DURABILITY OF INTERNALLY CURED CONCRETE WITH RECLAIMED SANDS

ABSTRACT

 A significant portion of municipal solid waste has traditionally been addressed through recycling; however, the recycling market has become unreliable due to the stringent contamination regulations imposed by China’s new recycling policy. Solid waste can be addressed through incineration which reduces the volume of the waste. Waste-toEnergy facilities provide an efficient means to carry out the incineration process by generating electricity through steam generation. Although it is not completely waste free, this process leaves a by-product known as municipal solid waste incinerator ash that can be further refined into a lightweight sand material known as reclaimed sands. This work investigates the use of reclaimed sands from the York County Solid Waste Authority in York, PA as a partial replacement for fine aggregates to make internally cured concrete. In internally cured concrete, interior particles release water during the cement hydration process and effectively help the mix cure from the inside out. This leads to a less permeable concrete that increases the freeze-thaw resistance, reduces chloride permeability, and improves the shrinkage resistance of the material. Reclaimed sands are effective internal curing aggregates, since they have a high absorption capacity and the ability to desorb water at a high relative humidity. The testing performed in this work explores the durability of internally cured concrete manufactured with reclaimed sands by assessing the freeze thaw resistance, rapid chloride permeability, and compressive strength of the concrete. As is discussed in later chapters of this work, it was found that reclaimed sands are a suitable replacement for lightweight aggregate in internal curing concrete applications.

 

TABLE OF CONTENTS

LIST OF FIGURES ………………………………………………………………………………………………….. v

LIST OF TABLES ……………………………………………………………………………………………………. vii

ACKNOWLEDGEMENTS ……………………………………………………………………………………….. ix

Chapter 1  Introduction ……………………………………………………………………………………………… 1

1.1 – Background and Motivation ……………………………………………………………………….. 1 1.2 – Project Statement ………………………………………………………………………………………. 3

1.3 – Thesis Outline …………………………………………………………………………………………… 3

Chapter 2  Background ……………………………………………………………………………………………… 5

2.1 – Municipal Solid Waste in the United States ………………………………………………….. 8

2.2 – Lightweight Aggregates and Construction Materials in the United States …………. 10

2.3 – Internally Cured Concrete …………………………………………………………………………… 12

Chapter 3  Materials and Test Methods ……………………………………………………………………….. 19

3.1 Reclaimed Sand Production …………………………………………………………………………… 19 3.2 Physical Properties ……………………………………………………………………………………….. 23

3.3 – Chemical Properties……………………………………………………………………………………. 27 3.4 Mix Designs ………………………………………………………………………………………………… 28 3.5 Test Procedures ……………………………………………………………………………………………. 31

3.5.1 Non-Destructive Testing …………………………………………………………………………….. 31 3.5.2 Rapid Freeze Thaw Testing ………………………………………………………………………… 35

3.5.3 Rapid Chloride Permeability Testing …………………………………………………………… 40 3.5.4 Concrete Cylinder Compression Testing ………………………………………………………. 44

3.5.5 Concrete Cylinder Split Tensile Testing ……………………………………………………….. 45 Chapter 4  Results and Discussion ……………………………………………………………………………… 46

4.1 Ultrasonic Pulse Velocity Testing Results……………………………………………………….. 46

4.2 Rapid Freeze Thaw Testing …………………………………………………………………………… 49

4.3 Rapid Chloride Permeability Testing Results …………………………………………………… 68

4.4 Concrete Cylinders Compression Strength Test Results ……………………………………. 70

4.5 Concrete Cylinders Split Tensile Strength Test Results …………………………………….. 72

Chapter 5  Conclusions ……………………………………………………………………………………………… 73

References……………………………………………………………………………………………………………….. 77

Chapter 1

 

Introduction

1.1 – Background and Motivation

The amount of solid waste produced in the United States is continuing to increase with growth in the population. This is creating a need for methods to dispose of and/or repurpose solid waste, as the current recycling market is influx due to an overdependence on importing recyclables to China. Recently, China placed limits on the amount of materials allowed to be imported into their country. These limits are due to more stringent contamination regulations. In addition, coal fired power plants are beginning to be decommissioned throughout the United States due to the resurgence of natural gas, which is posed to leave a gap in ash-based materials in the construction industry (i.e. fly ash). Alternatively, Waste-to-Energy (WTE) incinerator plants are attempting to bridge the gap between sustainable recycling of municipal solid waste (MSW) and power generation. These plants function by converting steam energy generated from the incineration of MSW to electricity to be used by surrounding municipalities. As a result of this process, there is a by-product known as incinerator ash that is produced. Upon refinement, this by-product can be converted into a usable construction material known as reclaimed sands (RS) that can potentially be used as a replacement for fine aggregate in cementitious materials. Penn

State Harrisburg has been working alongside the York County Solid Waste Authority

(YCSWA) WTE plant to utilize the incinerator ash in concrete and other cementitious materials. Previously, Penn State Harrisburg has worked closely with YCSWA exploring other alternatives for their recycled material such as traditional concrete and concrete masonry units (CMU). The testing began with studying the effects RS had as a lightweight aggregate in traditional concrete. When used as a replacement as fine aggregate in traditional concrete mixes, a hydrogen gas expansion occurred which led to concrete specimens that were of inadequate compressive strength. Several preparation methods of the RS were experimented with including an acid wash of the material, as well as rinsing with tap water. Although these preparation methods provided inconclusive results, further testing was necessary to draw conclusions about the material. In addition to traditional concrete, the material was tested as a replacement for fine aggregate in CMU. The CMU blocks were manufactured at Standard Concrete in York, PA and then transported back to Penn State Harrisburg where the compression strength and physical property testing took place. The compression testing of the CMU block provided an enhanced look at how the RS behaved when exposed to a cementitious curing environment. Through compression testing, one batch of CMU blocks passed the applicable standards, however, more testing was necessary to provide conclusive results. Although positive result came from testing the CMU block, further physical property testing was needed to achieve a better understanding of the RS material itself. The RS material was tested in greater detail for absorption capacity, desorption, and specific gravity in order to find a better application for the material.

 

 

1.2 – Project Statement

The work in this thesis focuses on the durability of internally cured concrete with RS replacement. Through the aforementioned physical property testing, it was found that the RS exhibit a high absorption capacity and the ability to desorb water at high relative humidity, both of which are crucial traits of aggregates used in internally cured cementitious applications. It has previously been found by other researchers that the durability of internally cured concrete improves with the introduction of lightweight aggregates.  For this study, multiple tests were carried out to assess the validity of utilizing reclaimed sands in internal curing applications. The tests described in this work include non-destructive test methods such as ultrasonic pulse velocity and rapid freeze thaw testing, as well as rapid chloride permeability testing. These tests were carried out for a number of different mix designs at the Penn State Harrisburg laboratory. The discussion of these results can be found throughout this work.

1.3 – Thesis Outline

• Chapter 2 of this work describes the background and use of municipal solid waste and its byproducts. Additionally, studies on lightweight recycled aggregates by other research professionals are outlined. These studies involve utilizing construction materials as a recycled aggregate in internally cured concrete applications. Chapter 2 also prefaces the motivation for this research to study the application of the reclaimed sand material within internally cured (IC) concrete.

The chapter provides an extensive look at how internally cured concrete works, factors that effect a materials success as a lightweight internally cured aggregate, and the improvements lightweight aggregates have on the durability of concrete manufactured with internally cured methodology.

 

• Chapter 3 of this work outlines material properties and test methods utilized to perform a complete evaluation of internally cured RS concrete. The test methods discussed include Non-Destructive Testing (i.e. Ultrasonic Pulse Velocity and Rapid Freeze Thaw), Rapid Chloride Permeability Testing, and Compression Strength testing of cylindrical specimens.

 

• Chapter 4 of this work discusses testing results for internally cured RS concrete.

 

• Chapter 5 describes the conclusions that can be drawn from the test results as well as directions for future work.

DURABILITY OF INTERNALLY CURED CONCRETE WITH RECLAIMED SANDS

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