Relationships Between Abrasion/Degradation of Aggregate Evaluated from Various Tests and the Effect of Saturation

Abstract

Aggregate is a fundamental component of construction works. It is widely used for different construction purposes especially as road stones and as the main ingredient of Portland cement concrete (PCC). It normally comprises between 75 and 85 % by volume of Portland and asphalt cement concrete mixes and hence it is not surprising that the quality of aggregate is of considerable importance in determining their suitability for any specific engineering application (Al-Harthi 2001). Aggregate that has little resistance to degradation can cause many problems for both PCC and hot mix asphalt (HMA) mixes. In the road pavement, aggregate is subjected to the abrasive forces of heavy wheel loads that can break the aggregate down over time and change its gradation. If the gradation of these mixes is changed in this manner, the pavement may no longer have the characteristics that it was designed for. This problem can cause early failure of pavement through consolidation, cracking, polishing and other problems (Rangaraju and Edlinski 2008). The Los Angeles abrasion value (LAAV) test is the most widely used method for measuring aggregate resistance to abrasion. The test measures the resistance of aggregate to wear due to attrition between rock particles and also to impact and crushing by steel spheres (Kahraman and Fener 2007). Aggregate crushing value (ACV) and aggregate impact value (AIV) are two well-known British tests for assessing the degradation of aggregate. ACV gives a relative measure of the resistance of aggregate to crushing under a gradually applied compressive load. AIV gives a relative measure of the resistance of aggregate to sudden shock or impact. Results of these tests are associated with aggregate toughness/abrasion resistance. Fookes et al. (1988) recommended that combination of three tests, ACV, AIV and LAAV, be used to assess aggregate durability. Kazi and Al-Mansour (1980) from the study of volcanic and plutonic rocks found that the grain size is a significant geological factor controlling the abrasion resistance. Finegrained rocks when compared with coarse-grained rocks having the same porosity were found to be more resistance to wear. Erichsen et al. (2011) studied the type and degree of degradation of aggregate in LAAV test by analyzing the particle size distribution of material after testing and concluded that the LAAV test for the standard fraction 10–14 mm can be assumed to represent a fragmentation test and for coarse material 31.5–50 mm, the aggregate is mostly affected by wearing. There are many studies in the literature that indicate good correlations between LAAV and some rock properties especially the strength of the aggregates. Kazi and Al-Mansour (1980) obtained a strong correlation between uniaxial compressive strength (UCS) determined by the Schmidt hammer and LAAV.Ballivy andDayre (1984) found a relation between UCS andLAAV for limestones, the degree of correlation being different for different types of limestone. Cargill and Shakoor (1990) found that the LAAV is related to the compressive strength. Al-Harthi (2001) indicated high degree of correlation between LAAV with both UCS and point load index. Kahraman and Fener (2007) found a good correlation between UCS & Massoud Palassi mpalas@ut.ac.ir