TB-0704 — Calculating Concrete Mix Proportions for FORCE® 10,000D Concrete Technical Bulletin

/ concrete / mix design

Introduction

This technical bulletin describes the steps required to adjust concrete mix proportions to accommodate the addition of FORCE 10,000D® dry-densified silica fume.

Specifications

The mix design process begins with a specification which may appear in several forms:

  • Prescription Specification–The specifier prescribes that a certain percentage of silica fume be used in the mix; e.g., 7.0% ± 0.5% silica fume by weight of cement. In this specification process, the amount of silica fume required is easy to determine since it is based on a percentage of the amount of cement in the mix design. FORCE 10,000 D®–The calculation is direct, i.e., 7% of 445 kg/m3 (750 lbs/yd3) of cement is 31.2 kg/m3 (52.5 lbs/yd3) of FORCE 10,000 D®.
  • Performance Specification–The specifier requires the concrete to have certain properties at a given age; e.g., “the concrete shall pass 1,000 coulombs or less at 90 days by ASTM C1202-94 (AASHTO  T277),” or “the concrete shall have a minimum compressive strength of 70 MPa (10,000 psi) at 90 days.” In a performance specification, test mixes must be run to determine the silica fume dosage necessary to meet the coulomb or strength requirements.
  • All mix designs must be tested before project start-up to ensure that the FORCE 10,000® concrete meets all of the performance requirements for the project. Job site conditions, such as weather, placement procedures and logistics should be anticipated and planned when the mix design is being evaluated prior to project start-up. Please Note: ASTM C1202 (AASHTO T277) should be used as an indicator only. It has a high degree of error and the 90 day testing requirement may create problems. This test method should not be used as a standard for payment penalties.
  • Combination Specification–The third type of specification combines both prescription and performance requirements. The specifier requires a certain performance level and a minimum silica fume content; e.g., “the concrete shall have a maximum coulomb reading of 1,000 coulombs at 90 days, and the concrete shall have a minimum silica fume content of 7.5% by weight of cement.” Maximum water/cement ratios, other admixtures and minimum cement factors may also be specified.

Part 1: FORCE 10,000 D® — Dry-densified Silica Fume

A concrete producer wants to use FORCE 10,000 D® to meet a specific requirement of 1,000 coulombs at 28 days. The specification also calls for a maximum water/cement ratio of 0.40. The producer plans to use 7.5% silica fume by weight of cement to meet this coulomb requirement. Concrete workability must also be taken into consideration.

Part 2: Concrete Mix Adjustments

Testing the concrete mix prior to the job start-up provides a performance history for the mix and allows adjustments that may be necessary to meet project requirements. These adjustments may include the following:

  • Increasing the Silica Fume Dosage—Silica fume dosage rates have to be adjusted upward to meet the performance requirements for a particular project.
  • Increasing the Superplasticizer Dosage—The addition of silica fume to concrete increases the cohesiveness of the mix and additional superplasticizer is normally required to provide the required workability.
  • Increasing the Air-Entraining Agent Dosage—The addition of silica fume to concrete may decrease the efficiency of the air-entraining agent. If this occurs, adjust the air-entraining agent dosage rates upward.

Step 1:

Start with a mix that meets the water/cement ratio requirement.

Materials SSD Mass, kg/m3 SSD Weight, lbs/yd3
Cement 386 650
Water 154 260
W/C 0.40 0.40
Fine aggregate (SG-2.65) 712 1200
Coarse aggregate 1068 1800
ADVA® 261 mL/100kg 4 oz/100 lbs
Air content 6.5% 6.5%

Step 2:

Convert 7.5% silica fume to kg (lbs) based on the cement factor.

Silicia Fume (SG=2.20): 386 kg X 7.5%=29 KG 650 lbs X 7.5%-49 lbs

Step 3:

Adjust the yield of the mix to account for the addition of the silica fume.

SI formula US formula
SF in kg X (SG of fine agg/SG of MS) = kg of sand to be removed from mix SF in lbs X (SG of fine agg/SG of MS) = lbs of sand to be removed from mix
SI calculation US calculation
29 kg X (2.65/2.20) =35 kg sand to be removed from mix 49 lbs X (2.65/2.20) = 59 lbs sand to be removed from mix

Step 4:

Adjust the amount of superplasticizer to maintain the same workability as the original mix. The amount of superplasticizer needed varies from job to job depending upon the materials used in the mix and the placement conditions.

Unit of Measurement SI US
Original ADVA® dosage 261 mL/100 kg cement 4.0 oz/100 lbs cement
Added ADVA® dosage to compensate for addition of FORCE 10,000® 261 mL/100 kg cement 4.0 oz/100 lbs cement
Total ADVA® dosage 552 mL/100 kg cement 8.0 oz/100 lbs cement

Step 5:

Recalculate the mix design for the addition of FORCE® 10,000 D®, dry-densified silica fume with the addition of ADVA®.

Materials SSD Mass, kg/m3 SSD Weight, lbs/yd3
Cement 386 650
Water 154 260
W/C 0.40 0.40
Fine aggregate  712-35=677 1200-59=1141
Coarse aggregate 1068 1800
ADVA® 552 mL/100kg 8 oz/100 lbs
Air content 6.5% 6.5%
FORCE® 10,000 D 29 49

Step 6:

Run a test on the mix to assure that it meets all project requirements prior to start of the job.

 

gcpat.com | North America Customer Service: 1 877-4AD-MIX1 (1 877-423-6491)

We hope the information here will be helpful. It is based on data and knowledge considered to be true and accurate and is offered for consideration, investigation and verification by the user, but we do not warrant the results to be obtained. Please read all statements, recommendations and suggestions in conjunction with our conditions of sale, which apply to all goods supplied by us. No statement, recommendation, or suggestion is intended for any use that would infringe any patent, copyright, or other third party right.

FORCE 10,000 is a trademark, which may be registered in the United States and/or other countries, of GCP Applied Technologies Inc. This trademark list has been compiled using available published information as of the publication date and may not accurately reflect current trademark ownership or status.

© Copyright 2018 GCP Applied Technologies Inc. All rights reserved.

GCP Applied Technologies Inc., 62 Whittemore Avenue, Cambridge, MA 02140 USA.

In Canada, 294 Clements Road, West, Ajax, Ontario, Canada L1S 3C6.

This document is only current as of the last updated date stated below and is valid only for use in the United States. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on www.gcpat.com. Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.

Last Updated: 2020-03-09

https://gcpat.com/en/solutions/products/tb-0704-calculating-concrete-mix-proportions-force-10000d-concrete-technical