Effect of internal water content on carbonation progress in cement-treated sand and effect of carbonation on compressive strength

2018 ◽  
Vol 85 ◽  
pp. 9-21 ◽  
Author(s):  
Lanh Si Ho ◽  
Kenichiro Nakarai ◽  
Yuko Ogawa ◽  
Takashi Sasaki ◽  
Minoru Morioka
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Internal Water

scholarly journals Utilization of Electroplating Sludge as Subgrade Backfill Materials: Mechanical and Environmental Risk Evaluation

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Yu Zhang ◽  
Peixin Shi ◽  
Lijuan Chen ◽  
Qiang Tang
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Content ◽  
Environmental Risk ◽  
Coal Fly Ash ◽  
Surrounding Environment ◽  
Electroplating Sludge ◽  
Backfill Materials ◽  
Standard Limit ◽  
The Impact

The electroplating sludge may pose serious threat to human health and surrounding environment without safe treatment. This paper investigated the feasibility of using electroplating sludge as subgrade backfill materials, by evaluating the mechanical properties and environmental risk of the cement-coal fly ash solidified sludge. In this study, Portland cement and coal fly ash are used to solidify/stabilize the sludge. After curing for 7, 14, and 28 days, the stabilization/solidification sludge specimens were subject to a series of mechanical, leaching, and microcosmic tests. It was found that the compressive strength increased with the increase of cement content, curing time, and the cement replacement by coal fly ash besides water content. Among these factors, the impact of water content on the compressive strength is most noticeable. It was observed that the compressive strength declined by 87.1% when the water content increased from 0% to 10%. Besides, leaching tests showed that the amount of leaching heavy metals were under the standard limit. These results demonstrated utilization of electroplating sludge in subgrade backfill material may provide an alternative for the treatment of electroplating sludge.

scholarly journals Preparation and properties of magnesite aggregate radiation - proof concrete

2018 ◽  
Vol 175 ◽  
pp. 01003
Author(s):  
Bingquan Sun ◽  
Jiajia Sun
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Structure ◽  
Water Content ◽  
Radiation Protection ◽  
Point Of View ◽  
Crystal Water ◽  
Ordinary Concrete ◽  
Mixing Water

This paper, from the point of view of improving compactness of density and crystal water content of radiation-proof concrete, using magnesite with high crystal water content as aggregate and alkaline potential water as mixing water, prepared ordinary density radiation-proof concrete and studied its mechanical properties, resistivity and pore structure. The results show that, compared to base ordinary concrete, the prepared concrete has better 28d compressive strength and resistivity, overall porosity decreases by 17%, and pore gradation at all ages improves significantly. It is indicated that the prepared magnesite aggregate radiation concrete has good density and durability, improves concrete radiation protection performance.

Physical properties, electrical resistivity, and strength characteristics of carbonated silty soil admixed with reactive magnesia

2015 ◽  
Vol 52 (11) ◽  
pp. 1699-1713 ◽  
Author(s):  
G.H. Cai ◽  
Y.J. Du ◽  
S.Y. Liu ◽  
D.N. Singh
Keyword(s):  
Compressive Strength ◽  
Electrical Resistivity ◽  
Water Content ◽  
Unconfined Compressive Strength ◽  
Ground Improvement ◽  
Strength Characteristics ◽  
Degree Of Saturation ◽  
Initial Water Content ◽  
Silty Soil ◽  
Reactive Magnesia

Soil electrical resistivity has been used quite extensively for assessing mechanical properties of chemically treated soils in the recent past. One of the most innovative applications of this technique could be in the field of ground improvement wherein carbonated reactive magnesia (MgO) is employed for treating soils. With this in view, a systematic study that targets the application of electrical resistivity to correlate physical and strength characteristics of the carbonated reactive MgO-admixed silty soil is initiated, and its details are presented in this manuscript. To achieve this, reactive MgO-admixed soils were carbonized by exposing them to CO2 for different durations, and subsequently their electrical resistivity and unconfined compressive strength were measured. In this context, the role of a parameter, the ratio of the initial water content of the virgin soil to reactive MgO content (designated as w0/c), has been highlighted. It has also been demonstrated that w0/c is able to correlate, uniquely and precisely, with the physicochemical parameters of the soils (viz., unit weight, water content at failure, porosity, degree of saturation, and soil pH), electrical resistivity, and unconfined compressive strength at various carbonation times. In addition, microstructural properties have been obtained from the X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry analyses. These properties have been used to substantiate the findings related to the carbonation of the reactive MgO-admixed soils.

scholarly journals Microbial-Induced Carbonate Precipitation for Strengthening Soft Clay

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
J. Z. Xiao ◽  
Y. Q. Wei ◽  
H. Cai ◽  
Z. W. Wang ◽  
T. Yang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Unconfined Compressive Strength ◽  
Soft Clay ◽  
High Water ◽  
High Water Content ◽  
Carbonate Precipitation ◽  
Experimental Conditions ◽  
Strength Enhancement ◽  
Complex Chemical Composition

Currently, calcite produced in sediments by microbial-induced carbonate precipitation (MICP) is mainly used as a strengthening binder in sand because sands are porous and have good permeability. Conventional wisdom does not consider MICP to be suitable for use in soft clay because of the clay particles’ small size and its minimal porosity. Because of the clay’s high water content and complex chemical composition, very little research has been done and not much is known about the use of MICP in soft clay for strength enhancement. For this paper, soft clay specimens were prepared by mixing a solution containing Sporosarcina pasteurii bacteria, solutions with different concentrations of nutrient salts, and soft clay. Unconfined compressive strength tests were carried out on these specimens after they had cured for 28 days in a moisture-controlled environment. These laboratory tests were used to study the chemical reactions, the clay’s strength, and other influencing factors. The results are as follows: (1) directly mixing a S. pasteurii solution, nutrient salts, and soft clay considerably improves the uniformity of the spatial distribution of the bacteria and the nutrients in the soft clay. Directly mixing these constituents promotes the formation of calcium carbonate and greatly simplifies soft clay sample preparation. (2) It is feasible to use MICP to increase the strength of soft clay. Compared to control specimens cured under the same conditions but without introduced nutrients and bacteria solution, the unconfined compressive strength of MICP-treated specimens can be increased by as much as 2.42 times to an unconfined compressive strength of 43.31 kPa. The water content in MICP-treated specimens was significantly reduced by the MICP reactions and in one case decreased from 40% to 30.73%. (3) The strength enhancement of microbially solidified soft clay is the result of two processes: urea hydration catalyzed by enzymes consumes water in the clay and the bacterially precipitated calcite forms in the sediment’s pores. (4) The micro-organism-produced calcite in the soft clay increases the calcite abundance from 0% to as much as 3.5%. (5) The MICP-treated strength of soft clay varies with the concentration of the nutrients provided. For the experimental conditions used for this paper, the optimum concentration of the CaCl2·2H2O and CH4N2O nutrients is 0.5 mol/L.

Use of Quartzite Quarries Wastes in Civil Construction

2013 ◽  
Vol 548 ◽  
pp. 135-140 ◽  
Author(s):  
Mario L. Cabello ◽  
Antonio E.C. Peres ◽  
Afonso H. Martins ◽  
Carlos A. Pereira
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Laboratory Tests ◽  
Minas Gerais ◽  
The State ◽  
Single Stage ◽  
Raw Material ◽  
Economic Viability ◽  
Dimension Stone ◽  
Alkali Aggregate Reaction

The extraction of the dimension stone quartzite in the state of Minas Gerais, Brazil, has been done mostly in small quarries, at very low recovery levels, generating approximately six million tons of waste by year. The aim of this investigation is to study the application of the quartzite waste as aggregate in the civil construction. Laboratory tests of crushing and grinding were done to assess the technical and economic viability of reducing the size of coarse material rendering it adequate to be used as raw material in industrialized mortars and concrete pre-molded components. Samples of concrete using quartzite waste as aggregate were molded in proportions and water content used in the production of pre-molded components and the final compressive strength was assessed. Then, samples of mortars with quartzite waste as aggregate were molded with variations in proportion, water content and top size of aggregates, to assess the workability and final compressive strength. It was concluded that with a single stage of crushing, the waste generated could be used in the production of pre-molded components. An additional stage of grinding would be required for use of a larger amount of quartzite waste in the production of mortars. The alkali-aggregate reaction was not considered in this study.

Compressive strength behavior of fine-grained frozen soils

1990 ◽  
Vol 27 (4) ◽  
pp. 472-483 ◽  
Author(s):  
Harsha Wijeweera ◽  
Ramesh C. Joshi
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Yield Stress ◽  
Constant Strain Rate ◽  
Unit Weight ◽  
Total Water Content ◽  
Total Water ◽  
Frozen Soils ◽  
Fine Grained ◽  
Dry Unit Weight

Constant strain-rate (0.01/s) uniaxial compression-strength tests were conducted on more than 200 saturated samples of six fine-grained frozen soils at temperatures between −5 and −17 °C. Saturated soil samples containing total water contents between 15% and 105% were prepared using a consolidation apparatus specially designed for this purpose. The effect of dry unit weight, total water content, temperature, and soil type on the behavior of peak compressive strength was studied. Test results indicate the peak compressive strength of fine-grained soils is sensitive to changes in the dry unit weight and the total water content. The temperature dependence of the peak compressive strength is represented by a simple power law. An empirical formula has been developed to predict the peak compressive strength of fine-grained frozen soils at a particular temperature using index properties, specific surface area, particle-size distribution, and dry unit weight. A linear relationship exists between the peak compressive stress and the yield stress. Key words: peak compressive strength, yield stress, frozen soils, fine-grained soils, dry unit weight, failure strain, temperature, total water content, slurry consolidation.

Research about the Effect of Polypropylene Fiber on Mechanical Properties of Curing Sludge

2011 ◽  
Vol 250-253 ◽  
pp. 788-794
Author(s):  
Shu Lin Zhan ◽  
Shu Sen Gao ◽  
Jun Ying Lai
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Shear Strength ◽  
Water Content ◽  
Unconfined Compressive Strength ◽  
Polypropylene Fiber ◽  
Physical And Mechanical Properties ◽  
Curing Time ◽  
Strength Tests ◽  
Different Content

In order to study the influence of modified polypropylene (PP) fiber on the physical and mechanical properties of curing sludge, the same amount of cement and different content of polypropylene fiber were mixed into the sludge. Unconfined compressive strength tests, water content tests and shear strength tests were carried out on different specimens with different curing time. The results show that the sludge curing effect is markedly improved by the addition of the polypropylene fiber. As to the curing sludge with the same curing time, when the content of the polypropylene fiber increases, the unconfined compressive strength and the cohesive strength greatly increase, and the internal frictional angle decreases.

Characterization of a cemented sand with the pulse-velocity method

2006 ◽  
Vol 43 (3) ◽  
pp. 294-309 ◽  
Author(s):  
Zahid Khan ◽  
Anwar Majid ◽  
Giovanni Cascante ◽  
D Jean Hutchinson ◽  
Parsa Pezeshkpour
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Wave Velocity ◽  
Unconfined Compressive Strength ◽  
Void Ratio ◽  
Cement Content ◽  
Pulse Velocity ◽  
Initial Water Content ◽  
Strain Property ◽  
Cemented Sand

The effect of variation in cement content, initial water content, void ratio, and curing time on wave velocity (low-strain property) and unconfined compressive strength (large-strain property) of a cemented sand is examined in this paper. The measured pulse velocity is compared with predictions made using empirical and analytical models, which are mostly based on the published results of resonant column tests. All specimens are made by mixing silica sand and gypsum cement (2.5–20% by weight) and tested under atmospheric pressure. The wave velocity reaches a maximum at optimum water content, and it is mostly affected by the number of cemented contacts; whereas compressive strength is governed not only by the number of contacts but also by the strength of contacts. Experimental relationships are developed for wave velocity and unconfined compressive strength as functions of cement content and void ratio. Available empirical models underpredict the wave velocity (60% on average), likely because of the effect of microfractures induced by confinement during the testing. Wave velocity is found to be a good indicator of cement content and unconfined compressive strength for the conditions of this study.Key words: wave velocity, low-strain stiffness, cemented sands, elastic moduli, unconfined compressive strength.

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