EFFECTS OF BLAST-FURNACE SLAG ON NATURAL POZZOLAN-BASED GEOPOLYMER CEMENT

A number of geopolymer cement mixes were designed and produced by alkali-activation of a pumice-type natural pozzolan. Effects of blast-furnace slag on basic engineering properties of the mixes were studied. Different engineering properties of the mixes such as setting times and 28-day compressive strength were studied at different amounts of blast-furnace slag, sodium oxide content, and water-to-cement ratio. The mix comprising of 5 wt.% blast-furnace slag and 8 wt.% Na2O with a water-to-dry binder ratio of 0.30 exhibits the highest 28-day compressive strength, i.e. 36 MPa. Mixes containing 5 wt.% of ground granulated blast furnace slag showed the least efflorescence or best soundness. Laboratory techniques of X-ray diffractometry (XRD), fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were utilized for characterizing a number of mixes and studying their molecular and micro-structure. Investigations done by scanning electron microscopy confirm that smaller blast-furnace slag particles react totally while the larger ones react partially with alkaline activators and contribute to the formation of a composite microstructure

Investigation and Prediction of Physical and Mechanical Properties of Gypsum/Rice Straw Composite Using ANFIS Model

Lack of environmental and economical resources leads to a quest for new alternatives in civil construction. In the recent decades, gypsum was used for plastering material on walls and ceilings. Many researches have been dedicated to natural fibers in order to be used as a reinforcement in cement and gypsum and some of them have been managed to decrease the density while enhancing the mechanical properties of the cement and gypsum composites. In this research, a lingo cellulose fibers which is rice straw in ten composition percentages are used in gypsum accordingly. In addition, Methyl cellulose, lime, starch, alkali lime saturated solution and one molar potassium hydroxide as a corrector of straw are used. From each composite three samples were made, based on the related standards, for assessment of axial and bending strengths However, Rice straw illustrated weak performances in axial and bending strengths it reduces density by 12 percent. While having the latter improvements, processed rice straw increased bending strength by 12 percent. Studying Scanning Electron Microscope (SEM) outputs confirmed the obtained results. Furthermore, utilizing ANFIS in Matlab software a model for predicting properties of new composites and reaching best composites is obtained

AN EXPERIMENTAL INVESTIGATION ON IMPROVING THE MEDIUM AND LATE-AGE COMPRESSIVE STRENGTHS OF CLASS G OIL WELL CEMENT

In this study, the effects of particle size distribution improvement and dense packing techniques on the 28- and 90-day compressive strengths of class G oil well cement have been investigated. It was observed that limited improvements in the particle size distribution of cement (regarding industrial possibilities) cannot result in a significant increase in 28- and 90-day compressive strengths. Also, in the application of the dense packing technique, silica fume and limestone powders with the grain size less than 45 micrometers cannot be utilized as substitutes for cement, because the addition of these materials simultaneously leads to the shortening of the setting times. The utilization of quartz powder as a filler exhibits partial pozzolanic properties at optimum substitution percentages, i.e. around 6 to 10% by weight; however, it can result in an almost 7% increase in the 28-day compressive strength of the hardened paste of the cement without any considerable effects on its setting times

Rheology of activated phosphorus slag with lime and alkaline salts

The present study aimed to determine the rheological behavior of activated phosphorus slag (AAPS) with a combination of Ca(OH)2 and Na2CO3 (CNC activator) or Na2SO4 (CNS activator) compared to OPC paste. The findings showed that the rheology of AAPS pastes fit with the Herschel-Bulkley model and behaved like a shear-thinning fluid. The AAPS pastes rheology is affected by concentration and nature of activator. The shear stress in AAPS pastes was lower than OPC paste, and increased with increasing the activator concentration. In early ages, reaction products of PS/CNC pastes included calcite-type compounds with the formed gel while gypsum compounds formed in the PS/CNS pastes. This resulted in higher shear stress and lower workability for PS/CNC pastes compared to PS/CNS pastes. The formed gel due to interaction between Ca2+ ions of CNC activator and Si4+ ions of Phosphorus slag caused an increase in the shear stress for PS/CNC during the time.This work was supported by the Science & Technology Park of Semnan University, Iran [grant ID: 1233/95/315, 2016]. The authors acknowledged the financial supports from the Ministry of Science, Research, and Technology of Islamic Republic of Iran who paid for the PhD scholarship and travel to Madrid for Hamideh Mehdizadeh.Peer reviewe