How to know the reasons that affect the concrete strength of automatic loading mixer truck?

一、試件形狀尺寸加氣混凝土

1、 Shape and size of specimen aerated concrete

自上料攪拌車，測定混凝土立方體試件抗壓強度，也可以按粗骨料大粒徑的尺寸而選用不同試件的尺寸。但是試件尺寸不同、形狀不同，會影響試件的抗壓強度測定結果。因為混凝土試件在壓力機上受壓時，在沿加荷方向發[本文先發在礦山機械/=百///科/=網]生縱向變形的同時，也按泊松比效應產生橫向膨脹。而鋼制壓板的橫向膨脹較混凝土小，因而在壓板與混凝土試件受壓面形成磨擦力，對試件的橫向膨脹起著約束作用，這種約束作用稱為"環箍效應"。"環箍效應"對混凝土抗壓強度有提高作用。自上料攪拌車，離壓板越遠，"環箍效應"小，在距離試件受壓面約0.866α（α為試件邊長）范圍外這種效應消失。

From the loading mixer, the compressive strength of concrete cube specimens can be measured, and the sizes of different specimens can also be selected according to the size of large particle size of coarse aggregate. However, the different size and shape of the specimen will affect the measurement results of the compressive strength of the specimen. Because when the concrete specimen is pressed on the press, while the longitudinal deformation occurs along the loading direction [this paper first occurs in mining machinery / = Bai / / Ke / = net], the transverse expansion also occurs according to the Poisson's ratio effect. The transverse expansion of the steel plate is smaller than that of the concrete, so the friction force is formed on the compression surface of the plate and the concrete specimen, which restricts the transverse expansion of the specimen. This restraint effect is called "hoop effect". "Hoop effect" can improve the compressive strength of concrete. From the loading mixer, the farther away from the pressing plate, the "hoop effect" is small, about 0.866 from the compression surface of the test piece α （ α This effect disappears outside the range of specimen side length).

混凝土受壓破壞在進行強度試驗時，試件尺寸越大，測得的強度值越低。

In the strength test of concrete compression failure, the larger the specimen size is, the lower the measured strength value is.

原因分析：

Cause analysis:

1、"環箍效應"；

1. "Hoop effect";

2、由于大試件內存在的孔隙、裂縫和局部較差等缺陷的機率大，從而降低了材料的強度。

2. Due to the high probability of pores, cracks and local defects in large specimens, the strength of the material is reduced.

二、表面狀態加氣混凝土

2、 Surface state aerated concrete

自上料攪拌車，當混凝土受壓面非常光滑時（如有油脂），由于壓板與試件表面的磨擦力減小，使環箍效應減小，試件將出現垂直裂紋而破壞，測得的混凝土強度值較低。

From the loading mixer, when the concrete pressure surface is very smooth (if there is grease), the hoop effect will be reduced due to the reduction of the friction force between the pressing plate and the surface of the specimen, the specimen will be damaged by vertical cracks, and the measured concrete strength value is low.

三、含水程度混凝土試件含水率越高，其強度越低。

3、 The higher the moisture content of concrete specimen, the lower its strength.

四、加荷速度

4、 Loading speed

自上料攪拌車，在進行加氣混凝土試件抗壓試驗時，加荷速度過快，材料裂紋擴展的速度慢于荷載增加速度，故測得的強度值偏高。在進行混凝土立方體抗壓強度試驗時，應按規定的加荷速度進行。

During the compression test of aerated concrete specimen by self loading mixer, the loading speed is too fast, and the crack propagation speed of the material is slower than the load increase speed, so the measured strength value is high. When carrying out the concrete cube compressive strength test, it shall be carried out according to the specified loading speed.

綜上所述，通過對混凝土強度影響因素的分析，提高混凝土強度的措施有：采用強度等級高的水泥；采用低水灰比；采用有害雜質少、級配良好、顆粒適當的骨料和合理的砂率；采用合理的機械攪拌、振搗工藝；保持合理的養護溫度和一定的濕度，可能的情況下采用濕熱養護；摻入合適的混凝土外加劑和摻合料。

To sum up, through the analysis of the influencing factors of concrete strength, the measures to improve concrete strength include: using cement with high strength grade; Adopt low water cement ratio; Adopt aggregates with less harmful impurities, good grading, appropriate particles and reasonable sand ratio; Adopt reasonable mechanical mixing and vibration technology; Maintain reasonable curing temperature and certain humidity, and adopt damp heat curing when possible; Add appropriate concrete admixtures and admixtures.

實踐證明，自上料攪拌車，影響自動上料攪拌車混凝土強度的原因有試件尺寸、形狀、表面狀態、含水率以及實驗加荷速度等實驗因素都會影響到自動上料攪拌車加氣混凝土強度。

Practice has proved that the reasons affecting the concrete strength of the automatic feeding mixer are the size, shape, surface state, moisture content and experimental loading speed of the test piece, which will affect the strength of the aerated concrete of the automatic feeding mixer.