Mortar strength crystal size

A bivariant linear eq uation, contain ing factors such as phase percentages, crystal sizes, morphology and cluster indexes, for predicting the 28-day mortar strength was presented by Sinha, Rao, and Akhouri (1991). The standard deviation was said to be 17.9 kg/ cm agreeing closely with the actual strength. 

The microscopy of two clinkers produced within 10 seconds by electron beam radiation at 1.2 MEV was described by Handoo and others (1992). Alite and belite appear well formed, with crystal sizes of 10 to 16 pm. Mortar strength at 28 days was said to be 470 kg/cm (46.1 MPa). 

A multiregressional equation predicting the 28-day mortar cube strength was presented by Rao, Akhouri, and Sinha (1992), the data coming from rotary and vertical shaft kiln clinkers. The prediction has a standard deviation of 17.9 kg/cm, utilizing alite and belite percentages and average crystal sizes. 

Detailed microscopical characteristics of clinkers from vertical shaft kilns, compared to laboratory burns, are presented by Ahluwalia and Raina (1992). Alite and belite crystal sizes in plant clinkers averaged approximately 21 and 19 pm, respectively, possibly accounting for high mortar strengths (44.8 MPa at 28 days). 

Zivanovic (1995) presented a description of clinkers made with silica fume, instead of quartz sand, as the primary silica component in the raw feed. The silica fume made up approximately 3.0 percent of the feed. Alite crystal size was reported to be from 50 to 200 pm and belite grains were said to be rounded and between 50 and 60 pm. No mention of belite nests was made. The cements made with silica fume or tuff and a particular marl, compared to other cements not made with these materials, did not require as much grinding and produced higher 28-day mortar strengths. 

Cement paste characteristics, for example, strength and permeability significantly depended on its nanostructure features in particular nanoporosity. In recent years, electron microscopy has been demonstrated to be a very valuable method for the determination of microstructure. Numerous studies on the influence of nano-SiO on the microstructure of plain cement mortar have been carried out. The results showed that nano-SiO particles formed a very dense and compact texture in the hydrate products and decreased the size of big crystals such as CH. In this chapter in order to study the microstructure of RHA mortar, with and without nano-SiO, a SEM was used. The microstrueture of the RHA mortar with 3% replacement of nano-SiOj and without nano-SiO at a euring age of seven days are presented in Fig. 5.5 and Fig. 5.6, respeetively. Results showed that the nano-SiOj particles improved the dense and compact microstructure of RHA and generated a more homogenous distribution of hydrated products. 

A relatively "hard-to-burn" feed from the western U.S., with a very impure dolomitic limestone, has 6.7% >125 pm and an acetic-acid insoluble residue of 9.5% >45 pm, the latter comprised of quartz, feldspar, medium to finely crystalline igneous and metamorphic rock fragments, and an abundance of ferro-magnesian minerals (mainly amphiboles and pyroxenes). = 1.6% and = 4.5%. Belite nests (many with tightly packed crystals), solitary belite, and periclase are abundant in this fine- to medium-crystalline clinker. Nevertheless, a high-compressive strength mortar (44.8 to 48.3 MPa) is made, mainly because of the small alite size and the well-scattered solitary belite. 

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