Mortar

About: Mortar is a research topic. Over the lifetime, 25024 publications have been published within this topic receiving 218739 citations.

Influence of transverse crack width on reinforcement corrosion initiation and propagation in mortar beams

Abstract: This paper discusses the relationship between crack widths, chloride diffusivity, and corrosion rate of cracked mortar beams. Flexural loads are introduced to generate crack widths ranging from 29 to 390 µm. The specimens were subjected to accelerated corrosion by immersion in a 5% NaCl solution and a constant voltage of 12 V. In addition, salt ponding tests were conducted to determine the chloride ion transport properties. The results showed that as the crack width increased, the effective diffusion coefficient (corrosion initiation) and mass loss of steel reinforcing bars due to the accelerated corrosion (corrosion propagation) also increased. For crack widths less than about 135 µm, the effect of crack width on the effective diffusion coefficient and mass loss of steel reinforcing bars embedded in mortar specimens was found to be marginal when compared with the virgin specimens. Therefore, it was concluded that the effect of crack width on the corrosion initiation and propagation period was more pronou...

Roles of water film thickness and fibre factor in workability of polypropylene fibre reinforced mortar

Abstract: For plain mortar without fibres, it has been found that its fresh properties are governed mainly by the water film thickness (WFT). For fibre reinforced mortar with fibres added, it has been suggested that the effects of the fibres may be evaluated in terms of a fibre factor (FF) combining the fibre volume and aspect ratio together. In two previous studies on the workability of polypropylene (PP) fibre reinforced mortar, the combined effects of WFT and fibre volume and the combined effects of WFT and fibre length have been separately studied. Herein, additional tests with both the fibre volume and fibre length varying simultaneously have been carried out to generate more data for evaluating the combined effects of WFT, fibre volume and fibre length. Based on the test results, a new model is developed whereby the workability attributes are each expressed as a single-variable function of the product of a linear function of WFT and an exponential function of FF. By this model, the roles of WFT and FF are revealed and the workability may be estimated for preliminary design of PP fibre reinforced mortar.

Corrosion of reinforcement steel embedded in high water-cement ratio concrete contaminated with chloride

Abstract: The aim of this investigation was to examine the role of internal chloride on the corrosion behaviour of steel in ordinary Portland cement (OPC), and sulphate resistant Portland cement (SRPC) mortar mixes of higher water-cement (w/c) ratios. For this purpose, the steel electrodes embedded in mortar specimens were subjected to short-term electrochemical monitoring. On completion of electrochemical monitoring, pore solution was extracted from the specimens for analysis. For the purpose of comparison, pore solution was also extracted from separate OPC and SRPC cylindrical mortar specimens hydrated in an environment isolated from the atmosphere. Results from microanalysis using scanning electron microscope (SEM) are also reported. The results demonstrated that mortars prepared with a cement of high tricalcium aluminate (C 3 A) content, even when the w/c ratio of the mix was maintained at 0.70, still passivated the steel embedded in it even in the presence of chloride as high as 1% by weight of cement. Under a similar condition, the steel embedded in mortar prepared with a cement of low C 3 A content was unable to passivate the steel electrode. The special protection mechanism by the lime-rich layer as proposed by Page for low w/c ratio concretes is also valid for the steel embedded in high w/c ratio mortar. The type of exposure condition (e.g. exposure to atmosphere) during the hydration period strongly influences the hydroxide ion concentration in the pore solution, while this has no effect on the freechloride concentration in the pore solution. This study reconfirms the significance of the C 3 A phase of cement in respect to chloride-binding processes.