This paper aims to study the effects of different sand grading and salinity of mixing water on setting and hardening of cement mortar. For this purpose, a newly developed measurement method based on ultrasound pulse echo technique was used. Using this method, the attenuation coefficient and the modulus of reflection coefficient are measured to characterize the early age behavior of tested mortars. Ultrasound P-waves were generated using a 1 MHz central frequency immersion transducer and mortar samples were prepared with Portland composite cement CPJ 45. Mortar samples were classified into two series: first series considered mortar mixes prepared using fresh water and different sand grading form $56\mu m$ to $400\mu m$. These laboratory tests (series 1) aimed to obtain the optimum grain size of respective mortar mixes in terms of optimum workability and rheology. Continually, the optimum grain size (from series 1) is used in the second series of experiments (series 2) mortar mixes prepared using artificial sea water with different concentrations of sea salt, i.e., 0 g/l, 10 g/l, 20 g/l, 37 g/l and 50 g/l. The results show that the increase of sand size grading in mortar allows faster setting and hardening and earlier occurrence of aluminate hydrates phase transition AFt – AFm, precipitates the solid percolation and achieves denser microstructure. Also, the stepwise increase of Sea Salt dosage in mixing water from 0 g/l to 37 g/l resulted in a later achieve of final set and later occurrence of AFt – AFm transition.

【摘要】：目的研究不同砂级配和拌合水盐度对水泥砂浆凝结硬化的影响。为此，使用了一种新开发的基于超声脉冲回波技术的测量方法。使用这种方法，测量衰减系数和反射系数的模量来表征测试砂浆的早期行为。超声波 P 波是使用 1 MHz 中心频率浸入式换能器产生的，砂浆样品是用波特兰复合水泥 CPJ 45 制备的。 砂浆样品分为两个系列：第一个系列考虑使用淡水和不同砂分级形式制备的砂浆混合物$56\mu 米$ 到 $400\mu 米$. 这些实验室测试（系列 1）旨在获得各个砂浆混合物在最佳和易性和流变性方面的最佳粒度。继续，最佳粒度（来自系列 1）用于第二系列实验（系列 2）使用人造海水和不同浓度海盐制备的砂浆混合物，即 0 g/l、10 g/l、20克/升、37 克/升和 50 克/升。结果表明，砂浆中砂粒级配的增加允许更快的凝固和硬化以及更早发生铝酸盐水合物相变AFt-AFm，沉淀固体渗流并实现更致密的微观结构。此外，将混合水中的海盐剂量从 0 克/升逐步增加到 37 克/升，导致较晚实现最终凝固和较晚发生 AFt – AFm 转变。