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In this study, a home-built Rayleigh scattering based optical frequency domain reflectometry (OFDR) technique is used for the measurement of strain distribution in a loaded cement paste. The system offers a spatially-continuous strain measurement on an optical fiber with a spatial resolution of 1 cm, dynamic range of 1 km, measurement accuracy of ±2 microstrain, and an update rate of 10 Hz. The feasibility and performance of this technique for detection of uneven strain distribution are studied and evaluated. The distributed optical fiber sensors are embedded in a cement paste cantilever. A controlled deflection is applied at the free end of it, and the strain is measured. The results are compared with the values obtained from theoretical analysis using Euler-Bernoulli beam theory and a finite element simulation. The comparison shows a reasonable consistence in overall deformation, demonstrating that the proposed technique can be used for real time strain monitoring in cement based materials; while this technique can reflect the uneven distribution of local strains due to the material heterogeneity with a controllable, high spatial resolution.

In this study, a new type of locally resonant unit is designed, analyzed and tested. Its effectiveness to be used as a sound-proof building envelop material is evaluated. Each unit consists of a hard circular plate adhered on the soft membrane that fixed in a rigid frame. This new type of locally resonant unit can easily be installed into building envelope materials, such as extruded hollow concrete, hollow wooden board and other types of light weight partition panels, to enhance their sound proof property. An analytical model is developed to describe the ability of this composite material in low-frequency sound blocking. The model provides a direct explanation for the nature of the system and an accurate method to calculate the effective mass per unit area. It is shown that the effective mass per unit area can turn to negative at certain frequency ranges, which could lead to a complete sound attenuation. In order to measure the sound transmission gap position and verify the theoretical model, experimental works are carried out. The experimental results show good agreement with the theoretical predictions.

When evaluating the carbonation resistance of paint coated concrete, the effects of both the strength grade and the curing conditions (standard curing and accelerated curing) of concrete substrate on carbonation resistance of paint coated concrete were investigated. The concept of the carbonation suppression ratio of paint was presented for evaluation of the anti-carbonation performance of the two types of paints (exterior and interior paints) when applied to a reference concrete substrate. The test results showed a good linear relationship between the carbonation depths of the paint coated concrete and the square root of exposure times. Concrete with higher strength grade exhibited greater carbonation resistance. The carbonation depth of the C35 standard cured concrete was reduced by 56% in comparison with that of the C25 standard cured concrete. It was found that concrete substrate prepared by accelerated curing method displayed lower carbonation resistance than standard cured concrete. Compared with the standard cured specimen, the carbonation depth of the accelerated cured specimen increased by 61% for the control C25 concrete and by 56% for the control C35 concrete. This phenomenon was attributed to the formation of a higher volume of capillary pores in concrete prepared by accelerated curing. Additionally, the exterior paint had a higher carbonation suppression ratio than the interior paint. The suppression ratios of the exterior and interior paint coatings applied on C25 standard cured concrete were 71% and 56%, respectively. The exterior paint coated concrete had a better carbonation resistance with longer effective blockage time and smaller carbonation rate.

The formation mechanism on the convection zone (“skin effect”) of chloride ingress are explored systematically by contrasting concretes in marine atmospheric, splash, tidal, and submerged zones. The depth of convection zone, Δx, and the maximum chloride concentration, Cmax, are two important indicators for estimating the degree of action of the skin effect. Influences of various factors on the skin effect are analyzed, including environmental conditions, mixture proportion, exposure time, and construction method. Statistics of the Δx and Cmax were extracted from field test data in the literatures. Influence of skin effect on the apparent surface chloride concentration (Cs) and diffusion coefficient (Da) was analyzed. Results show that the skin effects of concrete in atmospheric, tidal, splash and submerged zones are different, and it is highlighted that the convection zone exists even in submerged zone. The skin effect of concrete significantly impacts the fitting values of Cs and Da. Effective processing approaches can account for the skin effects of the concrete during durability design.