Page 157 - New Trends in Green Construction

New Trends in Green Construction NATURAL FIBERS FOR SUSTAINABLE CEMENT REINFORCEMENT
Lucia J Fernandez-Carrasco, Nourjmajal Gourgani
1. Introduction
Since Ordinary Portland cement is losing its hegemony in the field of research on cement-based materials to give way to the growing interest in the study and analysis of other more environmentally friendly cements, the number of studies on the properties and Aluminate Calcium cement applications in areas in which it had been discarded due to some technical problems in the past. Currently, it is therefore necessary to investigate new applications in which the CAC contributes with its good properties to the development of useful, sustainable and durable building systems.
The main raw materials used in the manufacture of CAC are limestone and bauxite. Once the fusion of raw material takes place, no material is added to the CAC clinker, the setting is controlled by its composition. The main reactive mineral in CAC is the monocalcium aluminate CaO·Al2O3 (CA), the properties are determined by its hydration process and depends on the curing temperature. At low temperatures metastable hydrates are formed which converts into the thermodynamicallystableones[2]. Thehighearlystrengthpropertiesofthisspecialcementmade its main initial uses in the production of prestressed concrete units were no high temperature was needed opposite to Portland cement. But after a series of unfortunate collapses, the CAC ceased to be used in structural applications. The chemical resistance of CAC also dealt with non-structural uses.
The natural fiber reinforcement in concrete mortar and cement paste can enhance many engineering properties of these basic materials. It should be noted that the major attentions of recent investigations have been done is focused on Portland cement (OPC) concrete systems but the systems fabricated with PC and cellulose fibers have shown certain durability concerns.
The aqueous media of OPC composite systems represents a serious problem of durability for natural fibers due to the alkalinity of the porous solution caused by the dissolution of the portlandite. This ambient produces the deterioration of the fiber and therefore the flexural resistant effect contributed by the fiber. In such context, this paper presents alternative cements – as Calcium Aluminate Cement (CAC) as a possible solution of the durability disadvantages of OPC. CAC is a special type of hydraulic cement, it is differentiated from the normal PC with a high characteristic performance such as normal setting time but with a very fast hardening process, high chemical resistance, high corrosion resistance, high resistance against acidic materials. All these advantages of CAC lead this material to be used widely in the construction industry.
This research compares the results obtained for matrixes elaborated with CAC and natural vegetable fibers. The analysis of the study was supported by the determination of Mechanical strength, Water absorption and Porosity, X-Ray and Infrared spectroscopy in manufactured samples.
2. Material and methods
A calcium aluminate cement (Electro-land) from Ciments Molins Industrial S.L. was used as the cementing material in this study. The sand used for mixtures is a kind of silica sand, is a natural
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