Mixing Performance of 2 n Mixing Theory for Lean Mortar
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RESEARCH PAPER
Mixing Performance of 2n Mixing Theory for Lean Mortar Tek Raj Gyawali1 Received: 2 December 2018 / Accepted: 9 November 2020 © Shiraz University 2020
Abstract Roller-compacted concrete (RCC) is very lean with its lower content of cementitious materials and water to control the heat of hydration. The quality of such concrete mainly depends on the performance of the coating condition of aggregates with cement paste/mortar, which itself is in very lean and serves as the binder. The prototype mixer, BR-100, was developed to verify the 2 n mixing theory based on the kneading and lapping mechanism. Very lean mortar, to be used in RCC, was mixed in the BR-100 mixer to compare its compressive strength and flexural strength. Twenty-eight-day compressive strength of lean mortar mixed with a combination of conventional and the new mixing method was 28.6 MPa, which was increased by more than 36% than that of mixed in the only conventional method. Similarly, the flexural strength of lean concrete mixed with the first method was 6.3 MPa, greater by more than 31% than that of conventional methods (4.8 MPa). It was concluded from the investigative research work that the 2n mixing theory enhances both compressive strengths and flexural strengths of lean mortar with the nice coating of paste around the surface of aggregates with the significant effect of kneading and lapping mechanism. Keywords RCC · Lean mortar · 2n mixing theory · Kneading and lapping mechanism · Compressive strength · Flexural strength
1 Introduction Mass concrete is referred to as the large volume of concrete to be used in the internal main body of the dam where thermal stress due to heat generated by the hydration of cement is problematic (JSCE 2007a). Dam concrete is defined as the conventional mass concrete, the slump of which ranges from about 2 to 5 cm, depending on the maximum aggregate size and the parts of a dam where the concrete is used. JSCE has defined roller-compacted dam (RCD) concrete as “stiff consistency concrete used as internal concrete of the dam body constructed by the RCD method”. “Because of the differences in mixture design methods, construction methods, quality control methods, etc., RCD concrete is defined separately from conventional dam concrete” (JSCE 2007b). Nowadays, this type of concrete is popular as roller-compacted concrete (RCC) in the world. ACI has defined it as “roller-compacted concrete (RCC) is a concrete of no-slump * Tek Raj Gyawali [email protected] 1
School of Engineering, Faculty of Science and Technology, Pokhara University, Pokhara, Nepal
consistency in its unhardened state that is transported, placed, and compacted using earth and rockfill construction equipment” (ACI 2011). It is also called as “rollcrete” (Choi and Hansen 2005). The effectiveness of activated pozzolan with Ca (Oh)2 and nano-SiO2 was investigated on microstructure and hydration of high-volume natural pozzolan paste. Its result can be applied to produce the lean mortar required for the RCC (Shakiba et. al 2018). Sakai ha
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