Segmental concrete construction

Grip layer. A layer of coarse aggregate may be bonded to the steel to form a rough layer onto which fresh concrete is subsequently poured. This technique has been the subject of some research involving slab panels, tensile reinforcement being provided in the form of a thin soffit steel plate. However, premature adhesive failures have been reported and an improved bonding technique is considered to be necessary(9). 

Pre-bonding. Fresh concrete is poured directly onto a layer of uncured adhesive spread over the prepared steel surface. This method, as used in the reinforcement of slab units by externally bonded plates, has been the subject of extensive research by the Wolfson Bridge Research Unit(lO). Open sandwich slabs, based on either a flat soffit plate or a plate curved slightly upwards to form a shallow arch have been recommended. The technique is described in some detail in Chapter 8. 

To fulfil these requirements the proposal suggests separate programmes of testing for (a) choosing an appropriate bonding agent and (b) site testing. The properties required and the proposed test methods are summarised in Tables 7.2 and 7.3. 

Epoxy adhesives were used in 1978 during the construction of the U.S. s first segmentally constructed cable-stayed bridge across the Columbia River(15). Here the deck is made monolithic by a combination of post-tensioning and compressive forces from the horizontal components of the stay cable forces the epoxy mortar is called upon to provide both shear and tensile resistance across the joint. 

Open time series of tensile bend tests with time 

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Moreton, A.J. Epoxy glue joints in precast concrete segmental bridge construction, Proceedings of the Institution of Civil Engineers, Part 1, No. 70, February 1981, pp. 163-77. 

Figure 1.20 Segmental bridge construction takes advantage of room (cold)-temperature hardening, epoxy-based adhesives for bonding and sealing the concrete units.

Today, ceramic materials find widespread applications in both the consumer and industrial market segments. In the home, ceramics are commonly used in kitchens and bathrooms and for decoration and ornamentation. As construction materials, ceramics are widely used as bricks, tiles, and concrete sidewalks. 

In many countries, the largest market segment for the sale of limestone is as an aggregate in the construction and building industry. The major uses are in concrete and roadstone (both bound and unbound). Other applications include sand for mortar, rip rap, armourstone for sea defence works, land fill, filter media, pebble dash and roofing gravel. Finely divided limestone is used as an inexpensive filler for asphalt concrete. 

A similar concept to glulam and concrete segmental construction can involve the fabrication by bonding, usually with epoxides, of awkward or special shapes and units made of concrete or clay brick. Examples include special roof tiles and building blocks formed by cutting and bonding standard production shapes to provide new forms. 

Federation Internationale de la Precontrainte. Proposal for a standard for acceptable tests and verification of epoxy bonding agents for segmental construction. Cement Concrete Association, Slough, 1978. 

Another segment for recyclate is the substitution of conventional construction materials such as hardwood, non-structural lumber, or concrete. It is precisely the plastics specific characteristics from which technological advantages can be derived, leading to a low system cost as long as a comparable lifetime can be achieved [251, 267, 268]. 

In subway construction, concrete segmental liners generally do not receive a secondary lining, since slight seepage is tolerated. 

The production of concrete bridges with prefabricated parts is only possible up to a certain length, because such parts cannot be transported. An improvement of the precast construction is the allocation of portions (segments) that are assembled on site and then are tightened by threaded clamping cables (prestressing). 

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