Effects of Adhered Mortar Content on Quality of Recycled Coarse Aggregate of Concrete

Abstract

Although the adhered mortar content affects the properties of recycled aggregate concrete, there are few papers describing those effects. This paper presents the results of a series of experimental study on the effects of adhered mortar content on the quality of recycled coarse aggregate of concrete. 5 kinds recycled coarse aggregates made with heating and rubbing method, mechanical crashing method and separating lightweight particle with water stream method were tested for specific gravity, absorption and adhered mortar content. Specific gravity in oven-dried condition ranged from 2.35g/cm3 to 2.59 g/cm3, absorption ranged from 1.58% to 5.83% and adhered mortar content ranged from 8.0% to 68.4%, depending on manufacturing method of recycled aggregate. Absorption decreased linearly with the increase of specific gravity. Specific gravity decreased and absorption increased with the increase of adhered mortar content. Recycled aggregate made by heating and rubbing method showed lower adhered mortar content corresponding to lower absorption and higher specific gravity, while those made by mechanical crushing method showed higher adhered mortar content corresponding to higher absorption and lower specific gravity. In conclusion, the upper limit of adhered mortar content of recycled coarse aggregate is considered to be 15%, in order to keep up the quality of coarse aggregate and properties equal to natural coarse aggregate.

Experimental Study on the Effects of Recycled Concrete Powder on Properties of Self-Compacting Concrete

“…RFP-R, the recycled fine powder used, was obtained as by-products in the recycling of a concrete made of Portland fly ash cement, river gravel and sand, and the age of recycling was 6 month. Specific gravity was 2.42 g/cm 3 and specific surface area was 395 m 2 /kg, as shown in Tables 1 and 2. The ground blast furnace slag used had specific gravity of 2.89 g/cm 3 and specific surface area of 412 m 2 /kg.…”

“…Specific gravity was 2.42 g/cm 3 and specific surface area was 395 m 2 /kg, as shown in Tables 1 and 2. The ground blast furnace slag used had specific gravity of 2.89 g/cm 3 and specific surface area of 412 m 2 /kg. The ground limestone used had a specific gravity of 2.70 g/cm 3 and specific surface area of 500 m 2 /kg.…”

“…Cement: Three brands of normal Portland cement in equal parts were used, and the average specific gravity was 3.16 g/cm 3 and specific surface area was 335 m 2 /kg. The characteristics of cement used are given in Table 3.…”

“…The ground blast furnace slag used had specific gravity of 2.89 g/cm 3 and specific surface area of 412 m 2 /kg. The ground limestone used had a specific gravity of 2.70 g/cm 3 and specific surface area of 500 m 2 /kg. In the series 2, three types of recycled powders, RFP-A, RFP-B and RFP-C, were used for self-compacting concrete.…”

“…Characteristics and chemical composition of the recycled powders are shown in Table 1 and Table 2. The recycled fine powder RFP-A, obtained from a concrete made of normal Portland cement, crushed stone and river sand at the age of 6 months, had a specific gravity of 2.37 g/cm 3 reducer used for self-compacting concrete was a water soluble methacrylic graft polymers, having carboxylic groups and sulfonic groups as anion groups as well as polyoxylene groups as side chains in their molecules.…”