Mortar

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

Strength and durability aspects of calcined kaolin-blended portland cement mortar and concrete

Abstract: Economic and sustainability arguments require carefully assessing the potentialities of indigenous resources for the production of mortar and concrete for the construction industry. In Vietnam, significant efforts should be bestowed on urban development, coastal protection and harbour construction works. In a joint Vietnamese-Dutch co-operation program, the practical use for this purpose of relevant resources in Northern Vietnam is assessed experimentally. This paper concentrates on kaolin, which is widely available in this region. The key issues this paper is dealing with are the effects of partial replacement of Portland cement by calcined kaolin in mortar and concrete on compressive strength as well as on durability characteristics of mortar and concrete mixes pertinent to the coastal environment. Workability measures are also mentioned. Data are therefore presented on compressive strength development over a maximum curing period of 180 days of mixes in which the water to binder ratio was varied between 0.40 and 0.53. Moreover, partial replacement was considered in the range from 0% to 30% by weight. The results of this study render possible the assessment of optimum replacement percentages of Portland cement by calcined kaolin, and the associated strength gain. Additionally, this paper reports on the performance aspects of similarly blended mortar and concrete specimens stored for a period of one year in a low concentration of a sodium sulfate solution. It could be concluded that a strength gain due to blending will be accompanied by improved durability in this environment.

Calcite-Forming Bacteria for Compressive Strength Improvement in Mortar

Abstract: Microbiological calcium carbonate precipitation (MCP) has been investigated for its ability to improve the compressive strength of concrete mortar. However, very few studies have been conducted on the use of calcite-forming bacteria (CFB) to improve compressive strength. In this study, we discovered new bacterial genera that are capable of improving the compressive strength of concrete mortar. We isolated 4 CFB from 7 environmental concrete structures. Using sequence analysis of the 16S rRNA genes, the CFB could be partially identified as Sporosarcina soli KNUC401, Bacillus massiliensis KNUC402, Arthrobacter crystallopoietes KNUC403, and Lysinibacillus fusiformis KNUC404. Crystal aggregates were apparent in the bacterial colonies grown on an agar medium. Stereomicroscopy, scanning electron microscopy, and x-ray diffraction analyses illustrated both the crystal growth and the crystalline structure of the CaCO3 crystals. We used the isolates to improve the compressive strength of concrete mortar cubes and found that KNUC403 offered the best improvement in compressive strength.

Corrosion behaviour of rebars in fly ash mortar exposed to carbon dioxide and chlorides

Abstract: Addition of fly ash has beneficial effects on some mechanical properties of concrete, as well as on the corrosion process induced by the chloride ion. The aim of this study was to investigate the effect of fly ash addition on the corrosion process occurring in reinforced concrete exposed simultaneously to carbon dioxide and chloride. The corrosion process of steel rebars embedded in mortar with 15% and 30% of fly ash was tested under carbon dioxide and sodium chloride contamination. Monitoring of open circuit potential and electrochemical impedance spectroscopy (EIS) were used to follow the corrosion process. Results have shown that under accelerated carbonation fly ash mortar shows higher corrosion rates. The chloride content in mortar exposed to accelerated carbonation increases with the amount of fly ash. However, under natural carbonation it decreases with the addition of fly ash.