Early determination of correct cement dosage for concrete mixes and prediction of their compressive strengths are very valuable in construction industry. This article presents a few compressive-strength prediction models for ordinary concrete using early-age measurements of relative complex permittivity. Both the dielectric constant and loss factor of the first-seven-day concrete with four types of mix proportions were measured for building the mathematical models composed of exponential functions at 6 GHz, whereas the measured dielectric data at 28 d were used for model validations. The proposed models not only have high regression accuracy with R²-values of greater than 0.97 but also the low prediction errors of within 10%, which significantly outperform the existing models of the same kind. Through Cole–Cole plot analysis, this article reveals an interesting finding that a minimum loss factor was located at 3 GHz regardless of the age of concrete, which would be useful for wireless network design and planning inside a building. The average loss tangents of various concrete mixes have also been verified to have the same value (~ 0.33) regardless of concrete age, which explains the confidence in use of early-age dielectric properties. Moreover, this article also initiates a precise prediction method of using loss factor and dielectric constant simultaneously in a 3-dimensional plot, wherein no explicit mathematical model is required.

早期确定混凝土混合物的正确水泥用量并预测其抗压强度在建筑行业中非常有价值。本文介绍了一些使用相对复介电常数的早期测量值来预测普通混凝土的抗压强度模型。测量了具有四种配合比的前 7 天混凝土的介电常数和损耗因子，以建立由 6 GHz 指数函数组成的数学模型，而在 28 d 时测量的介电数据用于模型验证。所提出的模型不仅具有R ^{2 的}高回归精度-值大于 0.97，而且预测误差在 10% 以内，显着优于现有同类模型。通过 Cole-Cole 图分析，本文揭示了一个有趣的发现，即无论混凝土的年龄如何，最小损耗因子都位于 3 GHz，这对于建筑物内的无线网络设计和规划非常有用。无论混凝土年龄如何，各种混凝土混合物的平均损耗角正切也已被证实具有相同的值 (~ 0.33)，这解释了使用早期介电特性的信心。此外，本文还开创了一种在3维图中同时使用损耗因子和介电常数的精确预测方法，其中不需要明确的数学模型。