Field investigation of slab deterioration due to carbonation in a concrete building

This paper presents an investigation on a deteriorated slab of a two-story building located in Johannesburg, South Africa. The structure has been in use as a residential building for more than 60 years. The top slab of the first floor was delaminated and reinforcement bars were severely corroded. Condition assessment of the building was done using the Schmidt hammer test, cover-meter survey and half-cell potential measurements. In addition to the non-destructive tests done, X-ray diffraction and scanning electron microscopy were also conducted on the deteriorated concrete.

Ambliopia anisometropia

Anisometropic amblyopia is blurred vision due to refractive anomaly without any anatomical disorders of the eyes. It is frequently found among children in their growth and development periods. The prognosis depends on the ambylopia severity, management, patient’s obedience to the management, and age. We report a case of anisometropic amblyopia in a 8-year-old boy with his main complaint was blurred vision of both eyes. The ophthalmological examination showed the visual acuity of both eyes 6/40, PH 6/9. Several tests that showed normal results were as follows: eyeball movements to all directions; pupil responses to light; Hischberg test; cover test dan cover uncover test at near and far distance fixation; alternate cover test; and worth four dots and Maddox rod tests. Cyclopegical refraction with streak retinoscopy at 50 cm distance resulted in right eye S-4.00 C-3.00 x1800 6/9 and left eye S-1.25 C-3.25 x1800 6/7.5; autorefraction of right eye S-4.50 C-3.25 x70 and of left eye S-1.25 C-4.25 x1710. Anterior and posterior segments of both eyes were normal. Conclusion: In this case, the diagnosis was confirmed as anisometropic amblyopia and compound myopic astigmatism of the right and left eyes. The prognosis was dubia ad bonam. The patient was treated with maximal correction glasses and observed for the first four weeks, and then would be evaluated continuously untill the vision was normal. Keywords: amblyopia anisometropia, vision, refraction anomalyAbstrak: Ambliopia anisometropia merupakan gangguan penglihatan akibat kelainan refraksi tanpa disertai adanya kelainan anatomik pada mata yang sering terjadi pada masa perkembangan anak. Prognosis sangat tergantung pada derajat ambliopia, penanganan, kepatuhan pasien terhadap penanganan, dan usia pasien. Kami melaporkan kasus ambliopia anisometropia pada seorang anak berusia 8 tahun, dengan keluhan utama penglihatan kedua mata kabur. Dari pemeriksaan oftalmologik didapatkan visus ODS 6/40, PH 6/9. Beberapa pemeriksaan yang dilakukan memperlihatkan hasil normal, yaitu: pergerakan bola mata ke segala arah; respon pupil terhadap cahaya; Hischberg test; cover test dan cover uncover test pada fiksasi jarak dekat dan jauh; alternate cover test; serta worth four dots test dan Maddox rod test. Pemeriksaan refraksi sikloplegik dengan streak retinoscopy pada jarak 50 cm didapatkan mata kanan S-4,00 C-3,00 x1800 6/9 dan mata kiri S-1,25 C-3,25 x1800 6/7,5 dan pemeriksaan autorefraksi mata kanan S-4,50 C-3,25 x70 dan mata kiri S-1,25 C-4,25 x1710. Pemeriksaan segmen anterior dan posterior mata kanan dan kiri dalam batas normal. Simpulan: Diagnosis pada kasus ini ialah ambliopia anisometropia ODS dan astigmatisma miopikus kompositus ODS, dengan prognosis dubia ad bonam. Terapi yang diberikan ialah kacamata koreksi maksimal dan diobservasi selama 4 minggu pertama, dan akan dievaluasi terus sampai ketajaman penglihatan normaL. Kata kunci: ambliopia anisometropia, ketajaman penglihatan, kelainan refraksi

Changes in geosynthetic clay liner (GCL) properties after 2 years in a cover over arsenic-rich tailings

A test cover comprised of three different needle-punched geosynthetic clay liner (GCL) products and covered with up to 1 m of cover soil (gravelly sand) was built over arsenic-rich tailings at a former gold mine in Nova Scotia, Canada, to evaluate the performance of the GCLs under local climatic conditions. Of the GCLs examined, one had untreated and two had polymer-enhanced natural sodium bentonite. The three GCLs each had different carriers: one with a woven geotextile, one with a scrim-reinforced nonwoven geotextile, and one with a woven geotextile laminated with a polypropylene film. At some locations, each type of GCL was placed in direct contact with the tailings. At other locations, each GCL was separated from the tailings by 0.15 m of cover soil. Samples of each GCL, tailings, and cover soil were recovered 1 and 2 years after construction. Tests show that the GCL with untreated bentonite maintained a low hydraulic conductivity (≤5 × 10−11 m/s) at locations where there was ≥0.7 m of cover soil above the GCL even though there was significant cation exchange of the sodium in the GCL with divalent cations in the tailings-soil porewater (the mole fraction of sodium (exchangeable sodium percentage (ESP)) decreased from 65% to 10%–17%). The GCL with polymer-enhanced bentonite had a lower hydraulic conductivity (≤3 × 10−11 m/s under ≥0.7 m of cover soil above the GCL) and experienced less cation exchange (ESP decreased to 19%–28%) than the standard GCL. The other GCL with polymer-enhanced bentonite and a carrier geotextile coated with a geofilm demonstrated the best hydraulic performance regardless of the thickness of cover soil or presence of an initially uncontaminated foundation layer. The presence of a foundation layer between the GCL and tailings impeded the migration of arsenic from the tailings into the GCLs. All GCLs were serving as an effective barrier to arsenic migration.