From Bricks and Tile Magazine

1 Preface

Coloured concrete pavement blocks are also known as pavement blocks. In recent years, the production and application of coloured concrete paving blocks has flourished with the construction of municipalities and buildings in China. The combination of slab shape and colour creates a unique and pleasing coloured pavement, which contributes positively to the beautification of urban roads. However, the current production of coloured concrete pavement blocks has problems such as alkali flooding, varying shades of colour and uneven surfaces, where the quality of the colour is the key to its decorative effect. The following is a discussion of the factors that affect the quality of concrete pavement blocks, and proposes measures to prevent and control them.

2 influence concrete pavement brick colour quality factors and preventive measures

2 .1 The influence of the water-cement ratio on the quality of the colour

2 .1 .1 Causes :

①After the concrete has hardened, some of the excess water evaporates out of the concrete and forms pores, which are very small and numerous and scatter the incident light, resulting in a lighter concrete colour. The higher the water to ash ratio, the lighter the concrete colour;

② In the process of producing the same batch of concrete pavement blocks, the water-cement ratio is arbitrarily changed, so that the colour of the produced pavement blocks varies, resulting in unevenness.

2 .1 .2 prevention and control measures:

① choose the best concrete ratio and water-cement ratio, that is, forming conditions allow, try to reduce the water-cement ratio, so that the production of the product is dense, the concrete in the capillary pore is less, the less bubbles produced;

② Strict control of sand and stone moisture content, to ensure the accuracy of water-cement ratio control. At the same time, in the process of producing the same product, the water-cement ratio cannot be changed at will.

2 .2 The influence of cement colour on colour quality

2 .2 .1 Causes:

(1) The large specific surface area of cement, the large quantity used and the inaccurate measurement can cause different shades of colour in each batch of material, and the colour of the products produced will be uneven;

② The colour of silicate cement, whether light grey or dark grey, will have a weakening effect on any colour. For dark colours (red, brown, black, etc.), the use of grey and white cements has little effect on the colour quality of the products; for light colours (yellow, green, blue, etc.), the effect of the colour of the cement is greater.

2 .2 .2 Prevention and control measures:

① Cement measurement should be accurate, the general cement measurement error should not be greater than 1%, and the measurement scale should be regularly calibrated;

The lighter the colour of the grey cement, the more vivid the colour of the product, so light-coloured cement or white cement should be used as far as possible, and the same type and batch of cement should be used to produce the same batch of concrete road block products.

2.3 The effect of pigment quality and admixture on colour quality

2 .3 .1 Causes:

① Concrete pavement blocks produced in the same batch have a large colour difference, the colouring ability is not strong, and the pigment is not evenly dispersed;

② inaccurate pigment colour matching. The more pigments, the darker the product, which affects the physical and mechanical properties of concrete pavement blocks and increases the cost of the product.

2 .3 .2 Prevention and cure measures :

① synthetic iron oxide pigment coloring ability is strong; natural iron oxide pigment, coloring ability is not strong, should choose to use synthetic mineral pigment;

②When the pigment doping amount in the product reaches a certain value, then increase the doping amount, the colour of the product will no longer improve. General iron oxide pigment saturation point doping for 4 % to 8 %. If the pigment with poor colouring power is used, the saturation point of the pigment is also increased, and more dosing is needed to achieve the required colour effect;

③ Ensure the same mixing time for the same batch of pigments, usually 0.5 to 1 min. It is also possible to add dispersant to make the pigments evenly mixed and dispersed.

2.4 Influence of forming parameters on colour quality

2 .4 .1 Causes: vibration time and vibration force forming parameters are different, to the concrete pavement brick surface brings different spots, which will cause different degrees of light scattering, so that the colour products vary in shade.

2 .4 .2 prevention and control measures:

① the same batch of products used in the best vibration time and vibration force and other molding parameters should be the same, can not be arbitrarily changed in the middle;

② Trial production of solid specimens on the forming machine, to obtain the best forming parameters for each, so that the concrete forming to achieve the best density.

2.5 Influence of maintenance temperature on colour quality

2.5.1 Causes: The effect of maintenance temperature on the colour of concrete pavement blocks is mainly due to the thermal stability of the pigments themselves, which can vary greatly when heated. The higher the curing temperature, the lighter the concrete itself.

2 .5 .2 Prevention and treatment measures:

To prevent steam condensation from contaminating the surface of the product during low temperature maintenance, cover the decorative surface with plastic sheeting;

② Establish a good maintenance system to ensure the consistency of colour quality.

3 Conclusion

The production of uniformly coloured, brightly coloured concrete paving blocks is a systematic project that is carried out throughout the entire production process. There are many factors that affect the colour quality of concrete pavement blocks, including the quality of raw materials, mix ratio and measurement, forming and maintenance. Only through comprehensive management can the colour quality of concrete pavement blocks be guaranteed. At the same time, a quality assurance system and related rules and regulations are set up to establish operating procedures for each process, and each production department and management department pay attention to the quality of the product, so that the colour of the concrete pavement blocks produced can be of good quality and play a colourful and decorative role.