Search

This article discusses the effects of glass powder (GP) replacements and sodium hydroxide (NaOH) molarity on the rheological, fresh, mechanical and microstructure characteristics of slag-based mechanochemical geopolymer (MG) grout. A conventionally activated geopolymer grout and an ordinary Portland cement (OPC) grout were also investigated for comparison. Four glass powder replacement ratios were used (0%, 10%, 20% and 30% by the total precursor weight) to prepare slag-based mechanochemical geopolymer at three NaOH concentrations (1.25, 2.5 and 3.75 molars). The experimental results showed that the rheological behaviour of MG grouts was considerably reduced, whereas the setting time and the bleeding capacity value increased when slag was substituted with 0%–30% GP. However, after 28 days, the unconfined compressive strength (UCS) improved by 2%–13% when 10%–20% GP was used as a slag replacement, then dropped by 4% when 30% GP was substituted. The results confirmed that both geopolymer grouts irrespective of the activation method had shorter setting time and more stable bleeding capacity than OPC grout. The results also revealed that the UCS of geopolymer grout is enhanced by 18% when the source materials are activated by the mechanochemical method compared to the conventional activation of geopolymer grout. The microstructure results revealed that the activation method had a considerable effect on the microstructure of geopolymer grout because the ball milling process increased the surface area and reduced the particle size of slag compared to conventionally activated geopolymer grout. [ABSTRACT FROM AUTHOR]

One-part geopolymer (OPG) grout offers advantages over two-part geopolymer grout in the handling and storage of feedstocks, mainly because of the large quantities of caustic solutions that must be handled for producing two-part geopolymer. However, OPG often suffers from a low degree of reaction, a high number of crystalline by-products and, as a result, low strength. Here, one-part geopolymer was assisted by mechanochemical activation (MC-OPG) to produce grout. The precursor materials (slag and fly ash) and sodium silicate were mechanochemically activated utilising co-grinding to produce a geopolymeric precursor, after which water is the only additive required to initiate the geopolymerisation reaction. The effects of slag/fly ash ratios on grout mixtures were also investigated. A series of tests was examined, including rheological characteristics, setting time, bleeding, unconfined compressive strength (UCS), ultrasonic pulse velocity, scanning electron microscopy and X-ray diffraction. The results showed that the mechanochemical activation technique increased the rheological characteristics and reduced the fresh properties (setting time and bleeding) of geopolymer grout compared to the one-part geopolymer. Considering mechanical properties, the UCS of MC-OPG grout was higher (41–73%) than that of OPG grout. Furthermore, slag content significantly affected the rheological, fresh and mechanical properties of all the geopolymer grouts regardless of the activation method. [ABSTRACT FROM AUTHOR]

This paper evaluates the unconfined compressive strength (UCS), stability (bleeding), modulus of elasticity and failure patterns of cement-based grout mixtures that were prepared by placing of rice husk ash (RHA) with cement at various water to binder (w/b) ratios. In order to investigate these parameters, UCS and bleeding tests were conducted on the soilcrete samples that prepared at 5, 10, 20 and 30% replacement level of RHA with cement for.75, 1.00 and 1.25 w/b ratios. Test results showed that the UCS values of the samples for 28 day curing are higher than 1 MPa and E/qu ratios obtained from soilcrete mixtures were less than the corresponding value from slurry clay–cement mixes given in the literature. In addition, all bleeding test results are lower than the level of.5%. Finally, most of the mixtures prepared for this study failed along foliations. [ABSTRACT FROM AUTHOR]

Peat is found in many countries throughout the world where it can be generally seen in thick layers in limited areas. Peat is an extreme form of soft soil and is considered problematic due to the low shear strength and large compressibility. This project presents laboratory finding on the compressibility and shear strength characteristics of fibrous peat with sand column. The peat used in the study is classified as fibrous peat and H1–H4 in Von Post scale. Its liquid limit is 119%. In all tests, the peat used for the tests passing 2 mm and remain on.15 mm. The rounded sand used for making sand column is poorly graded passing from 2 mm sieve size and retaining on 1 mm sieve size. The tests conducted to investigate effect of area ratio of sand column on shear strength and compressibility of the peat. Three different area ratios were used for both compressibility and shear strength tests. Consolidation test results showed that when the area ratio increases compressibility characteristic of the peat improved. Shear strength of the organic soil was also affected from the sand column. [ABSTRACT FROM AUTHOR]

In order to provide a fast and cost-effective solution, particularly for preliminary evaluations in many design situations of constructions, a number of numerous empirical equations for estimation of compression index simply established with soil index properties are intensively used for consolidation settlement. However, they may not be appropriate when considered for different regions dependent upon local site conditions. Thus, it is important to know the performances of the empirical equations with local data. This paper investigates the performances of some of the empirical equations for estimation of compression index for fine-grained soils of Baghdad City along the Tigris River. Four criteria including error and ranking measurement were employed as bases of evaluation: root mean square error, the ratio of estimated to measured (laboratory) compression index, ranking index and ranking distance (RD). The last two (ranking index and RD), a relatively new approach of ranking measurement, involve with the accuracy and precision of estimated result with actual data. The assessment ultimately has been done regarding the RD, since it is a comprehensive statistical parameter that gives equal weight to the accuracy (mean) and precise (standard deviation) of estimation, as compared with others. It is found from the analysis results that the overall best estimation of compression index for the data of Baghdad was obtained by the empirical equations established with liquid limit proposed by Cozzolino and Azzouz, Krizek, and Corotis. The results indicate that the most reliable equation correlates compression index with liquid limit. [ABSTRACT FROM AUTHOR]

Sixty four tests were performed in a steel tank to investigate the axial responses of piles driven into organic soil prepared at two different densities using a drop hammer. Four different pile materials were used: wood, steel, smooth concrete, and rough concrete, with different length to diameter ratios. The results of the load tests showed that die shaft load capacity of rough concrete piles continuously increased with pile settlement. In contrast, the others pile types reached the ultimate shaft resistance at a settlement equal to about 10% of the pile diameter. The ratios of base to shaft capacities of the piles were found to vary with the length to diameter ratio, surface roughness, and the density of the organic soil. The ultimate unit shaft resistance of the rough concrete pile was always greater than drat of other piles irrespective of soil condition and pile lengtii. However, the ultimate base resistance of all piles was approximately close to each other. [ABSTRACT FROM AUTHOR]

This article presents a program called Pile-D developed for the teaching of pile foundation design to undergraduate level geotechnical engineering students. The program performs drained and undrained analysis for frictional resistance of the pile in clay, and uses critical depth approach for the analysis of the pile in sand. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ 15: 355–366, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20206 [ABSTRACT FROM AUTHOR]

This research aims to experimentally investigate the potential use of a geopolymer made from various stabilizers or byproducts (fly ash (FA-F, FA-C), slag (SL), glass powder (GP), metakaolin (MK), marble powder (MP), bottom ash (BA), rice husk ash (RHA), silica fume (SF)) to enhance the mechanical performance of soil (clay) via a deep mixing technique. Strengths of geopolymer soilcrete specimens were determined by unconfined compressive strength (UCS) tests regarding curing times (7 to 365 days) by comparing with Portland cement (PC). In addition, ultrasonic pulse velocity (UPV) tests, the effect of molarity (8–16 M), stress-strain behavior, failure modes, and microstructure (SEM, EDX) of geopolymer specimens were examined. Compared to PC, UCS responses of geopolymer specimens yielded: (i) a decreasing trend for FA-F, GP, MK, BA, and MP + FA-F, (ii) an increasing trend for FA-C, SL, and combinations of SL (BA + SL, RHA + SL, SF + SL, MK + SL) favorable with fewer proportions of stabilizers, and (iii) higher increments due to long-term curing (90, 365 days). Despite some decrements, most UCS values were found acceptable (>0.2 MPa) for sufficient enhancement of soft clay. The UCS results were mostly confirmed by UPV performances. The geopolymer specimens were also found to present: (i) strength development for alkaline concentrations from 10 to 14 M, (ii) brittle behavior of stress–strain curves that failed in axial splitting and near axial directions, and (iii) intensity of the silica peak for strength responsibility of the dense microstructure. The findings relatively support the usage of stabilizers or byproducts in the production of geopolymers for potential use in deep mixing. Thus, this research could be a basis for further efforts in this area. [ABSTRACT FROM AUTHOR]

Nowadays, Iraq is experiencing a rapid reconstruction process during which a significant amount of construction waste material is generated. One of such materials is RAP (reclaimed asphalt pavement) which is obtained from the removal of surface pavement of roads and used especially as an aggregate substitute in asphalt mix, granular base and sub-base material for roads, or as road fill material. From this point of view, the primary objective of this study was to evaluate the possible effects of adding sand to RAP in terms of compaction and strength properties and to suggest a possible recycling application. For this purpose, RAP and sand samples were collected from Iraq. Then, RAP/sand blends were prepared by mixing RAP with 5%, 10%, 15%, 20%, 25%, and 50% sand by weight. Modified Proctor Compaction and California Bearing Ratio (CBR) tests were performed on these samples. The results have revealed that the compaction properties of the RAP/sand blends were significantly improved as compared to RAP samples resulting in increased maximum dry density and optimum moisture content. CBR values of the tested mixtures had also increased with increasing sand content similar to the results of previous studies. The primary finding of this study was that RAP/sand blends with a sand content of 20% or more were defined to be suitable for use as road fill material according to the American Association of State Highway and Transportation Officials (AASHTO) standards in terms of tested parameters, providing a new field for recycling of RAP in the studied region. [ABSTRACT FROM AUTHOR]