Incorporation Of Admixtures Research Articles

Experimental study on the mechanical properties of desert sand improved by the combination of additives and bio-cement.

Bio-cement is a green and energy-saving building material that has attracted much attention in the field of ecological environment and geotechnical engineering in recent years. The aim of this study is to investigate the use of bio-cement (enzyme-induced calcium carbonate precipitation-EICP) in combination with admixtures for the improvement of desert sands, which can effectively improve the mechanical properties of desert sands and is particularly suitable for sand-rich countries. In addition, the suitability of tap water in bio-cement was elucidated and the optimum ratio of each influencing factor when tap water is used as a solvent was derived. The results showed that peak values of unconfined compressive strength (maximum increase of about 130 times), shear strength (increase of 27.09%), calcium carbonate precipitation value (increase of about 4.39 times), and permeability (decrease of about 93.72 times) were obtained in the specimens modified by EICP combined with admixture as compared to the specimens modified by EICP only. The incorporation of skimmed milk powder, though significantly increasing the strength, is not conducive to cost control. The microscopic tests show that the incorporation of admixtures can provide nucleation sites for EICP, thus improving the properties of desert sand. This work can provide new research ideas for cross-fertilization between the disciplines of bio-engineering, ecology, and civil engineering.

Compressive strength of SF and FA based self curing HSSC: An experimental study

Typical High-strength concrete (HSC) mixtures are characterized by low water-cementitious material ratio, high content of cementitious material, and the incorporation of admixtures. Concrete needs a favourable atmosphere by providing moisture for a minimum base period of 28 days for hydration and to attain targeted strength. In the present scenario of water scarcity, the water required for curing concrete is a troublesome constraint. Self-curing concrete is one of the peculiar concretes for coping with insufficient curing caused by human error. The prime goal of this study is to identify the self-curing compound’s optimum dosage for High Strength Self-Compacting Concrete (HSSC). Likewise, it is aimed to investigate the compressive strength characteristics of HSSC. For the study, a self-curing agent namely “PEG-400” with varying percentages (0.5%, 1%, 2% & 3% by weight of cement) was investigated. An attempt was made to identify the effect of the self-curing compound on the fresh and hardened properties of HSSC, workability tests and compressive strength tests were conducted. The tests on hardened concrete were conducted after curing for 28 days for conventional HSC specimens and ambient curing for HSSC. It was observed that with the addition of 1% of PEG-400 self-curing compound, the compressive of HSC was found to be increased by 1.86% in comparison with the conventionally cured HSC. It was observed that with the addition of 1% of PEG-400 self-curing compound, the compressive strength of HSSC was found to be increased by 1.87% in comparison with the conventionally cured HSSC.

Effect of Concrete Admixtures on Structural Properties and Corrosion Resistance of Steel Reinforcements

Concrete structural properties are compromised largely due to corrosion susceptibility of steel reinforcements. This results in weakening and eventual failure of structures. Several strategies have been employed in past to control corrosion and increase mechanical strength of concretes, in particular for structural applications. In this study, fly ash and polypropylene fibers were utilized as the admixtures for preparation of concrete blocks with variable water-cement (w/c) ratios i.e. 0.45, 0.5 and 0.65. Three different grades of cements were selected in this study namely OPC 43, OPC 53 and sulfate resistant one. Also, two different steel alloys were used i.e. ASTM-615 and ASTM-706, since both of them are very common reinforcement materials (rebars). The curing time of 56 consecutive days was employed before testing and characterization. The results suggest remarkable improvement in the mechanical properties of blocks upon the incorporation of admixtures. However, rebars exhibited highest corrosion rate in the presence of OPC 43 cement at w/c ratio of 0.65.

Effects of Fine LWA and SAP as Internal Water Curing Agents

Typical high-performance concrete (HPC) mixtures are characterized by low water-cementitious material ratios, high cement contents, and the incorporation of admixtures. In spite of its superior properties in the hardened state, HPC suffers from many practical difficulties such as its sensitivity to early-age cracking (which is associated with self-desiccation and autogenous shrinkage). In this context, conventional curing procedures are not sufficiently effective to address these limitations. In order to overcome this issue, two strategies, which are based on the use of internal reservoirs of water, have been recently developed. One of these strategies is based on the use of lightweight aggregates (LWA), while the other is based on the use of superabsorbent polymers (SAP). This paper studies and compares the efficiency of the LWA and SAP approaches. Moreover, some of the theoretical aspects that should be taken into account to optimize their application for internal curing of HPC are also discussed. Two fine LWA’s and one SAP are studied in terms of autogenous deformation and compressive strength. Increasing the amounts of LWA or SAP can lead to a reduction of the autogenous deformation and compressive strength (especially when adding large amounts). By selecting appropriate materials and controlling their amount, size, and porosity, highly efficient internal water curing can be ensured.

Analysis of Fly Ash Cement Concrete for Road Construction

This experiment study aimed to investigate the physical, chemical and mechanical properties of fly ash cement concrete for road construction. Research has shown that 30% of fly ash and 70% of cement has a superior performance. Characteristics compared to the standard requirements conformable code. Moreover, the use of fly ash would result in reduction of the cost of materials in construction and the reduction of greenhouse gas emission. High strength of concrete can be made and the incorporation of admixture or substitute to improve the properties of concrete. Test result of specimens indicates the workability, and bonding strength of properties, and different reaction when the water ratio a change its content. Slump test having an appropriate workable mixing the slump of a concrete, gave sufficient compressive strength. Test results of 14 days specimens having different results but it only treated when it downs to minimum level of required conformable code.

Scrapt Waste Tire as an Additive in Asphalt Pavement for Road Construction

This experiment study aimed to use of the waste tires in asphalt mixture as additive. Research has shown that scrap waste tire can be partial replacement by 2% total weight of aggregate retained in No. 4 sieve has an average performance. Characteristics compared to the standard eequirements conformable code. Moreover, the use of scrap waste tire would result in the reduction of waste. High stability of asphalt mixture can be made and the incorporation of admixture or substitute to improve the properties of the mixture. Test result of specimens indicates the stability, and bonding strength of properties, and different reaction when gradation and scrap tire contents have varied. Marshall test having an appropriate workable mixing and right temperature gave sufficient compressive strength and lessen its flow or it deformation under a certain loads.

Scrapt Waste Tire as an Additive in Asphalt Pavement for Road Construction

This experiment study aimed to use of the waste tires in asphalt mixture as additive. Research has shown that scrap waste tire can be partial replacement by 2% total weight of aggregate retained in No. 4 sieve has an average performance. Characteristics compared to the standard eequirements conformable code. Moreover, the use of scrap waste tire would result in the reduction of waste. High stability of asphalt mixture can be made and the incorporation of admixture or substitute to improve the properties of the mixture. Test result of specimens indicates the stability, and bonding strength of properties, and different reaction when gradation and scrap tire contents have varied. Marshall test having an appropriate workable mixing and right temperature gave sufficient compressive strength and lessen its flow or it deformation under a certain loads.

Adsorption mechanisms of the nonequilibrium incorporation of admixtures in a growing crystal

The nonequilibrium partition of components between a crystal and solution is mainly controlled by impurity adsorption on the surface of the growing crystal. The specificity of adsorption on the faces of various simple forms leads to the sectorial zoning of crystals. This effect was studied experimentally for several crystallizing systems with different impurities, including isomorphous, 2d-isomorphous, and nonisomorphous, readily adsorbed impurities. In all systems, the sectorial selectivity of impurity incorporation into host crystals has been detected with partition coefficients many times higher than in the case of equilibrium partition. Specific capture of impurities by certain faces is accompanied by inhibition of their growth and modification of habit. The decrease in nonequilibrium partition coefficients with degree of oversaturation provides entrapment of impurities in the growing crystals. Thereby, the adsorption mechanism works in much the same mode for impurities of quite different nature. The behavior of partition coefficient differs drastically from impurity capturing by diffusion mechanism.

The use of attachers in electron-beam sustained discharge switches—theoretical considerations

Electron-beam sustained discharges can be used in opening and closing switch applications for producing bursts of energy in pulsed power systems. The incorporation of admixtures of attachers with low attachment rate at low values ofE/Nand high attachment rate at high values ofE/Nin the gaseous switch dielectric has been proposed to achieve low forward voltage drop in the conduction phase as well as rapid opening when the sustaining e-beam is terminated. This paper presents model calculations on the characteristics and transient behavior of an electron-beam sustained discharge in the high current density regime in N2. The influence of an attacher (N2O), with the property described above, and of the circuit parameters on the discharge is investigated as an illustrative example. The advantage of using such an attacher is demonstrated for the steady state conduction phases and for the opening phase, while the closing process is obstructed by the attacher. Additional possible control mechanisms, such as photodetachment to aid the closing process are discussed.