Effects of chloride on the early mechanical properties and microstructure of gangue-cemented paste backfill

Strength properties of dredged soil at high water content treated with soda residue, carbide slag, and ground granulated blast furnace slag

A chemo-damage-transport model for chloride ions diffusion in cement-based materials: Combined effects of sulfate attack and temperature

Studies have shown that the incorporation of waste tire rubber aggregates reduces the strength, increases permeability and decrease thermal conductivity of concrete. However, only a few studies have investigated the effect of surface-modified rubber aggregates on the properties of concrete. This study investigates the effect of the surface treatment of waste tire rubber as coarse aggregates with different oxidizing solutions and different treatment durations on the mechanical, durability and thermal properties of concrete. The properties of concrete incorporated with 8% rubber coarse aggregates (by volume of natural aggregates) which were treated with three different solutions: water (H2O), 20% sodium hydroxide (NaOH) and 5% calcium hypochlorite [Ca(ClO)2] (both as% weight of water) for durations of 2, 24, and 72 h, respectively. The effect of these treatments on the compressive strength, splitting tensile strength, water permeability, thermal conductivity and diffusivity of concrete was investigated. Results show that Ca(ClO)2 has a more positive effect on the strength and permeability compared to NaOH solution and water. Experimental results were statistically analyzed using ANOVA and Post Hoc tests. The analyses showed that the improvement of concrete strength is only significant when the treatment with NaOH and Ca(ClO)2 is prolonged to 72 h. Furthermore, the microstructural analysis of concrete showed that the improvement in the strength is due to the improved bonding between cement paste and rubber aggregates as a result of surface treatment. This microstructural improvement also resulted in lower water permeability of concrete. However, the thermal conductivity and diffusivity increased when the surface treatment duration increases as there are less air voids in the samples. This study shows that, with appropriate pretreatment, a certain percentage of natural aggregates can be safely replaced with waste tire rubber aggregates while maintaining sufficient quality of the resulting concrete.

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Impact of Chemically Treated Waste Rubber Tire Aggregates on Mechanical, Durability and Thermal Properties of Concrete

This study examined soda residue (SR) and ground granulated blast furnace slag (GGBS) to stabilize soft soil in comparison with using portland cement (PC). The shear strength of samples was...

Shear Strength of Stabilized Clay Treated with Soda Residue and Ground Granulated Blast Furnace Slag

In the field of soil stabilization, only calcium silicate hydrate (CSH) and ettringite (AFt) as hydration products have been reported to directly contribute to the strength enhancement of the soil. A chloride dredger fill, an artificial chloride saline soil, and a non-saline soil were stabilized by Portland cement (PC) and PC with Ca(OH)2 (CH) with different contents. A series of unconfined compressive strength (UCS) tests of stabilized soil specimen after curing for 7 d and 28 d were carried out, and the hydration products and microstructure of the specimens were observed by X-ray diffractometry (XRD), scanning electronic microscopy (SEM), and energy-dispersive X-ray analysis (EDXA). The results showed that the strengths of PC+CH-stabilized chloride saline soils were much higher than those of PC-stabilized soils. A new hydration product of calcium aluminate chloride hydrate, also known as Friedel’s salt, appeared in the PC+CH-stabilized chloride saline soils. The solid-phase volume of Friedel’s salt expanded during the formation of the hydrate; this volume filled the pores in the stabilized soil. This pore-filling effect was the most important contribution to the significantly enhanced strength of the PC+CH-stabilized chloride saline soils. On the basis of this understanding, a new optimized stabilizer was designed according to the concept that the chloride in saline soil could be utilized as a component of the stabilizer. The strength of the chloride saline soils stabilized by the optimized stabilizer was even further increased compared with that of the PC+CH-stabilized soils.

Effect of Friedel’s salt on strength enhancement of stabilized chloride saline soil

In this paper how to utilize industrial wastes in soil stabilizer preparation with high added value is discussed. Firstly the characteristics of stabilized soil structure formation process and its special demand of stabilizer components were explored. Based on this, the design thought for the soil stabilizer prepared with industrial wastes is proposed and the examples are presented. Then technical, economical and environmental comprehensive index is analysed. Only if stabilized soil structure formation process was understood deeply and industrial waste was chosen properly according to the special demand of stabilized soil structure to components, the change from waste to resource can be realized. And then the stabilizer can be prepared with excellent performance, cost, environment effect and comprehensive benefit.

Utilization of Industrial Wastes for Soil Stabilizer Preparation and Technical-Economical-Environmental Analysis

There is large-area saline sludge which should be stabilized in China. However when cement is used as a stabilizer the strength and stabilization effect on the soil is relatively poor. In this paper, In this paper Portland cement PC is compared to a soft soil stabilizer A developed by the authors for use in stabilizing chloride saline soil from the Tianjin Binhai New Area. The strength of stabilized soil was tested by comparative Analysis, and XRD and SEM tests were used to analyze the hydrate types in stabilized soil. Preliminary tests results suggest that the salts present in hydraulic sludge and stabilizer A were able to react and formed a new hydrate----- Ca4Al2Cl2O6 • 10H2O which cannot be produced by cement alone, and which can greatly increase strength of stabilized soil.

A Study of Stabilizer for Saline Sludge

In this paper, relevant experiments had been conducted on the stabilized mixture of hydraulic fill sand and silt in coastal areas, include the study of optimum mixing ratio of hydraulic fill sand and silt and the appropriate curing agent; as well as the change law for the strength of solidified sediment mixture with different curing agent content. The results show that strength of the stabilized mixture showed the highest when mass ratio of hydraulic fill sand and silt was 60% :40%, and using G2 as the curing agent. Strength of stabilized sediment mixture all increased in different degrees as the mixing amount of curing agent increased.

Yin Cheng

Papers

Effect of Friedel’s salt on strength enhancement of stabilized chloride saline soil

Utilization of Industrial Wastes for Soil Stabilizer Preparation and Technical-Economical-Environmental Analysis

A Study of Stabilizer for Saline Sludge

The Study of Stabilization of Hydraulic Fill Sand and Silt Mixture in Coastal Area