Laboratory Testing Program Research Articles

Mechanical performance of cement-stabilised soil containing recycled glass as road base layer

The increase in the volume of solid waste constitutes a global environmental challenge. The use of recycled materials in road construction reduces the environmental impact of civil engineering works and contributes to the achievement of recycling targets. Waste glass is 100% recyclable, non-biodegradable and has potential uses as engineering material. This paper aims to evaluate the potential use of Recycled Glass (RG) as aggregate replacement in road applications. The effect of RG inclusion in soil strength is studied. For that purpose, a laboratory testing programme was conducted, including the modified Proctor compaction, compressive strength and the California Bearing Ratio tests. Different proportions of RG and stabilising cement are tested. The results indicated an improvement in the shear resistance of tested mixtures, and also met the standards requirements for road base layers design. This study supports the technical feasibility of adding RG to cement stabilised soils for it use in base layers in light-load roads.

Methods used to determine maximum and minimum dry unit weights of sand: Is there a need for a new standard?

Known challenges exist with maximum (γdmax) and minimum (γdmin) dry unit weight measurements; the respective dry unit weight results depend very much on the method or standard used. A laboratory testing programme was completed to systematically determine and compare γdmax and γdmin values derived for six different sand types by using different methods. The tested sands contained a wide variety of mineralogical and fines contents. The γdmax and γdmin determinations were performed according to the following methods: British Standards Institution (BS) standards; American Society for Testing and Materials (ASTM) standards; Deutsches Institut für Normung (DIN) standards; Dansk Geoteknisk Forening (DGF) guidelines; Norwegian Geotechnical Institute (NGI), Geolabs, and Fugro proprietary methods. Differences in testing procedures, material requirements for testing, and the effects of soil degradation during testing introduce challenges and large differences in γdmax and γdmin values for each of the six sand types were observed. Therefore, it is concluded that there is a need for the development of new standards for a robust determination of γdmax and γdmin values. Specifically, a standard for determining γdmax is required to consistently obtain results at the upper bound of dry unit weight values for the likely range of sands — without crushing the sand grains.

Effect of water on the triaxial behavior under dynamic loading of asphalt concrete used in impervious barriers

Abstract Dams with an asphalt concrete core are a viable alternative in the construction of rockfill dams; therefore, characterization of the materials used in their construction is required. Part of this characterization requires obtaining the response parameters upon applying cyclic loads under different stress and temperature conditions. The objective of this research is to determine the effect of water on the dynamic properties of asphalt concrete after prolonged contact. To this end, an extensive program of laboratory tests was carried out in which specimens of this material were prepared, saturated and exposed to water. After the saturation process, the results of the tests indicated that the asphalt concrete presented a decrease in the shear modulus of 6.5% and an increase in the damping ratio of 16.1%, on average, with respect to the values obtained for the dry material. No significant change in the mechanical response was observed as a result of exposure to water for a period of up to 12 months.

Effect of asphalt binders with identical PG grading from different suppliers on the laboratory performance of asphalt mixture

Bituminous binders have significant effect on the overall performance of the asphalt mixtures, although binders are not the main component of the asphalt mixture (4–6% by weight). This paper presents an overview of research efforts undertaken to evaluate the sensitivity of asphalt mixture performance to the change of the binder suppliers in the State of Arizona. The binders used in the asphalt mixture have identical Performance Grade (PG). However, the binders were from different suppliers. The laboratory testing program included the dynamic modulus and the repeated load/flow number tests. Asphalt mixtures were collected from four sections on a project constructed in northern Arizona. This project was unique in that all four asphalt concrete mixtures had the same aggregate structure and source but used PG 76-16 binders obtained from four different suppliers. Based on the test results, the tests were sensitive to variations in the properties of the same PG binders obtained from different suppliers. This was also confirmed through statistical analysis and comparison with the binder test data. In order to assess the sensitivity of the four asphalt binders on the pavement performance, the binder and mixture data were input into the Mechanistic-Empirical Pavement Design Guide (MEPDG) and design simulations were run to compare rutting and fatigue cracking associated with each of the four PG76-16 binders included in this study. Significant statistical differences in both distress mechanisms were also observed for the different mixtures with changing only the binder supplier.

Investigation and geotechnical characterization of Perniö clay, Finland

Understanding the behavior of soft sensitive clays is a key aspect of geotechnical design, especially in those regions where constructions are planned in marine clay areas. In Finland, one of the major geotechnical issues is the stability and deformation of the railway embankments located on soft soil deposits. The Tampere University of Technology (TUT) and the Finnish Transport Agency (FTA) have been carrying out a research project aiming to a better understanding of strength and deformation properties of Finnish soft clays. As a part of this project, a detailed site investigation was conducted at Pernio site in Western Finland. This paper presents the details of the geotechnical investigation, including field testing, sampling operations, and the laboratory testing program. In particular, an open drive tube sampler with 132 mm diameter, designed at TUT, was used to collect high quality samples. For comparison, samples were also taken using the conventional piston samplers and Sherbrooke Mini-block sampler. Field testing included piezocone, vane shear, and seismic piezocone. Laboratory testing consisted of index, consolidation, triaxial and simple shear tests. A comprehensive study of all these data is presented in a framework to describe Pernio soft clay.

A geochemical, mineralogical and geotechnical characterization of the low plastic, highly sensitive glaciomarine clay at Dragvoll, Norway

The sediments at the NTNU research site Dragvoll, Trondheim, Norway accumulated in seawater close to the glacier front during the Pleistocene-Holocene transition. A comprehensive site investigation and laboratory test program was carried out to characterize the quick clay at Dragvoll. Downsized block samples, mini-blocks, were extracted and tested in the laboratory. Index testing, constant rate of strain oedometer tests and anisotropically consolidated undrained compression tests were carried out on all quick-clay samples. Pore-water chemistry, bulk and clay mineralogy, cation exchange capacity and specific surface area were determined. Resistivity cone-penetration tests and electrical resistivity tomography surveys were carried out and correlated to the laboratory results. With a clay mineralogy dominated by illite and chlorite, the Dragvoll clay is electro-chemically very active. Leaching has diluted the salt content in the pore water to~0.7 g/L, corresponding to a very low soil conductivity of only 20 mS/m. Due to the low salt content and a composition of cations in the pore-water dominated by sodium (85-92%), the repulsive forces between the clay particles are large. Therefore, the clay liquefies when remolded and has a very brittle behavior. The clay is slightly overconsolidated in top, with an overconsolidation ratio decreasing towards 1 at around 6 m depth. Developing new cost-effective ground improvement methods that may also serve as landslide mitigation measures in quick-clay areas is needed. Detailed knowledge on mineralogy and geochemistry is necessary to fully understand the behavior of clays, and in developing effective ground improvement methods by chemical additives. This paper present geochemical, mineralogical and geotechnical data from the quick clay at Dragvoll. A field experiment at Dragvoll showed that potassium chloride can be used as landslide mitigation in quick-clay areas, inhibiting retrogressive landslides and reducing the risk for progressive landslides.

Influence of sample slenderness and boundary conditions in triaxial test - a review

In the past decades an extensive work was done in order to improve the performance and increase the reliability of triaxial testing. Among the several changes made in order to solve the inaccuracies of the traditional test configuration, two of them are discussed in this paper: the sample slenderness [in other words, the H/D ratio] and the introduction of smooth end platens instead of the rough ones. By using H/D=1 and not the usual H/D=2 ratio, the formation of a single line-rapture and the bulge shape seem prevented. The smooth ends decrease the restrain at the top and bottom of the sample. From a theoretical point of view the effects of these changes are clear, but experimentally, the results coming from various studies are contradictory. The purpose of this paper is to elucidate the previous findings on the topic, including both laboratory and FEM modelling test programs.

Geology and engineering properties of sensitive Boston Blue Clay at Newbury, Massachusetts

This paper describes the geology and geotechnical engineering properties of a sensitive marine clay deposit at a research site located in Newbury, Massachusetts (MA) in the northeast USA. Results from in situ testing, soil sampling, and laboratory testing are presented. The clay is locally known as Boston Blue Clay (BBC) which is a glacial marine clay that was deposited approximately 14,000 years ago in the greater Boston, MA area during retreat of the Laurentide Ice Sheet. The thickness, stress history, and soil properties of BBC can vary significantly depending on location. At the Newbury research site, the BBC deposit consists of a shallow thin desiccated crust underlain by a 12-meter thick low plasticity clay with an overconsolidation ratio ranging from 2 to 3. Sensitivity of the clay ranges from approximately 10 to 30, based on field vane and fall cone measurements. In situ testing performed at the site included seismic piezocone and field vane. Soil sampling was performed using a variety of samplers including Sherbrooke block, fixed piston thin-walled Shelby tube, and a thick-walled drive sampler. A full suite of advanced laboratory tests was performed on the various quality samples collected, which ranged from very poor (thick-walled drive sampler) to excellent (Sherbrooke block), including constant rate of strain consolidation, consolidated undrained triaxial and direct simple shear. The efficacy of the Recompression and SHANSEP procedures to mitigate sample disturbance was evaluated using results from the advanced laboratory test program. The paper presents data from these advanced tests as well as other soil classification, index, and engineering properties based on in situ measurements and laboratory test results. A synopsis of constructed facilities built on and in BBC within the greater Boston area is also presented.

Estimation of tensile strength of ultramafic rocks using indirect approaches

Because the estimation of the tensile strength is very important in any geotechnical project, many attempts have been made to determine. But the immediate determination of the tensile strength is usually difficult owing to well-shaped specimens, time-consuming, expensive and sometimes unreliable. In this study, engineering properties of several ultramafic rock samples were measured to assess the correlations between the Brazilian Tensile Strength (BTS) and degree of serpentinization, physical, dynamic and mechanical characteristics. For this purpose, a comprehensive laboratory testing program was conducted after collecting thirty-two peridotite and fifty-one serpentinite rock samples, taken from central Greece, in accordance with ASTM and ISRM standards. In addition, a representative number of them were subjected to petrographic studies and the obtained results were statistically described and analysed. Simple and multiple regression analyses were used to investigate the relationships between the Brazilian Tensile Strength and the other measured properties. Thus, empirical equations were developed and they showed that all of the properties are well correlated with Brazilian Tensile Strength. The curves with the 45o line (y = x) were extracted for evaluating the validity degree of concluded empirical equations which approved approximately close relationships between Brazilian Tensile Strength and the measured properties.

Static and Dynamic Parameters of Railway Tracks Retrofitted With Under Sleeper Pads

Abstract The paper presents results of the laboratory tests made for the prototype resilient under sleeper pads in the Warsaw University of Technology laboratory unit. These pads are dedicated to reduce vibrations transmitted to the vicinity of the railroad and to improve the resistance of the railroad structure. The laboratory testing program was carried out for elastomeric materials (polyurethane and rubber based) due to the PN-EN 16730 standard. The obtained values of the key parameters were used in order to determine the insertion loss vibration level by applying analytical method. The paper presents the influence of selected parameters i.e. static and dynamic moduli on the reduction of vibration and structure-borne sound level.

Lime render, shrinkage cracks and craftsmanship in building restoration

Abstract The present project concerns early shrinkage cracks in renders. This problem relates to the type of lime and rendering methods used in Sweden during the 19th and early 20th century as well as in current restoration practice. Results from different render restoration projects have indicated that a high frequency of shrinkage cracks could be related to the slaking procedure and the reworking of the slaked lime putty. The aim of the project was to investigate whether there is a connection between different handling procedures for wet-slaked lime putty and early shrinkage cracks in render. An investigation involving practical application and a laboratory test programme was initiated to examine the problem of early shrinkage cracks in renders based on wet-slaked sub-hydraulic lime. This type of lime was commonly used in Sweden in the 19th century. The laboratory work in the project included 3 different mix proportions based on reworked and non-reworked lime putty. The renders were applied after 1, 8, 15, 32 and 68 days storage of the lime putty. This gave 30 mortar mixes applied as rendered test surfaces. The flow number of the fresh mortars was determined and the workability, mixability and open time were assessed. The frequency of shrinkage cracks in the rendered surfaces was measured. The results showed that the frequency of shrinkage cracks was related to the methods applied in the slaking process and the storage time. Reworking and storage of the lime putty increased the frequency of shrinkage cracks. The properties of the fresh mortar were also influenced.

Laboratory performance of steel mechanically stabilized earth reinforcements

ABSTRACT Mechanically stabilized earth (MSE) techniques have proven to offer reliable and cost-effective solutions to many poor and unstable ground problems. However, till now there are many uncertainties regarding the selection of appropriate types of reinforcement and the evaluation of design parameters for MSE wall structures. This paper presents the results of a significant programme of large-scale laboratory tests conducted to examine the performance of two types of soil reinforcement namely smooth plain steel and ribbed steel strips. The reinforcements were subjected to a series of axial static and slow repeated loading under different levels of normal stress and their ultimate pullout capacity were determined. The mechanics of load mobilization at the soil-reinforcement interface and the failure modes of the reinforcements were analyzed. In general, the results showed that ribbed steel strips are more load efficient and safer reinforcements than smooth steel strips under both static and repeated loading.

Water Saturation Influences on Engineering Properties of Selected Sedimentary Rocks of Pakistan

This study is focused on the evaluation of water saturation influence on the mechanical and physical properties of 34 sedimentary rock units selected from different geological formations in Pakistan. The laboratory testing program comprised the determination of physico-mechanical rock properties of both air-dry as well as fully water saturated rock specimens. Further thin section analyses of all rock samples were also performed to explain their petrography. According to the statistical analyses overall reductions of around 40 and 50% were found in UCSsat and BTSsat values, respectively, measured on saturated rock samples in comparison to their corresponding dry strength values, i.e. UCSdry and BTSdry. Linear correlations were found between ultrasonic wave velocities as well as density of both dry and saturated rock samples. In addition, the dry and saturated UCS values were exponentially related with the rock porosity. Multiple regression technique was also utilized to develop a predictive linear model of UCSsat with geotechnical rock properties in the dry condition and petrographical characteristics of rock samples. Finally the validity of multiple regression model developed in this study and an existing correlation for the conversion of UCSdry into UCSsat was statistically assessed.

Correlation Between Mechanical Properties of Sandstones and P-Wave Velocity in Different Degrees of Saturation

The aim of this study is to correlate the strength parameters of sandstones with P-wave velocity at different degrees of saturation. For this purpose, six different sandstone types were collected from several locations of upper red formation in southwestern Qom and a comprehensive laboratory testing program was conducted. Experimental results indicated that strength and deformability properties of the sandstones decreased with increasing degree of saturation, while Vp showed increasing trend with increasing degree of saturation. The trends are more consistent for low to medium strength sandstones than those of high strength which display less predictable behavior. The sandstones used in this study show a significant reduction of up to 61% and 58% in UCS and E, respectively, between the dry and saturated states. Simple regression analysis results indicate that prediction of the strength properties of rocks directly from Vp at different degrees of saturation is possible. A series of different prediction relationships were also developed by using independent variables such as Vp and degree of saturation.

Strength and Shrink/Swell Behavior of Highly Plastic Clay Treated with Geopolymer

This paper presents findings from an experimental study in which a novel, non-energy intensive, environmentally-friendly stabilizer known as geopolymer was used for stabilization of a highly plastic clay. Two forms of the stabilizer were synthesized, one using metakaolin (MK) and the other using fly ash (FA) as the alumino-silicate precursor. The paper describes the process of geopolymer synthesis as well as quality control tests conducted during geopolymer synthesis. Synthesized geopolymers were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). The paper also presents results obtained from a comprehensive laboratory test program that examined the effectiveness of the stabilizer in improving strength and controlling moisture induced swelling of a highly plastic clay soil. The geopolymer content of the soil ranged from 3% to 15% by weight ratio. SEM-EDX and XRD were performed to investigate the treated specimen for uniformity and stabilization mechanism. The data obtained from unconfined compressive strength tests conducted after seven days of curing showed three- to four-fold improvement in strength for geopolymer stabilized soils with MK geopolymer consistently providing better performance than FA geopolymer. The results from one-dimensional swell tests indicated significant reduction of swell behavior in FA geopolymer treated specimens while no improvement in swell behavior was observed in MK treated soil. This study demonstrates that, while geopolymers can overcome many limitations that exist in traditional stabilizers, the strength and swell performance of geopolymer stabilized clay soil can vary significantly depending on the source of alumino-silicate used in the production of the geopolymer.

Internally Cured Concrete for Pavement and Bridge Deck Applications

Abstract Laboratory and full-scale slab testing programs were conducted to evaluate the performance of internally cured concrete (ICC) using lightweight aggregates for application in bridge decks and concrete pavement. The laboratory testing program evaluated three standard mixes (SM) and three ICC mixes with the same water-to-cementitious materials (w/cm) ratio and cementitious content. The amounts of water-reducing admixtures needed for the ICC mixes to achieve the same workability was less than that needed for the corresponding standard mixes. The compressive strength, flexural strength, elastic modulus, splitting tensile strength, and coefficient of thermal expansion of the ICC mixes were lower than those of the SM mixes with the same w/cm ratio. Restrained shrinkage testing indicated that the ICC mixes, despite having higher drying shrinkage, had a substantially greater resistance to shrinkage cracking than the standard mixes. One SM and two ICC test slabs were constructed to evaluate the performance of ICC in pavement slabs. The results of the critical stress analysis from finite element models show that, at a critical loading condition, the computed stress-to-strength ratios for the ICC slabs were lower than those of the SM slab. Heavy vehicle simulator (HVS) testing of the SM slab produced some hairline cracks next to the wheel path. These hairline cracks possibly occurred when microshrinkage cracks developed into hairline cracks after the slab was loaded repetitively by the HVS. No surface cracks were observed for the two ICC slabs after HVS testing. Based on these results, the ICC test slabs had higher resistance to cracking than the SM test slab.

A comprehensive in situ and laboratory testing programme supporting seismic risk analysis of URM buildings subjected to induced earthquakes

The reliability of a risk assessment procedure is strictly dependent on the adopted hazard, exposure, fragility and consequence models. This paper presents the methodology adopted to support the assessment of the seismic vulnerability of buildings in the Groningen province of the Netherlands by means of a comprehensive in situ and laboratory testing programme. The area, historically not prone to tectonic ground motions, experienced seismic events induced by gas extraction and subsequent reservoir depletion in the last decades. The peculiarity of the input ground motions, the distinctive features and a general lack of knowledge on the seismic response characteristics of the Dutch building stock, and the goal to also assess the collapse risk drove the design and execution of a comprehensive test campaign comprising in situ tests and full-scale shaking table tests of buildings. An overview of the whole campaign is presented, focusing on the merits and roles of the different experimental techniques. The main outcomes of the experimental tests are summarized and additional and wider research findings together with potential research avenues for future studies are also identified.

The Keck Cosmic Web Imager Integral Field Spectrograph

Abstract We report on the design and performance of the Keck Cosmic Web Imager (KCWI), a general purpose optical integral field spectrograph that has been installed at the Nasmyth port of the 10 m Keck II telescope on Maunakea, Hawaii. The novel design provides blue-optimized seeing-limited imaging from 350–560 nm with configurable spectral resolution from 1000–20,000 in a field of view up to 20″ × 33″. Selectable volume phase holographic (VPH) gratings and high-performance dielectric, multilayer silver, and enhanced-aluminum coatings provide end-to-end peak efficiency in excess of 45% while accommodating the future addition of a red channel that will extend wavelength coverage to 1 micron. KCWI takes full advantage of the excellent seeing and dark sky above Maunakea with an available nod-and-shuffle observing mode. The instrument is optimized for observations of faint, diffuse objects such as the intergalactic medium or cosmic web. In this paper, a detailed description of the instrument design is provided with measured performance results from the laboratory test program and 10 nights of on-sky commissioning during the spring of 2017. The KCWI team is lead by Caltech and JPL (project management, design, and implementation) in partnership with the University of California at Santa Cruz (camera optical and mechanical design) and the W. M. Keck Observatory (observatory interfaces).

Assessing the empirical correlations between engineering properties and P wave velocity of some sedimentary rock samples from Damghan, northern Iran

In the present research, engineering properties of some sedimentary rock samples were measured to assess the correlations between P wave velocity and physical, index, and mechanical properties. The physical properties include dry and saturated unit weights, porosity, and water absorption. The index properties contain Schmidt rebound hardness and slake-durability index. The mechanical properties include uniaxial compressive strength, point load index, Brazilian tensile strength, and block punch strength. For this purpose, a comprehensive laboratory testing program was conducted after collecting 15 various sedimentary rock samples of four rock types from northwestern parts of Damghan, northern Iran. In the following, empirical equations were developed by using regression analyses between P wave velocity and the measured properties. The obtained results showed that all of the properties have strongly correlated to P wave velocity. Hereof, the relationships between P wave velocity and porosity and water absorption were inverse linear. But, P wave velocity has direct linear correlations with the other properties. Prepared contour maps indicated that P wave velocity is more affected by porosity of the rocks. The curves with the 45° line (y = x) were extracted for evaluating the validity degree of concluded empirical equations which approved approximately close relationships between P wave velocity and the measured properties.

A review of jet grouting practice and development

The jet grouting technique was originally initiated in the UK and progressively developed following the needs for larger geometries, ease of implementation, economic rationality, and better mechanical properties. This paper presents a comprehensive review of the development and practice of jet grouting through some fundamental concepts and relevant case studies. Subsequently, a laboratory testing program is performed to investigate the factors affecting the efficacy of the twin grouting system. The principal objective of this study is to define the suitable conditions for the jet grouting efficacy regarding economic rationality as well as quality control. For the first phase, a particular emphasis is placed on the properties of jet columns, site geological conditions, implementation methods, and the justification of each selected treatment option, while the second phase mainly focuses on the unconfined compressive strength (UCS) tests. It follows that the mono-fluid jet grouting system presents a valuable flexibility in dealing with complex configurations; yet, the double- and triple-fluid systems are more indicated for cases of mass treatments for which large portions of space must be treated and overlapping is fundamentally important for the reliability of the treatment. Furthermore, it was established that the efficacy of the twin-jet method primarily relies on the proper adequacy of some critical parameters, namely, the cement content, the water-cement ratio, and cement slurry-water glass ratio. In spite of some uncertainties inherently related to the technique, the UCS test represents the quintessential laboratory index for evaluating the mechanical properties of grouted elements, deriving jet grouting efficacy and the economics of jet grouts.