Concrete by Preplaced Aggregate Method Using Silica Fume and Polypropylene Fibres.

Muhammad Faisal Javed,Muhammad Ishtiaq,Kashif Nazir,Farooq Azam Khanzada,Muhammad Ali Musarat,Fahid Aslam,Kseniia Iurevna Usanova,Sardar Kashif-Ur-Rehman

doi:10.3390/ma15061997

Abstract

Preplaced aggregate concrete (PAC) is prepared in two steps, with the coarse aggregate being initially laid down in the formwork, after which a specialised grout is injected into it. To enhance the properties of concrete and to reduce the emission of CO2 produced during the production of cement, supplementary cementitious materials (SCMs) are used to partially substitute ordinary Portland cement (OPC). In this study, 100 mm × 200 mm (diameter x height) PAC cylinders were cast with 10 per cent of cement being substituted with silica fume; along with that, 1.5% dosage of Macro polypropylene fibres were also introduced into the coarse aggregate matrix. Compressive strength test, splitting tensile strength test, mass loss at 250 °C, and compressive strength at 250 °C were performed on the samples. PAC samples with 10% of cement replaced with Silica Fume (SPAC) were used as control samples. The primary objective of this study was to observe the effect of the addition of Polypropylene fibres to PAC having Silica fume as SCM (FRPAC). The aforementioned tests showed that FRPAC had a lower compressive strength than that of the control mix (SPAC). FRPAC had greater tensile strength than that of NPAC and SPAC. Mass loss at 250 °C was greater in SPAC compared to FRPAC. The compressive strength loss at 250 °C was significantly greater in FRPAC compared to SPAC. FRPAC exhibited a greater strain for the applied stress, and their stress-strain curve showed that FRPAC was more ductile than SPAC.

Highlights

First introduced in the 1930s, preplaced aggregate concrete (PAC), otherwise called two-stage concrete [1,2], as the name suggests, is prepared in two steps
The cement was obtained from a local supplier at College Road, Abbottabad, Pakistan
Silica fume was procured from Imporient Chemicals (PVT) limited, Islamabad, Pakistan

Summary

Introduction

First introduced in the 1930s, preplaced aggregate concrete (PAC), otherwise called two-stage concrete [1,2], as the name suggests, is prepared in two steps. Clean, gap-graded coarse aggregate is packed within the formwork a specialised grout of sufficient flowability is used to fill the openings and voids in the coarse aggregate matrix. Conventional concrete is prepared by mixing all the components and placing that mix in the formwork. PAC has greater coarse aggregate content, accounting for 60% to 70% of the total volume. The coarse aggregate content takes up only 40% to 50% of the total volume [5,6]. The shrinkage in PAC is far less than that of conventional concrete [7]. PAC has a more dense matrix having greater strength as a result of higher pressure and point-to-point contact of the coarse aggregate particles [8]. PAC’s production cost is 25% to 40% less than that of conventional concrete [3]

Objectives

Methods

Findings

Conclusion