Cement Concrete and Aggregates 

About: Cement Concrete and Aggregates is an academic journal. The journal publishes majorly in the area(s): Portland cement & Cement. Over the lifetime, 462 publications have been published receiving 7646 citations.

Influence of Water-Reducing Admixtures on Properties of Cement Paste—A Miniature Slump Test

Abstract: A miniature slump test has been developed for the evaluation of the influence of water-reducing admixtures on the workability of neat portland cement pastes. Resulting paste pat areas rather than heights are measured, and the results are expressed as the percentage of water reduction. Relative effects of various admixtures on a portland cement are illustrated, and influences of specific admixtures on different cements are also shown. Effects of different superwater-reducing admixtures and combinations of ordinary and superwater-reducing admixtures are compared. The mini-slump method has also been used for the evaluation of the loss of workability (slump loss) with time for various admixtures and admixture combinations. The simplicity of the method facilitates accurate and effective evaluation of water-reducing admixtures.

Influence of Pozzolanic, Slag, and Chemical Admixtures on Pore Size Distribution and Permeability of Hardened Cement Pastes

Abstract: Durability of concrete is greatly influenced by the permeability of the cement paste which in turn is governed by the pore size distribution. Some mineral and chemical admixtures are known to enhance the durability of portland cement concrete. The objective of this work was to investigate how the pore size distribution and permeability of portland cement pastes are modified by the addition of pozzolanic admixtures, blast furnace slag, and chloride salts. The effectiveness of pozzolans in reducing the volume of large pores and permeability was found to depend on the reactivity of the pozzolan used. Large additions of granulated blast furnace slag increased the total pore volume, however the pore size distribution was shifted toward finer pores and therefore the permeability of the paste was reduced. Among the chloride admixtures, namely calcium, magnesium, and sodium chloride, magnesium chloride was most effective in reducing both the volume of large pores and permeability of the cement pastes.

A model of complex travel behavior: part i. theoretical development

Abstract: This paper presents a policy sensitive approach to modeling travel behavior based on activity pattern analysis. A theoretical model of complex travel behavior is formulated on a recognition of a wide range of interdependencies associated with an individual's travel decisions in a constrained environment. Travel is viewed as input to a more basic process involving activity decisions. A fundamental tenet of this approach is that travel decisions are driven by the collection of activities that form an agenda for participation; the utility of any specific travel decision can be determined only within the context of the entire agenda. Based on the theoretical model of complex travel behavior, an operational system of models, STARCHILD (Simulation of Travel/Activity Responses to Complex Household Interactive Logistic Decisions), has been developed to examine the formation of household travel/activity patterns, and is presented in a companion paper (Recker et al, 1985).

The Maturity Method: Theory and Application

Abstract: The maturity method may be used to predict the in-place strength of hardening concrete based on its thermal history A theoretical basis for the maturity method is presented The general form of the time-temperature function is found to be the time integral of the rate constant For the case of linear dependence between temperature and the rate constant, the time-temperature function becomes the traditional maturity function The Arrhenius equation is shown to be an accurate representation of the temperature dependence of the rate constant, and the concept of equivalent age is explained for practical application of the Arrhenius equation It is explained how the accuracy of strength prediction by the traditional maturity method can be improved by using the proper datum temperature Results illustrate that the appropriate value of apparent activation energy or datum temperature for concrete may be obtained from strength-gain data of isothermally cured mortar specimens

Cementitious Composites Containing Recycled Tire Rubber: An Overview of Engineering Properties and Potential Applications

Abstract: One of the major environmental challenges facing municipalities around the world is the disposal of worn out automobile tires. To address this global problem, several studies have been conducted to examine various applications of recycled tire rubber (fine crumb rubber and coarse tire chips). Examples include the reuse of ground tire rubber in a variety of rubber and plastic products, thermal incineration of waste tires for the production of electricity or as fuel for cement kilns, and use of recycled rubber chips in asphalt concrete. Unfortunately, generation of waste tires far exceeds these uses. This paper emphasizes another technically and economically attractive option, which is the use of recycled tire rubber in portland cement concrete. Preliminary studies show that workable rubberized portland cement concrete (rubcrete) mixtures can be made provided that appropriate percentages of tire rubber are used in such mixtures. Achievements in this area are examined in this paper, with special focus on engineering properties of rubcrete mixtures. These include: workability, compressive strength, split-tensile strength, flexural strength, elastic modulus, Poisson's ratio, toughness, impact resistance, sound and heat insulation, and freezing and thawing resistance. The benefits of using magnesium oxychloride cement as a binder for rubberized concrete mixtures are discussed. Various applications in which rubcrete could be advantageous over conventional concrete are described.