Laboratory Measurement and Analysis of the Deteriorated Layer Permeability Coefficient of Soil-Cement Deteriorated in a Saline Environment

The deterioration of soil-cement in a saline environment leads to a reduction in strength and an increase in permeability. Effective methods of determining the deteriorated layer permeability coefficient of soil-cement are currently lacking. A laboratory test method for measuring the permeability coefficient of the deteriorated layer was proposed using the modified permeability coefficient testing apparatus. According to the proposed method, the permeability coefficient of the deteriorated layer could be obtained after testing the permeability coefficient of the soil-cement specimen in acuring room and testing the equivalent permeability coefficient and deterioration depth of the soil-cement specimen in a deteriorated environment. Using the marine dredger fill from Jiaozhou Bay as a case study, the deteriorated layer permeability coefficients of soil-cements with different cement contents were tested. It turned out that the permeability of the deteriorated layer increases with age. At the beginning of the curing age, higher cement content led to a smaller permeability coefficient of the deteriorated layer of soil-cement. As the curing age increased, the deteriorated layer permeability coefficient of the soil-cement with higher cement content increased. The evolution of the permeability coefficient of a deteriorated layer with age can be formulated as the Logistic function. This study provides support for anti-permeability designs of soil-cement structures in saline environments.

Laboratory Measurement and Analysis of Deteriorated Layer Permeability Coefficient of Corroded Soil-Cement

The deterioration of soil-cement in corrosive environment leads to the reduction of strength and the increase of permeability. Effective methods of determining deteriorated layer permeability coefficient of soil-cement are currently lacking. A laboratory test method for permeability coefficient of deteriorated layer was proposed using the modified permeability coefficient testing apparatus. According to the proposed method, the permeability coefficient of deteriorated layer can be obtained after testing the permeability coefficient of the soil-cement specimen in curing room and the equivalent permeability coefficient and deterioration depth of the soil-cement specimen in corrosion environment. Taking the marine dredger fill of Jiaozhou Bay for example, the deteriorated layer permeability coefficients of soil-cements with different cement contents were tested. It turned out that the permeability of deteriorated layer increases with the increase of age. At the beginning of curing age, larger cement content leads to smaller permeability coefficient of the deteriorated layer of soil-cement. As the curing age increases, the deteriorated layer permeability coefficient of the soil-cement with larger cement content becomes larger. The evolution of the permeability coefficient of deteriorated layer with age can be formulated as the Logistic function. This study provides a support for anti-permeability designs of soil-cement structures in corrosive environment.

Recycling waste papers in green cement mortars

This work investigates the utilization of waste papers (natural and industrial) i.e (citrus aurantium and papers A4) mortars containing specified contents 0.5%, 1%, 1.5% of waste papers were prepared and cured. Mechanical characteristics such as compressive and bending strengths, hardness and water absorption were determined for the mortars mixed with the waste papers and compared with those obtained from the pure mortars. Results showed that the addition of waste paper leads to increase the hardness to (69 - 68.5) shore D for (natural and industrial) wastes materials respectively comparing with pure specimen 66 shore D. The compressed strength of the mortar cement specimen cured for 28 days from 13 MPa to (17-18) MPa for (natural and industrial) wastes materials, respectively.

Coal gasification ash and Weathered fly ash, as partial replacement of Portland cement – effect on selected durability properties of concrete

This study uses Sasol ashes as cement extenders to contribute to the technology of partially replacing Portland cement by mass. There are two types of Sasol ashes; coal gasification ash (CGA) and weathered fly ash (WFA) produced from low grade coal. These ashes are disposed of by Sasol with no specific utilisation. In this investigation, PC will be partially replaced by mass with WFA, CGA and FA at 10%, 15% and 30% proportions for each type of ash. The durability indices will be measured and compared for all blended specimen (PC/WFA, PC/CGA and PC/FA). A 100% Portland cement specimen will be used as a control. The durability properties will be used to determine the potential of Sasol ashes being used as a cement extender.

In Vivo Evaluation of Chelate-Setting Cement Fabricated from Hydroxyapatite Including Bone Minerals Using a Rabbit’s Tibia Model

Hydroxyapatite (HAp) is one of components of bone and teeth, and has an osteoconductivity. Thus, the HAp has been used as biomaterials for bone graftings. We have succeeded in development of the novel chelate-setting calcium-phosphate cement (CPC) using pure HAp particles surface-modified with inositol phosphate (IP6). While, biological apatite presented in bone and teeth of mammals contains various ions: Na+, K+, Mg2+, Cl-, F- and CO32-, in addition to Ca2+ and PO43- ions. In this work, in order to create the chelate-setting CPC with enhanced osteoconductivity, the above-mentioned biological apatite powder (hereafter, bone HAp), instead of pure HAp, was used as a starting powder for fabrication of the chelate-setting cement. The biocompatibility of the resulting chelate-setting bone HAp cement (hereafter, IP6-bone HAp cement) was examined using a rabbit’s tibia model. When the living reaction to hard tissue was histologically examined after 4 weeks implantation, we could observe that newly-formed bone directly bonded to the surface of the specimen. The newly-formed bone was also present around the cement specimen. The amounts of newly-formed bone around IP6-bone HAp cement was about 1.5 times those around IP6-pure HAp cement without bone minerals. The above findings demonstrate that the present IP6-bone HAp cements are one of the promising candidates as novel CPC with enhanced osteoconductivity.

Biocompatibility of Silver-Containing Calcium-Phosphate Cements with Anti-Bacterial Properties

We have previously synthesized silver-containing hydroxyapatite (Ag-HAp) powders by an ultrasonic spray-pyrolysis (USSP) technique. On the other hand, we have successfully fabricated novel calcium-phosphate cements (CPCs) composed of mainly β-tricalcium phosphate (β-TCP) phase with anti-washout property (hereafter, β-TCP cement), which was set on the basis of chelate-bonding ability of inositol phosphate (IP6). In this study, we developed novel CPCs with both anti-bacterial and anti-washout properties by adding the Ag-HAp powder into the above β-TCP cements, and examined their anti-bacterial property and cytotoxicity. The Ag-HAp powders with Ag contents of 0, 2, and 5 mol% as a nominal composition were synthesized by an USSP technique. The raw powder for β-TCP cement was prepared by ball-milling the commercially-available β-TCP powder in the IP6 solution. The Ag-HAp/β-TCP powders were prepared by mixing Ag-HAp powder and β-TCP cement powder at a ratio of 25:75 in mass. The Ag-HAp/β-TCP cement was fabricated by mixing the above-mentioned Ag-HAp/β-TCP powder and 2.5 mass% Na2HPO4 solution at a powder/liquid ratio of 1/0.3 [g/cm3]. The anti-bacterial property of resulting cements was evaluated using Staphylococcus aureus by biofilm formation test. The Ag-HAp/β-TCP cements containing 2 and 5 mol% Ag showed strong anti-bacterial property among examined specimens. Furthermore, the cytotoxicity of Ag+ ion eluted from these cements was also examined using osteoblastic MC3T3-E1 cells and Transwell® kit. The relative cell viability cultured on each Ag-containing cement specimen was over 80 %, compared with the control (polystyrene plate). These results demonstrate that the present Ag-HAp/β-TCP cements containing 2 mol% Ag are promising one of the candidates as CPCs with both anti-bacterial property and biocompatibility.

Damage Detection and Localization on Cement Specimens

This paper is focused on cement specimen testing by impact excitation non-destructive technique. The impulse excitation method was used for measuring of the natural frequencies and modes of longitudinal, transversal and torsional vibration of the specimens. The objective was to find dynamic properties of the specimens without a crack, with a crack and with a healed crack by cement paste and based on their comparison detect and localize the crack.

Additional Aging Effect after Carbonation Process of Fly Ash Based Eco-Materials

The purpose of this study is to enhance the mechanical strength of specimens containing fly ash from fluidized bed type boiler, which the recycling rate will be eventually increased. Specimens containing fly ash in a certain portion were made and aged for 3, 14, and 21 days. The carbonation process under the super critical condition was performed to enhance the mechanical property of specimens by filling the voids and cracks existing inside cement specimen with CaCO3 reactants. The additional aging effect after the supercritical carbonation process on mechanical strength of specimens was also investigated by comparing the compressive strength with and without 7 day extra aging. Carbonation under the supercritical condition and additional 7 day aging was very effective for enhancement of mechanical strength and compressive strength increased by 44%, which reached up to 88MPa.

Alkaline Cements of Waste Glass and Metakaolin, Strength as a Function of the Chemical Composition

ABSTRACTPastes of waste glass (WG) and metakaolin (MK) were prepared by chemical activation with sodium silicate solutions of modulus Ms = 0.5, 0.75, 1 and 1.25 adjusted with sodium hydroxide. An experimental design was carried out using the Taguchi method. The compressive strength (CS) was followed for up to 120 days and then 4 selected formulations of the higher CS were further characterized by X-ray diffraction and scanning electron microscopy. The results showed that the CS depends on the experimental conditions of %WG, %Na2O and Ms and showed a maximum of 70 MPa after 120 days for the paste with 100%WG (%wt.), 8% Na2O and Ms=1.25; while a Portland cement specimen cured at 20°C reached 43MPa. The WG is more reactive than the MK under less alkaline conditions. The features of the microstructures varied notably with the %WG; however all showed relative dense matrices of reaction products, in agreement with the CS attained.