The Effects of Air-Entraining Agent on Fresh and Hardened Properties of 3D Concrete

Abstract

Three-dimensional concrete printing (3DCP) is becoming more common in the construction industry nowadays; however, the aspect of durability of printed concrete is not well-studied yet. Frost resistance is a very important factor for durability of concrete structures located in northern regions. Since air-entraining agents (AEAs) are widely used in conventional concrete, this paper focuses on exploring the potential of using AEAs in 3D concrete as well—the main objective is to determine how it affects fresh and hardened properties, including frost resistance of 3D concrete. Three different mixes were printed and cast—the dry mix consisted of ordinary Portland cement (OPC), limestone filler (LF), sand, as well as viscosity modifying agent (VMA) and superplasticizer (SP). Two mixes contained different amounts of AEA, the third one was used as reference. First, fresh state properties were tested—air content, density, and mini cone flow test. Second, 28-day compressive and flexural strength tests were carried out; bulk and particle densities were also determined. Next, both cast and printed concrete samples were subject to freeze–thaw cycles according to provisions of CEN/TS 12390-9, mass loss due to surface scaling was determined for each sample. As a result, printed concrete samples containing AEA in the amount of 0.06% of binder mass showed the highest frost resistance—addition of AEA decreased both flexural and compressive strength of this printed concrete mix by 30–40%. To conclude, the obtained results give an insight of how addition of AEA to printed concrete mix affects its properties both in long and short term. Further research of certain aspects, for instance, the air void system and pore distribution is needed to gain a deeper understanding on how to increase durability of 3D concrete.

Influence of Variatropy on the Evaluation of Strength Properties and Structure Formation of Concrete under Freeze-Thaw Cycles

“…From a methodological point of view, these factors can be divided into technological (the method of selecting the composition of concrete, the technology for manufacturing concrete and reinforced concrete products, etc.) and prescription (chemical [23] and mineral additives, such as fly ash [24,25] and slag [26], ilmenite mud waste [27], various types of fiber, water-cement ratio, a fineness of grinding of Portland cement clinker, use of recycled aggregate concrete [28][29][30] and etc.). A rational combination of technological and prescription factors directly affects the structure of the concrete composite at all its levels.…”

Additive Manufacturing of Lightweight Gypsum and Expanded Polystyrene Granulate Composite

“…The printer frame allows for print region dimensions of 1500 × 1000 × 1000 mm. For more information on the used printer see [21], while video of the printing can be seen in Video S1.…”

Influence of Carbonated Bottom Slag Granules in 3D Concrete Printing

“…The printer head nozzle has a diameter of 20 mm, a layer width ranging from 35 to 45 mm, and a layer height of 10 mm. The printer construction is shown in Figure 8[43].…”