Perlite is a volcanic glass that, under thermal treatment, expands, producing a highly porous and lightweight granular material which finds application in the construction, horticulture, insulation and other industrial sectors. Proper control of the feed properties and the expansion conditions allows the production of purpose-oriented grades, while the primary evaluation of its appropriateness for use in each sector is performed by the proper characterization of relevant physical, thermal or/and mechanical properties. However, due to its extreme fineness, low density, and friability, most of the available characterization methods either fail in testing or provide erroneous results, while for certain properties of interest, a method is still missing. As a consequence, the way towards the evaluation of the material is rife with uncertainties, while a well-defined methodology for the characterization of the critical properties is of practical importance towards the establishment of a pathway for its proper analysis and assessment. This article presents the available methodology for determining the main properties of interest, i.e., the size and density, water repellency/absorption and oil absorption, the microstructural composition, crushing and abrasion resistance and isostatic crushing strength, and also sampling and size reduction processes. The issues raised by the application of existing methods are analyzed and discussed, ending up to a proper methodology for the characterization of each property, based on the long-term experience of the Perlite Institute. The study is supplemented by updated insights on ore genesis, physicochemical properties, mineralogical composition and the expansion mechanism, as background information for the sufficient comprehension of the nature and properties of perlite.

The integral abutment bridge concept allows removal of expansion joints, bearings, piles for horizontal earth loads, and other uneconomical details. These details not only add to construction costs but also increase the maintenance work and expenses. When expansion joints are eliminated from a bridge, thermal stresses must be accounted for in the design. This paper describes the design challenges for a 45.6 m one-span integral abutment bridge, nearby Gatineau, Quebec, Canada. According to the geotechnical report, the soil under the foundation of the bridge consists of a 1.0-5.4 m granular embankment mixed with organic material and layers of wood chips, 15 m layered deposits of granular and cohesive soils, and a 35.7 to 40.8 m thick clay that is laid on a till layer. Because a 5.3 m granular backfill of abutments would lead to remarkable consolidation settlement and maintenance issues, it was decided to substitute 3.7 m of the granular backfill with a lightweight material to minimize the long-term settlement problem. A 3D bridge model in CSiBridge was used to simulate the construction stages and nonlinear behavior of soil around the piles to predict the induced efforts in the bridge due to different loads, including thermal and deck shrinkage loads. Structural design of piles was accomplished by taking into account the plastic hinge at the top of the piles and estimating the buckling free length of piles based on analysis of pile under lateral load in L-PILE software. While some Canadian provinces have developed standard details for approach slab joints, Quebec's ministry of transportation (MTQ) does not propose any standard expansion joint detail for integral bridges. Therefore, the typical strip seal expansion joints detail of MTQ was adapted for this project to reduce water infiltration inside the joint even though it is away from the deck and is located at the end of approach slab. During the construction, the result of test piles revealed that excess pore water pressure due to pile driving operation needs some time to disappear. Thus, minimum waiting times for the main stages of construction were defined. [GRAPHICS] .