为筛选冻融环境下混凝土的优良配比,开展不同配合比条件下的水泥水化热试验、冻融循环试验及冻融后混凝土单轴压缩试验,探明掺合料和水胶比对混凝土结构性能的影响,确定寒区混凝土优良配合比,并建立冻融后全过程应力—应变预测曲线。结果表明:(1)随着矿物掺合量增加,水化热总体释放量减小,但少量硅灰掺入可促进早期水泥水化热释放,矿物早期活性为:水泥＞硅灰＞粉煤灰;(2)少量粉煤灰和硅灰掺入混凝土可发挥微集料和火山灰效应,提高混凝土密实度,可加强结构抗冻性能及力学性能;(3)低掺量硅灰(0~10%)掺入对结构抗冻有利,粉煤灰(0~20%)掺入导致结构抗冻性能先升高后降低,因此粉煤灰掺量存在最优值,而较大水胶比导致结构抗冻性能显著降低,试验得出15%粉煤灰—10%硅灰—0.36水胶比是适用于寒冷地区的优良混凝土配比;(4)提出的冻融后混凝土抗压应力—应变预测曲线可应用于严寒地区混凝土结构非线性分析。
In order to screen the good proportions of concrete under freeze-thaw environment, cement heat of hydration tests and uniaxial compression tests of concrete after freeze-thaw are carried out under different conditions to investigate the effects of admixture and water-cement ratio on the structural properties of concrete, to determine the good proportions of concrete in cold areas, and to establish the stress-strain prediction curve of the whole process after freeze-thaw. The results show that: (1) The total heat of hydration decreases with increasing mineral admixture content. However, a small dosage of silica fume can enhance early-age heat release. The reactivity of the materials at early ages follows the order: cement > silica fume > fly ash; (2) A small amount of fly ash and silica fume admixture into concrete can play the microaggregate and volcanic ash effect, improve the concrete compactness, and strengthen the structural frost resistance and mechanical properties; (3) Low admixture (0~10%) silica fume incorporation is beneficial to structural frost resistance, fly ash (0~20%) incorporation leads to first increase and then decrease in structural frost resistance, so there is an optimum value of fly ash incorporation, water-cement ratio leads to significant decrease in structural frost resistance, 15% fly ash—10% silica fume—0.36 water-cement ratio is an excellent concrete ratio applicable to cold regions; (4) The prediction curve of compressive stress-strain of concrete after freeze-thaw is proposed, which can be applied to the nonlinear analysis of concrete in cold regions.
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