# Presentation: 125589

## Slide 1

## PURPOSE

- To investigate the ability of internal curing including measured absorbent polymers and saturated light-weight aggregate to mitigate autogenous shrinkage and restrained shrinkage.
- To also examine the changes in properties of concrete and mortar such as permeability when water absorbent polymers, light-weight aggregate or shrinkage reducing admixture are introduced to the mixture.

## DEFINITIONS

- Drying Shrinkage
- “The reduction in concrete volume resulting from a loss of water from the concrete after hardening”
- 	[B. Mather, 1964]
- Autogenous Shrinkage
- “The macroscopic volume reduction of cementitious materials when cement hydrates after initial setting. It does not include volume change due to loss or ingress of substances, temperature variation, application of an external force and restraint.” [E. Tazawa, 1998]

## SCOPE OF WORK

**Mortar**

**Strength**

**Shrinkage**

**Physical Properties**

**Cubes**

**Autogenous Shrinkage**

**Drying Shrinkage**

**MIP**

**SEM**

**Dilatometer**

**Degree of Hydration**

## SCOPE OF WORK

**Concrete**

**Prism**

**Shrinkage**

**Drying Shrinkage**

**Restrained Shrinkage**

**Shrinkage Rings**

**Strength**

**Physical Properties**

**Permeability**

**RCPT**

**Density, Absorption, and Void**

**Compressive**

**Splitting Tensile**

**Static Modulus**

**Dynamic Modulus**

**Modulus of Elasticity**

## MATERIALS FOR INTERNAL CURING

**Lightweight Aggregate**
**LWS****  Sand: Absorption =17.0%**
**LWA****  19mm Coarse: Absorption = 19.8%**
**SAP**** Superabsorbent Polymers (60-300um size)**
**SRA**** Also included Shrinkage Reducing Admixture (propylene glycol type) for Comparison**

## LIGHTWEIGHT AGGREGATE(Expanded Shale - Northeast Solite)

## Aggregate Size Distributions

## SUPERABSORBENT POLYMERS

## Evaporation Tests on Raw Materials: 50% rh, 23C after starting  with equal volumes of water

- SAP and SRA Evaporated Like Water

## MATERIALS AND MIXES

**MATERIALS AND MIXES**

| Mix ID | Cement Type | w/cm | Internal Curing Material | Chemical Admixture | Percentage of Internal Curing Materials [%] |
| --- | --- | --- | --- | --- | --- |
| 35-LOW | Type 10 | 0.35 |   |   |   |
| 35SF-LOW | Type 10SF | 0.35 |   |   |   |
| 35 | Type 10 | 0.35 |   |   |   |
| 35-MC (4 Day) | Type 10 | 0.35 |   |   |   |
| 35SF | Type 10SF | 0.35 |   |   |   |
| 45 | Type 10 | 0.45 |   |   |   |
| 35IC50 | Type 10 | 0.35 | Lightweight Sand |   | 50 |
| 35IC50-25M | Type 10 | 0.35 | Lightweight Sand |   | 50 |
| 35IC50SF | Type 10SF | 0.35 | Lightweight Sand |   | 50 |
| 35IC75 | Type 10 | 0.35 | Lightweight Sand |   | 75 |
| 35LWS32 | Type 10 | 0.35 | Lightweight Stone |   | 32 |
| 35LWS32SF | Type 10SF | 0.35 | Lightweight Stone |   | 32 |
| 35LWS50 | Type 10 | 0.35 | Lightweight Stone |   | 50 |
| 45P30 | Type 10 | 0.45 | SAP |   | 0.3 |
| 45P60 | Type 10 | 0.45 | SAP |   | 0.6 |
| 45P60SF | Type 10SF | 0.45 | SAP |   | 0.6 |
| 42P30 | Type 10 | 0.42 | SAP |   | 0.3 |
| 35SRA | Type 10 | 0.35 |   | SRA |   |
| 35SRASF | Type 10SF | 0.35 |   | SRA |   |

## Concrete Mix Details

- Mixes designed to constant paste content: 32%
- 0.35 w/cm mixes had ~490 kg/m3 CM with water reducer and Superplasticizer
- 0.45 mixes had ~430 kg/m3 CM with water reducer
- 10mm limestone aggregate was used
- LWS and LWA (SSD) replaced part of normal aggregates.
- SAP Mixes at 0.45, but should be similar to 0.35 after water absorption of dry SAP
- Concretes were stored at 50%rh @ 23oC

## SHRINKAGE RINGS

- Dimensions:
- 3 inch (75mm)high
- 12 inch (300mm Internal Diameter)
- 15 inch (375mm Outer Steel Form)
- 1⁄2 inch (12.7mm) thick steel ring
- Environmental Conditions
- 230C/50% humidity
- Wax coating on top surface
- Outer circumference exposed
- Internal Temperature and Strain Monitoring

## strain and time to cracking for 2 restrained shrinkage rings (mix 35SF) 

## SHRINKAGE RINGSEffect of Silica Fume

**SHRINKAGE RINGS****Effect of Silica Fume**

| Mix ID | Net Time-to-Cracking [Days] | Steel Ring Strain @ Cracking          [μ-strain] | Stress rate @ cracking (S) [MPa/day] | Strain Rate Factor, α | Maximum Tensile Stress (σmax) [MPa] |
| --- | --- | --- | --- | --- | --- |
| 35IC50-Ring1 | 13.7 | -40.00 | 0.15 | -15.71 | 2.91 |
| 35IC50-Ring2 | 15.2 | -59.67 | 0.18 | -19.74 | 4.34 |
| 45-Ring1 | 11.7 | -56.43 | 0.20 | -19.15 | 4.10 |
| 45-Ring2 | 14.6 | -27.62 | 0.10 | -10.96 | 2.01 |
| 35SF-Ring1 | 3.3 | -37.68 | 0.98 | -48.56 | 2.74 |
| 35SF-Ring2 | 6.4 | -37.66 | 0.54 | -37.31 | 2.74 |
| 35SRA-Ring1 | 53.7 | -51.11 | 0.03 | -6.36 | 3.72 |
| 35SRA-Ring2 | 47.0 | -37.75 | 0.03 | -5.48 | 2.75 |
| 45P60-Ring1 | 24.0 | -66.60 | 0.11 | -14.62 | 4.84 |
| 45P60-Ring2 | 26.3 | -44.00 | 0.07 | -9.74 | 3.20 |
| 35-Ring1 | 4.8 | -35.56 | 0.56 | -33.55 | 2.59 |
| 35-Ring2 | 6.1 | -34.58 | 0.33 | -22.55 | 2.51 |
| 35MC-Ring1 | 14.9 | -47.75 | 0.21 | -22.60 | 3.47 |

## SHRINKAGE RINGSEffect of SAP

**SHRINKAGE RINGS****Effect of SAP**

| Mix ID | Net Time-to-Cracking [Days] | Steel Ring Strain @ Cracking          [μ-strain] | Stress rate @ cracking (S) [MPa/day] | Strain Rate Factor, α | Maximum Tensile Stress (σmax) [MPa] |
| --- | --- | --- | --- | --- | --- |
| 35IC50-Ring1 | 13.7 | -40.00 | 0.15 | -15.71 | 2.91 |
| 35IC50-Ring2 | 15.2 | -59.67 | 0.18 | -19.74 | 4.34 |
| 45-Ring1 | 11.7 | -56.43 | 0.20 | -19.15 | 4.10 |
| 45-Ring2 | 14.6 | -27.62 | 0.10 | -10.96 | 2.01 |
| 35SF-Ring1 | 3.3 | -37.68 | 0.98 | -48.56 | 2.74 |
| 35SF-Ring2 | 6.4 | -37.66 | 0.54 | -37.31 | 2.74 |
| 35SRA-Ring1 | 53.7 | -51.11 | 0.03 | -6.36 | 3.72 |
| 35SRA-Ring2 | 47.0 | -37.75 | 0.03 | -5.48 | 2.75 |
| 45P60-Ring1 | 24.0 | -66.60 | 0.11 | -14.62 | 4.84 |
| 45P60-Ring2 | 26.3 | -44.00 | 0.07 | -9.74 | 3.20 |
| 35-Ring1 | 4.8 | -35.56 | 0.56 | -33.55 | 2.59 |
| 35-Ring2 | 6.1 | -34.58 | 0.33 | -22.55 | 2.51 |
| 35MC-Ring1 | 14.9 | -47.75 | 0.21 | -22.60 | 3.47 |

## SHRINKAGE RINGSEffect of SRA

**SHRINKAGE RINGS****Effect of SRA**

| Mix ID | Net Time-to-Cracking [Days] | Steel Ring Strain @ Cracking          [μ-strain] | Stress rate @ cracking (S) [MPa/day] | Strain Rate Factor, α | Maximum Tensile Stress (σmax) [MPa] |
| --- | --- | --- | --- | --- | --- |
| 35IC50-Ring1 | 13.7 | -40.00 | 0.15 | -15.71 | 2.91 |
| 35IC50-Ring2 | 15.2 | -59.67 | 0.18 | -19.74 | 4.34 |
| 45-Ring1 | 11.7 | -56.43 | 0.20 | -19.15 | 4.10 |
| 45-Ring2 | 14.6 | -27.62 | 0.10 | -10.96 | 2.01 |
| 35SF-Ring1 | 3.3 | -37.68 | 0.98 | -48.56 | 2.74 |
| 35SF-Ring2 | 6.4 | -37.66 | 0.54 | -37.31 | 2.74 |
| 35SRA-Ring1 | 53.7 | -51.11 | 0.03 | -6.36 | 3.72 |
| 35SRA-Ring2 | 47.0 | -37.75 | 0.03 | -5.48 | 2.75 |
| 45P60-Ring1 | 24.0 | -66.60 | 0.11 | -14.62 | 4.84 |
| 45P60-Ring2 | 26.3 | -44.00 | 0.07 | -9.74 | 3.20 |
| 35-Ring1 | 4.8 | -35.56 | 0.56 | -33.55 | 2.59 |
| 35-Ring2 | 6.1 | -34.58 | 0.33 | -22.55 | 2.51 |
| 35MC-Ring1 | 14.9 | -47.75 | 0.21 | -22.60 | 3.47 |

## SHRINKAGE RINGS50% LWS was similar to 4d moist cure

**SHRINKAGE RINGS****50% LWS was similar to 4d moist cure**

| Mix ID | Net Time-to-Cracking [Days] | Steel Ring Strain @ Cracking          [μ-strain] | Stress rate @ cracking (S) [MPa/day] | Strain Rate Factor, α | Maximum Tensile Stress (σmax) [MPa] |
| --- | --- | --- | --- | --- | --- |
| 35IC50-Ring1 | 13.7 | -40.00 | 0.15 | -15.71 | 2.91 |
| 35IC50-Ring2 | 15.2 | -59.67 | 0.18 | -19.74 | 4.34 |
| 45-Ring1 | 11.7 | -56.43 | 0.20 | -19.15 | 4.10 |
| 45-Ring2 | 14.6 | -27.62 | 0.10 | -10.96 | 2.01 |
| 35SF-Ring1 | 3.3 | -37.68 | 0.98 | -48.56 | 2.74 |
| 35SF-Ring2 | 6.4 | -37.66 | 0.54 | -37.31 | 2.74 |
| 35SRA-Ring1 | 53.7 | -51.11 | 0.03 | -6.36 | 3.72 |
| 35SRA-Ring2 | 47.0 | -37.75 | 0.03 | -5.48 | 2.75 |
| 45P60-Ring1 | 24.0 | -66.60 | 0.11 | -14.62 | 4.84 |
| 45P60-Ring2 | 26.3 | -44.00 | 0.07 | -9.74 | 3.20 |
| 35-Ring1 | 4.8 | -35.56 | 0.56 | -33.55 | 2.59 |
| 35-Ring2 | 6.1 | -34.58 | 0.33 | -22.55 | 2.51 |
| 35MC-Ring1 | 14.9 | -47.75 | 0.21 | -22.60 | 3.47 |

## RESTRAINED SHRINKAGE RINGS

- Concrete Tensile Stress at Cracking: 2.0-4.3 MPa

- Controls

## FREE SHRINKAGE - CONCRETE

**FREE SHRINKAGE - CONCRETE**

- SRA

- Control Moist Cured to 4 days

- LWS

## DRYING SHRINKAGE - MORTAR

**DRYING SHRINKAGE - MORTAR**

- SRA

- 40% LWS graded to C109 sand

## DTU Autogenous Shrinkage Test

- 22mm diam. x 305mm GL tubes
- Tests on mortars
- Were not able to measure shrinkage after setting

## COMPRESSIVE STRENGTHS0.45 SAP Mixes: Entrain Air

**COMPRESSIVE STRENGTHS****0.45 SAP Mixes: Entrain Air**

- Excess bleeding and foaming with 0.3% SAP—210mm slump

- Effect of 4% air due to SAP

## COMPRESSIVE STRENGTHS0.35 Mixes with LWS, LWA

**COMPRESSIVE STRENGTHS****0.35 Mixes with LWS, LWA**

- 50% LWS improved SF Mix

- 75% LWS improved PC Mix

- LW- C. Agg. Reduced fc

## TENSILE STRENGTH

**TENSILE STRENGTH**

- Control-50%rh

- Control 4d Moist

- SAP

- LWS

- SRA

## RCPT – 28 Days

**RCPT – 28 Days**

- Big Effect of Silica Fume and w/cm

## RCPT – 90 Days

**RCPT – 90 Days**

- SAP

## SEMControl Mixture: Unhydrated Cement and Porous ITZ

**SEM****Control Mixture: Unhydrated Cement and Porous ITZ**

## SEM Lightweight Sand [Expanded Shale]

- with 40% Lightweight Sand Replacement

**SEM ****Lightweight Sand [Expanded Shale]**

## Lightweight Sand [Expanded Shale]

- Mortar: 0.35 W/CM, Quartz Sand
- with 40% Lightweight Sand Replacement

## OPTICAL MICROSCOPY  IMAGE

- Concrete: 0.35 W/CM, Type 10 Cement
- 50% Lightweight Stone Replacement

## 0.45 Mortar with 0.6% SAP

- ASTM C 457 Air Void Analysis of the Same Concrete Mix:
- Air = 4.0%
- Spacing Factor
-           = 0.208mm

## SEM Superabsorbent Polymers

- 0.6% SAP by mass of cement

**SEM ****Superabsorbent Polymers**

- EDX of SAP Rim shows Ca, C with minor K and O

## SEM Superabsorbent Polymers

- 0.6% SAP by mass of cement

**SEM ****Superabsorbent Polymers**

- Agglomerates of SAP
- Not Optimum

## CONCLUSIONS/RECOMMENDATIONS

- SRA provided the most significant reduction in drying shrinkage and restrained ring cracking.
- Lightweight sand was more effective at internal curing than lightweight coarse aggregate.
- Concrete containing lightweight aggregate and SAP produced higher coulomb values using RCPT.
- The restrained shrinkage ring test was effective at determining the relative tensile and drying shrinkage properties of concrete.

## CONCLUSIONS/RECOMMENDATIONS

- SF blended cement, when applied in the same paste volume, did not show a significant increase in drying shrinkage compared with CSA Type 10 portland cement.
- BY SEM, the ITZ of lightweight aggregate concrete was superior to that of normal weight aggregate concrete due to the interlocking bond between paste and aggregate.
- For these mixtures, SRA may be most favorable for use in construction because of its ease of inclusion and dispersion in the concrete mixture. This may have been affected by use of a constant paste volume in the mixes.

## CONCLUSIONS/RECOMMENDATIONS

- Use of 0.6% SAP resulted in better improvements to the properties of concrete and mortar compared to 0.3% SAP.
- 0.6% SAP also provided adequate Air Voids for frost resistance.
- More research needed in the understanding of chemical and autogenous shrinkage as well as the benefits of internal curing.

## ACKNOWLEDGEMENTS

- Portland Cement Association for Funding
- Ole Mejhede Jensen for SAP
- John Roberts/NorthEast Solite for LWA
- Grace Construction Products for SRA
- Lafarge for Cements

## QUESTIONS

**QUESTIONS**