The mixing cement with soft soil to increase their strength has been used in many construction sites and it is important that soil and cement are well mixed. In order to evaluate the mixing accuracy during construction, it may be required to measure the cement content by sampling the cement mixed soil. While there are several methods for measuring cement content, the hydrochloric acid heat reaction (HAHR) method is easiest and quickest and is relatively high in precision to measure the cement content in fresh concrete. However, to apply HAHR to the fresh soil cement, there were many questions about a test condition. This study investigated conditions to apply the HAHR method to cement mixed soil. At first, cement are mixed to the local soil samples in the ratio of 0 to 10g/100g. Initial temperatures (T0) of the mixed soil and hydrochloric acid are measured. 100 g of mixed soil is put in an insulated container. 100mL of hydrochloric acid is added, and reaction temperature (T1) is measured. Relationship of temperature rise (T1-T0) and cement content is a calibration graph. The relation is proportional. And, the temperature rises are measured about 100g of cement mixed soil of the site. Its cement content is obtained using the calibration curve. It is optimal to use 6M hydrochloric acid for this method. It is necessary to examine it with local soil and local cement to prepare a calibration curve. When the water content ratio of the soil greatly changes, it is necessary for the calibration curve to be updated. HAHR tests are done in 10 to 60 minutes after having mixed soil and cement in the case of samples containing a little water. But, in the case of containing much water, the tests are done under the specified elapsed time. As an example of the result, the cement content of soil can be determined from the rising temperature of the sample soil.
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