International Concrete Abstracts Portal

This paper presents the performance characteristics of a newly developed polyolefin fiber-reinforced concrete. The polyolefin fibers were used for the first time for a full-depth pavement, a thin bridge-deck overlay, a jersey barrier, white-topping on scarified asphalt pavement, and a full-depth bridge deck slab. An attempt is made to assess, evaluate and appreciate the behavior of the polyolefin fiber-reinforced concrete. The performance of fresh concretes and the properties of hardened concretes with and without fibers are compared. A comparison is also made between the non-metallic polyolefin fiber-reinforced concrete and steel fiber-reinforced concrete. The test program on fresh concrete included: slump, concrete temperature, air content, vebe time, and unit weight. The hardened concrete properties included: compressive strength, static modulus, modulus of rupture, load-deflection curves, first crack toughness strength and post crack behavior, ASTM toughness indices, Japanese toughness index, equivalent flexural strength, fatigue strength and impact strength. The polyolefin fibers performed well in the mixing operation without causing any balling or segregation. Hardened concrete properties such as, fatigue strength, impact strength, modulus of rupture, ductility and toughness were greatly improved over the plain and steel fiber-reinforced concrete. The mixture proportions used, the procedure used for mixing, transporting, placing, consolidating, finishing, and curing during the construction of highway structures are described. This new polyolefin fiber-reinforced concrete with enhanced fatigue, impact resistance, modulus of rupture, ductility, and toughness properties is particularly suitable for the construction of thin bridge deck overlays, bridge deck slab and white-topping.

The premature deterioration of concrete structures is a major problem in many countries across the world and this has prompted the search for a method of predicting their service life. Whilst prediction methods are in their infancy it is evident that in order to improve their effectiveness it will be necessary to develop more reliable and convenient ways of measuring the relevant in-situ properties. In this context it is widely recognised that results obtained from permeation testing give useful information on the likely durability of concrete. In this paper, based on an holistic model relating permeability to durability the experience gained from the use of the “AUTOCLAM” permeability test, which is convenient and easy to use on site as well as in the laboratory, is presented. Details are included of a laboratory study correlating the “AUTOCLAM” permeation properties with the results of carbonation and freezing and thawing tests. In addition, the results of a field study on a motorway bridge are given. It is concluded that in-situ permeability and strength testing can be used to develop durability based design criteria for concrete, and to assess the remaining life of existing structures.

Deicing salt scaling resistance of high-strength concrete with a water-cement ratio < 0.40 remains clearly under the CDF (Capillary Suction of Deicing Chemicals and Freeze-Thaw Test) acceptance criterion of 1,500 g/m* after 28 freezing and thawing cycles even if no air-entrainment is used. It was confirmed by our investigations that a high-strength concrete without air-entrainment and with a low water-cement ratio and consequently almost no capillary pores may have a very high freeze-deicing salt resistance. The effect of phase transformations in hydrated cement under freeze-deicing salt attack which is practically harmless in air-entrained concretes should, however, be taken into consideration when dealing with high-strength concretes without air-entrainment.

It has been reported that the chemical/mineralogical composition of modern Portland-cement clinkers has changed in recent years to such a degree that cements made from them may lead to concrete durability problems even if such cement passed the applicable specifications. The effect of sulfur compounds in clinker on concrete deterioration due to delayed ettringite formation is cited as an example. In this paper, the relevant issues are briefly evaluated in light of available laboratory data and field experience.

This paper describes changes of stress and strain during the setting of prismatic specimens incorporating polymer mortar. A new apparatus measures setting shrinkage stress and strains developed at both ends of polymer mortar specimens while at constant temperature. This apparatus is simple in structure, consisting of a noncontact type displacement device and a load measuring device. The relationships of setting shrinkage stresses and strains, and elastic modulus of three kinds of polymer mortar are reported. Furthermore, the mechanical properties of three kinds of polymer mortar were investigated. Finally, the deflection and strain that occur when polymer mortar is overlaid on ALC (Autoclaved light weight concrete) beams includes both analysis and experimental data on the two layered structure.