Effect Of Air Voids Research Articles

Prediction of Asphalt Cement Content of Compacted Hot-Mix Asphalt Specimens Using Nuclear Gauges

Determining asphalt cement (AC) content of hot-mix asphalt (HMA) for quality control/quality assurance using extraction methods is a lengthy, time-consuming, and hazardous process. A demand for a faster and safer method led to the development of different nuclear gauges capable of predicting the AC content of HMA samples. Measuring the AC content of compacted specimens by nuclear gauges is a new technique whose feasibility was evaluated. A total of 216 Marshall compacted specimens were cast and tested in an attempt to develop correction models. The study program investigated the effect of various HMA parameters on the measured AC content, including aggregate gradation and type, air void content, moisture content, AC content, and specimen weight. Specimens were prepared at two different mix design formulas using AC-30 and compacted at two different compaction efforts to investigate the effect of air voids. Specimens (1200 g each) used for calibration were prepared at 3 to 7 percent AC content, whereas specimens prepared for measurements were prepared at 4 to 6 percent. Quartzite and diabase aggregate were used as open and dense graded in prepared mixes. Three levels of moisture content in HMA were evaluated. Different calibration models were developed for different asphaltic mixtures. The evaluated nuclear gauge for measuring AC content for compacted HMA specimens produced satisfactory results when the parameters of tested and calibration parameters were the same. The study found that specimen weight is the most significant factor. Other parameters have different degrees of influence on the measured AC content. Statistical models were developed to correct for the evaluated parameters.

Studies of radiation penetration and effect of air voids in bulk concrete shield configurations

Experimental measurements have been carried out to study the effect of air-filled voids on γ-rays and slow neutron distributions through multilayer assemblies. It has been found that the presence of the air-filled voids increases the γ doses and also the slow neutron fluxes both along the void axis and pependicular to it. Also, we can see that this increase is marked more as the air-filled void diameter increases. The concrete assembly was placed in front of one of the horizon tal channels of the ET-RR-1 reactor (2MW). Gamma-rays and the slow neutron distributions were measured using LiF-7 and LiF-6 TLD dosimeters, respectively.

Theorectical analysis of the Effects of Air Voids in Concrete

A PHYSICALLY DESCRIPTIVE MODEL IS ESTABLISHED FOR POROUS MATERIALS SUCH AS CONCRETE. THE MODEL CONSISTS OF A SOLID MATRIX CONTAINING RANDOMLY DISTRIBUTED, FLUID-FILLED VOIDS OF IRREGULAR SHAPES AND VARIOUS SIZES. THE ELASTIC MODULUS AND SPEED OF SOUND IN THIS MODEL ARE INVESTIGATED ANALYTICALLY, AND MATHEMATICAL RELATIONSHIPS BETWEEN THESE PROPERTIES AND THE POROSITY ARE OBTAINED. USING DATA DUE TO KAPLAN THE THEORETICAL RESULTS ARE FOUND TO DESCRIBE THE BEHAVIOR OF POROUS CONCRETE VERY NICELY, AND SOME INSIGHT IS GAINED INTO THE DIFFERENCES BETWEEN THE EFFECTS OF ENTRAINED AIR AND AIR DUE TO INCOMPLETE CONSOLIDATION. /AUTHOR/