Effects of aggregate packing optimization and cement paste volume on the properties of natural and recycled aggregate concrete

Abstract

This paper investigates the influence of aggregate packing optimization based on a particle packing method (PPM) and cement paste volume (CPV) on the workability and mechanical properties of both natural aggregate concrete (NAC) and recycled aggregate concrete (RAC). The slump, compressive strength, flexural strength and Young's modulus of concrete were first examined, followed with the characterization of macro-pore structure inside RAC by using X-ray computed tomography (CT). The results indicate that the PPM can help to densify the granular skeleton of aggregates in concrete by reducing the void around the aggregates and the cement paste film thickness, and subsequently enhances the mechanical properties of the concrete with a constant CPV. This enhancement is higher for RAC than NAC, particularly for the Young's modulus. The particle packing optimization can also decrease the number of macro pores in RAC, contributing to the enhancement in the mechanical properties of RAC. Moreover, increasing CPV in concrete with a maximum aggregate packing status considerably decreases the mechanical properties of concrete, whereas increases its workability. This is mainly caused by the increased number of macro pores in the cement paste and at the interfaces between RCAs and hardened cement paste.

Test Results of the Modulus of Elasticity of Concretes with Various Coarse Aggregates and Standard Recommendations

“…However, it is more glaring that there is a lack of information and recommendations for reducing the standard modulus values when using granite aggregate. It is clear from own research, as well as from the examples cited domestically [5,10,11,12] and abroad [7,8], that the deformability of concrete with granite aggregate is significant, and the values of modulus of elasticity given in the standard are greater than the actual ones, which was confirmed by the tests results. It seems that this should be taken into account in the form of a national annex to the standard, while it is advisable to conduct more extensive studies in advance on the most commonly exploited Polish granite deposits.…”

“…1. Eff ect of aggregate type on the elasticity modulus of concrete according to Alexander [7] basalt aggregate, lower value by about 10% was obtained with diabase, dolomite and limestone aggregate, and even lower (by about 20%) with granite and porphyry aggregate [5]. On the other hand, Deja [6], referring to the results of foreign studies of the ultimate deformability of concrete depending on the mineral composition of the aggregate (granite, porphyry, diabase, basalt, limestone, quartz, gravel) in 1972, reported that at the highest tensile strength of concrete with limestone aggregate has the lowest elongation.…”

“…Despite the correct common opinion about the very good quality of this rock in a wide range of properties, it should be noted that basalt deposits are also characterized by a rather high variability of parameters, sometimes even within a single deposit. The modulus of elasticity of Polish basalts are equal to 56-115 GPa, depending on the deposit [5,14]. In addition, some of the basalts and concretes made with them are characterized by deterioration of properties due to the sunburn and weathering [15,16,17].…”

Plastic settlement and hardened state assessments of manufactured sand made concrete for varying microfine levels

“…Especially, the angular and rough textured particles when they are bound with cement paste create a better interlocking behavior. This enhances a better bonding characteristic once cement is hydrated and enable a good resistance to compression 68 . These characteristics of concrete are reduced when it incorporates round shape and smooth textured particles due to the lower bonding characteristics.…”

“…This enhances a better bonding characteristic once cement is hydrated and enable a good resistance to compression. 68 These characteristics of concrete are reduced when it incorporates round shape and smooth textured particles due to the lower bonding characteristics.…”