Concrete magnified, drying with magnifying glass.

Unseen Clay: How Drying Concrete Could Be Costing You Strength

Kai Mendoza in Science & Nature August 2025 • 4 min read.

"New research reveals that the way we prepare concrete samples for testing drastically underestimates the impact of superplasticizers, potentially weakening structures."

Concrete: it's everywhere. From towering skyscrapers to the foundations of our homes, this ubiquitous material shapes our world. But how well do we truly understand it? Recent findings are shaking up the established methods of concrete analysis, suggesting that a common lab practice—drying samples before testing—may be giving us a distorted view of its inner workings.

At the heart of this revelation lies the role of superplasticizers, those chemical additives that enhance concrete's workability and strength. For years, scientists have been studying how these additives interact with clay particles present in concrete, an interaction that can either boost or hinder performance. The standard approach involves drying concrete samples before examining them, but new research indicates this drying process could be throwing off our measurements.

This article dives deep into the groundbreaking study that's challenging conventional wisdom, exploring why drying concrete samples matters, what it means for the future of construction, and how we can ensure the concrete structures we rely on are as strong and durable as they need to be.

The Drying Deception: What Happens When Concrete Loses Moisture?

Concrete magnified, drying with magnifying glass.

The established method for examining concrete involves creating a paste containing cement, clay, and those all-important superplasticizers. This paste is then subjected to a process called X-ray Diffraction (XRD), which allows scientists to measure the spacing between layers of clay within the concrete. These spaces expand or contract depending on how the superplasticizers interact with the clay, and this expansion is a key indicator of the concrete's overall performance. However, before the XRD analysis, the samples are typically dried.

Here's where the problem arises: the new research reveals that drying the concrete samples causes a significant change in the clay layer spacing. Specifically, it underestimates the expansive effect of the superplasticizers. When the samples are analyzed in their fresh, wet state, the clay layers show a much greater degree of expansion. This suggests that the drying process forces some of the water and superplasticizer molecules out of the clay layers, leading to a misrepresentation of how the concrete behaves in its actual, working state.

Underestimated Strength: Drying reduces the apparent effectiveness of superplasticizers, leading to inaccurate strength predictions.
Misleading Data: Data from dried samples doesn't reflect the real-world behavior of concrete.
Compromised Structures: If we're designing structures based on flawed data, their long-term integrity could be at risk.

To put it simply, imagine trying to measure the fluffiness of a cake by first squashing it flat. You wouldn't get a true sense of its airy texture, would you? Similarly, drying concrete samples distorts their internal structure, giving us a false impression of their true characteristics.

A Wet Future for Concrete Testing?

The implications of this research are significant. It calls for a re-evaluation of current testing procedures and a shift towards analyzing concrete samples in their fresh, undried state. This more accurate approach will provide a clearer picture of how superplasticizers truly affect concrete strength and durability, leading to better designs, more resilient structures, and a safer built environment for all.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.cemconres.2018.11.015, Alternate LINK

Title: Influence Of Experimental Procedure On D-Spacing Measurement By Xrd Of Montmorillonite Clay Pastes Containing Pce-Based Superplasticizer

Subject: General Materials Science

Journal: Cement and Concrete Research

Publisher: Elsevier BV

Authors: Pere Borralleras, Ignacio Segura, Miguel A.G. Aranda, Antonio Aguado

Published: 2019-02-01

Everything You Need To Know

Why is drying concrete samples before testing potentially problematic?

Drying concrete samples before conducting X-ray Diffraction (XRD) can underestimate the expansive effect of superplasticizers. This is because the drying process forces some of the water and superplasticizer molecules out of the clay layers within the concrete, leading to a misrepresentation of how the concrete behaves in its actual, working state. As a result, the data obtained from dried samples does not accurately reflect the real-world behavior of concrete, leading to inaccurate strength predictions and potentially compromising the long-term integrity of structures.

How do superplasticizers affect the properties of concrete, and why is it important to accurately measure their impact?

Superplasticizers are chemical additives that enhance concrete's workability and strength by interacting with the clay particles present in the concrete. Accurately measuring their impact is crucial because these interactions directly influence the concrete's overall performance. If the effectiveness of superplasticizers is underestimated due to flawed testing procedures like drying, it can lead to inaccurate strength predictions and potentially compromise the structural integrity of buildings and other constructions. Therefore, understanding the true effect of superplasticizers is essential for ensuring safer and more durable built environments.

What is X-ray Diffraction (XRD), and how is it used in concrete analysis?

X-ray Diffraction (XRD) is a technique used to measure the spacing between layers of clay within concrete samples. During XRD analysis, scientists subject a concrete paste containing cement, clay, and superplasticizers to X-rays. The way these X-rays diffract reveals information about the arrangement of atoms and molecules within the material, including the spacing between clay layers. These spaces expand or contract depending on how the superplasticizers interact with the clay, providing key insights into the concrete's overall performance. Accurate XRD analysis is essential for understanding how superplasticizers affect concrete strength and durability.

What are the potential consequences of designing structures based on data from dried concrete samples?

Designing structures based on data from dried concrete samples can have serious consequences. Because drying underestimates the effectiveness of superplasticizers, the strength predictions derived from this data may be inaccurate. This can lead to the construction of structures that are weaker and less durable than intended, potentially compromising their long-term integrity and increasing the risk of failure. Inaccurate data can jeopardize the safety and reliability of the built environment, highlighting the need for more accurate testing procedures that analyze concrete in its fresh, undried state.

How might shifting to analyzing fresh, undried concrete samples improve construction practices and the built environment?

Shifting to analyzing fresh, undried concrete samples would provide a more accurate understanding of how superplasticizers affect concrete strength and durability. This more accurate approach would lead to better designs for concrete structures, resulting in more resilient and durable buildings, bridges, and other constructions. By ensuring that structures are built to their intended strength, we can create a safer and more reliable built environment for all. Furthermore, optimizing the use of superplasticizers based on accurate data could also lead to more cost-effective and sustainable construction practices.