pore size distribution curves is confirmed by MIP, such as, the first peak in hardened cement paste with water to cement ratio 0.53 is very distinct, however, with the decrease of water to cement ratio, the first peak gradually disappears. The pore diameter corresponding to the first and second peak is critical pore diameter of capillary pore and gel pore, respectively.

An Experimental Study of Water in Pore System of Hardened Cement Paste by Magnetic Resonance

2013 ◽  
Vol 539 ◽  
pp. 14-18
Author(s):  
An Ming She ◽  
Wu Yao ◽  
Wan Cheng Yuan
Keyword(s):  
Cement Paste ◽  
Water Distribution ◽  
Transverse Relaxation Time ◽  
Bimodal Distribution ◽  
Early Age ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Initial Water ◽  
Cement Ratio ◽  
Water To Cement Ratio

The water distribution in hardened cement paste with different ages, water to cement ratio (w/c) and different cured methods were investigated by low field NMR. The transverse relaxation time, T2, was used as a parameter to describe the water phase constrained in pores. The results show that the T2 distributions of pastes in the early age are bimodal distribution. As the curing time increase, the T2 distribution peaks shift gradually to the short T2 values reflecting the decrease of mean pore dimension as well as the increase of specific surface area resulted from the gel products. In addition, the influences of initial water to cement ratio and cure methods on water distribution are occurred mainly during the early age. When cured to 28 days, the differences of water distribution in various samples are unconspicuous.

Composite materials based on cement matrices

1983 ◽  
Vol 310 (1511) ◽  
pp. 191-202 ◽  
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Cement Paste ◽  
Metal Wire ◽  
Hardened Cement ◽  
Paper Briefly ◽  
Hardened Cement Paste ◽  
Recent Developments ◽  
Reinforced Cement ◽  
Cement And Concrete

All materials produced from inorganic hydraulic cements are composites of one kind or another because of their multiphase nature. This paper briefly considers the relevance of composite principles in predicting the mechanical properties of hardened cement paste, mortar and concrete and then discusses recent developments towards enhancing these properties by the addition of polymers and more particularly fibres. Fibres derived from glass, polypropylene and cellulose with metal wire are currently being used as cement reinforcements. Important properties of some of these practical fibre reinforced cement and concrete (F.R.C.) materials are discussed with particular reference to the replacement of asbestos products. Some examples of recent innovations in the manufacture of F.R.C. materials are given together with projections for their future use.

In Situ Observation Microstructure Character Changes in the Carbonation Process of Hardened Cement Paste Using ESEM/EDS

2011 ◽  
Vol 194-196 ◽  
pp. 873-877
Author(s):  
Jian De Han ◽  
Gang Hua Pan ◽  
Wei Sun
Keyword(s):  
Calcium Hydroxide ◽  
Cement Paste ◽  
Environmental Scanning ◽  
Hardened Cement ◽  
In Situ Observation ◽  
Hardened Cement Paste ◽  
Carbonation Process ◽  
Water To Cement Ratio ◽  
Before And After

Environmental Scanning Electron Microscope (ESEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to in situ observation microstructure character changes of hardened cement paste due to carbonation. Three types water-to-cement ratio of 0.53, 0.35 and 0.23 were research. When w/c=0.53, Carbonation enlarged the cracks, and some calcium carbonate spots appear on the calcium hydroxide crystals. When w/c=0.35, less cracks appear, and some white flocculent calcium carbonated appear on the calcium hydroxide crystals than above w/c=0.53 cement paste. When w/c=0.23, the microstructure character before and after carbonation have distinct changes, and some cracks become small or disappeared. Unhydrated cement clinkers continue to hydrate reactions and there are many white SiO2•nH2O (silica gel) after C-S-H gel carbonation in cement paste matrix.

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