Laboratory investigation of the strength development of alkali-activated slag-stabilized chloride saline soil

Saline soil stabilization is being increasingly applied in foundation treatment engineering. Chloride saline soil obtained from sites and laboratory-made chloride soil (ZS) with various NaCl concentrations prepared artificially were stabilized using alkali-activated slag (AS). A series of unconfined compressive strength (UCS) tests, X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDXA), thermal gravity-differential thermal gravity (TG-DTG), and ion concentration tests were conducted to investigate the strength variation and mechanism of the AS-stabilized chloride saline soils. The results showed that NaCl has a significant influence on the strength of AS-stabilized chloride saline soil and the strength of AS-stabilized ZS (GZS) increases with increase of chloride content in soil samples. Friedel’s salt (Fs) and NaOH are generated by the reaction of NaCl and CaO·Al2O3 (CA) in the slag in the GZS. Fs can fill the pores in stabilized soil, and NaOH can promote calcium silicate hydrate (CSH) generation. These two effects combine to enhance the strength of GZS. The relationship between the rate of increase of 28-d UCS of AS-stabilized chloride saline soil and the chloride content in soil was obtained through regression analysis of the increase of UCS of GZS.     

Teachers’ Use of Scaffolding Strategies During Read Alouds in the Preschool Classroom

Relatively little is known regarding preschool teachers’ use of specific scaffolds, including those high support scaffolds (e.g., co-participating, eliciting, reducing choices) that may be important for children who are struggling to acquire language and literacy concepts. The goal of this study was to characterize preschool teachers’ use of six types of scaffolds (generalizing, reasoning, predicting, co-participating, reducing choices, eliciting; see O’Connor et al. in Ladders to literacy, Paul H. Brookes Publishing, Baltimore, MD, 2005) within the whole group read aloud session. Two specific questions were addressed: (1) To what extent do preschool teachers use high and low support scaffolds during whole group read aloud sessions? and (2) To what extent does preschool teachers’ perceived frequency of use of specific scaffolds correspond to their actual use of scaffolds? Videotaped classroom observations were carried out for five preschool teachers conducting whole group read alouds in their classrooms; frequency of use for six types of scaffolds was coded using systematic observation procedures. Results indicated that teachers showed a preference for three types of scaffolds, all of which were low support, and that the three types of high support scaffolds occurred at very low rates. Additionally, results showed a substantial discrepancy between teachers’ perceived frequency of use of specific types of scaffolds relative to their actual use. Together, findings suggest that preschool teachers may benefit from professional development focused on using a range of scaffolds, to include high support scaffolds beneficial to children who may need high levels of support to participate in read alouds.     

Investigating the learning challenges presented by digital technologies to the College of Education in Kuwait University

There is now widespread recognition that digital technologies, particularly portable hand held devices capable of Internet connection, present opportunities and challenges to the way in which student learning is organized in schools, colleges and institutions of higher education in the 21st Century. Traxler, Journal of the Research Centre for Educational Technology, 6(1), 3–15 (2010) suggests such devices are pervasive and ubiquitous, conspicuous and unobtrusive, noteworthy and taken-for-granted with everyone typically owning one, using one and often having more than one. As a consequence it has been argued that the availability of such devices, controlled mainly by the student and not the teacher, has the potential to change the traditional dynamics and pedagogical patterns of the learning environment (Burden et al. 2012). Education institutions, however, typically remain organized around spatial and temporal considerations such as buildings, timetables, calendars and internal structures which are designed to classify and manage students. In the case study reported here students and faculty teaching staff from the College of Education in the Kuwait University were surveyed in order to assess their access to such technologies, their capability to use them effectively in support of achieving planned learning outcomes and the implications for change that could emanate from such findings.     

Reduction rate of dragload and downdrag of piles by taper angles

Taper angle is one of the effective methods to reduce the dragload and downdrag of piles under the surcharge load. The model tests on the tapered pile and uniform cross-section pile embedded in sand were carried out under the surcharge load. The values of dragload and downdrag of piles versus the surcharge loads were measured. Based on the concentric cylinder shearing theory, a simplified theoretical model for calculating the dragload and downdrag of tapered piles with small taper angles under the surcharge load was proposed considering the angle effect. The correctness of the developed theoretical model was validated through comparing with the model test results obtained in this study and previous literature. Then the parametric studies of the taper angle, surcharge, strength and modulus of soil were discussed. It is shown that the tapered pile with the taper angle of 3° can reduce approximately 65% of the maximum dragload value and 30% of the downdrag value compared with a uniform cross-section pile. The value of downdrag can be decreased by approximately 50% compared with a uniform crosssection pile in the same average pile diameter.