Grain size distribution of aggregates of crushed concrete

Abstract

The results of studies of recycling aggregates obtained by crushing concrete scrap are presented. The heterogeneity of the material received as a result of crushing concrete scrap, complicates the task of selecting the fractional composition of aggregates. The presence of the mortar component in recycled aggregates significantly increases their water demand. This indicates the expediency of their use in a mixture with natural ones. This work aimed at optimizing the granulometry of recycling rubble and sand. Concrete scrap was used for the research. It was represented by destroyed samples of heavy concrete cubes. Standard methods for determining the grain composition and properties of aggregates of concrete, manufacturing and testing mortar mixes were used. It has been shown that recycling rubble of the 5-20 mm fraction has a minimum voidness when it contains 35% of the 5-10 mm grains and 65% of the 10-20 mm grains, which is close to the ratio of these fractions in the initial crushing product. Therefore, it is advisable to use recycling rubble fractions of 5-20 mm without separation into fractions. The rather high content in the recycling sand of grains with a particle size of more than 0.63 mm indicates the feasibility of using it in a mixture with natural fine and very fine sand. A grain-optimized mixture of natural very fine sand (46% of the total mass of mixed sand) and coarse fractions (0.63–5 mm) of recycled sand (54%) is proposed. Should be considered that recycled sand has increased water demand.

Geotechnical Properties of Anthropogenic Soils in Road Engineering

“…The C U value is equal to 30.0, and C C is equal to 0.53. The soil was, therefore, classified as well-graded, according to Eurocode 7 [55][56][57]. The fractions composition of the tested gradation curve has led to recognizing the soil as gravelly sand (grSa), according to [56,57], and as well-graded sand or gravelly sand (SW), according to Unified Soil Classification System (USCS) [58].…”

“…The soil was, therefore, classified as well-graded, according to Eurocode 7 [55][56][57]. The fractions composition of the tested gradation curve has led to recognizing the soil as gravelly sand (grSa), according to [56,57], and as well-graded sand or gravelly sand (SW), according to Unified Soil Classification System (USCS) [58]. In this test, compacted soil specimens were loaded axially in constant stress steps until the primary consolidation ceased.…”

“…The soil was, therefore, classified as well-graded, according to Eurocode 7 [55][56][57]. The fractions composition of the tested gradation curve has led to recognizing the soil as gravelly sand (grSa), according to [56,57], and as well-graded sand or gravelly sand (SW), according to Unified Soil Classification System (USCS) [58]. Soil gradation curve for Natural Aggregate (NA) and Anthropogenic Soils (AS) tested in this study (solid green line, the tested soil material was first sieved into fractions, and then the universal soil grain composition was created for each kind of soil), the red dashed line-British standards requirement, blue dashed line-American standards requirement, black sashed line Polish standards requirement.…”