Effect Of Gypsum Content Research Articles

Effect of gypsum content in cement on its adaptability to alkali-free accelerator at different temperatures

The setting times and early strength of shotcrete are greatly affected by the gypsum content of the cement used. In this work, the setting times, compressive strength and microscopic analysis (X-ray diffraction quantitative analysis, thermogravimetric analysis and scanning electron microscopy) were used to determine the effects of changes in gypsum content on the hydration and mechanical properties of cement mixed with an accelerator at different temperatures. The results showed that an increase in the gypsum content of the cement promoted the formation of ettringite (AFt) and decreased the setting times of the cement pastes at 0°C, 20°C and 40°C. Mortar compressive strength tests showed that, after curing at 0°C, 20°C and 40°C, the highest compressive strength was exhibited with a final molar aluminate-to-sulfate ratio (C3A/SO3; henceforth called the MASR) of 0.84, 0.84 and 1.18, respectively. The mechanical properties of the hardened cement pastes were adversely affected by MASRs that were too high or too low. When the MASR was too high, the conversion of AFt to monosulfate (AFm) was facilitated and C3S hydration was slowed. Conversely, when the MASR was too low, this enabled large amounts of AFt to occupy the space where calcium silicate hydrate (C-S-H) gels were formed, resulting in decalcification of the C-S-H gels.

Do soil features condition seed germination of gypsophiles and gypsovags? An analysis of the effect of natural soils along an alkalinity gradient

Gypseous soils are widespread across drylands worldwide. They present remarkable challenges to plants and host a unique flora. We aimed to assess if the specificity and distribution of species on gypsum might be driven by species-specific germination responses to soil gypsum availability. We analyzed the germination of six gypsum specialists (gypsophiles) and four closely related generalist plant species (gypsovags) from the Iberian Peninsula and the Chihuahuan Desert in different field soils with contrasting concentrations of gypsum, pH and soil texture. Plant restriction to gypsum was unrelated to the germinating ability of seeds on different substrates. Irrespective of their affinity for gypsum, most species germinated better on mixed gypsum-calcareous soil and worse in the acidic soil treatment. Our data suggest soil pH and Ca availability were the main soil features driving seed germination, while the effect of gypsum content was generally not significant. The main exception was the Iberian gypsophile Helianthemum squamatum (L.) Dum. Cours., which showed increased germination on gypseous soils and higher germination in response to increased soil gypsum content. Except for this species, our findings indicate alkaline soils with high Ca availability favor the germination of most of the species analyzed, irrespectively of their gypsum content.

The Effect Of Gypsum Content And Seasonal Variations On The Enzyme Activity And Respiration Properties Of Heavy Soils In Reclamation Status

This article discusses the effect of gypsum content and seasonal variations on the enzyme activity and respiration properties of bad melioration content of soil in Uzbekistan. Furthermore, this paper provides some datas about their origins and how to eliminate it.

Effect of Gypsum Content on CSAB Cement-Based Immobilization of Se and SO 4 from Industrial Filter Sludge and Sodium–Selenium Salts

Abstract Release of different heavy metals from various industries is a significant environmental hazard worldwide. In order to reduce the threat from these chemicals, different treatment methods a...

Effect of gypsum content in sprayed cementitious matrices: Early age hydration and mechanical properties

Sprayed materials must present short setting times and a fast early strength development for safety and productivity reasons. In order to improve these characteristics, the construction industry has focused on the development of new formulations of accelerators. Research and improvement of other components of the mix, such as cement or additions, have not advanced at the same rate despite being also crucial for the reaction kinetics. The objective of this work is to evaluate the influence of gypsum content on the hydration and mechanical strength development in sprayed mixes. Sprayed pastes and mortars were prepared with one type of cement, two types of accelerators and different gypsum contents. Kinetics, mechanisms of hydration and mechanical properties were evaluated. Results showed a better performance in sprayed mixes that contain ideal doses of gypsum. Such approach provides valuable information for the improvement of the formulation of cement used in sprayed concrete applications.

Review on the effect of gypsum content on soil behavior

Abstract Increasing the utilization of urban soil usage brings along very important problems to be addressed at the international level regarding the use of sulfate bearing soils as construction materials. After briefly exploring current research perspective, this paper captures the current state of the art in the field of sulfate bearing soils used as construction materials through a detailed discussion of different studies that pave the way to the possible treatment of such soils to be used in road construction. Additionally, the purpose of this paper is to acquaint geotechnical and pavement engineers with the present state of the art of the physical and chemical properties of gypsum and hence its effect on the subgrade soil performance. On the other hand, this paper discussed an opposite action in which some researchers have mixed recycled waste gypsum components with soil in order to stabilize it. In other words, a number of open research issues are highlighted with the intension of inspiring new conditions and developments in stabilizing problematic gypsiferous soil as well as adding gypsum to stabilize non gypsiferous soils of weak performance.

Soil–water characteristic curve of lime treated gypseous soil

The determination of water holding capacity variations with environmental conditions, in particular relative humidity (suction), is essential in the assessment of the behaviour of gypseous soil. The relationship between suction and moisture content is expressed by the soil-water retention curve (SWRC) or soil-water characteristic curve (SWCC). This relationship was determined for the first time for lime treated gypseous soil, using tensiometric plate, osmotic membrane and vapour equilibrium techniques, in the suction pressure range of (10–1,000,000 kPa). Soil samples containing (0, 5, 15 and 25%) gypsum were treated with 3% lime and cured for 28, 90 and 180days at 20°C and 40°C. Results showed that the water holding capacity of the soil samples increased with increasing gypsum content, curing period and curing temperature. The effect of gypsum content on SWCC was greater than the effect of curing conditions, although microstructural properties of the treated soil samples showed that curing conditions also had a significant effect on the SWCC. All the experimental data fitted well to the Fredlund and Xing (1994) and Van Genuchten (1980) models for SWCC.

Effects of Gypsum on Cementitious Systems with Different Mineral Mixtures

Gypsum is an indispensable component of ordinary Portland cement. The main function of gypsum is to regulate the setting time of cement. Gypsum has a great influence on water consumption of standard consistence and strength simultaneously. In this article three cementitious systems are prepared by three main mixed materials: limestone, fly ash and slag. The effect of gypsum content and the relation between gypsum quantity and the fluidity of cement with Marsh cone method are studied. Experimental results show that when the gypsum was added in the three kinds of cementitious system, water consumption of standard consistence decreased obviously, and with the quantity of gypsum increased, water demand for normal consistency reduced first, up to a certain extent tended smoothly. With the increase of gypsum quantity, initial and final setting time had different degrees of extension. While a saturation quantity is achieved, setting time will keep steady. The flexural strength and the compressive strength increased gradually and tended to be stable with the increase of gypsum quantity. When gypsum content exceeded a certain range, compressive and flexural strength decreased gradually. But gypsum content and the mobility of systems had little relativity with Marsh cone method.

Studying of the Gypsiferous Soil Suction Using Filter Paper Technique

Gypsiferous soils have specific feature under its suction studying. These soils contain salt solution that affects on the suction components at high water content levels. This paper investigates soil suction of three types of gypsiferous soils namely: Al-Muhallabeia, Al-Jarin, and Al-Slmanii using filter paper technique. The investigated soils were located in Nineveh province (400 Km north Baghdad capital) and found to have a gypsum content of about 35, 23, and 6%, respectively. This study includes some factors (water content, gypsum content, and clay content) that affect the soil suction for gypsiforous soils. The effect of gypsum content on slope of the relationship between soil suction with pF unit and water content was examined. The results revealed that there is a linear relationship between soil suction and its water content for three studied soils. Both total and matric suction values increase as soil water content decrease. On the other hand, the difference between total and matric suction values increase with soil samples water content. The soil clay content has more effect on gypsiferous soil suction than its gypsum content. Key words: Gypsiferous soil, Soil suction, Total suction, Matric suction, Gypsum content

Tertiary gelation of oilwell cement

The aim of this research was the investigation of the origin of the oilwell cement slurry gelation problem which can appear during well-cementing operations. In this study, the relations between the development of consistency of cement slurry, the hydration process and surface growth in the paste were studied for several commercial oilwell cements. The effect of gypsum content on the consistency of cement slurry was evaluated. In order to relate the hydration process and the consistency development, the hydration of cements was followed by thermogravimetric analysis (TGA), X-ray diffraction and by proton NMR spectroscopy. A comparison between the results obtained and some published data is presented.

Effect of gypsum content on compressive strength of cements

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Effect of Gypsum Content and other Factors on Shrinkage of Concrete Prism

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