by Mallory A. Westbrook and David W. Harris, PhD, PE, F.ASCE, F.SEI

Courtesy Getty Images 2018

We’re sitting in the laboratory and we can smell smoke. Wildfires are raging in Colorado and although we are south of Denver and the fires are, 45 to 60 miles away, we still see and smell the smoke. I drove through the Black Forest about a week ago and there are still hundreds of charred acres with ash, a few black tree trunks, and serious concerns of flooding and toxic runoff. …


by Jon S. Belkowitz, PhD and Mallory A. Westbrook

What is soft water attack?

Soft water attack concrete is considered to occur in areas where the water immediately adjacent to a concrete structure or concrete infrastructure (flowing or standing) is characterized by a low dissolved ion content. When Portland cement-based concrete is in contact with soft water, the calcium hydroxide (portlandite, Ca(OH)2) in the hardened cement matrix is leached out as the water tries to establish an ion balance. …


Mallory A. Westbrook and Jon S. Belkowitz, PhD

Introduction

Concrete is one of the oldest and most reliable construction materials in the world. Concrete is at the foundation of our civilizations providing everything from the sidewalks in urban, suburban, and rural areas; to the enormous concrete dams, like the Hoover Dam, spillways, and locks that hold back awesome rivers, like the Colorado River.

The purpose of this article is to identify the factors (historical and present day) that explain the title’s question and short and long-term influence on concrete structures.

Renewable energy movement and the loss of durable concrete

In the last few decades, the renewable energy movement has started gaining traction. The ultimate objective of the renewable…


Phase Rules [1, 4]

C-S-H

When a diffusing CSH species collides with either solid C3S or C2S or previously deposited CSH, it is converted into solid CSH with a probability of 1.

CH

For each diffusion step, a random number is generated to determine if nucleation of a new CH crystal is probable; if so, the diffusing CH is converted into solid CH at its present location. In addition, if a diffusing CH collides with solid CH, it is converted into solid CH with a probability of 1.

FH3

For each diffusion step, a random number is generated to determine if nucleation of a new FH3 crystal…


[1] Bentz, D. P. Influence of water-to-cement ratio on hydration kinetics: simple models based on spatial considerations. Cement and Concrete Research. 36. 238–244. 2006.

[2] Mindess, S. Concrete. Wiley and Sons, Inc. 2nd Edition. 2003.

[3] Neville, A.M. Properties of Concrete. 2nd Edition. 2000.

[4] J. Thomas, Biernacki, J., Bullard, J., Bshnoki, S., Dolado, J., Schere, G., Luttge, A. Modeling and Simulation of Cement Hydration Kinetics and Microstructure Development. Cement and Concrete Research. 2011.

[5] D.P. Bentz, National Institute of Standards and Technology Interagency Report, Technology Administration. U.S. Department of Commerce. NISTIR 7232. June. 2005.

[6] Sun, Z., Garboczi, E…


by Whitney B. Belkowitz and Jon S. Belkowitz, PhD

Testing materails in the laboratory.

In the present work three water to cementitious ratios were introduced to the concrete composites for the determination of benefits ascertained in compressive strength, heat signatures, and hydrated products. The use of modeling and simulation was proposed as a viable option in when analyzing concrete mix design. Several conclusions can be drawn on the comparison and use of laboratory testing and VCCTL software for concrete mixture design and analysis:

  • The similar trends in strength development over time between the experiments and model suggest that the model is a conservative tool for strength design and analysis.
  • The accuracy of the saturated…


by Whitney B. Belkowitz and Jon S. Belkowitz, PhD

Simulated hydrated microstructure in VCCTL.

Results and Discussion

Young’s Modulus — Both the experiments and simulation exhibit a growth in strength of the composite. The Young’s Moduli of the tested samples were derived off of the maximum compressive strength using ACI 318 [14]. The Young’s moduli from the tested sample are greater than the simulated values for all three water to cementitious ratio, in Figure 2. While the discrepancies between the two values stay relatively minor, the trend displays that the discrepancies increase as the samples are left to cure longer. The increase of the Young’s Modulus found in the experimental mixes at later dates could be attributed…


by Whitney B. Belkowitz and Jon S. Belkowitz, PhD

Setting up samples to run concurrently with VCCTL mixes.

Materials

A Type I/II Portland Cement (PC) with a Blaine fineness of 3790 cm2/g was used as the primary cementitious material. The composition of the OPC used in the experiments and VCCTL software is listed in Table 1. For the compression and calorimetry experiments the PC was mixed with potable tap water and a washed alluvial aggregate. The alluvial aggregate contained a grain size distribution of 8.2 mm to 11.2 mm. The absorption of the rounded rock was 1.1% and had a specific gravity of 2.64. Three water-to-cement (w-c) ratios were used throughout the experimentation. …


by Whitney B. Belkowitz and Jon S. Belkowitz, PhD

Figire 1 — An example of the simulated cementitious microstructure from VCCTL.

Microstructure Development

In creating the final concrete composite and its hydrated properties, it is first necessary to develop a picture of the unhydrated concrete composition. VCCTL randomly places cement particles in a digital box in-order to develop anhydrous microstructure, Figure 1, which can be used to initiate the dissolution and chemical reaction of the cementitious components to develop the hydrated microstructure [12]. This anhydrous microstructure will have characteristics based off of the 2D image and user input a lot of factors such as distribution, surface area, phase volume.

A three-dimensional (3D) image is developed based on user defined concrete constituents and algorithms…


by Whitney B. Belkowitz and Jon S. Belkowitz, PhD

An example of the simulated cementitious microstructure from VCCTL.

Concrete is one of the most popular construction materials used throughout the construction industry. Concrete formulation and experiments are needed to determine fresh and hardened properties need to place the material as well as ensure its engineering properties are adequate to support structural loads. Concrete experiments in the laboratory and field require excessive amounts of: time, money, labor, and materials. New means and methods for understand specific mix design is needed.

Purpose

The purpose of this research was to illustrate a new approach in concrete design and analysis, modeling and simulation, which can establish an approximate understanding of materials and how…

Intelligent Concrete

Specializing in Concrete Research, Development & Education. At Intelligent Concrete, we make concrete do the impossible!

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