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Cementitious material is the basic construction material of modern construction, where flowability is always the difficult problem. General cement slurry, mortar and grout are high viscosity and low pumpability that can not go into limited space. Solution of flowability of the mixture system is provided by cenosphere, which is hollow ceramic microsphere derived from coal fly ash. Hebei Hezhen Industrial Co., Ltd. Company provides crush, process, sale, etc, of nonmetallic minerals, such as cenospheres. We have over 60 engineers and college educated employees. Combined the advantages of high technology and local resources, we could provide high quality cenospheres, which can enhance cement based system.
Understanding the Ball Bearing Effect of Cenospheres
The main process through which the cenospheres enhance flowability is commonly referred to as the ball bearing effect. Cenospheres are completely smooth, spherical particles. When incorporated into a concrete mix, these minute balls move past each other, and past other solid particles with little friction. This rolling movement will decrease the internal shear stress in the mixture and therefore the cement paste will move freely under the same applied force. Spherical cenospheres, unlike irregularly shaped particles which interlock and develop resistance, are microscopic lubricants. The ball bearing effect is most pronounced at moderate and high cenosphere loadings, but even small additions can noticeably improve flowability. Hebei Hezhen Industrial Co., Ltd. produces cenospheres to get high sphericity and smooth surface finish in cement systems to maximize this favorable impact.
Reducing Water Demand While Maintaining Workability
The most popular method of increasing the flowability of cement is to add water, although there are serious disadvantages associated with adding water. Increased water content will reduce the final compressive strength and increase porosity, leading to an increase in shrinkage cracking, segregation of aggregates, etc. Cement slurries incorporating cenosphere will have the same spread or slump with less mixing water because of their rounded shape and fine texture. This reduced water is reflected directly as a increase in strength, hardness and reduced permeability of the hardened cement. With oil well cementing being crucial in its ability to form zonal isolation and needing low w/c ratios, cenosphere's use is to prevent the water content limit from being exceed while maintaining the workability required. Hebei Hezhen Industrial Co. Consults with cement formulators in order to ensure a higher amount of cenosphere to attain the lowest possible water content with required workability.
Lowering Density to Enhance Pumpability
The denser the slurry, the greater the energy required to convey it through pipes and the more likely it is to segregate or settle on the path. Cenospheres typically have densities of 0.4-0.8 g/cm 3 of particles vs. 2.6-3.1 g/cm 3 of cement solids. Substitution of some of the cement or other heavier aggregates with cenospheres lowers the density of the mixture considerably. This reduced density causes the slurry to be easier to pump, the pumps do not need as much pump pressure and the pumps and pipelines wear less. Long-distance pumping (tunnel grouting or mine backfilling) can save a lot of energy. During cementing of offshore oil wells, the lighter slurries reduce the hydrostatic pressure of the weak formations preventing lost circulation. Hebei Hezhen Industrial Co., Ltd. offers cenospheres of different grades of density and the customers are able to factor in the weight of the slurry to a particular application.
Preventing Segregation and Bleeding
The problem that is often encountered with highly flowable cement mixtures is the issue of segregation of the cement, whereby the heavier particles will separate out of suspension with water rising to the surface. Cenospheres have the ability to eliminate segregation in a mix of ways. They are not buoyed in most cement slurries since they are low density and thus they do not settle quickly. Their small size and spherical shape enables them to interstitialize larger particles to form a more stable particle network that cannot settle. Also the fine size of the particles of cenospheres occupying empty spaces that could be taken by the free water decreases the channels of bleeding. The outcome is a homogenous cement system that is maintained in its homogenous state throughout the placement and curing process. Hebei Hezhen Industrial Co., Ltd. conducts a strict quality control of particle size distribution in order to obtain the best packing properties in customer formulations.
Compatibility with Other Admixtures
Cenospheres are usually used with superplasticizers, retarders, accelerators, air entrainers and with viscosity modifiers. Luckily, cenospheres are inert and can be used with almost all common cement admixtures. They do not interfere with the water-reducing effect of superplasticizers and the setting time modifications offered by retarders and accelerators. This compatibility enables the formulators to match the cenospheres with other additives to meet the flowability targets besides meeting the strength, setting time and durability requirements. Cenospheres and superplasticizers are complementary in other instances, and each plays a role in the flowability in a different manner. Hebei Hezhen Industrial Co., Ltd. offers technical assistance to assist customers to incorporate cenospheres in their existing formulations without any undesired interactions.
The combined benefits of cenospheres for cement system workability are highly attractive. The hollow ceramic microspheres effectively lower water requirement, density, and avoid segregation, which is helpful to produce pumpable and fillable cement slurry, after hardening to be rigid and hard. Hebei Hezhen Industrial Co., Ltd. is pleased to negotiate with domestic and international customers, seeking sincere cooperation and mutual growth. Our high quality cenospheres can be used to enrich your products, whether it is oil well cements, construction grouts, or specialty mortars.
