International Concrete Abstracts Portal

A review is presented of the work carried out in the author's laboratory over the past ten years concerning the fire endurance of concrete masonry walls. After defining fire endurance, the author surveys the material properties of concrete and the geometric features of the component units that affect the performance of concrete masonry walls in fire.

Two series of lightweight concrete mixes made with expanded shale and slag aggregates were prepared for heat exposures between 300 C and 1000 C (572 F to 1832 F)/ To some concretes microfillers such as fly ash, silica flour, and calcined shale dust were added to replace 25 and 40% of the portland cement in the binder.

The results of a research program that studied the effect of elevated temperature on the behavior of air-entraied concrete are presented.

High Early strengths can be achieved by mixing concrete at elevated temperatures.

An investigation is discussed which had as its aim the clarification of the causes of strength loss in heat cured concrete as compared with normally cured concrete. It is concluded that the dominant causes are of a physical nature, i.e., increased porosity and cracking, which can be the result of the pressure which occurs in the air pores upon heating. Criteria for the occurance of cracking have been formulated and with the aid of these the minimum tensile strength necessary to avoid cracking can be determined.

A study was conducted on the influence of low temperature on the properties of hardened air-entrained concrete which was subjected to four different curing conditions. One of the curing conditions was related to the prevalent winter curing practice in Whitehorse, Yukon Territory, Canada. The tests consisted of compression, splitting tension, impact and elastic strains. In total, over four hundred specimens were tested.

This paper discusses winter curing of concrete in the light of the New Canadian Standard. The effect of freezing fresh concrete at various ages is dealt with in some detail and tests results are given to illustrate the absolute minimum protection period and minimum protection methods.

This paper reports the relationships of the strength of standard laboratory-cured cylinders to the strength of concrete in 24x24x66-inch (0.61 x 0.61 x 1.68-meter) columns and 24 x 24 x 8-inch (61 x 61 x 20-cm) slabs to that of cylinders cured under exposed winter conditions.

The effect of freezing temperatures on the compressive strength and ultrasonic pulse velocity of vacuum processed and nonprocessed concrete was investigated for two concretes with initial water/cement ratios of .71 and .45.

The thermal coefficient of expansion and the dynamic modulus of elasticity of concrete have been determined under short-term steady state temperatures, -100 to 150F (-73 to 66C). Specimens were cured both saturated and air-dried in the laboratory and tested at 7, 28, 84 days at at one year.