Aiming at the adverse effects of low temperature environment on concrete, the effects of sodium nitrate on concrete strength at different temperatures were studied. The results show that the strength of concrete can be greatly improved at - 5 ℃ and - 10 ℃ when polycarboxylic acid water reducer is combined with sodium nitrate, and the excellent content of sodium nitrate is 0.27% of cementitious material.

混凝土在冬季施工中，由于氣溫低，水泥水化作用減弱，新澆筑的混凝土強度低，容易出現多種混凝土病害，影響建筑工程的質量，在氣溫降低到一定程度時，混凝土強度甚會發生不增長，給混凝土施工帶來一系列的問題。

During concrete construction in winter, due to the low temperature, the weakening of cement hydration and the low strength of newly poured concrete, it is prone to a variety of concrete diseases and affect the quality of construction projects. When the temperature decreases to a certain extent, the concrete strength will not even increase, which will bring a series of problems to concrete construction.

目前冬季施工一般采用在混凝土中添加早強劑來緩解低溫對混凝土造成的不良影響，早強劑大體分為無機鹽早強劑和有機物早強劑，其中無機鹽早強劑主要包括：氯化鹽，碳酸鹽，硝酸鹽，硫代硫酸鹽，硅酸鹽，鋁酸鹽等，有機類早強劑主要有：三乙醇胺，二乙醇胺，甲酸鈣，乙酸鈣，尿素，草酸等。本論文主要研究無機早強劑NaNO3對混凝土性能的影響。

At present, early strength agents are generally added to concrete in winter to alleviate the adverse effects of low temperature on concrete. Early strength agents are generally divided into inorganic salt early strength agents and organic early strength agents. Inorganic salt early strength agents mainly include chloride, carbonate, nitrate, thiosulfate, silicate, aluminate, etc. organic early strength agents mainly include triethanolamine, Diethanolamine, calcium formate, calcium acetate, urea, oxalic acid, etc. This paper mainly studies the effect of inorganic early strength agent NaNO3 on the properties of concrete.

一、實驗部分

1、 Experimental part

1.實驗原料

1. Experimental raw materials

所用硝酸鈉為分析純，減水劑為自制質量分數為40%的聚羧酸減水劑液體，水泥為聲威P·O42.5水泥。

The sodium nitrate used is analytical pure, the water reducing agent is polycarboxylic acid water reducing agent liquid with self-made mass fraction of 40%, and the cement is Shengwei P · o42.5 cement.

2.實驗儀器

2. Experimental instruments

混凝土試驗用攪拌機為無錫建儀儀器機械有限公司HJW60型攪拌機。

The mixer for concrete test is HJW60 mixer of Wuxi Jianyi Instrument Machinery Co., Ltd.

3.混凝土強度檢測

3. Concrete strength test

根據國標GB/T50107-2010《混凝土強度檢驗評定標準》對混凝土強度進行檢測。

The concrete strength is tested according to the national standard GB / t50107-2010 standard for inspection and evaluation of concrete strength.

二、實驗與討論

2、 Experiment and discussion

硝酸鈉在-5℃下對混凝土強度的影響

Effect of sodium nitrate on concrete strength at - 5 ℃

將不同質量的硝酸鈉與聚羧酸減水劑復配使用，按照表1配合比制備混凝土并裝入試模，放置于溫度為-5℃冰柜中冷凍，7天后取出拆模，繼續在標準養護條件下養護28天，分別對冷凍7天和冷凍后繼續標準養護28天的試塊強度進行檢測。

Mix sodium nitrate of different quality with polycarboxylate superplasticizer, prepare concrete according to the mix proportion in Table 1, put it into the test formwork, place it in the freezer with the temperature of - 5 ℃, remove the formwork after 7 days, continue to cure under standard curing conditions for 28 days, and test the strength of test blocks frozen for 7 days and after freezing for 28 days.